11 Jul 2015
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*** UPDATED : jump at the end of the post
It's time for a little test! The Sony a7s is extremely popular these days for it's ability at managing low noise, thanks to it's huge sensor and low megapixel count. But How will it perform for the kind of light-painting work I'm doing? I put a Canon 6d and a Sony a7s side by side with similar high quality lenses. My first assumption was that the Sony would give me a much better quality picture as I have been fighting with noise for so long. But my real question was about the shutter reliability. I need extremely high precision for the shutter. As you might know, my exposure time is nearly always one second. But I need to be able to control that duration using a remote. I ditched my first generation Yongnuo triggers a while ago because they had a 1/10 second delay which was giving me a headache. My doubts were more pointed at the general mirrorless cameras than specifically the a7s. But it's the first time I have one of those units in my hands, so I'll go with that.
Shooting went flawlessly, both cameras were very responsive, giving me similar results on the preview monitor. But I could hear by the sound of the triggers that the Sony was slower, and that I was missing about a thirds of the shots (yes, that's a lot!). I had a 100% success rate with the Canon.
On a side note, if you recently have assisted one of my workshops, you know that I get sometimes random problems with my triggers due to a release cable glitch. This has been fixed.
A few hours later, I downloaded the images on the computer and things got very clear. None of the pictures from the Sony contained my complete shape of light. So there was a delay ranging from 1/20 to 1" on each picture. Yes I really said one second! Some pictures were just totally blank, and the exif showed a 1/200 exposure while I really did was a 1 second exposure. (confirmed by looking at the exifs side by side).
But is it caused by the remote control? Nope. I ran a couple of quick tests by writing letters with a flashlight and using the shutter button on the camera. All of the letters were incomplete. Then I did the same tests on the 6d and had 100% success rate.
But is there a way to make the Sony a7s shutter more responsive? I'm not familiar with this camera yet, so please tell me if you have any tips. I googled and found a couple of possible workaround: The electronic front shutter setting, the silent shutter one... and no, nothing helped.
So for the moment, the a7s is really not an option for me for this kind of work. My test was about light-painting, but I was also currious to see if I would eventually be able to use those cameras in a 360 degree bullet time setup. So I guess the answer is no. I need a 1/400 precision on that kind of work. I would really like to test with other mirrorless cameras though.
How about the noise?
Well, as most of the images from the a7s are darker thant the ones from the 6d, I had to boost them a little bit to be able to compare, and that brings more noise, so it's not really a good test. And the difference is not that much. My tests are not scientific at all, and I'm not a pixel peeper. But what I can definetly say is that there is absolutely no wow factor involved here. I'll be happy to stick with my current equipement (not that I had any intention to change, mirrorless is not for me for the moment).
Additionnal details / observations:
Model / dancer: Kim Henry
Have any of you experimented with the a7s? How do you like it?
If you have any idea about how to solve the shutter precision problem, please let me know.
*** UPDATE. So I got some help from a very precious friend. Udi Tirosh from DIY Photography pointed to me that link of a review of the a7s (thanks Imaging Ressource) which indicate the delays I was experimenting : (0.129 second). But there is a also a mention about a prefocused shutter response of 0.024 second. This is the kind of performance I'm looking for. Please don't hit me, but I had to google what "prefocus" means. I'm working with manual lenses, and mostly with light painting, so I'm not used to half-pressing anything. So I went back in the dark room, and used my Yongnuo triggers (the POCKETWIZARD PLUS II doesn't have the half-press option). Then I got a 100% success rate! YES! So does that mean that I want to use the a7s? No! There is no way my brain can be trained to half press the button for every shot, especially when doing stop motion (that is one picture of a 1 second duration every 2 seconds). But there should be a workaround to hack the trigger so it keeps the prefocus mode (half press). There is obviously nothing about the focus here, but it's probably a way to keep the cameras ready to shoot. Please note that during my tests, I was shooting one picture every 3 seconds, so there is nothing about "sleep" or "power saving" issues here.
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