Test Bokeh and shutter mode

addieleman

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I read somewhere that the shutter mode makes a difference in the amount and kind of background blur, especially with fast lenses. With shutter mode I mean the use of EFCS (electronic front curtain shutter or "e-Front Curtain Shut." in the A7R2 menu) or silent shutter ("Silent Shooting" in the menu). As I use my Voigtländer FE 1.2/40mm more and more at large apertures, I decided to check if this is true or just another one of those urban legends.

Spoiler: it's true. Bokeh is noticeably different between EFCS on or off, and SS looks a lot like EFCS off. I won't use SS a lot because of the rolling shutter effect, which becomes very visible if something moving is photographed, so it comes down to choosing EFCS on or off. From what I've seen, the effect is almost negligible at 1/500 s and shows itself progressively when upping the shutter speed to 1/8000 s. I think I'll start to consider switching EFCS off when I'm at 1/1000 s or faster. A neutral density filter is a very useful addition for such a fast lens, although it's a pain to mount the filter and take it off again when the light changes.

Another remarkable effect is a change in the brightness of the raw files between the various shutter modes, amounting to 1/3 stop at most, so that's not a big deal (to me at least, I only work with raw files).

All photos made with the Sony A7R2 and Voigtländer FE 1.2/40mm at f/1.2.

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At the fastest shutter speed the effect of EFCS is readily visible: the blur pattern is more detailed in the lower picture and also the scene looks like it's shifted upwards (watch the upper border). There is some sort of vertical compression with EFCS on.

Another set at 1/8000 s:

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Also here the difference in bokeh is visible. In Lightroom I can easily toggle between the two pictures and it's immediately obvious that the object in focus stays put, whereas the out-of-focus area seems to shift upwards.

At 1/500 s the effect is very subtle and I'll consider it irrelevant.

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All test pictures can be viewed here.
 

bdbits

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Thanks, Ad. I saw a similar demo of the effect about a year ago, I think it was a Manny Oritz vlog. I found out there was actually a one-liner in the user manual to leave EFCS off at shutter speeds > 1000. But it is, as you've shown, demonstrable.

EFCS should also always be off when mounted on a tripod. I've read speculation these issues are physics, so I suspect they would occur with a lot of different bodies even from other manufacturers. Perhaps a smaller body would not be so egregious.

Really Sony ought to automatically turn it off based on the shutter speed, why they do not is a mystery to me. Annoyingly, I cannot assign this to a button/FN menu on the A7ii either. Honestly, I don't know why Sony does not allow anything that appears on a menu to be assigned. I think this ability is improved on newer bodies, but I am stuck for now.

Thanks for the informative post, a good reminder, too.
 

WoodWorks

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EFCS should also always be off when mounted on a tripod.
I've read that IBIS should be turned off when using the camera on a tripod. Which makes sense, given that it may introduce sensor shake. But what possible problem could EFCS introduce (other than at very high shutter speeds) when using the camera on a tripod?
 

bdbits

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Grrr, I meant to type IBIS, hence the "also". Sorry. I will crawl back to my dark corner in the back of the room now. :hide:
 

addieleman

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Really Sony ought to automatically turn it off based on the shutter speed, why they do not is a mystery to me. Annoyingly, I cannot assign this to a button/FN menu on the A7ii either. Honestly, I don't know why Sony does not allow anything that appears on a menu to be assigned. I think this ability is improved on newer bodies, but I am stuck for now.
Totally agree. I played with a Fuji XT-3 (I think) which offered option in the menu for automatic switching between EFCS on/off and silent shutter. Would love to have that. And it's a real annoyance to have to go into the menu to toggle EFCS. It'll be one of the things I'll check for when the A9 Mark II comes out; until then the A7R2 will have to do.
 

tino84

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Sorry, but I can’t see what you’re seeing.
It seems to me that the first two Sample have a slighty little difference exposure, instead of bokeh quantity.
To me bokeh in those shot is the same.

Maybe something went wrong during the test?
 

bdbits

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In the first two shots, look at the top center area. The first has a mild bokeh ball look. In the second, the same area looks more like a lot of partial bokeh balls. I actually thought it was easier to see in the first couple of shots than the rest.
 

tino84

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To me it’s not a Matter of bokeh, but exposition and contrast. i see the same bokeh, but in the second frame, it’s darker and with more contrast.
For me, the little difference in exposition is what Makes to think there’s something different in the two images
 

WoodWorks

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Just look at the shape of the bokeh balls in the first two shots, Tino. With EFCS off, the shapes are almost round, but with EFCS on the shapes are cut off at the bottom and much more semi-circular. It's not exposure and contrast, the out-of-focus highlights are distinctly different.
 

bdbits

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I found the Manny Ortiz video I had mentioned earlier.
Interestingly, he notes that the exposure does actually change over 1/1000 with EFCS (which is where Sony recommends you turn it off). Not sure if he was on auto or full manual settings, though.

 

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