I am not quite sure how a densitometer could help with converting from a RGB digital image to a monochrome digital image. It certainly helps with analyzing a negative but as far as I understand the OP's process is purely digital.Let me ask a question first. Do you have a densitometer?
No, I don't have a densitometer.Let me ask a question first. Do you have a densitometer?
I am using "basic" image files, but my system works in the OKHSL color space, which implies : RGB -> linear RGB -> XYZ -> OKHSL - so the "gray" data from the image is linear. I chose OKHSL because the whites - blacks - grays are well distributed on the gray scale.This is a very good point. Are you using a RAW file or a processed image file? I suggest you start with a RAW file with linear gamma.
Never heard of OKHSL. Is it a single person’s model (Björn Ottosson on Github)?
It also looks like you have “reversed” each image, turning it into a positive
Can you add a dimension of spectral sensitivity? Try a simulation of orthochromatic film for example or different types of panchromatic film.
If you want more fun you could try superimposing the curve of a reducer. For example a superproportional reducer can change the film curve
Thanks Alan, I'll have a look at your thread, it looks interesting, I love DIY challenges. In fact I don't even know how much a real densitometer costs.If you don't have a densitometer you could use a digital camera to simulate one
It started with curiosity, continued with science, and most of all it was (and still is) fun, and I learned a great deal and it is not finished
What are the plans for this software?
Now film developing has curve families depending how long you develop
yes I implemented color filters too
I am wondering what algorithm you used to implement filters
I am already using spectral data for the films
Your Ortho and Panchromatic examples look very convincing. I would like to understand how the spectral sensitivity curve of a film or film with a filter is applied to the input RGB image. I tried to figure out how to convert from (r, g, b) to wavelength but could not find a satisfactory solution.
I don't know if sticking that much to reality will be as effective as obtaining a direct positive, then using classic retouching functions on it, if the result of virtually printing on paper is mostly about contrast? As I wrote above, there can be nice things to add too, like tinting, paper surface aspect, paper grain, etc.
For the moment I'm just trying to simulate the film properties as well as I can, and you (all) helped a lot to make me understand I was wrong about the way I simulated the grayscale from densities, and now I don't even have to think about completing curves, my system is good enough to exploit the raw curves without any adaptation, the solarization test was convincing.
The next step is perfecting film grain, I already achieved good results but I am not that satisfied, I'll surely ask other questions later.
And frankly I appreciate the spirit of these forums, it feels like I'm in good company.
You might even be able to reverse engineer questions like how did Hurrell get that look?
Ah, this is another subject. Technically, maybe some clues could be found, but there's also something intengible. Beauty is in the eye of the beholder.
Reversing the process would show the "original" scene (maybe even the original colors with more work), but it would loose all the charm - and I don't want to loose that
Yeah, that would be a good thesis subject
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