Rolling Shutter: Sony A7s Compare to Other Major Players; Meh…

One of the things that cinematographers care about when selecting a camera for shooting is how significant is the rolling shutter effect.

as7-rolling-sutter-03

Rolling Shutter is a ‘side effect where vertical lines in the real universe appear as diagonal lines ‘on film’. For example it smears buildings when shot out of a moving car or create  a jello effect when the shooting camera is unstable, we explained this in length in this post.

The good guys at Cinema5D took the crown challenger – Sony A7S with its remarkable low light performance and put it to the test against some of the other leading video cameras in the market: Arri Amira, Panasonic GH4, (Canon C300), Canon 5D mark III and Canon 1D C. Sadly it did not do all that well.

First here is a simple visual explanation of the effect caused by rolling shutter:

This is how a rolling shutter ‘scans’ an image

What Is Rolling Shutter And Why It Is Cool

Resulting in smeared diagonal lines:

What Is Rolling Shutter And Why It Is Cool

How the test was done?

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Cimena5D explains the test procedure:

Above you can see a framegrab from the A7S video file used to determine its rolling shutter. We used a rotating test chart framed identically with all cameras. The amount of horizontal offset between the first and last line of pixels determines the severity of rolling shutter which we measured in milliseconds. These are approximate values (Precision is limited by our method of testing as it involves a slight amount of motion blur).

Results

I would have loved it if the A7S came in high, sadly it did not, I am not surprised it came in after the Amira, but it also came in after the 5D mkIII, if you plan on using the camera for shooting action or use it on a moving rig, this is something to consider.

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Our test results show that the A7S’ rolling shutter in full frame HD mode is severe, but we also found that the Canon 1D C performs similarly in 4K mode. Among DSLR style cameras in our test the GH4 in 4K mode performed best and is more or less on par with the A7S’ crop mode, and the 5D mark III coming in right behind that

With the megapixel war coming to an end, low light/ high ISO conquered and 4K practically becoming a necessary, I wonder if rolling shutter is going to become the new battlefield for new video cameras.

[Rolling Shutter – Sony A7S vs. the others | Cinema5D via nofilmschool]

 

  • http://www.gecofilms.cl Gerardo Campos

    did you try the A7s in 120fps mode???

  • http://twitter.com/jasondhsd Jason D

    @vincentlaforet Cmon $40k Amira vs $2k A7S, less RS then 1DC that costs $10k. Crop hd with speedbooster a7s holds its own

    • http://2epicbits.com/ theSUBVERSIVE

      Well, the Black Magic Production Camera is not that much more expensive and has no rolling shutter. It’s a matter of having global shutter or not, not so much as not being fair because of the price tag.

      • Ufupuw

        BM camera has crappy low light though. Global shutter reduces the sensitivity by close to one stop

        • http://2epicbits.com/ theSUBVERSIVE

          Not just that, it loses DR as well, global shutter in a CMOS sensor has its cons but again, the test is about a rolling shutter not prices or low light performance. They set parameters for the test so people can understand the differences, counter argumenting a rolling shutter test with anything else starts to sound like a unnecessary lame excuse. It’s like going to a singing competition and saying that you may not be able to sing well but you can really dance, what’s the point of that? A test is just a test, they are just showing how they did and the results, just that. If you are ok with the downside of the A7s by its upside, there is no problem with that at all, but I was just saying that we should stick to the matter when using arguments about the test.

          • joe_average

            “global shutter reduces sensitivity”… “loses dynamic range.” how so? it is a function of the read-out integrated circuits (ROIC) programming/capability. dynamic range and sensitivity are only a function of the materials involved in the photon-to-electron physics (e.g., CCD vs. CMOS vs. InGaAs vs. InSb, etc.) and color filters (bayer), and not how/when each pixel value is digitized in the analog to digital converter (ADC). global shutter systems have ‘very fast’ read-outs and digitizer(s) or some way to buffer the analog pixel values. rolling shutters are simply not as fast (i.e. cheaper ROIC).

          • http://2epicbits.com/ theSUBVERSIVE

            It’s not the global shutter itself, but global shutter circuits occupy a much bigger area of the sensor than rolling shutter ones, so by losing sensor area, you lose sensibility, DR, etc. if it was so easy as just materials itself and nothing else, you would had solved an industry’s problem but it’s like comparing different sizes of sensor, more area, bigger pixels, more DR, sensitivity, etc.

          • joe_average

            ah, the real-estate problem. thanks for clarifying.

  • http://2epicbits.com/ theSUBVERSIVE

    How is the rolling shutter of the GH4 in 1080p? All I know is that it’s better than in 4K, so I wonder how much better.

  • ext237

    Wow, great explanation of rolling shutter! When people complain to me about plane rotors looking funny in their pictures, I’m going to point them to this article, thanks!!

    • joe_average

      aliasing. also known as the effect that makes wheels look like they’re spinning backwards.

      • 2G

        Aliasing ? No… Rolling shutter. Aliasing is when you see “stairs”

        • joe_average

          Your talking about spatial aliasing, I’m referring to temporal aliasing.

  • Thierry Dauga