Match and mixing lenses.... DX/FX

Discussion in 'Nikon' started by rene|4, Sep 19, 2012.

  1. Like almost everyone else, after so many years of reading, practicing and learning, there is still so much I don't know, understand, etc.
    Anyway, I know many people talk about getting a better bokeh on FX than DX. My primitive eyes can't see the difference. For instance, if I use a D700 with with an AFS 85 G and then mount the lens on a D300, besides the different angle of view the bokeh looks the same to me...
    If someone could take the time to show me the difference I would appreciate it.......
    Second part:
    If you have an AFS 24 G which you use on DX and FX, WHY or WHY not would you buy an AFS 35 G? (The 24 on DX comes to 36 mm angle of view)
    Cheers!!
     
  2. The difference, I think, Rene, is when you compare, say, a 60mm lens on DX with a 90mm lens on FX...
    But I, too, have no problems with the bokeh, when I need it, on DX.
     
  3. On the AF-S DX 35mm f1.8G Nikkor ($220.00 new) Vs. the FX 24mm f1.4G Nikkor lens ($1,999.00 - USA model; $1,849.00 - Grey model) ... is the f1.4 lens going to make you that much happier over a f1.8 lens?
    Only you can determine if you have a need to help Nikon sales in the lens department....
     
  4. Jerry... Thank you for your contribution. But it is not about money, need or want... I just want to know what the difference would be. I already have a 24 1.4f which I used on a D300 and a D700. And I live in Japan so my 24 costs more than 2,500 USD.
    My question is how much better a shot would be using a D700 with a 35 1.4f over using a D300 with a 24 1.4f. I hope it is clearer now....
     
  5. Rene' -
    Better in terms of what exactly? Bokeh? Field of view? Magnification?
    Field of view wise the 2 would be approximately the same.
    Bokeh wise I believe that the D700 would win - simply because of the larger sensor. Nothing to do with the lenses. (Although I'm sure someone will argue that one has better bokeh than the other).
    I would think most of the difference between the two images would come from the sensors (FF vs Dx) and software in the camera body. Pixel density will make a difference to.
    The only reason I can think of that someone would buy both (other than a collector who wants an example of every Nikon lens) would be a person who has an aversion to zoom lenses. There also may be the person who has both bodies and wants comparable fov between them when switching bodies.
    Dave
     
  6. It's not about bokeh (the qualities of the blur), but about the slightly shallower depth of field that can be created with the larger format for a given composition, and thus the quantity of blur. The quality of those out-of-focus blobs still depends on the optical characteristics of the lens (and, usually, it's not going to get better looking than what's seen on that 24/1.4, or the 85/1.4, etc). But if you like shooting with shorter focal lengths, and like to isolate your subject by throwing the background out of focus, you can go a bit shallower with the DoF when using the bigger sensor rig for the same shot.

    This probably makes the most difference when shooting on the shorter focal length side of things. Of course it's a two-way street: if you have to shoot with a wide aperture because of low light, the larger format is going to stick you with that much less DoF, whether you want it or not.
     
  7. "besides the different angle of view the bokeh looks the same to me.." Well, you are sort of correct. If you are 6' away from the subject and take the same shot with the same lens, one on DX and one on FX, the bokeh will be identical. But, if you compose the pictures the same in the frame, meaning you are 6' away with DX, but to fill the frame with FX identically to DX, you need to move 2-3' closer (just a guess as to the distance), the bokeh changes (and is typically improved). This is where the difference is.

    As to the second part, I believe it would be because the FOV changes on both lenses when used on DX and the compression of the image is a bit different from 24mm to 35mm.
     
  8. Actually, I do think several of my lenses do show a bit different 'character' on my D700 compared to the D300. It's not that the bokeh is vastly different, but due to having less depth of field, at an equal aperture, the FX looks even more blurred - the outlines of the OoF blobs less visible, so it seems a different bokeh rendering. Probably when comparing at equal DoF (i.e. f/5.6 on DX versus f/8 on FX), they'll look roughly the same. But there are just smaller things that seem different - f.e. on the 105 f/2.5, the transition from in-focus to out of focus just looks more gradual and elegant on the D700 than it does with the D300. Nothing massive, but subtle changes. The difference in the quantity of OoF to me is really noticeable (but I shoot a lot wide open).
    Though maybe it is just so, because I want to see this, as a self-fullfilling prophecy. I'm not deluded enough to exclude this possible reason ;-)
    A second thing is that on the D700, lens flaws are a bit less explicit. The amount of CA of my AiS 35 f/1.4 on the D300 wide open was incredible (50 pixels I think - really way over the top), while on the D700 it actually doesn't look there is that much CA at all. The f/1.4 and f/2 apertures became a lot more useful.
     
  9. Using a different lens, I saw no real difference at all when I took the same shots with D300 and D700 a couple of years ago. Neither did a magazine editor who buys from me. There is one stop less DoF on an FX than a DX per given apeture.
    Kent in SD
     
  10. When I put my 85 f1.4 on a DX camera vs FX I have to back up quite a bit to get the same angle of view. Now that I'm further away I have more DoF even at the same aperture just because I'm further away. The whole reason I got the 85 f1.4 was to shoot at f1.4 and have extremely shallow DoF. I've found that I often can't back up enough when using it on DX and even if I could I'm now too far away to feel part of what's going on and direct.
     
  11. I would imagine the 35mm on FX would look better than the 24mm on DX, but not to the point where it's really noticeable to the casual viewer. I know for a fact the 85mm f/1.4G looks way better on FX than it or the 50mm f/1.4G on DX (apples and oranges...I know).
    I have a 24mm f/1.4 that I used for concerts in a D300s along with the 50 and 85. I am very happy with the field of view of the 24mm prime on DX. However, I recently bought both the D800 and a used D700 (for the frame rate on FX) and I have to say that the 24mm prime is just too darn wide for practical purposes on FX in my opinion. I'm thinking about the 35mm f/1.4G for FX use, but after "treating" myself to the 24mm, I really don't want to buy another expensive prime. I may sell the 24mm to finance the 35mm...still thinking.
     
  12. My question is how much better a shot would be using a D700 with a 35 1.4f over using a D300 with a 24 1.4f. I hope it is clearer now....
    What Matt says... On FX you have a bit more control over DoF; usually, you can always close the longer lens a bit to match the DX camera. In the other way, you cannot always open the DX lens to match the FX DoF.
    Distortion, resolution, bokeh, etc. must be checked on each individual lens, it can be quite different.
    Time ago I did a couple shots regarding this issue; both at f2.8, first one with a 55mm lens on FX, second one with a 35mm lens on DX. Focus in on the "Ilford" print. If you look at the air can, the differences are a bit clearer. Check them by yourself:
    1. 55mm lens on FX format
    [​IMG]
     
  13. 2. 35mm lens on DX format
    [​IMG]
     
  14. If you have an AFS 24 G which you use on DX and FX, WHY or WHY not would you buy an AFS 35 G? (The 24 on DX comes to 36 mm angle of view)
    • Personally, I find 35mm (FF) a very useful focal lenght; I achieved this on DX using a 24/2.8AFD.
    • On FX I also use 24mm lenses, but not so much if compared to 35/50mm lenses.
    • I`m so picky, so I`d prefer to have a 35/1.4 on FX that 24/1.4 on DX... for the "creative abilities" of the bigger format.
    But having said this, the difference is obvious, but not so big. My "creative capacities" are too small, so buying a 35/1.4 lens could be for sure a bad investment if the lens cost is over, say $1000... :)
    (BTW, there is a new Sigma 35/1.4 taking off... )
     
  15. gdw

    gdw

    Good gravey, the question was "what is the difference in bokeh using the SAME lens on the two different sensors." There were a few correct answers which is--there is no difference, with the caveat--you are using the lens from the same shooting distance at the same aperture. Changing sensors does not alter the focal length of the lens. Viola, as long as the aperture is the same, shot from the same distance the DOF will be identical because the size of the image does not change. The smaller sensor simply crops out the center of the larger sensor. If the DOF is the same the appearance of the bokeh is the same.
    A couple of the posters correctly stated that changing distance so that the framing is identical on each of the sensors, thus changing the size of the image on the sensor, indeed does affect DOF and thus bokeh because the appearance of the bokeh of a lens is governed by DOF. DOF is governed by the size of the image on the sensor, not the focal length of the lens. A 24mm lens at 2 feet has for all practical purposes has identical DOF as a 100mm lens at 8 feet because the size of the image on the sensor is approximately the same.
    One poster mentioned that there may be a difference in the capture quality or characteristics of the two sensors. That may be a factor but I would imagine it would be minimal. But again I do not know. I do know what governs the bokeh of a lens, DOF, and what governs DOF is the size of the image on the sensor in combination with the aperture. Change the size of the image by changing distance or change the aperture and you will change how pronunced the bokeh will appear. But it won't be changed by changing the size of the sensor which was the original question.
     
  16. I do know what governs the bokeh of a lens, DOF, and what governs DOF is the size of the image on the sensor in combination with the aperture.​
    Those are the things that govern how much blur is present. That's not what governs the aesthetic qualities of the blur. You could use two different 85mm lenses at f/2 and see things more or less equally "blurry" but also see very different qualities in the blur (that's the "bokeh" that people talk about - how lines are rendered, what bright points look like). The optical recipe of the lens, the materials used, the coatings, the number of iris blades - that's what governs the bokeh. The aperture, distance, etc., govern DoF, and that dictates how much is out of focus ... just not what those out of focus areas actually look like.
     
  17. gdw

    gdw

    Matt, the OP is asking about using the same lens, not two different lenses. Yes bokeh is affected by the number of shutter blade as well as other lens design factors--neither of which is going to change just because the lens is put on different camera bodies. The aesthetic quality of the blur is not going to change.
     
  18. Gary: I noticed him talking about the 24mm and the 35mm lenses, used on the different format bodies, which is why I'm mentioning the extra variable of the optical recipes (which likely differ between the two lenses).
     
  19. Here we go again. :) (Sorry Rene' - I hope this helps you.)
    Let's consider - to make the numbers easy - a 200mm f/2 lens used wide open. The entrance aperture (disk through which light entering the lens passes) is 200/2 = 100mm. For any object at the focal distance in the image, light will spread out, and that light which hits the entrance aperture gets refracted back by the lens design to a single point on the sensor. The relevant portion of the light coming from that point forms a cone with the circular aperture at the base, and the point at the focal distance at the point. Anything which intersects that intrudes on that cone adds to the point in the image, partly blocking anything at the focal distance.
    If there's nothing at the focal distance at the point we're considering, the cone of light continues, expanding behind the focal plane to infinity. Anything that intrudes on this cone will also contribute to the point on the image (assuming the light ray in question isn't blocked by something closer to the lens).
    So, imagining these cones of light, we can also see that any object in front of or behind the focal plane forms a circle of confusion on the image plane according to how far the object is form the subject distance.
    The reason I'm talking about projecting cones in the real world is that this has nothing to do with the sensor behind the camera - it's entirely defined by the absolute entrance aperture (focal length x f-stop, bearing in mind that we normally talk about relative aperture) and the focal distance.
    The upshot is that a DX camera image looks exactly like the middle chopped out of an FX image.
    If you enlarge the DX image to the size of the FX image, the DX camera's depth of field is reduced (yes, it's shallower than the FX image in this case) because you've zoomed in on details - but you've not got the same image as you took with an FX lens, because the field of view is different.
    If you move the DX camera back 1.5x farther from the subject, the subject size will match in the final image (relative to the total image size). However, the perspective is different, because you're not shooting from the same place - and depth of field is larger for the DX camera.
    Now consider changing lenses, which is why we keep talking about equivalence. A 150mm lens on an FX camera has the same field of view as a 100mm lens on a DX camera, once we're talking in terms of the whole captured image size. Shoot from the same place and you'll get the same image. However, bear in mind that a 150mm f/4 lens has an entrance aperture of 150/4 = 37.5mm. If we shoot the DX lens at f/4, its entrance aperture is only 100/4 = 25mm, which means the "cone of light" is more acute, and the DX camera has a deeper depth of field. Were we instead to set the FX lens to f/6, we'd have the same entrance aperture - 150mm/6 = 100mm/4. We then have to adjust the ISO as well to compensate for the exposure difference we've just produced with the smaller relative aperture (the FX camera would have to be shot at 2.25x the ISO of the DX camera to match). Then the output of the two cameras should look identical.
    If we don't adjust the ISO and the aperture in this way, but still use lenses with the same field of view, the FX camera's depth of field is narrower.
    All of this assumes an optically perfect lens. It's easier - especially for a telephoto lens - to design a lens with little optical aberration at smaller relative apertures. Therefore it's not surprising that a 150mm f/3 (say) lens on an FX camera is likely to be an optically better performer than a 100mm f/2 lens on a DX camera. This may explain why some people talking about preferring the "look" of FX. By equivalence, a 150mm f/2.8 lens on a 5x4 large format camera is likely to be optically pretty decent - and it's likely to outperform a 50mm f/1 lens used on an FX camera, wide open.
    There's a limit to how fast lenses can be made. I have a 200mm f/2, which I use on FX. Aberrations aside, this would be equivalent to a 133mm f/1.33 on a DX camera. Nobody actually makes one of those. There aren't many DX 35mm f/0.95 lenses out there either, especially not at the cost of a 50mm f/1.4.
     
  20. gdw

    gdw

    Rene, from some of the answers posted here your confusion is understandable. I’m not sure how such a simple topic can be made so complicated. Accept the fact that your “primitive eyes” are more accurate than most of the information you are getting. Your eyes are correct: same lens at the same aperture and distance on the two different sized sensors will have identical bokeh.
    As Matt says, yes, lens design affects bokeh so changing lens will or at least can change bokeh appearance.
    Changing aperture will change DOF which will change the appearance of bokeh.
    Changing distance will change DOF which will change appearance of bokeh.
    Bokeh is a function of the lens. So, in spite of all the complicated, convoluted and confusing explanations—changing sensors does not affect bokeh.
    I apologize for not addressing your second question. Why a person buys any piece of photographic equipment has about as many answers as there are photographers. Most often we justify our purchases to ourselves whether or not there is any actual basis in reality to our justification.
     
  21. Hehe! Well, I know everyone is trying to help and that is welcome.... Right or wrong answers, we can still learn. Now I understand a bit more about using 2 different lenses on 2 different sensors..... Then again, as I suspected or should I say: as I have noticed with my primitive eyes, using the same lens on 2 different sensors, the shots look 99% identical..... to be honest 100% but I am sure they are not the same.
    What I did today was testing with the only zoom lens I have, 35-70 f2.8. I was shooting wide open at 52 mm on FX and 35 mm on DX and I can't see any difference really with the exemption that some how the angle of view of the lens at 52 on FX looks wider than 35 on DX..... Now I am curious about the 1.5 crop of DX sensors.... IS IT REALLY 1.5 crop? Next I'll check it again with my 24 on DX and 35 f2 on FX :) But we can talk about that later.....
    So thank you all.... and if there is anything else to be added, don't be shy and go for it....
    Cheers!
     
  22. Rene said "Anyway, I know many people talk about getting a better bokeh on FX than DX. My primitive eyes can't see the difference."
    Rene, I found the same to be true. I am a longtime Nikon guy. Recently I switched to mirrorless (Fuji X Pro-1). One good thing about mirrorless is that you can use hundreds of legacy lenses with adapters (you of course can only use F mount lenses on Nikon cameras).
    If "better Bokeh" is your goal and you only have a Nikon body you're best option is probably the 58mm 1.2 Noct-Nikkor Noct for 3 thousand of dollars or more. However, if you go mirrorless, you can find much cheaper legacy lenses with exceptional bokeh (at least as good as the Noct - Nikkor) for much less money (e.g. Minolta MC 58mm f/1.2 for $600)!
     
  23. We usually talk about amount of bokeh (well, the depth of field change) being different between FX and DX. The quality difference, while I'd expect it to exist, should be tiny once you've normalized everything else. It'll be a function of how well the lenses are corrected.
    If you can't tell an FX 50mm f/2.8 shot from a DX 35mm f/2.8 shot, I suggest you try a different subject. DX at 35mm f/2.8 should look more like FX 50mm at f/4 - and I'm assuming you can tell the f/2.8 and f/4 shots apart.
     
  24. try shooting a 1.4 lens at f/2.
     
  25. gdw

    gdw

    Rene, to your first inquiry, does the appearance of the out of focus area change when the same lens used on two different sensors sizes. I replied that it does not. I said that your eyes were correct when they could not see the difference because there was no difference. I did mention a caveat--the shooting distance and the focal length used MUST remain the same for both sensors. However, to your second inquiry, where you changed the focal length of the lens when you changed between bodies and still could not see the difference, your eyes were not functioning nearly as well. Because in that case there is a difference in the appearance of the out of focus areas because there is a difference between the DOF of a 52mm lens and the DOF a 35mm lens.
    You say that when you switched sensor sizes you switched focal length; you "adjusted" the focal length. That does indeed change the depth of field and WILL change the appearance of the out of focus areas. Now the difference in appearance may not be pronounced enough that it is a big difference or even a discernible difference. It will depend upon what is in the background and how close or how far away those objects are to your point of focus--but it will change because depth of field between the two focal lengths will be different. And as far as bokeh is concerned it could well depend upon whether or not you had bright areas or point light sources in the background that makes the bokeh of a lens more evident. As explained before, bokeh and the appearance of out of focus areas is not the same thing although the word bokeh has been corrupted and often used to mean the appearance of any out of focus area.
    When you move a lens from one sensor size to the other it does not change the focal length of the lens. I know this is confusing because it is such an ingrown urban myth of photography when we talk of putting a 50mm lens on a DX sensor as though it becomes a 75mm lens. It doesn't. All the DX sensor does is crop out the center of the FX sensor, the center of a 50mm lens. Switching between the two in no way affects the focal length of the lens. It is still very much a 50mm lens with all the same characteristics on the DX as it had when it is on a FX sensor--identical. If you want to compare the appearance of the out of focus areas you will need to leave the focal length, and the shooting distance, the same on both cameras.
    Because the focal length does not change is why we talk of DX sensors having a greater depth of field than FX sensors. They don't. The just give what appears to be a 75mm lens the same DOF as a 50mm lens because it actually is a 50mm lens.
    If you can, wrap your head around that one simple fact: the focal length of the lens is the same on both sensors. That will simplify a lot of your questions. It's something that a lot of photographers that fall for conventional wisdoms can't seem to do.
     
  26. I'd think you'd buy the 35mm 1.4 if you want to be able to shoot at 35mm and 1.4 on FX. But I think if you're talking
    about such an expensive lens and wondering why you'd need it, the answer is, don't buy it. If you we're talking about
    the 35mm DX lens, the answer would be, buy it if you want something smaller and lighter than your 24mm to use on a
    DX camera.
     

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