Page 1 of 4 123 ... LastLast
Results 1 to 10 of 33

Thread: Color Neg to Pos Conversion - Blue Cast

  1. #1
    JLNims JLNims's Avatar
    Join Date
    Jan 2022
    Location
    Washington State
    Posts
    23

    Color Neg to Pos Conversion - Blue Cast

    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?Click image for larger version. 

Name:	Jeff MF0226_Neg.jpg 
Views:	17 
Size:	30.0 KB 
ID:	226810Click image for larger version. 

Name:	Jeff MF0226_rebate.jpg 
Views:	14 
Size:	5.4 KB 
ID:	226811Click image for larger version. 

Name:	Jeff MF0226Neg and rebate.jpg 
Views:	14 
Size:	40.3 KB 
ID:	226812Click image for larger version. 

Name:	Jeff MF0226_Inverted.jpg 
Views:	27 
Size:	40.3 KB 
ID:	226809
    ~Jeff

    "it is better to overexpose slightly than to under expose." Ansel Adams, The Negative

  2. #2

    Join Date
    Nov 2017
    Posts
    275

    Re: Color Neg to Pos Conversion - Blue Cast

    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.

  3. #3
    JLNims JLNims's Avatar
    Join Date
    Jan 2022
    Location
    Washington State
    Posts
    23

    Re: Color Neg to Pos Conversion - Blue Cast

    Quote Originally Posted by maltfalc View Post
    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.
    ~Jeff

    "it is better to overexpose slightly than to under expose." Ansel Adams, The Negative

  4. #4

    Join Date
    Jun 2013
    Posts
    154

    Re: Color Neg to Pos Conversion - Blue Cast

    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.

  5. #5

    Join Date
    May 2019
    Location
    Belgium
    Posts
    260

    Re: Color Neg to Pos Conversion - Blue Cast

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

  6. #6
    JLNims JLNims's Avatar
    Join Date
    Jan 2022
    Location
    Washington State
    Posts
    23

    Re: Color Neg to Pos Conversion - Blue Cast

    Quote Originally Posted by Bernard_L View Post
    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!
    ~Jeff

    "it is better to overexpose slightly than to under expose." Ansel Adams, The Negative

  7. #7
    JLNims JLNims's Avatar
    Join Date
    Jan 2022
    Location
    Washington State
    Posts
    23

    Re: Color Neg to Pos Conversion - Blue Cast

    Quote Originally Posted by PatrickMarq View Post
    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!
    ~Jeff

    "it is better to overexpose slightly than to under expose." Ansel Adams, The Negative

  8. #8
    JLNims JLNims's Avatar
    Join Date
    Jan 2022
    Location
    Washington State
    Posts
    23

    Re: Color Neg to Pos Conversion - Blue Cast

    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...
    ~Jeff

    "it is better to overexpose slightly than to under expose." Ansel Adams, The Negative

  9. #9
    Alan Klein's Avatar
    Join Date
    Jun 2015
    Location
    New Jersey was NYC
    Posts
    1,630

    Re: Color Neg to Pos Conversion - Blue Cast

    Quote Originally Posted by JLNims View Post
    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?

  10. #10
    JLNims JLNims's Avatar
    Join Date
    Jan 2022
    Location
    Washington State
    Posts
    23

    Re: Color Neg to Pos Conversion - Blue Cast

    Quote Originally Posted by Alan Klein View Post
    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:

    Click image for larger version. 

Name:	Day Care Neg.jpg 
Views:	18 
Size:	46.1 KB 
ID:	226828Click image for larger version. 

Name:	Day Care.jpg 
Views:	26 
Size:	78.3 KB 
ID:	226829Click image for larger version. 

Name:	Jeff MF0224.jpg 
Views:	18 
Size:	28.3 KB 
ID:	226830Click image for larger version. 

Name:	Jeff MF0224_1.jpg 
Views:	24 
Size:	47.0 KB 
ID:	226831
    Last edited by JLNims; 1-May-2022 at 01:30.
    ~Jeff

    "it is better to overexpose slightly than to under expose." Ansel Adams, The Negative

Similar Threads

  1. E6 partial color cast
    By kleinbatavia in forum Darkroom: Film, Processing & Printing
    Replies: 0
    Last Post: 20-Oct-2015, 13:26
  2. Color Cast after Developing
    By AndreasResch in forum Darkroom: Film, Processing & Printing
    Replies: 7
    Last Post: 22-Dec-2011, 04:55
  3. Blue Cast in Drum Scanned Files
    By Eric James in forum Digital Processing
    Replies: 10
    Last Post: 19-Jun-2007, 09:07
  4. Blue cast on velvia.
    By Paul White in forum Darkroom: Film, Processing & Printing
    Replies: 5
    Last Post: 22-Apr-2004, 08:57
  5. Blue cast to transparencies
    By Mike Mahoney in forum Darkroom: Film, Processing & Printing
    Replies: 18
    Last Post: 15-Aug-2001, 12:44

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •