In preparation for the next round of camera evaluations I asked for comments and got a lot regarding the type of charts I was using.
I’ve been thinking a lot about this and I think we may have it all backwards.
Conventional rec 709 TV has a DR of at most 6 stops and if the charts are slavishly adhered to only 5 stops.
However, once the knees and hypergammas etc are taken into account we are actually working with 8 stops at least.
10 bit log-c will contain about 11.5 stops of DR and that’s more than the best available domestically HDR sets can handle.
Of course that limitation isn’t the camera, it’s the record format and that’s why I record RAW for these tests with a few odd exceptions that are forced on me like rendering 6K to 4K before recording.
So what are the tests trying to do?
I think that we, or I, have lost focus on this.
The tests are to find out what the usable DR of the cameras is.
To establish where the highlights actually begin to clip.
To see what colour distortions appear with exposure change.
To see if there are motion artifacts created by the cameras.
To check what happens to skintone with the different cameras and different lighting.
I acknowledge that I can’t check all lighting and camera combinations, although this would be a really useful experiment.
This is why I created the stress test chart, it’s not designed to show how a camera reacts to rec 709 conditions, it’s designed to see how far a camera can be pushed until it breaks.
THAT is what I’m interested in, it’s the kind of information that will affect how I shoot and what I use.
Just as ACES is designed to work regardless of output space, that can be changed later, so the CML tests will be conducted regardless of any “Standards”. We will try and establish the limitations of the cameras.
Of course some of you will only ever see those results within the limitations of a 709 or sRGB environment. They will at least show you what happens within that environment.
For those who want more I will make available both EXR’s in 16 bit ACES and, eventually, the original camera files.
I am now working out how to get the most information out of these evaluations. Part of this will be using a “standard” tungsten light source, the old fashioned kind that creates light by burning something 🙂 It will also involve charts lit at different levels within the one shot.
Which charts is another matter!
I’m leaning towards a CML stress Test and a Macbeth on either side of the frame, one side lit “normally” and one side 3 stops over. In the middle will be a Kodak grey scale plus card as this has been my reference for a very long time. A movement test will be below the Kodak chart. If I can get a small CDM chart then I will probably squeeze it in below the Kodak chart just for the traditionalists. Oh and a CamBelles chart will feature somewhere 🙂
I will also try and do some comparisons between faces lit with tungsten and LED light. This will include the DSC VFX chart.