Feedback on Spektrafilm documentation

Software darktable
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21

This module will follow reference spektrafilm and it depends on which stocks the project adds.

22

Yes, but spektrafilm is not ‘yet another tone mapper’… i switched in general to AGX, but spektrafilm is not a general tone mapper.

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My solution: A style with spektrafilm enabled and disabled instances of the other tonemappers. I set it to a keyboard shortcut (ff) to quickly throw spektrafilm at an image.

BTW the idea of a multi-tonemapper-warning is not recieved well in the discussion on github - if you guys would find it useful it might make sense to chime in over there :slight_smile: .

24

I have been talking with several other people about the new spektrafilm module. While the general feeling is that we have awesome new capabilities to look forward, we also have a bit of worry: it might be (very) hard for people that don’t have a background in film photography to wrap their heads around this module.

While the documentation on darktable.org is mainly a reference guide. It be very helpful to also have a page on:

  1. which film stock is recommended for which scenario? Personally, I have not shot film in a meaningful way. So to know which film is good in which situation is extremely helpful (I would assume that Kodak Portra is for portraits, but that is about it.

  2. additional, it would be very nice to have a short of workflow that describes how to use the module. What do you do after you have selected your film type and paper. What decisions do you take if you want have a certain effect.

The current documentation describes very well what the sliders are doing, but not how to use the module…

3 Likes
25

I’m a user that experiments based on looks and what I like and not when something should be used, so I might not be the best to judge here. I found:

or

I think if we’d reproduce this for all settings the module offers it will be a book.

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I agree, this is a general weak point of the manual as a whole. The second half of usage and FAQ is based on questions I tried to answer for myself. Are there “questions” that you @martinus et al. had to answer for yourself that we could include as pointers in the usage section?

Maybe we could link to the two articles @piratenpanda provided and point to the presets as inspiration, too.

27

Hello.

I’ve been looking at spektrafilm documentation. I have a few (hopefully helpful) suggestions:

  1. format and frame long edge. These two are not very clearly explained as much as I try to follow. Or, rather, the frame long edge is quite clear both in terms of what it does and what its effect is, but format does not say what the effect is. If these two are linked - why do we need both settings controlled independently? (This is not me asking the question here hoping for an answer, this is just to point out that whatever the reason for the module settings is, it could be clarified in the docs).
  2. Exposure reads “changes brightness similar to exposure”. If it is similar to exposure, it means it is not identical. So it would be helpful to explain how it is different from exposure, imho.
  3. push/pull. This process involves changing film exposure and development time, both. It would be helpful to explain here if enabling push or pull automatically adjusts development settings, or if they have to be changed manually.
  4. Fast/slow layer gamma. These don’t say at all what they do. I guess it’s obscure because these can’t be traditionally controlled independently in film development - which even more is a reason to explain these controls. Right now it feels a bit like the documentation throws its hands up in the air and goes “no clue, just try and see what happens” :slight_smile:
  5. Dir couplers - very very nice and clear explanations!
  6. Diffusion - this section reads a bit confusing. It says there are two stages - a. film exposure with the filter before the camera lens and b. Filter before the print. However: (I) the documentation then talks how to enable a. and ignores b. (II) it’s confusing to learn know that the module simulates a camera lens filter, which to me does not seem to be directly related to film process because I can put a diffusion filter on either film or digital camera anyway.
  7. Quality - why would I want to use it? Does it apply to previews in the main darktable window, exported files, or both? Is the processing traded off here?
  8. Gamut compression - the first sentence is not clear. I’m not sure what it’s saying. Can it be broken down into two shorter sentences maybe?
  9. Print exposure compensation - “always an offset” - I think we are missing a verb here. Always IS an offset? Always SHOULD BE an offset?
  10. Enable print diffusion - ah, that answers partially my point 6 above. But I maintain that it would be good to clarify this earlier.
  11. Grain - “Silver crystals in the emulsion develop or don’t” - this sentence has 0 information value. I would not use precious docs space for it.
  12. Grain strength - needs comma after “unlike granularity”. “Reach for granularity” is not clear.

Phew! I stopped before the halation section, will continue later (if the suggestions above are helpful, at least).

1 Like
28

Thanks for your very clear and detailed feedback!

“Quality” is already gone in master, I’ll think about the rest!

1 Like
29

I reworded with your feedback. So please check the current version please :slight_smile: darktable user manual - spektrafilm

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Hi Benjamin,

As a brand-new user for this awesome module, I have one comment on the manual entry. I think that the introductory technical information section should include some mention of tonemapping.

Spektrafilm serves not only as the film-simulation tool within darktable, but also serves as the tonemapper. Thus, for general use, spektrafilm should be used in place of other tone mappers, such as filmic rgb, Sigmoid, and AgX. Those tone mappers have other advantages, but for film simulation tone-mapping is performed within spektrafilm.

When selecting a default workflow in darktable, in “darktable preferences > processing > auto-apply pixel workflow defaults” one may select a default tonemapper. This could be, for example, filmic, Sigmoid, AgX, or spektrafilm. With any default selection, however, one may show other optional modules including other tonemappers. For example, if you generally use Sigmoid as your tonemapper and want to test spektrafilm on select images, you may add the spektrafilm module in “manage module layouts” which is found in the darkroom right panel “hamburger icon.” In this example, one may add spektrafilm to the set of base modules (circle icon). Remember to de-select Sigmoid (or other tonemapper) when enabling spektrafilm for the intended use as a tonemapper.

Something like that.

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31

I made a PR, thanks :slight_smile: spektrafilm: make tone mapping clearer and also add workflow in processing by piratenpanda ¡ Pull Request #1166 ¡ darktable-org/dtdocs ¡ GitHub

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32

Hello. I checked the updated documentation. Thank you, I think pretty much all my suggestions have been taken on board, I’m glad to know I could contribute. A few very minor points on the earlier suggestions:

  1. enable print diffusion:

diffusing the print instead of the exposure

Perhaps we can say “diffusing the light at the print (as opposed to film) exposure stage”? Because both film and print get exposed.

  1. grain

The simulation builds such an emulsion

Feel free to ignore, but I think this might read a little better (though not sure if is more accurate): “The module simulates such an emulsion”

I also continued my review from the halation section onwards and have a few additional points:

  1. scatter size - I would say “how far the light scatters” (instead of “it”)
  2. scanner -

or the negative, in scan the film mode

In here, I wanted to suggest that it could be helpful to indicate where this mode would be enabled. However, I get a bit lost. When I scroll up in the documentation, this mode is documented under film > exposure section, but in my darktable version the mode shows above the 5 module tabs and in the “print paper” dropdown. (I am however using a darktable version with the new flex mask system, so maybe I have an outdated spektrafilm version?). So I think there are two points here

  • is the ‘scan the film’ mode documentation pointing to its location accurately
  • in the scanner section, shall we say “in scan the film mode (enabled in XXX)”

Lastly, a general point: the current technical information section on the very top has a “description” subsection which… isn’t very technical. If there’s a good reason for it to be there that’s of course no big deal, but it’s a bit strange to see it there, and then have MUCH more technical information below, outside of the technical information section.

I think that’s it for my points. Seeing how it’s been a bit of a workout for me to, ahem, review the documentation, I can’t imagine the workload or thank enough to people who actually created the documentation, created the module, or created the original simulation engine. Chapeau.

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33

Thank you so much. Created another PR spektrafilm: address second review of the module documentation by piratenpanda ¡ Pull Request #1169 ¡ darktable-org/dtdocs ¡ GitHub

The scan film toggle was a bad oversight, thanks for finding!

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Just noticed: the pickers for pre compression boost and post compression scale are not documented. I think it would make sense to explain what they measure and what they target :-).

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