Dynamic Range – Sony A7S vs. the others

Lab Test

by Sebastian WöberJuly 18^th, 2014

This is a dynamic range test and comparison between the Sony A7S, Arri Amira, Panasonic GH4, Canon C300, Canon 5D mark III and Canon 1D C.
The dynamic range is the range in luminance any given camera can capture. More range allows for more flexibility in post production and usually provides a more natural and hence more cinematic end result.

What is the cinema5D test lab?
cinema5D has established their own scientific testing facility to accurately measure and evaluate the performance of cameras. As a platform for reviews about cinematic cameras we strive to provide objective comparisons and share insights to help you choose the right camera for your projects.

The cinema5D test lab has been developed over the past 6 months. We are using precise imaging tools, techniques and software to evaluate each camera’s performance precisely. The following test indicates one of several attributes we test when looking at a camera sensor. Stay tuned for more.

The Sony A7S is a stunning new compact camera that currently makes a lot of headlines due to its amazing lowlight capabilities. In this regard it outperforms any other cinema camera we know and therefore offers interesting new applications.

Johnnie Behiri reviewed the A7S and found numerous points that make it a candidate to replace our all time favourite, the Canon 5D mark III (see full review here).

Some of the strengths include not only lowlight performance, but also the high resolution OLED viewfinder, a strong cinematic picture, full-frame coverage, ease of operability, 50p mode, crop-mode and more.

In this first scientific test in a series that we will publish over the next weeks, we want to take a look at the aforementioned dynamic range in comparison to several other very important cameras.

Interpretation
We tested usable dynamic range of the given cameras. With 12 stops the usable dynamic range of the A7S comes surprisingly close to the Arri Amira (13.1 stops) with its legendary Alexa sensor (see our full review here).
This is an extremely good dynamic range rating and is fascinating considering that the A7S is available at a fraction of the Amira’s price and is also in a completely different weight and size class. While the Amira will outperform the A7S in other tests, the dynamic range is a very important attribute to consider when working with a camera.

The Canon cameras come in at 10-11 stops of usable dynamic range. This is still a very strong dynamic range rating, but in comparison to the A7S the Canon’s are way behind.

The Panasonic GH4 had the worst dynamic range in our test. This is in line with the rather videoish look and contrasty colors we can subjectively observe.

Why did the C300 perform worse than the 5D mark III?
Before we go into details about how we test let me explain why the Canon 5D mark III outperformed the C300 and 1DC in our test. As mentioned before we’re measuring usable dynamic range. This means we’re observing actual dynamic range relative to the noise ratio of the signal. In other words, we only measure dynamic range where the signal still upholds a certain quality which is measured in noise.
This is where the bad resolution and codec of the 5D mark III gets a few extra points of dynamic range rating, because its softness blurs the visible and measurable noise. While this might be deemed unfair, the worse quality also gives the viewer an impression of a cleaner image in view of its actual resolution.

How did we test?
On the left you can see a framegrab from the A7S video file used to determine its dynamic range. We use the DSC labs XYLA-21, a high quality LED-backlit transmissive chart that displays 21 stops of dynamic range. Each vertical bar represents one stop of light.
The chart is filmed in a completely dark room using the same very sharp Zeiss 50mm CP2 T/2.1 makro lens with interchangeable mount adjusted for the camera bayonet.

This second picture on the left shows how the same stepchart is recorded on the Panasonic GH4. Each camera is set to its native ISO and the F-stop of the lens is adjusted accordingly.

After extracting i-frames which retain the highest image quality from the video files they are loaded into the testing software. Our software of choice is coming from IMATEST. They are among the industry leaders, provide very flexible and complete solutions as well as being very supportive and helpful in setting up testing standards and understanding the science behind it.

Please stay tuned for more tests which we will publish over the course of the next two weeks. In our upcoming tests we will compare actual resolution (sharpness), rolling shutter, lowlight performance, line skipping issues, moiré and will also give you an insight at codec performance and color reproduction. We will certainly try to include more cameras in the future.

Please share your opinion and thoughts on these test results in the comments.
Disclaimer: We’re not getting paid to do these tests. If you consider buying a camera please help us continue our efforts and investment by simply buying your gear through our links to B&H.

Note: We have at one point in 2014 updated our dynamic range evaluation scale to better represent usable dynamic range among all tested cameras. This does not affect the relation of usable dynamic range between cameras.