How to invert color negative "scan" via DSLR without clipping the red channel?

Question

I am trying to convert color negatives into positives and struggling with removing the orange mask and getting usable colour after inverting.

It seems that I constantly clip the red channel no matter what I do, please can some of you take a look at my set up and offer some advice?

Here's my current workflow / setup -

• Nikon D810 - 100mm Tokina Macro - Copy stand - LED Lightpad (artograph A920)- Negatives held in old carrier from enlarger - I use a custom WB of 2900K.

• I then 'scan' as Raw files, put in Adobe Lightroom > set the camera profile to 'camera flat' take off sharpening etc. then open in Photoshop.

• In Photoshop

1. I Open two files - one is the image I'm going to correct, and one is a blank film leader taken from the same role and exposure (I use this for the WB).

2. I open a levels adjustment layer and using the grey dropper I select the blank film leader and this helps to correct some of the orange mask. I then invert and use auto level curves layer. Finally I tweak the colours to try and remove colour casts (this has varying levels of success). The full steps can be found on this blog http://mfphotography.ca/blog/2015/3/23/colour-film-scanning-revisited-part-2 and in the youtube video that Mike made - https://www.youtube.com/watch?v=bVxtIqmEnTk

Questions / Things I have noticed with my technique -

1. When scanning the negative, I have to underexpose the image quite significantly to avoid clipping the RED highlights in the histogram of my Nikon D810. How do I get a good exposure without clipping the red? I am guess that when I clip the red it makes it harder to get good inversions in Photoshop. Maybe I could use a filter? Any idea which screw in filter would work?

2. The negs that for some reason don't clip the red channel as badly, seem to convert better. For e.g. I have an old roll of Kodak Portra 400 at home from when I used to shoot film a few years back, that seemed to scan much better than a recent Fuji 400proh that I converted. The Fuji neg mask seemed more dense, perhaps this is bad processing at the lab that was affecting my results?

3. I have tried the trial version of colorperfect and the results of this don't seem to be as good as the Photoshop method, they also seem to vary wildly with each negative that I open.

4. I am working sRGB on camera, in Lightroom and in PS - is this recommended?

5. Has anyone tried this approach.

6. Sometimes I get best results from using the white balance tool in Lightroom before opening in PS and doing the inversion.

Finally I would just like to say that so far I have got good results from DSLR scanning in terms of quality of image / sharpness, but I am really disappointed in the colour aspect - I am almost thinking of trying a scanner like the Epson v700 instead. There must be a way around it however - I hope at least!

Answer 1

I filter the orange cast of the color negatives via the light box so that the red channel on the D810 camera I use is not shifted and compressed using 3 sets of gels. My light box is powered with two SB700 flash units and a CFL bulb for focus and composition. I have described my setup twice on this forum before. Here are the gels I use.

Cinegel #3202: Full Blue (CTB),

Cinegel #3204: Half Blue (1/2 CTB),

Cinegel #4415: 15 Green

You can buy the blues on Amazon.com and the green you have to get from Rosco.com. Keep in mind that some negatives have a strange color and you may have to play with the gels combo some but usually not. Main thing is to control the channels RGB to get them to line up better. Some negatives are more yellow and some are more magenta.

If you do not do this with the gels then your capture accuracy of the colors in the negative is poor and subsequent edits in Photoshop yields weird colors. This technique also keeps you from clipping the red channel. Ideally if you had a perfect camera with more than 14 bit capture you might be able to skip the gels but I found there really is no camera that can handle all that orange! Just make sure no matter what camera you use that you use the widest byte capture. Most DSLRs have a 14 bit RAW option. Also when converting your RAW image pre Photoshop and invert, use the Camera Neutral calibration.

Also you should expose less than you would normally think when capturing color negatives on a digital sensor. Remember that the shadows in the original scene are the clear (minus the orange cast) areas of the film so overexposing those makes your shadows in your final inverted image weird and the highlights look strange as well. The color gets crossed over and strange casts in highlights often and sometimes shadows. Middle tones are easy.

Lastly I should state that unless the camera you are using has excellent color rendering you will have issues. I have a D7000 and a D5000 and get poor results with both. Final image grain is high in the highlights (dark areas on the negative) and the colors are strange and never look right (crossed over) no matter what I do. I went with the D810 for better color and resolution and now get stellar results. It is much more linear in the shadows and highlights and thus works great for color negatives capturing and inverting.

See my physical setup on http://www.fechnerimaging.smugmug.com

Answer 2

If you have an enlarger with a color head, this one can make your dslr scanning a breeze!

• First you can use the column in repro mode to greatly help with focusing and flatness of field
• The enlarger lens makes a perfect scanning lens, paired with cheap extension rings to get the proper scaling (without the bellows mechanism going in the way)
• The color head, reversed on the enlarger, makes a perfectly uniform light box
• The color dials of the head can be used to make a white balance and totally put out the color of the negative (yellow: 0, magenta: 60, blue: 60, as an example but it can vary depending on the head and the negative)
• The enlargers film carrier, reversed, is perfect to help with the film flatness
• The timer is perfect to keep the heat low, using the light only when you need it
• And the best of all... You can even print pictures with it!!! Yay!!

Happy scanning

Joël Obrecht aka Silent Fabrik Instagram : https://www.instagram.com/p/BihGX6FDFuZ/ Flickr : https://www.flickr.com/photos/quatrecouleurs