Forgotten in its old age

by Aditya

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While searching for info about Sony SLT-A37 shutter lag (good results btw), I also read this question: Disadvantages of electronic viewfinders. There Itai said in a comment about the lag between action in front of camera and seeing it in EVF:

As stated, the lag is only a concern for action photography. Some are better than others. (...) Again, we are talking in the 10ths of a second, so not problematic for mostly still subjects.

So, my question is about this Viewfinder / Live View lag. Is there an internet site that has tested this lag? A search found the shutter lag test results easily enough, but no luck with this other kind of lag.

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If a site were to capture that data, it probably would be @itai's site www.neocamera.com but I don't see it anywhere. –  dpollitt Mar 11 '13 at 23:35
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Unfortunately, I do not have this data. It is something noticeable but I do not have the technology to measure it. If one camera would have a faster EVF refresh rate it would most likely by the Olympus OM-D E-M5 because the sensor is read at 240Hz and the read-out speed puts a cap on lag. –  Itai Mar 12 '13 at 2:44
    
Perhaps rear lcd lag could be captured with a high framerate videocamera pointed at a setup that includes a moving object, the camera to be tested with its display panel visible and a gate thru which the object will pass. Measuring the time that it takes for the object passing the gate show up on the camera display after the object did pass thru the gate in real. Now, one second split into 30 frames is 0,033 sec per frame, it seems the videocamera won't need to be such a high framerate device, any videocam should do the job. –  Esa Paulasto Mar 12 '13 at 10:29

2 Answers 2

I made a quick-n-dirty test of rear LCD display lag myself. My friend came over with his Casio EX-F1 compact camera, which can record a video at 1200 fps. We shot a video of the Olympus SP-550 rear lcd panel at 300 fps and then slowed the result down to 1 fps. On the slowed video a one second represents 0,00333 second in real life. I had a Metz flash illuminate a piece of white paper from behind and both the Casio and Olympus pointed at the paper.

The flash goes off and 13 frames later it starts showing on Olympus rear display, taking 3 more frames to come to noticeable brightness. So, 16 frames x 0,00333 second is 0,053 second lag on the rear display of this old compact camera. (Repeated the test four times, variations noticed within +/- 1 frame)

Test video in YouTube

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Good try. You also should know that the lag is variable. In low light cameras have to boost the gain which case the EVF/LCD image to be grainy but to avoiding too much grain they also often slow down the refresh rate which causes a longer lag. You also have to repeat any test a number of times (9 seems good and is what I normally use) to avoid variations depending on how movement coincides with a read-out cycle. –  Itai Mar 12 '13 at 16:38
    
Thanks @Itai. Good to know about the low-light scene affecting lag. I don't think i'll repeat this test soon, but if i get my hands on a high-framerate videocam, a new test might be on the to-do list (having another camera to test by then). –  Esa Paulasto Mar 12 '13 at 17:32
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Low light does affect the viewfinder view indeed. With my old point 'n shoot I encountered fps drops (of the viewfinder/screen). Camera's with live view as primary viewing mode usually do not lag a lot. Live view on normal dslr cameras is a bit more laggy in my opinion. –  FW. Apr 2 '13 at 21:26

I found something about Sony SLT A77's viewfinder. It still repeats what @Itai said about varying refresh rates in different lightning conditions, but what I found interesting was what they said about lag in good light. It is hardly noticeable. A quote below (bolding done by me):

When not in continuous shooting mode, viewfinder responsiveness is a function of refresh rate; essentially the frame rate of the "live movie" that constitutes the viewfinder image. Specs for this are almost never published, in part because the refresh rate is usually a strong function of the amount of light falling on the camera's sensor. In dim lighting, the camera needs longer exposure times for each frame of the movie it's capturing and playing into the viewfinder display, setting an upper limit on the viewfinder's refresh rate. Indeed, as noted above, the Sony A77's refresh rate drops pretty dramatically when faced with very dim shooting conditions. (A trade off we're happy to accept, given that the resulting viewfinder image is much more visible than that from an optical viewfinder under similar circumstances.)

We don't have any way to measure the Sony A77's viewfinder refresh rate under bright lighting conditions, but our sense is that it's quite high: Motion was very smooth and fluid, and we had no sense of a delay or lag between the subject's motion and what we were seeing in the viewfinder. - source: Imaging Resource

Now, as there is no, and perhaps never will be, a reliable way to test electronic viewfinder display lag in varying conditions, I think this question is ready to be closed.

It is hard to say more than that there is some lag in dim light, and practically no lag with the best e-viewfinders in best conditions. Catching a moment that you have been waiting to photograph, your own human reaction time is the biggest lag there is.

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