11 Replies Latest reply on Sep 25, 2012 8:02 AM by spl00

    Linear RGB input/output from ACR? (a question for the ACR developers)


      I have an idea I’d like to develop using the camera RAW import, but it’s based on some assumptions about how the processing works. I find the ACR sliders (Shadows/Highlights/Exposure etc.) very useful and intuitive, and operating on the original camera RAW data obviously gives the most information from which to extract detail. I would however like to take multiple RAW files and blend them together (using some software I'm writing myself) before bringing a single merged image into ACR, in order to adjust the image as necessary.


      Clearly it would be time-consuming to reverse engineer a camera’s RAW format myself, so reading and writing RAW files directly is impractical. So, I was wondering if there’s any way I could inject RGB image data into the relevant stage in ACR?


      I’m assuming the basic overview of the processing performed by the ACR tool is something like: RAW file -> [Perform de-Bayer/de-mosaic] -> Unadjusted linear RGB data -> [Apply sliders] -> Adjusted linear RGB data -> [Apply settings from Workflow Options including color space/profile] -> RGB data in Photoshop. (If the sliders are instead performed directly on the sensor data (before the de-Bayer/de-mosaic steps) then that probably knocks my idea on its head).


      If there is however an intermediate working RGB dataset (the Unadjusted linear RGB stage above), could that be exported (so I can do it for multiple images, and blend) and then reimport that data back into ACR?


      My experiments so far were to open the RAW files (with no adjustment) into Photoshop CS6 (ProPhoto RGB, 16bit), save as TIFF, blend externally, then load the TIFF back into ACR. However, even if I load a completely unmodified TIFF back into ACR and make adjustments, I get different results than editing the original RAW file (gamma, color balance). It’s been suggested that this is because the TIFF already has a profile applied.


      Would this (the route via TIFF files) potentially be possible if I could choose a linear RGB color space in ACR's Workflow Options? I note MadManChan2000's 24-Jun-2012 post in this thread: http://forums.adobe.com/message/4514579#4514579