Curves

[varmsaus]

A curves edit window like in photoshop? Sorry for getting this from ai, but it's been a while since I used photoshop. I got excited when I found negpy, and remember this being an amazing tool for correcting film scans:

Photoshop’s native Auto Tone, Contrast, and Color commands often fail on film scans because elements like sprocket holes or uneven scanning backgrounds confuse the algorithm’s sampling. To automatically fix contrast and color on a 35mm scan containing sprockets, select only the exposed image area using a rectangular marquee tool, then create a Curves Adjustment Layer.

Hold Alt (Option on Mac) and click the Auto button within the Curves panel, then select "Enhance per channel contrast." This applies automatic color and tonal correction based solely on the selected pixels, ignoring the sprockets. You can then disable or delete the adjustment layer after flattening if you prefer a non-destructive workflow or wish to use it as a starting point for manual tweaks.

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It was especially the "Enhance per channel contrast" option that was useful.

[akesher123]

+1, big fan of curves as a tool. I know it's kind of antithetical to the concept of Negpy trying to emulate darkroom printing and providing controls based on that, but a curves tool would save me from having to bring exports into LR or PS.

Simple adjustments like:

• Per channel black point (on my last roll my black point was quite cyan, couldn't correct with the color sliders set to shadows)
• lifted black point (big pain point with Negpy for me, images that I want there to be true black, I can't achieve without way increasing the grade, which pushes highlights in a way I don't want)
• easier to correct color shifts in the highs - in my last roll i had to shift the highlights crazy magenta, which dragged too much of the mids that way, so had to drag the mids back down toward green, fighting back and forth
• more tunable contrast via S shaped RGB curve.
• Quick and dirty gamma/brightness adjustment with midpoint slider

I know curves is much more of a digital domain tool that I don't think really has an analog (ha) in darkroom printing, but it would go a long way in making negpy more of a one stop shop. Would love it as a sort of "final operation" after all the darkroom-style settings that setup the base of the image.

[marcinz606]

I plan to look into that but more as a ways to shape H&D curve than "lightroom-like" curves

[jboneng]

I plan to look into that but more as a ways to shape H&D curve than "lightroom-like" curves

I started on this mentioned functionality before I saw this thread

If there is other plans for curves adjustment, or if this goes against the philosophy of NegPy, I just shelf this feature branch

[marcinz606]

That's very lightroomy :) I want to do it as more selective H&D curve manipulation at "print"/exposure stage.

[marcinz606]

[varmsaus]

NegPy as a one-stop shop would be incredible.

[marcinz606]

and now also global / r / g / b fine controll for white & black point offsets

[marcinz606]

I'm playing with those new controls on my scans and it opens a lot of extra possibilities for finetuning. It's on feat/split-curve if anyone wants to test it out before it's merged to main and bundled as next release

[marcinz606]

merged to main

[akesher123]

Nice! Not sure the right terminology, but does this affect the black point of the inversion step, or the print step? I love the ability to make sure the black and white is correctly tuned on the inversion, but if I understand things right that would not resolve the issues of a raised black point on the final output.

I guess, if these are basically per-channel analogues of the existing black and white point settings I'm not sure it accomplishes what I and maybe others are hoping for. I would like the ability to push the actual output to the point of clipping, and I think changing the grade will remain the only way to achieve that?

[marcinz606]

Nice! Not sure the right terminology, but does this affect the black point of the inversion step, or the print step? I love the ability to make sure the black and white is correctly tuned on the inversion, but if I understand things right that would not resolve the issues of a raised black point on the final output.

I guess, if these are basically per-channel analogues of the existing black and white point settings I'm not sure it accomplishes what I and maybe others are hoping for. I would like the ability to push the actual output to the point of clipping, and I think changing the grade will remain the only way to achieve that?

"Process" section covers inversion (negative densiometry) so white point / black point are offsets to auto-detected d-min and d-max.

Regarding black point and what you mentioned here:

lifted black point (big pain point with Negpy for me, images that I want there to be true black, I can't achieve without way increasing the grade, which pushes highlights in a way I don't want)

I implemented "true black" toggle that sets it to digital black instead of "paper black" for the print stage.

[akesher123]

Implemented in a version to come, or is it in the release version? I know I'm a version behind, but I don't see it in 0.34.0, only a paper white toggle

[marcinz606]

in version to come, early sneak peak always available if you just run it from main branch :)

[akesher123]

Wall of text warning:

It seems the general way tools like this work, (NLP, Nikon Scan, and Negpy, e.g.) are:

1. Create the baseline inversion. NLP and Negpy let you parameterize this, Nikon Scan barely does.
2. Allow modification of that base inversion. NLP has some sliders for it, but really the heavy stuff is editing a copy in LR. Most of what Nikon Scan has applies here. Negpy the same, but as a user the tools aren't sufficient on this stage for the digital realm. Perhaps it's great for printing and seems really good for mimicking RA4 printing.

Negpy has lots of control over 1 but feels really limiting in 2 to the point where it feels like it's basically required to bring it into LR on some images. I think a separate "mode" designed for digital output with basic LR-esque controls would be really helpful to users.

I personally don't really care for fine tuning the inversion. I think Negpy's baseline is great. No clipping, pleasing contrast by default, great color on batch rolls. But sometimes the output needs massaging with curves to suit my taste, and it's a real pain to go from scanner software -> negpy -> LR, when the adjustments would be really basic curve editing.

I think this is something other softwares really nail. Nikon Scan is a clunky mess and crashes all the time, but it has basic contrast, brightness, color balance, histogram, chrominance, hue, and other controls built in. I actually love it for some stocks where the inversion comes out well, but I've recently started shooting ECN-2 film where it completely fumbles. NLP in my experience can produce some truly AWFUL results out of the box, but again, you kinda have all the tools you need in a one-stop shop.

I know Negpy isn't an image editor but I would love some basic image editing thrown in.

[marcinz606]

per channel curve/levels adjustments and split-grade / split-density controls are in 0.36.0 release :)