X-Rite Color Checker Passport: Calibrating Camera to backlight

Has anyone ever thought about reproducing the X-Rite color checker passport as a transparency, or a negative so you could profile your backlight source?

I think it would be helpful for:

Transparency Capture: Including slides, medium, and large format. This would give you the ability to capture the slide base including any discoloration due to age of the acetate. Then you’d have a duplicate of the absolute original before any corrections are applied in LR.

Negative Capture: Ditto here but now you’d have an accurate profile to apply to the negative stock. Maybe this could make conversions more consistent and help NLP do it’s thing better.

I don’t know of anyone who has tried doing this. I think the problem might be that no one I know owns a densitometer to read the white point of a transparency or a negative. I suppose the late it would be processed at would have one but then we’re also talking about testing color filtration over the lens of a film camera.

Has anyone else thought about this?

Here is a page on X-Rites website that shows what the white patch (#19) color build should be. https://xritephoto.com/ph_product_overview.aspx?ID=2572&Action=Support&SupportID=5159

Taking a (reflective) shot of a color checker is certainly possible. Getting a profile from it will correct deviations caused by both the backlight and the lens/camera combination.

If you go through an intermediate positive or negative, they will simply add to the chain of deviations, not really something you want, specially in view that all films are not created equal. It’s not worth it, just get a decent backlight.

Higher precision is one thing, but will it automatically give you better results? The answer is “most probably not”. There is so much variation in an analog process, that your personal judgement is as good as - or even better than - any precision. The target image is In your mind and no software can read that today. But you can push sliders to get as close to you vision as you like or you knowledge of the tools you use allows…

Sounds as good a reason, not to dig a rabbit hole. Thanks for your input.

I have IT.8 target for that purpose - https://www.silverfast.com/buyonline/en.html#targetfilter

I do use it for comparision between different light sources for example.

I have the IT8 target too. But they don’t make a negative version of it. So I thought since a large number of people have been using the Color Checker Passport, there might be resources for trans/neg versions. Was thinking of making it myself but as @Digitizer pointed out, it’s probably a lot of work for something that moves all over the map.

I also like Silverfast’s SRDx for cleanup. I’m amazed they are the only one who has come out with something to clean up dust. I think it still needs work, but that’s another topic thread.

Just an FYI, these guys have done something very similar:


They’re a high end scanning lab in Paris, although their process is slightly different from what you mention (though not by much)

They photographed a colour checker on all the various film stocks they get asked to scan, then had a pro-lab make an RA4 darkroom print for each. The same colour checker negative then gets matched to the print and (if I’m correct in thinking) an ICC profile for each film stock/paper is made and used as a base

For anyone curious about the quality, I had some test scans sent over in various formats both colour and B&W, 35mm, medium format, large format 4x5’s - all amazing. Beats the Imacon system hands down as you get a true RAW file perfectly inverted, for every frame you’ve taken on your shoot, and probably the biggest benefit, it works in Capture One - which is what everyone in the high-end fashion and commercial space use