Color Neg to Pos Conversion - Blue Cast

[JLNims]

Greetings all,

I know the negative to positive conversion topic has been discussed ad-nauseam. But this is a bit different. Please stay with me on this one. I scanned the neg with a Nikon D7200 with the neg on an LED light table into Capture One version 22 (latest). Then I exported the tif to Affinity Photo for processing. Here are my first steps:

1. Bring in the color negative MF0226_Neg.png below

2. Sample the rebate color to remove the orange cast (MF0226_rebate) and create a fill layer filled with the rebate color. Then change the fill layer blend mode to divide which yields MF0226 Neg and Rebate below. The rebate has been neutralized leaving only a negative without the cast.

3. Then I use the Invert command from the Adjustment Layers which flip the neg to a pos (MF0226_Inverted).

NOW here is the problem: I have an overall blue cast that cannot be balanced out.

I did process this Ektar 100 film at home using CineStill chemistry. The chemistry was new and just mixed. I checked and rechecked my mixing volumes and temperatures - all OK.

Any ideas?

[maltfalc]

gel the backlight to correct the orange cast. it's a lot easier to do colour corrections in software if you start out with all three channels properly exposed and you can correct the colour cast more precisely if you aren't limited to simple rgb values.

[JLNims]

gel the backlight to correct the orange cast. it's a lot easier to do colour corrections in software if you start out with all three channels properly exposed and you can correct the colour cast more precisely if you aren't limited to simple rgb values.

Well, by creating the fill layer with the color of the rebate, I believe the resulting channels have been synced properly . The orange cast from the film is gone as per the third photo. The remaining orange converted to the bluish/cyan cast that I was left with. I am going to work a bit more on this so I can come up with some answers that others might find useful however.

[Bernard_L]

What kind of tif file do you start with? Are you sure the RGB numbers represent linear red, green, blue intensities? Because if they are, say, AdobeRGB, they map to color intensities via some mildly complex equations. "Divide blend" may not be the proper solution.
Furthermore, the orange mask is not just an added color, like sandwiching the negative with an orange gel; the intensity of the mask varies with the actual colors recorder on film. Which is why a correction that appears to work on the rebate leaves an orange (negative) or bluish (positive) cast on values above unexposed film.

[PatrickMarq]

There is a good tutorial by Ales Burke
https://www.alexburkephoto.com/blog/...-negative-film

[JLNims]

What kind of tif file do you start with? Are you sure the RGB numbers represent linear red, green, blue intensities? Because if they are, say, AdobeRGB, they map to color intensities via some mildly complex equations. "Divide blend" may not be the proper solution.
Furthermore, the orange mask is not just an added color, like sandwiching the negative with an orange gel; the intensity of the mask varies with the actual colors recorder on film. Which is why a correction that appears to work on the rebate leaves an orange (negative) or bluish (positive) cast on values above unexposed film.

I start with a tiff generated from Capture One tethered directly to my digital camera (Nikon D7200). Then the tiff is exported to Affinity Photo where the editing happens. I don't use Adobe anything. I refuse to subscribe to that juggernaut. To answer your question, yes the channels default to sRGB IEC61966-2.1 Linear. However I believe you're correct in that the rebate may not only be the best reference by itself causing the opposite cast. Please see my comment below to Pat.

Thanks for the help Bern!

[JLNims]

There is a good tutorial by Ales Burke
https://www.alexburkephoto.com/blog/...-negative-film

Thanks Pat! I will read with great intensity . Here's the reference I used for this instance: https://retro-pixel.com/converting-c...thout-plugins/

Now to compare the two; and factor in Bernard's excellent points. I'll let you all know what I find in case you might be interested in this hybrid technique.

Thanks fellas!

[JLNims]

I just finished using Alex Burke's method (Thanks Pat). I had much more color control; and ended up with a very acceptable positive conversion. Interestingly enough, Alex used the same method as I did by sampling the rebate color to generate a fill layer. The difference was Alex inverted the negative before creating the fill layer instead of after. The made the rebate a cyan instead of orange. But since the inversion was first, the blend method was 'subtract' instead of 'divide'. This resulted in a far more closely blended RBG color scheme before manipulating the colors for final finishing. Also the blended colors were very dim and low in intensity allowing a huge amount of headroom for color adjustments before clipping. In my case, no clipping even occurred. Very nice indeed!

Thanks again Pat! Alex' method should be posted in its own non-editable thread heading under Digital Processing for all to scan over. Hint, hint moderators...

[Alan Klein]

I just finished using Alex Burke's method (Thanks Pat). I had much more color control; and ended up with a very acceptable positive conversion. Interestingly enough, Alex used the same method as I did by sampling the rebate color to generate a fill layer. The difference was Alex inverted the negative before creating the fill layer instead of after. The made the rebate a cyan instead of orange. But since the inversion was first, the blend method was 'subtract' instead of 'divide'. This resulted in a far more closely blended RBG color scheme before manipulating the colors for final finishing. Also the blended colors were very dim and low in intensity allowing a huge amount of headroom for color adjustments before clipping. In my case, no clipping even occurred. Very nice indeed!

Thanks again Pat! Alex' method should be posted in its own non-editable thread heading under Digital Processing for all to scan over. Hint, hint moderators...

Why don't you post the results so we can see?

[JLNims]

Why don't you post the results so we can see?

Well thanks for asking Alan. I'll show the neg and the finished product. PLEASE do not judge focus! I am waiting on a new negative carrier for my light table. These negs just laid on the table; but had a vertical curve with just the amount to blow my scanning camera focus. I did try a smaller aperture; but to no avail. When I get my new carrier next week, maybe we can do this again. I left the rebate so you can see it turned black as it should. Having said that, here we go: