Discussion in 'Nikon' started by Rick Helmke, Nov 28, 2018.

  1. While the Z AF aren't as good as the D5 but Sony A9 is up there.

    Is it? I find the user reports and reviews mixed; suggesting that in some areas it is worse, in some better. "As good" in my view means as good in any situation, and in no situation, worse, because a photographer may depend on the performance of a camera in a particular situation.


    Sony a9 Full Review: Mirrorless Redefined

    "On the other hand, the a9 images during bursts would fall in and out of crisp focus (as we will see with some frisbee and cycling bursts coming up in the review), whereas the D5's seemed to be more consistently spot-on in this regard. The D5 was also less prone to jump to a different subject after an obstacle blocked the initial subject (though it's not perfect, as you can see in sample bursts provided below)."

    "Perhaps the biggest difference between the two, though, was that the D5 still just feels more immediate. I found that I still prefer the D5's optical viewfinder, though shutter blackout does put it at an objective disadvantage compared to the a9. Also, AF acquisition speed on the D5 is just absolutely instantaneous, whereas the a9 still appears to have a bit of a hiccup before it begins tracking with Lock-On. It was fast enough for these subjects, but the D5 is still just that smidgen faster."

    Anyway, the D5 is a 2016 body, the A9 2017, in 2019 or 2020 we can expect both manufacturers' cameras to be at a different level.
  2. I am not a mirroless fan but I know the only thing a mirrorless is lacking is the reflex viewfinder. To me it means everything but to some the reflex viewfinder isn't as good as EVF. Other than that AF and battery life isn't a mirrorless weak points. In fact I expect in the future it would be the mirrorless strong point.
  3. Quick question: Thom Hogan's review of the Z 7 is up, and he reports (and I'd not realised) that it resorts to electronic shutter above 5.5fps (in addition to locking metering). That's possibly tied with the normal requirement to close, then reopen the shutter (he mentions that the shutter lag on the Z 7 is worse than the D850, which surprised me - I'd expected the mirror to be the limiting step). While I like having a true silent mode, electronic shutters currently have a downside in terms of rolling shutter effects, which still gives an edge to the cameras with fast mechanical shutters (like the D5). Am I right in saying that the Z 6 has the same 5.5fps limit for a mechanical shutter? (I think so, reading the manual, but...)

    I'm now curious whether the D1's high shutter speed mode had rolling shutter or was actually a global shutter.
  4. Err, I'm guess it then it becomes, effectively, a video 'still' but at full res?
  5. Nikon seem to have more or less sorted out the viewfinder issue, the Z7 EVF is really good. I wouldn't have thought I would say this, based on my experiences with other EVFs, which I've felt were awful. As for the AF, mirrorless has some advantages and some disadvantages because of the differences in the AF sensors. To perform well, mirrorless needs tailor-made lenses that have optical and motor solutions optimized for mirrorless use, so if you want to take advantage of the good sides of mirrorless AF, be prepared to replace all your AF lenses. A DSLR needs to process only a small amount of data to continue focusing whereas with mirrorless a large amount of data is read, processed, and displayed/acted on, to keep the viewfinder and autofocus updated, thus the power consumption is likely to be several times greater than in a DSLR. Of course they could put in a larger battery but then you'd lose some of the compactness and light weight advantages. I'm not saying these issues aren't manageable but I think we are a long way from a situation where mirrorless is in all respects better than DSLR.
  6. I didn't even think about it in the past, but when pressing the shutter button on the Z7, it does create a sequence of sounds (in normal mechanical shutter sound) and there would then be two shutter cycles for each picture taken in this way. Jim Kasson reports that the Z7 shutter causes more vibration than the DSLR if EFCS is not used, this could be because of the additional vibration due to shutter closure before reopening, also it could be due to the differences in the body structure and how vibration is managed in the body. So, for intermediate shutter speed work, with mid teles or longer focal lengths, EFCS is probably something that should be used by default with the Z7, to avoid vibration. It feels very odd indeed that a mirrorless camera would create more vibration than a corresponding DSLR, but that's what is reported. So, it's probably best to turn EFCS on, unless you run into some limitation of it (in the Nikon DSLRs, there is a limit of 1/2000s max shutter speed in EFCS mode if I recall correctly, and there may be uneven exposures when EFCS is used with tilt-shift lenses with movements in use).

    I wonder how long it will take to develop a high-resolution sensor with fast read time (to avoid or minimize rolling shutter) and what drawbacks it might have (dynamic range and high cost have previously been reported as a drawbacks of global shutter sensors). Once global shutter without any image quality drawback is possible and economical then the mechanical shutter can be removed. But it may also be that slowly rolling shutters always have a dynamic range advantage and in that case the mechanical shutter is likely to stay in mirrorless cameras, with two shutter cycles per picture (!).
  7. More or less is relative. I would use less to describe a viewfinder that lags when you pan (and has parts in the image that move fast, such as the wheels on a car) and a viewfinder that always superimpose some information over the image. In my book the Z7 still has some basics to sort out before I call its viewfinder really good. (I am not blaming Nikon as much as I note that we still have a long way to go before mirrorless is truly better than DSLRs in all respects.)
  8. Why use a mechanical shutter at all, unless your subjects are moving A LOT and FAST?

    My J5 could do 60fps, until the buffer fills after 20 pix either JPEGS or NEFs.....:(

    ...and it's totally SILENT!

    The only way you know it's done it, is the buffer is full and the little green BUSY LED glows.
    Last edited: Dec 4, 2018
  9. The tilt-shift thing is news to me, but Thom is also suggesting EFCS where possible. I assume EFCS has a fast way to "reset the sensor" line by line, racing the speed that the shutter passes it. I'm sure the speed limitation (including 1/200s synch) is merely a design choice of the Z series (although IIRC they did have to design a special slimline shutter) rather than anything fundamental about mirrorless.

    I wondered whether Sony would get there with the stacked sensor tech. IIRC the older CCD sensors effectively had a per-pixel "storage area" for the charge which wasn't exposed to light, but it took up some of the sensor area (this could be very confused). Stacking circuitry behind the sensor area ought to allow something similar without actually losing exposure area. This is distinct from just doing a very fast read-out; the problem may resolve itself by sensor read-out getting fast enough.

    Having the sensor active contributes to heating and has been known to affect static images. I do track birds and insects enough that I'd be cross if they got stretched out across a 1/9s exposure, not that a 1/250s mechanical shutter is perfect either. Sadly, for now, phase detect AF is my main motivation with the D850 - although the lighting conditions I shoot in might not play all that well with a Z7, especially absent cross-type AF points. People have complained about the shutter noise, so I might have to go back to my D810 some of the time.

    And the D850 can do 6fps silently or 30fps in JPEG 8MP. Small sensors have advantages for speed of data transfer and heating issues.
  10. With 1/15s read time of the Z7 sensor, the movement would not have to be very fast at all to see with distorted geometry in the recorded image.
    Andrew Garrard likes this.
  11. It is listed by Nikon as a limitation of EFCS. The mechanical shutter curtain is in front of the sensor and the electronic curtain is within the sensor plane, so there is a certain asymmetry to how oblique rays are rendered around the two curtains. The 1/2000s shutter speed limit of EFCS is likely because the asymmetry would be too great to render a visually consistent image.

    I don't know. After they made the stacked 24MP sensor for the A9, they subsequently made the A7 III which also has a 24MP sensor but with slower read time and better low ISO dynamic range. I don't know if it is possible to go around this or if fast read sensors will always trail behind the slow ones in this respect.
  12. I was playing around with my friend's Z7 in my apartment and the viewfinder didn't show any of the noisy pixelation that I've seen with Sony and other cameras' electronic viewfinders in live view, when panning around in indoor artificial light, there was also no flickering that I could see, in fact I had to look hard to see any sign of the electronic nature of the view. There is a slight delay when panning but that's not my primary concern about EVFs; I look at people's faces and I want to see their expressions and emotions evolve in time, which I use to determine when the shot should be taken, and the artifacts in previous viewfinders really prevented me from being able to work in this way. If the viewfinder flickers, there is a band that rolls from top to bottom slowly (due to some interference between the update and the flickering of lights), and there is obvious pixelation and jaggies, I can't work with that. The Nikon viewfinder seemed completely clean in this respect, so it is quite possible that I would be able to (and willing to) work with it. However, I understand that people who photograph fast action are interested in the refresh time and how much lag there is, which is a separate consideration than mine (of course I too want a fast refresh, and don't want to look at something that happened in the past). Anyway, from my point of view the Z7 EVF is the first EVF which doesn't completely turn me off the prospect of using the camera.
  13. Thanks, Ilkka - I wondered whether the asymmetry was the reason.

    I've heard good things about the live view. I don't know whether there are any dynamic range concerns (I've yet to see a Z body), which has been my biggest worry - I gather it's a lot less bad than some old screens. Other than the option of some additional information on the finder, I don't desperately feel the need for an EVF, especially with live view on the rear screen or HDMI readout as an option, and I like the low-power nature of a mirror, but I don't find the idea toxic. I'm glad technology is improving.
  14. I still prefer the optical viewfinder but for some applications there are benefits from the EVF. I have no plans on buying a Z camera now, but may get one later once the native telephoto lenses are available (mainly 85/1.8 which I would pair with the currently available 35/1.8) mainly for the quieter sound of the camera relative to DSLR, for concert applications and such things where quietness is a priority. Nonetheless the F mount system with its DSLRs are likely to be my main system in the foreseeable future even if I get a Z camera for special needs.
  15. So, err, how do you have a shutter speed of say, 1/16000th second (my lovely J5 again) and a 'read time' of 1/15?

    Where does that put subject movement?

    1/16000 is fast enough to freeze movement with a flash, why not a shutter?
  16. Same way you can have shutter speeds faster than the 1/250s flash sync on a dSLR, kind of, or why there's rolling shutter on video. You reset the lines of the sensor independently, and read the results of some of them out while resetting others - 1/1000 of the sensor is still a few scan lines. I assume the resetting is faster than the read-out, which is why the EFCS can clear a line as fast as the mechanical shutter can move down the sensor (it can't be "all at once" or you'd have different exposures across the frame).

    Still moving as the different lines are read out. :) (Mechanical shutters have the same issue, just less badly because 1/250s is quite quick.)

    Because the flash illuminates the whole frame at once. It's not that you'll get blur, it's that different scan lines are seeing the frame at different time offsets, so if something is moving it'll likely get stretched or squashed.
  17. So it's not really a shutterspeed of 1/16000ths then? In realtime?

    It's a 1/15th exposure made of 1100 x 1/16000th second strips.

    So there's no movement within a strip, but there is between them?

    So, if I fire a low powered flash (say 1/20000 th duration) in the middle of a 1/2 second exposure in the dark, i'll get the electronic shutter equivalent of shutter-blade-shade?

    ie most certainly NOT like film!
  18. Andrew,
    Shun already has the Z6 why don't you have the Z7 yet?
  19. I doubt the electronic shutter exposes a whole strip at a time, just as the mechanical shutter doesn't judder. The line is reset (in the same way the whole sensor is prior to any exposure), then read back however much later is needed for the nominal exposure duration. Without a true global shutter, you can't do this for the whole frame at once (you might be able to clear it, but the read-out time is finite), but you can ensure that you only start exposing a line 1/16000th of a second before you'd be able to read it. If you're taking 1/15th of a second to pull the data off the sensor, each line would get reset 1/16000th of a second before it was going to be read, effectively one line at a time. The reset and read follow each other across the sensor like the first and second curtains of the shutter.

    At least, I assume. I've never been anywhere near the implementation of one of these.

    If it's a 1/2 second exposure, the whole sensor should be exposed concurrently, like a normal mechanical exposure longer than the flash sync speed. (This may not be true of some compacts or smartphones that compose longer exposures out of multiple shorter ones to manage motion blur, but that's not the issue here.)

    You'd get a partial exposure if you fired a fast flash part way through an electronic exposure shorter than the sensor read-out time (which we've been claiming is 1/15s-ish); even with a 1/15s exposure one part of the sensor would be just starting its exposure and the other would be just finishing, giving a variable blur from ambient light part way between first- and second-curtain flash depending on where you are in the frame. I believe Nikon disallow flash with the electronic shutter because they know the results are going to seem weird at common shutter speeds.

    It'd be what you got from film if you had a mechanical shutter speed with a 1/15s flash sync speed. I've never met one, but 1/50-1/60th isn't that rare (from Leica and the original F). You get the same thing from faster shutters too, it's just that the subject has to be moving faster for it to be relevant.

    I'm now mildly curious whether the EFCS could be mildly beneficial to shutter lag...

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  20. FWIW, the D1 series is often claimed to be able to sync at any speed. I've personally used one to test the flash duration on my Norman strobes, and know that depending on the power setting used on the pack I really shouldn't exceed 1/500(honestly, under my typical conditions any reasonable shutter speed isn't an issue because I'm often at f/22 or smaller and ISO 100 with the only other significant ambient light being 250W tungsten-halogen modeling lights that meter at several seconds long at the aperture I'm using). I think the maximum shutter speed is 1/16,000, and it's possible to sync at that speed, although you're going to see significant light loss from most any strobe.

    In any case, I THINK the key difference there is in the use of CCDs rather than CMOS sensors. I've been under the impression that CCDs can be "pulsed" and actually acquire the image in a way that a CMOS can't. I don't fully understand the quantum mechanics of it, but I recall talking about using CCDs in one of my graduate school instrumental analysis courses as a substitute for PMTs in some applications. Of course, that's a very, very specialized thing(and it's not uncommon for them to be liquid nitrogen cooled to increase the sensitivity...and even when that's done they still can't approach that of a PMT) but the response time is definitely good enough for certain applications. I don't THINK CMOS shares that characteristic...and of course often times in instrumental applications we're talking about CCDs with a few hundred pixels at most(perhaps larger versions of autofocus sensors) and not millions of pixels.
    Andrew Garrard likes this.

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