Spectral film simulations from scratch

[Anthonygansauer]

matched density and exposure, no color edits at all. its almost a perfect match. this is honestly insane

[Anthonygansauer]

going to try a real test one of these days with my nikon f4 as i have two 24mm lens i can adapt for my lumix & nikon. this is seriously some ground breaking stuff man.

i am definitely super excited for any kodachrome emulations as I wasnt even born when it was primarily used but all the work i admire from the natgeo, street, and photo journalist stuff-- I am anxious awaiting it to be developed further!

[mikae1]

@mikae1

Might have to look again then!

Here are a few possibly interesting ones:

• Fujifilm Professional Data Guide
• Development of Motion-picture Recording Film ETERNA-RDI
• Development of Fujichrome ASTIA100

@arctic

by the way. fun fact. digitizing datasheets is a very manual process and after a few days of trying to fix strange behaviors of kodak portra and supra papers, i found that their sensitivities had the wavelength axis stretched by 50 nm too much (that it is kinda huge). it made me crazy trying to understand the issues with green and those papers with the updated way of processing the datasheets. at last i fixed it one week ago, now is fine also in main. but the madness of the rabbit-hole-problem-hunting made me discover additional nice details.

That’s pretty wild, nice find! Love hearing these development stories!

[hanatos (jo)]

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oh, did everything become a lot darker? this is from the log_sensitivity table in the portra 160 data. what else should i be re-normalising in different ways now? without further changes i’ll render everything black. also need to re-calibrate the white balancing of course.

[edit: for now i mutiplied the film exposure light *1000.0 and it’s kinda back to normal. updated the vkdt data to upstream]

[arctic (Andrea)]

in negative and positive film i normalize with the spectrum upsampled for midgray = [0.184, 0.184, 0.184] (that is essentially the reference illuminant bandpass-filtered, i consider the bandpass as part of the spectral upsampling). so when inputting midgray as input i get zero log exposure for the three channels. the spectral upsampling spectra are computed with code very similar to the one you shared to me last year, i hope i didn’t add other weird normalizations there.

for print media i normalize sensitivities with the printing illuminant attenuated by the mid density published for the reference target film (portra 400 for kodak, vision3 250d for cine kodak, pro 400h for fuji paper) and enlarger filters set to Y50M50(C0) CC units (100 kodak CC units is 1 OD, and for Durst enlargers 100 steps is in the ball park of 50CC). in this way i get neutral filters fitted in a reasonable range without pushing the density of the enlarger filters too much. i changed also the scale of the filters, now linear in density, because they are like this in real enlargers, and i avoid to get filter values crashing to 1.