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 p.2 #11 · Sony A6700 vs newest A7C II. How do they compare | |
GHarris wrote:
No, that's not it. I will try to explain my flawed understanding of it, which also needs correction and improvement, but will nevertheless get you closer to the truth. (I hope someone will correct my own mistakes).
There are three things:
1) Electronic shutter
2) Electronic Front-Curtain Shutter (with a mechanical rear-curtain shutter), aka "EFCS". Call it "half mechanical", if you like.
3) Mechanical front- and rear-curtain shutter. Call it "full mechanical", if you like.
The a6700 has 1, 2 and 3.
The a7C has only 1 and 2.
The potential problem with 1) is that, if you are shooting rapid movement, there will be some kind of distortion, because the camera cannot read out the whole picture all at once, and you have no physical shutter ending the exposure, so one part of the sensor records its image later than the other part. A golf club in full swing will appear bent rather than straight, for example. Flickering lights may also bring up issues with banding across the image for similar reasons - some parts of the sensor capture the image during the bright part of the flicker, and others capture it during the dark part of the flicker.
This issue does not crop up with 2) and 3) because, with either, a physical shutter cuts off the light at the same moment for the whole frame - no more data being gathered, regardless of what's going on in front of the camera - and then the camera can get around to reading its sensor's captured data in its own good time without problems.
And the problem with electronic shutter doesn't (to a fair approximation) happen with cameras with stacked sensors like the a9, a1 and Z9. For them, electronic shutter is an almost disadvantage-free mode, and you might as well use it for almost everything (except maybe studio strobe shooting). But for all other cameras, it is imperfect and its drawbacks must be kept in mind, and it isn't appropriate for every kind of photography.
A camera can, of course, say to all pixels, all at once: "start the shot". There's no delay on that, it can send that command to every part of the sensor simultaneously.. It's much easier to do than to say to each pixel on the sensor, all at once, "send me the data you have captured" at the end of the exposure, and to get that data transferred, from all over the sensor, before the picture changes with time.
That's why 2), EFCS, doesn't create motion distortion problems.
But 2) does create bokeh oddities and strange non-uniform vignetting at extremely high shutter speeds. I only understand poorly why this is the case but I think it's to do with the physical shutter not being in quite the same place as the sensor. And you start with the "electronic" shutter, in one location (the sensor), for your exposure, and then you go to the physical shutter, which is positioned in front of the sensor, for the end of your exposure. This different location for the two 'shutters' is somehow, in a way beyond my understanding. the source of the teardrop-shaped bokeh balls and the vignetting at one side of the frame.
3) Doesn't have either of these issues. A physical shutter starts the exposure, and ends the exposure. The shutter is located in the same place all the time, and produces a hard physical cutoff to the light, both at the beginning and end of the exposure.
You have two shutter movements, of course, when shooting in full mechanical. So the shutter may age faster. The shutter gets louder than it would be, all else being equal, with just a one-movement rear-curtain (EFCS) shutter in use. And there's another potential issue: shutter shock. The movement of that front-curtain shutter, at the beginning of the exposure, can create vibrations that cause motion blur/shake across the picture. This was an issue with the first-generation A7 and A7R cameras, for example, because they didn't have an EFCS or electronic shutter option - you had to always use the full mechanical shutter. This "shutter shock" issue only occurs at specific shutter speeds - lower shutter speeds, comparable to the focal length of your lens. You can't fix it by putting the camera on a tripod, or whatever, because the shake is happening during the exposure - only by choosing a much faster shutter speed that outpaces the vibration.
Shutter shock basically stopped being an issue with the generation 2 of the A7 cameras, which began to introduce EFCS and (in some models, and all gen-3 and later models) the electronic shutter. Most people, most of the time, began using EFCS by default without thinking about it or noticing they were doing so. After a time, some noticed the bokeh and vignetting effects caused by EFCS - and when they did so, they had the option to get around them by switching to electronic shutter, with its tradeoffs and flaws, or full-mechanical shutter, with its tradeoffs and flaws.
I'm not sure whether, in addition to the lack of option to turn it off, the full-mechanical shutter in the first-generation a7 cameras was a particularly "shaky" one. Or whether the later shutters in gen 2, 3 etc are just as shaky, but we don't notice because we don't shoot in full-mechanical as often as we used to. Shutter shock with full-mechanical shutter is, however, fundamentally something that can happen on any camera with a front and rear curtain shutter in use.
EFCS can make the camera shake too, of course, but it matters less, because the vibration produced by the movement of that physical shutter is only propagating after the photo has ended. Whereas with a full-mechanical, physical front-curtain shutter, the shake begins during the taking of the picture. So EFCS shutters only produce shake, or blurry images on (for example) flimsy tripods when you're taking shot after shot after shot in quick succession without the camera/tripod having time to stop shaking from its last picture, before the next photo begins.
All that said... to get to your specific misunderstanding...
if you shoot in "1)", Electronic Shutter mode, with any camera, you won't get screwed-up, misshaped bokeh or non-uniform vignetting.
You might get motion distortion (bent limbs, bent golf clubs, bent drumsticks, oval soccer-balls, etc), if your subject is moving fast. Or flicker-issues under specific kinds of artificial lighting. But not the bokeh/vignetting issues. This is the case with both the a7c and the a6700 (though the a6700's issue may be less severe because of the better readout speed).
If you shoot in "2)", EFCS mode, you will get those bokeh and vignette issues sometimes at shutter speeds faster than 1/1000th, whether you're using the a6700 or the a7c.
If you shoot in 3), full mechanical, if your camera can even do it (the a7c can't)... you won't have the above issues but then you might get shutter-shock at specific, slow or middling, shutter speeds.
It would be good to have the option to choose from all three when it suits us, of course. Perhaps one day, the increasing speed of electronic shutter readout will make solution 1) the go-to option. For both the a6700 and a7c, electronic shutter is imperfect.
But if you had an a6700, and you set it to shoot in EFCS mode, it would produce the same bokeh and vignette issues that an a7c can. The readout speed is not an issue, when you have a physical shutter ending the exposure: the camera can take its sweet time once a physical shutter has cut the light. The readout speed is only an issue for fully electronic shutter mode, affecting the susceptibility to motion-distortion or flicker-banding in that mode....Show more →
Excellent description of the various shutter modes! Thank you!
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I was reading the IBIS footnote differently than you. The footnote does not say "only" for the 50 f1.2 GM, nor does it use a comma to indicate the 3 axis is for that lens only, the 2 sentences are separated by a period. Maybe a case of poor Japanese to English translation, but after digging into it, yes I agree it is the same 5 axis IBIS on the A6700 that is on the A6600, but now with added active stabilization for movies. And in the case of the new A7C's it has increased to 7 stops from 5.