4K Image Torture Test | Part 1

by | May 13, 2014 | All posts, AV Solutions, Home Theater | 0 comments

In our annual camera comparison for 2014 we wanted to see how the new mid-range 4K cameras compared to each other relative to their exposure latitude, image grain, and basic color characteristics. We created a scene which is almost impossible to capture while keeping both the shadow and highlight detail. As you can see from the image below, even a high end DSLR in still image mode could not even come close to providing shadow details in the “Canyon Image” and highlight details in the LED screen (behind the speaker) which is showing a city sunset. The cameras we compared and subjected to this “torture test” were the Sony PMW-F55, NEX-FS700, PXW-Z100, and the Canon C500, and EOS 1DC – all 4K cameras. Although the PXW-Z100 is not a “cinema large format sensor camera”, as are the others in this class, we decided to include it as it may be a worthy choice for some documentary and wildlife applications with its amazing 20X built-in power zoom lens and its internal 4:2:2 10 bit XAVC recording capability.

Basic seminar layout showing the camera room in front of participants and “canyon scene image” used for shadow detail and LED screen used for highlights.

Cameras compared included the Canon 1DC, Sony PMW-F55, Canon C500, Sony NEX-FS700R, and the Sony PXW-Z100, all 4K capable cameras.Before you view the video which we compiled from these cameras, please be aware that for this comparison we wanted to evaluate the internal recording only. External recorders, although they can record more color information and bit depth, vary greatly and are in some cases built by third party partners and range in cost from under $1,000 to well over $30K. Here is what we are actually looking at in terms of their internal codecs: Canon EOS 1DC 4:2:2 8 bit, Sony PMW-F55 XAVC 4:2:2 10 bit,Canon C500 4:2:2 8 bit, NEX-FS700R 4:2:0 8 bit, Sony PXW-Z100 4:2:2 10 bit. This is important to note as even though the codec does not affect the native latitude of the sensor it does affect the amount and level of control you have in post and in the grading process. Also note that with the exception of the NEX FS-700R all images were captured at their recommended or native ISO. The NEX-FS700 was changed by one of our participants to test the ISO of 4,000 and, unfortunately, was not returned to its native ISO before the tests. Because it does allow the use of S-Log2 we decided to leave it in even though the noise in the shadow areas does breakdown at this ISO if we push (torture) the codecs this hard.

This screen grab of a REC709 image with a log image on the far right shows the challenge.

1. If this scene were to be captured to correctly display the detail in the deep shadows of the canyon scene and to capture as much of the highlights as possible we would have have used a lower-than-standard ISO so that when shadow detail was pulled up there would be less noise in those areas. In other words, we purposely exposed the images at normal ISO and exposed skin tone at 40% in log to be able to bring up the noise floor in the canyon shadows and explore the ability to bring out detail. (It is a torture test after all and we knew these would not be “pretty pictures”).
2.Each of these cameras are capable of capturing excellent images with rich detail and color. We would always recommend that before you rent or purchase a 4K camera that you run your own tests and determine which camera is best for your project. Log does not have to be used only on RAW recordings, but it is important to understand how bit depth does affect the grading process.
3.The NEX-FS700R is included at high ISO (4,000) only to show what affect it can have on the grading process and what it looks like when the grading process exceeds the capability of the codec. We do not suggest you in any way consider this a fair test for the camera as any camera can be pushed beyond its capability. If the external RAW recorder with 16 bit depth or the internal recorder with normal ISO were used the image would be very different indeed. Since this adjustment was made without our knowledge we decided to use it to illustrate what happens when a codec breaks down in grading.
4. To see the real differences you will need to make sure you have a monitor or display that is set to see normal black levels. If you have a monitor which can see the blacker than black pluge bar and it is set properly you are all set. If not, you may need to raise your brightness up a little if you are watching this on a typical computer monitor which tends to favor contrast over accurate image reproduction.



TVS Pro is a sales and install organization specializing in providing best value professional audio and video products and solutions.


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