I'm working on an application that uses the iPhone camera for scientific purposes - and, as a result would like to receive video in as unprocessed format as possible.
In particular, I'm interested in getting pixel buffers that contain pretty much the bayer data as the sensor sees it - with the minimum processing of color possible.
Currently we configure the AVCaptureDevice to fix the focus and exposure, use a low ISO with no gain and set the white balance gains to 1. AVCaptureVideoDataOutput is using 32BGRA.
What I'd like to do is remove any additional color and brightness processing such that the data is effectively processed with a linear transfer function (i.e. gamma function is 1).
I thought that this might be down to using the AVCaptureDevice activeColorSpace - we currently use P3_D65 for this. But there only seems to be a few choices (e.g. sRGB, HLG_BT2020) all of which I think affect the gamma.
So:
- is it possible to control or specify the gamma / transfer function when using CaptureVideoDelegate?
- if not, does one of the color space settings have a defined gamma function that I can effectively reverse it from the pixel data without losing too much information?
- or is there a better way to capture video-ish speed images (15-30fps) from the camera sensor that skips processing like this?
Many thanks for any suggestions.
