

If you want something to convert to other than JPG or TIFF like JPEG2000 or HEIF/HEIC then you're going to have to use a non-Nikon app & sacrifice Capture's knowledge as to what the picture 'ought' to be. CaptureNX-D knows exactly what the camera was set to at the time & can reproduce it exactly - assuming your screen is correctly calibrated, otherwise all bets are off. Consider JPG to be 8-bit for practical purposes. It technically supports 12-bit but most apps don't, so that's probably out. This is very broad & ultimately you're going to have to make the call yourself… getting the best bitmap possible in order to discard the original. This question is similar, but outdated as well as a slightly different use case - uploading duplicates at non-specified quality vs.


I was thinking the best option would be to batch-convert with Capture NX-D, but it seems to mess with the colors compared to the standard NEF preview in MacOS (some problems I've noticed are less vivid colors, lost detail, lighter shadows, and temperature changes). I'd like to batch convert them to a bitmap format to save space, and I want them to look as close as possible to what the image would have looked like on my camera screen at the time (as I was probably optimizing for that). It's been 8+ years without me touching them, so I don't see a reason to assume I will ever process and edit them. I have ~9k NEF photos from a Nikon D5000 that are currently taking up ~100GB.
