You Might Be Surprised by the Dynamic Range of the New $550 Sony A5100
Earlier in the week, we were introduced to a brand new bite-sized camera from Sony, the A5100. We already knew that Sony's new camera, which comes in at $550 for the body, would have the ability to output uncompressed 8 bit 4:2:2 via the mini HDMI port and be able to record to the XAVC-S codec, both firsts for a camera of this size and price. However, we had no idea what kind of performance (in terms of dynamic range, rolling shutter, and overall image quality) would be possible with the camera's CMOS sensor. Luckily, just like they did with the A7s, the folks at Cinema5D put the A5100 to the test, and their results are fairly exciting.
[UPDATE: We just got word from Cinema5D that the test results for dynamic range performance were skewed because of a software bug. Here's their official statement:
The software manufacturer informed us that their software had a bug that misinterpreted the Sony A5100's blacklevels (that seem to inherit green noise) and strongly affected the results for the Sony A5100 dynamic range test. We apologise for any inconvenience this might have caused. At cinema5D we will no longer rely on software results should they ever again differ from subjective evaluation. The software we use has been updated and the bug has been resolved.
Below is the chart with the updated dynamic range results. Sadly, the A5100 doesn't fare nearly as well this time around.]
First up is dynamic range. Just like in their previous tests with the A7s, they used a DSC Labs Xyla 21 dynamic range chart. Here's how they tested the A5100, which doesn't have a specific native ISO (or at least it's not clear what that ISO is):
Testing the dynamic range on this camera wasn’t easy. We didn’t have an official native ISO and looked at all ISO combinations ranging from ISO100 up to ISO1600 and measured each with different “Creative Styles” that would provide the best rendering. Clearly the strongest ISO values are ISO200 and ISO800, while ISO800 provides slightly more dynamic range reaching 13 measured stops with Creative style “Portrait (-3, 0, -3)” and 12 with Creative Style “Standard (-3, 0, -3)”.
Here are the dynamic range results that Cinema5D labs came up with:
Cinema5D later updated their post with the following clarification about their results:
These test results are the exact numbers the software IMATEST provided in our test at a signal to noise ratio of 1/0.5 in the camera’s respective resolution and compression. Many factors influence these numbers and each sensor has its own characteristics. At this point we want to emphasise that these numbers differ from the subjective opinion we have about the cameras, which for us at cinema5D is a very big point as we want to give you an ideal understanding of what the cameras can actually do for you. So we decided to mention it here. Subjectively, in comparison to the other cameras the maximum rating we would give to the Sony A5100 is 12 stops.
Even considering that Cinema5D doesn't think that the A5100 really has 13 full stops of dynamic range, this is nevertheless an incredibly impressive result considering both the price and size of the camera. What's even more impressive is that even though the A5100 doesn't have any significant control over gamma interpretation (i.e. advanced picture and log profiles), it's still able to pull at least 12 stops of dynamic range. It's fun to think of what kinds of results this test would have yielded if a logarithmic curve, maybe even S-log, could be applied to the footage in camera.
At this point, there's not much reason to think that Sony would spend the money to incorporate advanced gamma profile control into the A5100, especially considering that this is a basically a lower-end prosumer camera. For that reason, it seems even less likely that an S-log update might happen in the future. With that said, at the $550 price point, the A5100 has the potential to be a really killer B-cam, C-cam, or crash cam.
The folks at Cinema5D Labs also tested the rolling shutter of the A5100 (where it performed relatively well), and they tested the overall image quality and sharpness of the A5100 against the A7s. To see those tests and get the full rundown on the results, head on over to Cinema 5D.