What is my histogram supposed to look like when entire light table is clipped to pure white?


I’ve been using a Negative Supply/Negative Lab Pro setup for a while and love it. What I don’t love is having to manually convert frame by frame which ends up taking hours.

This roll analysis feature looks like a godsend but I’m not sure how the original histogram should look before adding film.

Before, I’d just make sure the first frame was in focus, and then adjust the shutter until the negative looked the way I thought it should and keep those settings for the entire roll.

But the recent instructions I read on the v3 announcement page say that I should be “adjusting the shutter speed until the entire light table is clipped to pure white” before getting started.

Maybe I’m dumb but I don’t know what that histogram should look like?? Hoping if I get it right I’ll finally be able to invert an entire roll at once.

FYI I keep my ISO at 160 at f8. I’m using a Fuji X-T3 with a Fujinon Macro lens.

If anyone can please send me a screenshot of what my histogram should look like before scanning, I’d really appreciate it.


Also, for the record, I recently scanned the same negative twice, each time at different shutter speeds, and after adjusting the white balance on each one separately, the results were exactly the same after inverting. So maybe it doesn’t even matter?

Even before V3, you could convert an entire roll at once (with per-image analysis) by selecting multiple negatives in LR, using the command shortcut (ctrl + alt + N on Windows), and clicking “convert”. Then you’d still have to go photo by photo to tweak the result to your liking, but you didn’t have to run “convert” one by one at least.

With V3, roll analysis means that you can get possibly-better results for each photo due to the analysis engine taking into account the colors seen across different photo frames, but the process will only be faster if you are happy with the colors it chooses. In my own experience, I still need to tweak a lot of frames individually. Roll analysis does not make conversion faster; just saves me some editing time, sometimes.

Cameras that show a histogram do so from either the JPG taken, or an internal JPG converted from the RAW image if that’s what you take. Either way, the histogram is not a perfect indication of clipping, but it’s good enough for our purposes. In general, a photography histogram shows the distribution of values either in the luminance channel or for separate R, G, and B channels. Either way, spikes near the right hand side of the histogram conventionally mean a lot of values are on the bright end of the spectrum. For clipping to pure white, you’d expect to see values bunched up all the way on the right.

In practice for NLP I don’t worry about trying to get the white to clip hard, just so long as it’s close to the right.

In theory, it should make very little difference. A longer shutter speed at the same ISO and aperture should result in more signal vs. the inherent sensor noise, so you get a cleaner image - so long as you don’t clip the values in the negative (which you won’t, if you adjust to only just clip the light source under the negative). That in turn will mean less digital noise in the dark parts of the negative, which corresponds to less noise in the highlights of the converted photo. So if you want to assess if shutter speed makes a difference, try comparing the highlight regions to see if there is any difference in noise.

But more importantly, using a fixed shutter speed which is based on just barely clipping the light source will mean that (A) every single negative scan after that will have values which DON’T clip, i.e. are captured and not lost; (B) that none of the negative scans will be too dark / noisy (since we are capturing as much signal as possible; and (C) that the roll scan will be consistent, which is important for roll analysis to work well.

If you’re not doing roll analysis (V3) or batch conversion (V2 and V3), a consistent shutter speed doesn’t matter as much.


I wonder if your camera has a highliight clipping warning that you can switch on. Although that also works off the jpeg it’s a good visual indication that you are at least close to clipping the highlights. It can also help to identify any vignetting that might be present.

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