D700 vs df Viewfinder - Ease of focusing with manual focus lenses

Discussion in 'Nikon' started by patrick_boron, Jun 29, 2015.

  1. Hi there,
    A quick question for those who have got both. Given the fact that the Df was supposed to be used with legacy glass, is it's viewfinder better for manual focusing compared to the d700?
    Many thanks!
  2. ShunCheung

    ShunCheung Administrator

    First of all, there are many different opinions on this topic. I have no doubt that many would disagree with me. However, as far as I am concerned, a split-image focusing screen, perhaps with a ring of microprism, is a must for manual focusing with wider lenses. I don't find the Df's viewfinder any easier to use compared that on other Nikon DSLRs.
    Of course, with digital, using live view is now a better way to manual focus. But your camera needs to be on a tripod.
    SSepan likes this.
  3. a split-image focusing screen, perhaps with a ring of microprism, is a must for manual focusing with wider lenses​
    Funny, that was always the first thing I replaced in any of my film SLRs - but then the fastest glass I had to focus was f/2. The split-image and microprisms were pretty much useless on lenses with a maximum aperture of f/3.5 or slower.
    Inadequacies of the current AF focusing screens as well as "age-related" changes in my eyesight have made it pretty much impossible for me to reliably manually focus lenses on DSLR cameras - I very much prefer to do that in the EVF of a Sony A7.
  4. ShunCheung

    ShunCheung Administrator

    Dieter, that was the first thing you replaced in your film SLRs because split-image center with a ring of microprism was pretty much the standard in the last manual-focus film SLRs in the 1980's, before auto focus took over.
    My first SLR was a Minolta SRT-101 which had only microprism, which I found insufficient as I prefer image matching in rangefinders (such as the Leica M). At the time some Nikkormat only had split-image. By the mid 1970's, split-image + microprism was pretty much the standard for over a decade until the beginning of the AF era in the late 1980's.
    Of course, just because something is the "standard" since it fits a lot of people doesn't necessarily mean it will also meet your individual needs.
  5. I upgraded my D700 to a D800 before I got the Df. But, I did do a side-by-side manual focus test between the D800 and Df. Based on detailed review of 1:1 crops from both, I could not pick a winner.
  6. Don't the AF sensors work for a manual focus lens - the ball between two arrows. That's far more accurate than any split image or microprism screen. Nothing measures up to the precision of the continuous live view of an A7 with peaking and/or magnification.
    SSepan likes this.
  7. I using a Nikon D3s, a D4, and a Df. Never had a problem to focus and I us a mix of lenses from AI to AF-S. Every time some of my fellow photographer looking thru of the Df, saying, ohhh, how bright it is. I never paid attention to it, just focusing all of the time manually. All of my viewfinder optically adjusted to my eye-site. To add more, I like the images the most of the Df, technically. Most of my images shoot with the Df, lately.
  8. I am a film SLR user and since the start I don't use the microprism or split image (that's kinda defeat the purpose of an SLR) but I have found the Df is significantly more difficult to manual focus on the ground glass alone as compared to the F3, FM and a bunch of others like Pentax KX, Minolta XD-11, Minolta SRT 101.
  9. The first thing I did when I got my D700 was to replace the standard screen with a microprism screen from focusingscreen.com. All of my lenses are AI/AIS and I had little faith in the focus confirmation dot compared to my eyes, most especially in low light. The microprism focusing screen is spot on.
  10. I'm with Dieter. I always switched to a flat screen to focus because the split image, though great when it worked was almost useless in low light.
  11. While I've no problem with split prisms in general (I have a Pentax 645 with one), I really find them to be outdated compared with modern expectations. They are, of course, absolutely fine if you want to focus on the middle of the image - but I don't often want to focus there, either for composition (that's not where I want the focus plane) or lack of contrast at that point. Focus-and-recompose is a nice theory, but the rotation of the focal plane means you're limited when you want a shallow depth of field (unless you have Hasselblad's accelerometer-based refocus trick) and as pixel counts increase the definition of "in focus" and the size of the depth of field is becoming redefined. It'd be interesting if someone could implement a focus screen that allowed the split prism to be moved around the frame (but more than a small matter of engineering). Live view, especially with focus peaking, seems like a much better long-term solution.

    I'm prepared to believe a Df's finder is slightly better for manual focus - it's designed to be, obviously, although it certainly didn't stand out at me when I've tried one. Of course, if you're prepared to use the focus confirmation light as a back-up, the D700's MultiCAM 3500 has quite an advantage in coverage.
  12. Yes, I`m also another who replaced the original K screens with B ones; but some years ago my eyesight started to go down so I had to make the reverse... now I need the original split image/microprism ones, without them I`m unable assure focus under certain conditions.
    To me, eye fine focusing on a D700 is almost a dream. With loads of light, maybe.
  13. Patrick, yes, the Df's viewfinder is widely regarded to be easier to use for manual focus than the D700's. However, opinions vary on how easy this is to do exactly; I think individual eyesight and the lenses used affect the results. It is possible to purchase focusing screens modified to fit various DSLRs, e.g. the S screen is regarded better for large aperture lenses (available from focusingscreen.com).
    There is some discussion on manual focusabilility and replacement focusing screens on
  14. I have used most of the FX digital bodies, other than a Df. If I had to grab one and focus manually by eye quickly, the D3 I had would be my choice. The D600 I had seemed a little better for MF than the D800 I had at the same time. I did have a D700, but don't recall using it much with MF lenses.
    I struggled with wide angle manual focus lenses on the D800. The D810 seems a little better for eye and indicator focusing, I think. Short teles seem easier than wides for manual focus with the standard FX screens. I used a 75-150E on the D600 some with good results.
    It was and is easier to focus manually with the older film bodies, for sure.
  15. Can we lay this "faster lenses are easier to focus with a split image" myth to rest please?
    As has been known for some time, the visual focusing system used in Nikon SLRs and DSLRs shows absolutely no difference in brightness, nor any other aspect such as depth-of-field, at apertures wider than f/2. So it doesn't matter if the lens is f/1.4, f/1.2 or f/0.95; you simply won't see any difference in the viewfinder image over an f/2 lens - and this includes the behavious of the split image/microprism.
    OTOH there may be an advantage to the AF system and electronic rangefinder, because the AF sensor is in the bottom of the mirror box of the camera and bypasses the viewing system.
  16. R.J., What is restricting the viewfinder to f/2 brightness?
  17. As you stop down, your eye compensates for the change in brightness. Furthermore, your eye has a logarithmic response to light. You see very little change over one stop, but it makes a big difference in the results.
    Faster lenses have less depth of field, hence more "pop" when focused. At the same time, focus is more critical, hence easier to miss the exact spot in practice. The law of diminishing returns applies. DOF is proportional to the diameter of the iris, whereas the amount of light transmitted is proportional to the area.
  18. ShunCheung

    ShunCheung Administrator

    As has been known for some time, the visual focusing system used in Nikon SLRs and DSLRs shows absolutely no difference in brightness, nor any other aspect such as depth-of-field, at apertures wider than f/2. So it doesn't matter if the lens is f/1.4, f/1.2 or f/0.95; you simply won't see any difference in the viewfinder image over an f/2 lens - and this includes the behavious of the split image/microprism.
    R.J., What is restricting the viewfinder to f/2 brightness?​
    It is more than that. If you mount an f1.2 lens on your Nikon camera and leave it wide open @ f1.2, how can the Nikon optical viewfinder automatically increase the depth of field to what you would get at f2?
  19. It's not the viewfinder, that would not get brighter, R.J. The visual focusing system does what it cannot not do. More light is more light. Not a myth.<br><br>Depth of field is another matter. It depends on the screen. Is it an 'active' screen, with some sort of microlenses, or just a diffusing screen? Those old diffusing screens also show the depth of field nicely. And we do see the decrease, i.e. have more trouble focusing an image with very little depth. Screens that use optical tricks to direct light towards the viewfinder's pupil also change how the image, and more particularly the out of focus part, looks. I don't know that this would behave such that there is a limit to changes you can see at f/2.<br>I don't quite agree that fast lenses have more 'pop', Edward. There is not such a great contrast between in focus and just out of focus. The shallow depth of field makes focussing much harder than any 'pop' would compensate for.<br><br>Split image rangefinders are not really affected by f-stop, except that when the lens' exit pupil gets too small, or too far away, the rangefinder will no longer be illuminated. They work fine, and keep working fine with fast lenses.
  20. A fresnel screen, typically used to increase finder brightness in recent cameras, only captures light from a subset of the cone leaving the rear element. The amount of defocus that's visible from apertures larger than the amount captured by the fresnel would be invisible, which is why f/1.4 and f/2 look very similar on many cameras. Similarly, a split-image finder (like autofocus systems) relies on capturing images from either side of the rear of the lens; they don't "look" at the edges of a fast lens, so, while they won't work any worse than on a slower lens, they also won't have the wider separation that might have been possible (and helpful with a narrow depth of field) if the finder screen was optimised to the lens speed.

    Slight disclaimer: I only have a moderate understanding of how this works. But this seems informative.
  21. A Fresnel is 'old hat', has been included in viewfinders since the 1940s. They do redirect the entire cone projected on the focussing screen, in zones, making the angle of incidence less acute, i.e. directing that light more towards the screen and the viewer's eye on the other side instead of away to sides. That produces a more evenly lit viewfinder.<br>A Fresnel lens however does not create the visible image we need. A matte screen (etched or ground glass) does that by diffusing the light projected onto it. Most of that light will not be going towards ourr eyes, i.e. the finder is rather dark (compared to, for instance, the parts of the split image rangefinder).<br><br>New screens use techniques akin to what makes cat's eyes (the road markers) and projection screens work, i.e. instead of diffusing the light falling onto it, scattering it in many directions, they use tiny beads or cones all over the screen that direct the light towards one point, the place where our eye is supposed to be. So less loss, more light towards our eye = a considerably brighter viewfinder.<br>Those optical active screens however also have an effect on how the image looks, and in particular the out of focus parts do not look the way they will when captured on film or by sensor.<br><br>The difference between f/1.4 and f/2 is real and present. That we do not notice much is because of what Edward said: having enough light our eyes adjust to create a more or less equally bright impression. We will have to look for the difference conciously, compare the two, and then we will see it. Without paying special attention, we will start to notice things only when it gets either too bright or too dark.<br><br>Split image rangefinders are wedges, that divert light from the out of focus image, producing a lateral shift of the parts of the image each wedge covers relative to each other. The two images coincide when the light projected onto them is convergent on the wedges. They do not care about aperture size much, except that when the cone of light gets too narrow they no longer are completely illuminated and typically one half darkens (depending also on from where you look through them at the lens' exit pupil, i.e. depending also on the position of your eye.)
  22. I was referring to "popping" or snapping in and out of focus, not "pop" in the artistic sense of contrast and color. Sorry to have confused the terms.
    Focusing aids such as microprisms exaggerate this effect, and it is what we look for in a superimposed image rangefinder, such as on a Leica M. We look for the confused image to suddenly "gel" or snap into focus, rather than the presence or absence of a double image.
    Finders with a prism, using total internal reflection, tend to be brighter than those using mirrors. The latter are commonly used to reduce the weight and cost of components.
  23. I understood it that way, Edward.<br>The general idea appears to be that when DoF is shallow, it is easier to see when an image is in focus and when it is not. The differences between in focus and not in focus however are still small, the process of getting focus on the exact point where you want it to be (whether manually or using AF) is a nervous one, and i would say there really is no such 'pop'. It's harder, not easier, to focus a shallow DoF image, using a fast lens because there is not much DoF to cover mistakes. And as hard as ever to get it precise when not wanting to rely on DoF to cover mistakes.<br>But YMMV, and all that.
  24. The difference between f/1.4 and f/2 is real and present. That we do not notice much is because of what Edward said: having enough light our eyes adjust to create a more or less equally bright impression. We will have to look for the difference conciously, compare the two, and then we will see it. Without paying special attention, we will start to notice things only when it gets either too bright or too dark.​
    This was bugging me, so I did an experiment. Here's a capture from my RX100 on manual exposure settings taken through the finder of my D810, with an f/1.4 Sigma 35mm mounted on it. Wide open (the D810's meter is off). Sorry this and the following image are so blurry - my finder diopter is set to accommodate my weird eyes, and I didn't really register that this might be why the RX100 was struggling until it was inconvenient to reshoot; I don't believe the blurriness affects the comparison, and I didn't want to try to compensate by sharpening in case the image processing seemed to affect the results.
  25. Now trying that again. The D810 is focussed in the same place (the back of the chair - I didn't change the focus point). All I did is hold down the DoF preview button, set to f/2. The camera satisfyingly went "chunk" as the aperture lever moved. And there's no difference. Not looking through the finder (where I can actually see things in focus), not comparing these manual exposures - the white thing on the wall is almost exactly the same exposure. There's no difference to how out-of-focus the background is. There absolutely is a visible difference as you start to go to f/2.8.

    Sorry, but I'm standing by the accepted wisdom that a fresnel screen in a modern DSLR doesn't show you the difference between f/1.4 and f/2. A genuine ground glass obviously would. This doesn't mean you can't see the focus plane, of course - perfectly sharp is still perfectly sharp - it just means that the rate at which objects appear out of focus as they become more distant from the focal plane is not the same in the finder as they are in the final capture at wide apertures. And that's always the advice I've heard on these forums.
  26. "[...] accepted wisdom that a Fresnel lens doesn't show you [etc.]"? What accepted wisdom would that be?
    All a Fresnel lens does is create a more evenly illuminated finder image. There is nothing it does to hide differences between two arbitrarily chosen apertures.
    There is nothing it does to produce an image that we can inspect. We still need a matte screen for that, so whether Fresnel or not there is always a "genuine ground glass" in the finder.
    Basic optics.

    You will see the difference between f/1.4 and f/2 in the finder. If that difference isn't big enough for you to see, it would also be too small to see when going from f/4 to f/5.6. It has nothing to do with large apertures. Nothing to do with Fresnels and 'modern' finders. And since there's also nothing else that could explain such a supernatural phenomenon, It must be you. ,-)
  27. Andrew, I performed similar tests with an old film MF camera and a 50/1.2 with really confusing results. The blur difference between say f1.2 and f1.4 or even with f2 is minimal, so in my experience I found that I have to guess a difference between them.
    In the best (cleanest) of my tests, I placed the background (printed paper) a bit closer to have less blur, tried to be absolutely steady, to get a much closer exposure, and this time I found very slight differences between half stops, from f1.2 to f5.6 (I stopped the test at f5.6). Sincerely, I cannot get absolutely clear results, so I cannot use them to prove anything. I assume Q.G. is right, it makes sense. I have no clue on this, and my experience is also unclear.
    It was also my assumption that AF cameras are even more difficult to focus by eye; what Rodeo said. Time ago, I tried to find MF differences between F3, F6 and D700 screens. I think I wrote something in this forum, but I cannot recall it correctly. But for sure there were very slight differences, if any, between them. It is something very difficult to distinguish, and I`m not qualified to say anything because my eyesight is really bad. Only the split prism works for me under not so sharp conditions; it works perfectly with all my f1.2 or f1.4 lenses in all conditions.
    I wonder if the quality of the ground glass (I`m referring to the smoothness of the surface) make that differences.
    In my experience with LF screens, the smoother ones are darker but with a more "precise focus" feel, with them I can use stronger loupes, while the coarser ones maybe give a "sharper feel" but not as precise... and focusing loupes have to be less powered.
  28. At the risk of diverting the thread, but I hope of some interest to people, my professional pride requires that I try to be convincing to QG. If I was a real professional, I'd have brought two tripods and a macro rail with me to work rather than trying to hold my RX100 steady with one hand and press the DoF preview button with another, while engaging manual focus mode on the RX100 (painful one-handed) and fiddling with the D810's finder diopter. I resorted to standing my D810 on an ash-covered bin (the grey thing bottom right) - I don't smoke. Things I do for this forum... :)

    Firstly, consecutive shots within a few seconds of each other. I'll report the aperture and the averaged pixel colours of the bench for each shot. Apologies for the run of posts, but it seems cleaner than trying to squeeze everything in.
  29. Now to start stopping down...
  30. Now to start seeing differences - f/2.8.
  31. And to be more obvious - f/4.
  32. And finally, f/5.6.
  33. ShunCheung

    ShunCheung Administrator

    Of course the difference between the depth of field for f1.4 and f1.8 is small, as shown on this thread: http://www.photo.net/nikon-camera-forum/00b5BR
  34. Thank you for the prompt, Shun. Just to show you that this really is an f/1.4 lens, here's the f/2 shot from my D810's perspective.
  35. And now at f/1.4, to prove you can see the difference.
  36. Looking through the finder, I see no difference between f/1.4 and f/2. None. If the camera hadn't gone "chunk", I wouldn't know it had happened. An optical illusion might make the change look small, or allow me to compensate, but not completely hide a change while looking straight at the image - I should see something if the difference was visible in the finder. Even if it were an optical illusion, the point and shoot that was looking through the finder (on manual mode) would see a change in values. It doesn't. (1/255 is measurement error.) It didn't with my previous experiment either. Obviously this isn't perfect - all I could do is wedge the compact against the back of the finder, I wasn't equipped to keep the RX100 perfectly stationary compared with the D810. That would allow a scientific experiment of how large a difference is present, but almost exactly identical numbers on two separate attempts (do check yourself on the above images) does suggest I didn't mess it up completely.

    A figure often quoted on this forum is that faster than around f/2.2 or maybe f/2.5, no difference is visible. I didn't try to find the exact point where that's true for the D810, but I'd say the above does strongly suggest that f/2 is above the "no difference" point and f/2.8 is below it.

    I'm no expert in fresnel lenses, the exact optical path that's going on here, or Nikon's parts list - I'm fully prepared to believe that different cameras behave differently. But experimentally, I'd absolutely claim that the finder screen is hiding depth of field at larger apertures. With a pure ground-glass (non-fresnel) screen, I would not expect this to be the case. Forgive me for not trying to take photos of the live view image as well!

    Remind me not to try to do this again. Way more painful than it's worth. :) If I do need to, I'll have to bring a longer lens - I only brought the 35mm Sigma because we're due thunderstorms and I was optimistic for prettiness. The depth of field would have been much more obvious with something longer, but I hope it's visible enough.
  37. Andrew, i appreciate the effort you put in, but you're not going to convince me. There are no optical illusions at play. There is no magic involved. Fresnel lenses and such can only do what they can do. It's really all basic optics.<br><br>I think Jose is right, pointing us towards the origin of the myth you are trying to prove. As so often with photo-myths, it is a solid bit of reality, but misunderstood and turnied into something it really is not.<br>Yes, compared to many old cameras, the viewfinders of present day DSLRs are bad. Not as easy to use for anything but framing purposes as viewfinders once were. That, because people relied (and still rely) on AF anyway, and are not very likely to switch to manualk focus (which appears to be seen as a defect nowadays), so why bother making a high quality viewfinder with expensive screen. So they do not, and the finders in my Nikon DSLRs are indeed not as good as those of older film cameras i have and have used.<br>Somehow that will have been turned into the "accepted wisdom" (though i never heard that one before) that there is something that these finders do that restricts their usability (so far so good: they're bad) by magically (oops) stopping being a regular optical device once the apertue of a lens gets beyond a certain limit (it would indeed be magic if they did).<br><br>And again, there is no such magic you think Fresnels are capable of, Andrew. They are just field lenses, that converge a diverging beam of light a bit. There is nothing to be found chasing after a "pure-ground-glass (non fresnel) screen" and a screen that sits above a Fresnel lens.<br><br>But i'm open minded, believe it or not. So let's see a decent explanation of how that would work, and i'll gladly change my mind.<br>Let's begin, Andrew, with how this "hiding depth of field at larger apertures" would work.
  38. Actually, this issue not that simple. Out of curiosity, I did it again, trying to be as clean as possible. Results are maybe enough to have an idea of this behaviour, but I still find it somewhat confusing. It is more complex than it could seem at a first sight.
    FWIW, I have used a non-suspicious MF camera, a F3 with the HP finder. The lens is a 50/1.4 AiS, at half stop intervals, from f1.4 to f5.6. The images from the F3`s finder has been taken with a D700 and a 105/4 Micro @ f8 (with the second tripod and the macro rail Andrew was not willing to use :). The control of light has been done with the shutter speeds by adjusting the hystogram.
    The focus plane is on the "12" mark, check that the split image match the point. The crops are from the area below, around the "10" mark.
    Yes, I`d say there are differences in all f-stops, from f1.4 (or f1.2 in my previous test), but they are not that clear. Check it by yourself (attached is a 100% crop).
    First the whole image,
  39. Now, below are the crops starting from 1.4 to 2.8, and in a second row from 2.8 to f5.6. Notice that the pics are in focus, the ring portion at top is the outer side of the microprism image:
  40. And below there should be a link for the 100% crop:
  41. (Way of topic, but I hope still interesting to some...)
    Thanks Jose - and interesting. I'm actually struggling to see much DoF difference between f/1.4 and even f4. I'd claim you can just see it on my images (with apologies again for only having a 35mm lens to hand) but not between f/1.4 and f/2, except in the actual shots from the D810, where the background is clearly softer wide open.
    Notice that the pics are in focus​
    Show-off. :)
    Firstly, apologies for missing your previous post - I was too busy pasting my own sequence and just missed yours until QG brought my attention to it. For the record, quoting the Mir.com.my Nikon pages:
    Other than the Nikon F3AF model, the standard focusing screen used on any F3 camera is the Type K screen: It is a combination of Type A and J screens. It has a Matte/Fresnel field with 3 mm split image rangefinder spot surrounded by 1 mm-wide microprism doughnut.​

    I assume that's your screen. We may mainly be proving how hard this kind of thing is to photograph - though commendable effort. Sadly, taking two cameras into my office (where we're not really supposed to have any - hence shooting outside) was one thing; taking my tripods in was another. I should try some day - I've never actually used my macro rail...

    QG: I'm very prepared to believe that cameras are different. The assertion that larger apertures are indistinguishable has been common on this forum, and certainly wasn't started by me. I don't claim to know the mechanism, but I really stand by my measurements: there are clear pixel value differences as stops change (and I changed by a whole stop each time - not having an f/1.2 lens in my arsenal) except between f/1.4 and f/2. The sensor absolutely sees a very visible difference both in depth of field and in brightness between f/1.4 and f/2. Through the finder, I can clearly see differences at smaller apertures, but not at the f/1.4 and f/2 pair. As noted above, the bench, as shot through the finder with the aperture at f/1.4, had pixel value 147, 157, 160; by f/2, it was 146, 156, 159. That's easily within rounding error (I was averaging several pixels within the bench, but obviously my RX100 wasn't completely stationary). There really is no visible difference between the two fastest apertures, and no measurable difference as recorded by my RX100. The difference between, say, f/2.8 and f/4, or f/4 and f/5.6, is extremely visible and measurable. Actually taking a shot with the camera shows that f/1.4 and f/2 are just as differentiated - it's not that my Sigma is "lying" and actually only f/1.9. Irrespective of the optical design of the viewfinder and why this should be so, it really is a verifiable fact that, at least with this camera, you won't see the difference between the f/1.4 an f/2 apertures - it's not magic, whatever it is. I believe I've confirmed the same behaviour with a D700 in the past.

    I am interested to know how this works - but the measurements indicate that it is so, and the lack of explanation doesn't invalidate them. From this point on, I'll try some conjecture on the "why", in the hope of educating myself or inspiring others to do so. I'm expecting someone to tell me that at least some of the following is wrong...
    To try to see what was going on, I just had a go with my F5. Firstly, again, I can see absolutely no difference when stopping the aperture down from f/1.4 to f/2.2. By f/2.5, I can see a slight reduction in brightness. I'm prepared to believe that the f/2.2 view is also slightly darker but by a small enough amount that I can't see it, but I'm not prepared to believe that it's a whole stop darker than f/1.4 before I notice anything at all. What I couldn't try on my F5, and couldn't quite be bothered to get my D810 out to prove, is how visible the aperture changes are. The D810, like the D800, D3 and D4 series (and D750 I think), drives its aperture motor separately from the mirror so you can hold down DoF preview and adjust the aperture while looking through the finder. I'd have run out of hands to try this earlier.
    The reason I wheeled out the F5 is partly that I know what kind of screen Nikon claims it has - the standard EC-B "fine-ground matte field" shown with fresnel circles in the F5 manual - and I can also take it out and look at it (the first time I've done this - and it appears my F5 still works, so yay). Nikon do specifically make a type C with no Fresnel, and the type U screen is a fresnel "good for lenses longer than 200mm", which might be a clue to what's going on.
    Unfortunately, the EC-B is quite a complex bit of kit, and I still can't quite see what's going on (and I'm not prepared to unscrew it). Shining a light on the prism-facing side of the screen shows a completely smooth surface - other than fine traces for the LCD wiring - that's appreciably convex (the lens on the back of the finder screen is either not fresnel or not entirely fresnel). Shining a light off the mirror side produces diffraction patterns - but regular ones without an obvious circular component. Shining a light through the screen clearly shows the circular fresnel pattern. Without a couple of hours with a macro lens and a lot more lighting than my phone, reproducing that will be difficult, so I'm afraid verbal description is what you get.
    What's going on? Well, it looks a bit like there's a non-fresnel screen on the mirror side, a fresnel inside the screen arrangement, and a conventional lens on the back. But that could be rubbish.
    The way I had always thought a fresnel screen helped was by capturing the light cone from the exit pupil. As QG says, a fresnel is just a (thin) lens, so I'd assumed there was more to the arrangement than that. I'm prepared to believe that the behaviour I've been prescribing to the fresnel in terms of whether light hitting the screen at an acute angle is captured should in fact have been blamed on the microstructure of the screen - though if in fact there is still appreciable scattering at the back of the finder, maybe the fresnel still cannot capture all of it and is still partly to blame!
    I notice there was a brief discussion on the topic on this thread (including QG!) - and this confirms my report of a fresnel "inside" the screen with an additional lens on the back.
    The discussion here on Luminous Landscape says the following:
    Similarly, “focusing snap” and viewfinder brightness don’t exactly go hand in hand. The super-bright screens are essentially bundles of very small fiberoptic cables, sliced crosswise, or miniature fresnel (flattened) simple lenses. While they transmit a ton of light, they can be very difficult to focus on. Everything looks pretty sharp; it’s not very obvious what’s in focus and what’s not. (The effect is worse with wide-angle lenses, which have more depth-of-field.) Old-fashioned ground-glass screens had better focusing snap the coarser the grind (surface texture) was. But, the coarser the surface, the dimmer the finder.​

    To me, that doesn't quite explain the situation, but it's interesting.

    Anyway. Very wide apertures, not distinguishable in the finder of a D810, F5, or probably anything in between (the Df may be a little different; the Df and D810 finder views are supposed to be improved, but I thought that was down to prism coatings improving brightness - the Df may or many not additionally have a different screen). I'm interested in more details of why, though.

    As for whether the finder of a DSLR is as good as that on a film camera, that's another matter. Technology indubitably improves, but at least from the multicam-3500 generation, the entire finder screen is seen through an LCD - which is why everything goes dark and blurry if you take the battery out and look through the finder, although also how the active AF points get to go away when you're not using them. This is definitely not true of the F5, and obviously can't be true of manual cameras. How much effect the LCD has on the finder view I can't say, but I doubt it can improve visibility (and I'm kind of guessing there must be a polariser in there somewhere for the LCD to work, so there'd be some light loss). However, I don't remember a huge outcry when these LCD designs were launched, so I guess the effect can't be enormous. (My Eos 300D certainly doesn't do this - it just has LEDs that light up at the focus points - but being a pentamirror it doesn't really inform me about relative brightness in finders...)

    Fun evening. I think I'm zeroing in on an education. :)
  42. It's my understanding that the issue of inaccurate DOF representation of modern AF screen has to do with the fact that they are optimized for maximum brightness - a feat achieved by using microlenses that focus gather light and focus it upward into the prism. The viewing area does not consist of "ground glass" but an array of microlenses. The fresnel portion is embedded and serves to even out light distribution - it is not responsible for the appearance of "too much DOF". That's caused by the microlenses "seeing" only the center portion of the lens - and depending on their characteristics, they do not "see" an increase in aperture beyond a certain value - usually somewhere around f/2.8 or a little larger. So, on the viewfinder, f/1.2, f/1.4, and f/2 all look pretty much the same.
    IIRC, Canon has some different focusing screens that are optimized for manual focusing - those screens sacrifice brightness for the sake of "pop" - the image "springs" into focus like one was used to see with the screens in many film cameras. Which is the effect may not appear in the viewfinder of an F3 but does show in a D810 - they do not use the same type of focusing screen. MF film camera screen: "ground glass" not optimized for brightness, AF screen, optimized for brightness, sacrifices DOF preview (and thus focusing) accuracy at large apertures.
    Edit: Andrew cross-posted - didn't see his post while writing mine.
  43. Some image comparisons: actual image recorded vs image seen in viewfinder: http://www.jayandwanda.com/photography/dslr_man_focus/man_focus.html
    Viewfinder brightness as a function of aperture (Olympus E-1 and E-500): http://www.jayandwanda.com/photography/dslr_man_focus/ViewBright-3c.jpg
  44. This link will show you what is IMO the most recent, and conclusive, evidence that the "light pipe" sliced fiber optic based modern screens in Nikons create an optical limit of about f/2.8 in terms of how it processes the aerial image from the lens into the appearance of the illusion of depth of field. No supernatural here.
  45. "I assume that's your screen."
    Right. I haven`t checked it but I think it`s the "newer" ("red dot"), K type screen. (BTW, I also used a Beattie Intenscreen on the F3, but for whatever the reason I promptly returned to the Nikon original).

    My point is that even on a F3HP, which (I think) is considered amongst the best cameras to use with MF lenses, the DoF preview is not that sharp as I could expect. On AF cameras, we should expect it to be better. I can made a similar test with a good AF camera screen... (with my wife`s permission, obviously... ) :D

    At the Zeiss site (-manufacturer of the "premium" Zeiss ZF lenses-), I read that users should pay attention to the screen they are using. If I recall it correctly, they say AF screens are not optimized for MF just because they lack focusing aids like the split image and microprism things. They don`t even mention the GG type or quality in a first approach.

    After that, they mention some AF screens (cameras) are better than others. The good ones (which also lack that MF focusing aids), are the D and F one-digit pro series. They don`t mention any other "consumer" model (the site is somewhat outdated right now).

    DoF is also extremely subjective or dependant, sometimes it looks even an absurd concept. I`d say the "DoF preview" could be a silly idea, even more silly on a focusing screen where also happen the typical wide open softness, a possible focus shift, the roughness of the GG, the "true" speed of the less, the linearity of the aperture ring at the widest apertures, the light distribution (or whatever it is) when stopping down... etc. etc... the only thing I get from it is a more or less (rough) conclusion that the image looks sharper or not at the widest aperture. I assume it will be the same on AF cameras (with priority on the brightness of the screen).
    Maybe the real myth is about the "reality" of the "DoF preview" in such small viewfinders.
  46. Link to the Zeiss site; here.
    I knew Dieter`s linked site; it also remind me the "electronic rangefinder aid" issue (also mentioned at the Zeiss`site).
    Keith`s link make me think again on the LF screens. They are made in almost every form, with all fresnel position choices. No problem here, but I still tend to think that main differences are due to the ground glass type, not to the fresnel position. Again, I´ll ask to my wife`s permission... ;D
    And a typo above: "On AF cameras, we should expect it to be better... ". Obviously, we should`t.
  47. It's much too hard to use DOF to try and determine effective aperture. It also too hard to use apparent brightness to measure effective aperture.
    What you should do instead is to measure the size of out-of-focus point spread function.
    So find a point source light and shoot an out of focus image like the one below. Then shoot an image of the viewfinder. Then resize the images and compare the size of the "blobs".
    An f1.2 or f1.4 lens would be best. Make the blobs as big as possible.
  48. Thanks, everyone. Interesting threads.

    I'm prepared to believe that the issue with the screen not showing wider apertures is to do with another aspect of the microstructure of the screen (microlens or not) rather than with the fresnel. My apologies for conflating the two, especially if I was the first to do so - my confusion is based partly on Nikon's list of screens for the F5, for which most but not all of the screens show stylised fresnel rings.

    I'm also interested, but not enormously surprised, at the reports in Keith's post that the D5100 screen doesn't show aperture above f/5.6. (Actually, that's not quite what it says, but I'll go with that interpretation.) If the trade-off is brightness at a given aperture vs whether changes in aperture are visible at larger apertures, it makes sense that the D5100, which is expected to be used with f/5.6 (sometimes) kit zoom lenses, should be optimised for the brightness of those. I'd always assumed the same reasoning was true of the ~f/2.8 alleged limit on the pro bodies.

    I`d say the "DoF preview" could be a silly idea, even more silly on a focusing screen where also happen the typical wide open softness, a possible focus shift, the roughness of the GG, the "true" speed of the less, the linearity of the aperture ring at the widest apertures, the light distribution (or whatever it is) when stopping down... etc. etc... the only thing I get from it is a more or less (rough) conclusion that the image looks sharper or not at the widest aperture.​
    I'm not so sure. I would find it useful to know how out-of-focus the background is. I don't care so much about trying to judge the depth of the sharp region optically (it's always a plane, anything else is only "in focus" with caveats), but I would like to have a better idea of whether I've hidden a hideous background, sometimes.

    Pete: Agreed. Unfortunately I had the wrong lens - you can compare branch thickness in the images I shot, but they're a bit hard to see, even in the full-size versions. These are, for the record, a PiTA to shoot. I'll see if I can give it another go this evening - I was deliberately going for outdoor shots earlier because I didn't want to confuse matters with light strobing, but that isn't an issue if I'm just pointing at an LED. My turn to try two tripods and a macro rail. I'll give my D810 + macro lens and an F5 a go rather than the RX100. It will go down well with my wife - we have an anniversary this evening...
  49. Andrew, I agree that to make an idea the DoF preview works; but my point is that it is very relative. The idea it gives is very rough.
    (BTW, hope you have had a nice soiree... congrats. :)
    Again, if there is still anyone interested, below I`m posting similar shots to those above with the F3, this time they belong to a D700 screen, half stop intervals from f1.4 to f4 (50/1.4AFS). Due to technical limitations the quality is not the same, but again, it could work to have an idea.
    Notice that the last frame is f1.4 again (red characters), to make easier a comparison with the f4 shot. I`d say there is a very slight difference between them (f4 and f1.4), so there will be also diferences between all steps, although they are extremely small to be noticed. This could be the reason to think that "below f2.8" the screen is not capable of showing the "real" DoF... I`d say it is less capable to show DoF than others (the F3 is much better in this respect). We need a "jump" from f1.4 to f2.8 (or to f4) to see a difference.

    According to Zeiss, the F6 is a good one; I also tested it, but I cannot see a substantial difference with the D700.
  50. So. One of those posts I love making, and am slightly too familiar with...
    I was wrong. Q.G., you have my apologies. Please accept the above assertions as misinformation, or at least incomplete. I'm also very confused. But you get a 4am post because I don't like leaving misinformation on the internet with my name on it.
    I tried to do the set-up I mentioned (involving four tripods, two LED torches, an F5, a Samyang 85mm, a D810, a macro lens and a macro rail - I'm better equipped at home). Minimum focus distance on the Samyang, one LED at the focus point to check I wasn't moving, one in the background. F/2, depth of field preview... and the stopping down was instantly visible. Wait, what? I didn't take any definitive photos in the end, because I was too busy experimenting.
    Wondering if the F5 screen was different after all, I put the Samyang on my D810, put it at minimum focus distance and pointed the camera at a light. Instant difference on f/2. Suspicious of the Samyang, I tried the 50mm Sigma. Still visible. Worried about telecentricity as an explanation for why I didn't see this before, I put the 35mm Sigma back on my D810, since this was then lens I'd reported with before. And... I can see a clear difference (reduction in bokeh size) when I stop down to f/2. I'd swear I'm seeing a difference in brightness now as well, and still can at f/1.8. I can't at f/1.6, but I'm prepared to put that down to a fractional stop difference being hard to see.
    Waving the camera around, the difference in blur is very visible in the centre of the finder and arguably not visible at all at the edge - which I'm prepared to believe is a function of the vignetting of the 35mm (and possibly of the finder). Photozone reports two stops of vignetting on the Sigma 35mm, which is pretty spectacularly much. The 50mm would have been a bit less.
    So. Why on early didn't I notice this before? This time, I was explicitly at minimum focus distance - above, I was actually focussed on the flowers, so the background was less blurred. Possibly that may have been affecting the finder (at minimum focus and extreme background blur, you get the diffraction pattern break-up of the image in the finder that you don't get with more reasonable out-of-focus behaviour). Trying again with a near subject and the lens at infinity focus, I conclude f/2 is easy to tell from f/1.4 if the out-of-focus is enough for the image to have "broken up" in the finder, but very hard or impossible to see otherwise. I'd be interested to know if this tallies with the experience of others.
    As for the change in illumination... very hard to say what's going on. With my living room lights on full, f/1.8 is visibly darker in the finder than f/1.4. With more normal lighting, I struggle to see it more, so I'd put it down to my eye's difficulty in detecting brightness differences at lower light levels. Except... I also couldn't see a difference under sunlight when I was shooting outside.
    This confuses me a bit, but not nearly as much as the fact that when I used the RX100 to shoot through my D810's finder, it measured no difference in brightness. I deliberately did that to avoid any subjective component, and I really don't have an explanation of why the bench I measured above (from, admittedly, an out-of-camera JPEG rather than a fixed raw pipeline) had no detectable change in intensity from f/1.4 to f/2, but clearly did at smaller apertures. I'm prepared to believe, given the vignetting, that the change in T-stop of the 35mm between f/1.4 and f/2 is a lot smaller than the change in F-stop, but it still should have been measurable.
    I'm clearly not the first person to have come to the belief that the finder doesn't show wider aperture differences, so something confusing is happening here. I might currently claim that you can see wide aperture out-of-focus regions if they're very out of focus (to the extent that the focus screen grain makes the diffract) but not otherwise. Or even this might be incorrect.
    Jose: Thank you. :) And also for the images. If you feel like trying to reproduce Pete's request with some out-of-focus point lights, I'd be interested to know what you see - I no longer trust myself, but I also acknowledge that it's a pain of an experiment to set up (and I'm not sure my LED torches are small enough to count as "point lights" for the purposes of this discussion, at least through an 85mm). I can't see a visible difference in behaviour between the F5 and D810 screens, for what it's worth, so I'm not surprised the D700 and F6 are similar (except arguably that the D700 doesn't have a 100% finder).
    My education continues. Sigh.
  51. My experience with the metering confused me too; cannot explain why, you can be right about the vignetting and light transmission. I even removed the camera from the tripod to check if the diaphragm were really closing down... :D
    Thank you, very interesting. Of course I`ll perform a test following Pete`s recommendation (thanks Pete), I need to see this by myself (I must admit sometimes I get too obsessive). I was wrong with the orientation of my tests, I was trying to know were the differences started to be noticeable, but it is certainly more useful to show categorical differences.
    I`ll try to check it tonight, just for curiosity`s sake, although I agree it really is a pain of an experiment to set up... ! :D
  52. I find it hard to believe that the modern digital dslr's cannot be configured to use the focus indicator of the autofocus system while being used in manual focussing. I mean...REALLY!
  53. Edmund: They can, of course - although one could argue that it would be nice if the continuous digital rangefinder of the low-end cameras was an option on the high-end ones in addition to the three-segment display. I believe it's the case that autofocus lenses (or lenses chipped to think they're autofocus) will confirm focus more accurately - my understanding (source) is that the AF tolerance used for the digital rangefinder is greater in manual focus mode than in AF mode (presumably to make it "easier" to manual focus) - so AF with back button focus and manual override should be more accurate than switching to manual mode. Of course, most AF lenses have a focus ring with shorter throw than manual focus lenses, so actually controlling the focus may be harder. I wish focus accuracy was more continuous - I sent some suggestions on this to Nikon some years back. And I was one of those who complained when Nikon took trap focus out of the D800 (which they subsequently put back). Why trap focus requires an autofocus lens to work is another irritation...

    Jose: Good luck, and I'll be interested to see your experiments - your existing ones are informative, but I'd like to see your version of Pete's too (particularly if you can try different amounts of out-of-focus to differentiate the effects I think I saw). I now doubt my competence to do the same. I, too, checked that the diaphragm was moving on all these lenses.

    I should just give up and go mirrorless, because I know how that works...
  54. I don't have many DSLR just one but the Df screen isn't as good as one in the F5.
  55. BeBu: Just out of interest, can you clarify what you mean by "isn't as good"? I'm not disagreeing (well, one could argue about the amount of useful information that can be displayed in the finder, but in terms of a clear image...) but I'd like to know how you're comparing. The Df has an LCD screen to look through, but should have better coatings... without a Df, I can't really say. The D810 apparently has the same coatings as the Df (but possibly not the same screen), but without two identical lenses, it's hard to look through my D810 and my F5 and try to reach a conclusion. I'd take the D810 over the Df for manual focus (unless I had pre-AI glass!), but for the same reason I'd take the D700: I'd use the virtual rangefinder for focus confirmation.

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