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 p.111 #15 · Official: Sony A7 and A7R Fullframe Mirrorless | |
Samuli Vahonen wrote:
180mm Leica will do.
From 0.3s to ~"half of the sync speed" (over sync speed there is only horizontal band of sensor exposed to light).
Large tripod (Gitzo 3 series ok).
2s or remote should do fine.
...but you don't have A7r, I doubt it's issue with A7 since it has electronic first curtain.
With 5DmkII I can cause systematically smaller RAW file (=less detail due to vibration) with Leica APO 180mm by using mirror lockup vs. using live view electronic first curtain. I can do this with 180mm Leica if I attach camera's L-bracket to tripod head, instead of using lens collar OR by using flimsy plastic tripod collar (the Leica one). As far as I have understood Canon's mechnical first curtain is smoother than A7r - so I could imagine that A7r can have issue regarding this.
Samuli...Show more →
I couldn't find the mirror lockup on the A7, but I did a preliminary test to take a quick, early look if there is something which needs to be looked at closer here.
Setup:
Leica 180/2 at f/4 on Gitzo GT3541XLS tripod, only the thickest leg out, Burzynski Ball Head II (very, very strong, can carry 65kg, or more), RRS lens plate and clamp. Wooden floor (sorry, too cold on the concrete balcony for tests right now), so some vibration is possible (it is late, unlikely anyone is moving, and I was standing still, no cars driving by, no obvious earthquakes, but who knows). Of the crucial shot, I made three of each and looked at the sharpest.
I have not much light here, so I used ISO to vary shutter speed. I went from 2s to 1/125s, no movement anywhere, both with and without electronic first curtain. I am fairly confident, but will repeat with good light. All shots were as sharp as can be expected at the respective ISOs (from 100 to 25600).
Then I repeated everything with Nikkor 300/4 + 1.4TC, set to f/8, only ISO 25600 and 1/15s (often a problematic speed in my experience), and this time, there was a clear difference between the two setups. The shot with electronic first curtain was consistently sharper, not much, but clearly sharper. I think it would probably be possible to see it in 100% view, 50% and 25 %. After that probably not.
This is the A7, so 24MP.
I will repeat another time with more light, but clearly, there is potentially a problem here. 36MP is more sensitive, so with no electronic first curtain, there will be a limit to which shutter speeds and which focal lengths you can reasonable keep sharp.
Edited on Dec 01, 2013 at 06:50 PM · View previous versions
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