Add spektrafilm module documentation - #993
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add link to the spektrafilm github
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nice! |
anoderay
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anoderay
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Some editorial comments :-)
| {{< details summary="Technical information" class="technical-info" >}} | ||
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| description | ||
| : simulates the physical process of developing and printing analog film, using spectral emulsion and paper data from the [spektrafilm](https://github.com/andreavolpato/spektrafilm) project. |
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I'd move the spektrafilm link into the first paragraph to give this reference more visibility. The "technical information" block is collapsed by default
| # usage | ||
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| only use one display transform | ||
| : Never use _spektrafilm_ together with another display transform module (i.e. [_filmic rgb_](./filmic-rgb.md), [_sigmoid_](./sigmoid.md), [_AgX_](./agx.md) or [_base curve_](./base-curve.md)) -- _spektrafilm_ performs the film's own tone mapping as part of simulating development and printing. |
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I find never quite harsh. Nothing catastrophic happens by combining tonemappers. Maybe: "It is not recommended...".
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@anoderay The Sigmoid module description contains similarly worded advice:
"Never use sigmoid together with another display transform module (i.e. filmic rgb, AgX or base curve)."
Of course, any creative distortion of an image has a right to exist, including those created using more than one tone mapper. But applying a linear tone mapper to nonlinear data results in "burned-out" highlights, unnatural color distortion, and loss of shadow detail.
| : Slide and reversal film stocks are viewed directly rather than printed -- _scan the film_ is automatically enabled when you select one, and every print-stage control (print exposure compensation, auto print exposure, print contrast, print development time, filtration, preflash, print diffusion) has no effect while it's active. The scanner tab's _viewing glare_ is also inactive, since a directly scanned film has no print surface. | ||
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| auto print exposure is a real-world default, not a fixed brightness | ||
| : With _auto print exposure_ enabled, changing _film exposure_ does not change the final brightness -- print exposure automatically compensates, the same way a real printer exposes to a fixed target density regardless of how the negative was exposed. Disable it if you want film exposure to affect brightness directly, as it would with a fixed enlarger exposure time. |
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Needs update per the new default I think?
| : With _auto print exposure_ enabled, changing _film exposure_ does not change the final brightness -- print exposure automatically compensates, the same way a real printer exposes to a fixed target density regardless of how the negative was exposed. Disable it if you want film exposure to affect brightness directly, as it would with a fixed enlarger exposure time. | ||
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| narrow-spectral-sensitivity papers may need manual print exposure | ||
| : A few print stocks (duplicating films in particular) have a very narrow spectral sensitivity. _auto print exposure_'s metering can under- or over-shoot for these -- if a print looks implausibly dark or bright with auto print exposure enabled, use _print exposure compensation_ to correct it manually. |
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| # module controls | ||
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| Film stock, print paper, and the film format are always visible at the top of the module. Everything else is organized into tabs matching the stages of the physical process: _film_, _print_, _grain_, _halation_, _diffusion_, and _scanner_. |
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Maybe substitute "stages" with "aspects" as e.g. grain is not really a "stage" per se.
| : Contrast of the mid and slow emulsion sub-layers. | ||
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| developer exhaustion | ||
| : Local developer depletion in dense (highly-exposed) areas: blends the highlight shoulder toward a self-limiting rolloff without shifting mid-grey. 0 disables it. |
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From my experience this increases highlight contrast; maybe this fact could be added here. At least to me "blends the highlight shoulder toward a self limiting rolloff" is difficult to understand.
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| ### chemistry | ||
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| development time |
| The scanner stage models how the developed film or finished print is digitised, and the conditions it is viewed under. These act on the final image, after everything else. | ||
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| pre-compression boost | ||
| : Multiplies XYZ luminance immediately before the OkLCh output gamut compressor, pushing the histogram to the right while the film's own shoulder rolloff is preserved. 1.0 is neutral/off. Because it acts at the very end of the module, the picker measures the processed image rather than the input: use it on an area of highlights to set the boost so the brightest tone lands just past the compressor's knee. |
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Could be less technical IMHO
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Adds documentation for the spektrafilm module currently developed here darktable-org/darktable#21534 This is an initial commit and will be modified as the module evolves