Fitting your camera's look

What a fitted look is

greycard develops a sample of your frames, lays each camera JPEG over greycard's own version of the same frame, and learns the difference in color and tone. The result is a look like any other in the LOOK section, with a Strength slider.

There is one look for each camera body and picture style, named for both, such as "Canon EOS R6 Mark II Faithful". Faithful and Standard on the same body are different looks, because the camera renders them differently.

The look sits at the end of the edit, after your sliders. With the sliders at their defaults you get the camera's picture. After you move a slider, you get the camera's rendering of the changed picture.

What frames it needs

• Canon .CR3, Fujifilm .RAF, Nikon .NEF, Sony .ARW or Panasonic .RW2 raws. greycard reads the picture style from these; other makers' raws, and Canon's older .CR2, are not fitted yet. A library indexed before a maker was read reads that maker's frames again on its next pass.
• About 20 frames or more of one body and one style. A group is sampled down to about 40. A group under 20 can borrow a look (see below) or is skipped.
• The scene-adaptive settings off, where you can. These change the camera's JPEG from scene to scene, so a frame shot with them on teaches the look less. They come in two kinds, below.
• Variety. Frames from many shoots, places and light make a better look than one session. The sample takes a few frames from every folder first for this reason. In the library, a group whose sample is all from one folder gets no table ("all from one folder, so the fit would be narrow"); a backup copy of a folder counts as the same folder. Fitting This folder fits it anyway, and says it will be narrow.

The adaptive settings

Settings that bend the style's tone per scene leave the frame in its style's group. Once a group has 20 frames with them off, the rest are left out; a group with fewer uses frames with them on to make up its sample.

Settings that render in place of the style, or draw over it, take the frame out of every group: it was not rendered in that style, so it is never used, and the sheet counts it with the raws that have no fixed picture style. So does a style that adapts to the scene itself.

A setting greycard cannot read or does not recognize takes the frame out of every group too, so a frame is never taken as fixed on a guess.

Fitting a look

1. Open a frame, ideally from the camera you want to fit.
2. In the LOOK section, press Fit this camera's look….
3. Choose where to look for frames: Library (every root of your library) or This folder. The library is the default when you have one, since it holds the most variety. A folder fits too, with the note that the fit will be narrow; in the library, a group whose frames are all from one folder gets no look.
4. Read the list. Each line is one body and style: how many frames it has, how many have the adaptive settings off, and what the fit will do with it.
5. Untick the groups you don't want. Fit counts the ticked groups ("Fit 3 groups").
6. Press Fit.

The list fills in as greycard reads each frame's picture style, and the line under it counts the frames read ("Reading picture styles: 120 of 800"). A folder outside your library is read from the files themselves, which on a network share takes a few seconds for a few hundred frames. macOS's ._ files beside the raws are passed over.

Each group's result appears as a line when it is done. When the run ends, the new looks are in the LOOK section's list. Fit then stays off and Close is highlighted, since fitting the same groups again would give the same looks. Tick or untick a group, change where to look, or turn Replace existing looks on or off, and Fit comes back.

What the lines say

A borrowed look is not as close as a look of the body's own, but close when the bodies share a sensor or a generation.

The ticks you leave are remembered for the library and for each folder.

Replacing looks you already have

By default a run leaves an existing look alone when it would be worse to replace it: a look you added yourself under the same name, a body's own look that a borrow would replace, or a look fitted from more frames. The group's line says so. Turn on Replace existing looks to replace them anyway.

How long it takes

Each frame is developed and compared several times, a few seconds a frame, so a group of 40 takes a few minutes and a library with many bodies and styles can take much longer. A bar fills across the whole run, with the count of frames done and the group under it; while a group's look is fitted, the bar holds and the words count the frames held out. Stop ends the run after the frame in hand, or after the group whose look is being fitted; the groups already done are kept.

Reading the result

A fitted group's line reads like "fitted on 38 frames, ΔE 0.013 held out over every frame (0.011 fitted)". ΔE is how far the look lands from the camera's JPEGs: smaller is closer, and figures around 0.01 to 0.02 are typical. The held-out figure is the honest one: it is measured on frames the look did not learn from.

The line also says how many frames "did not register" (the JPEG would not line up with the raw) and, for each lens, how the corners differ from the camera's JPEG. That last figure is the camera's own vignetting correction against greycard's; the look does not change it.

Using a fitted look

Pick it in the LOOK section like any other look, and use Strength to take it part way. A preset can carry it.

The look gives you the camera's color and tone, not its brightness. Camera JPEGs come out at their own exposure from scene to scene, so the fit leaves brightness to the Exposure slider.

A look fitted on one body works on another body's frames. It is not swapped for that body's own look. When the look was fitted on another body than the open frame's, the section says "fitted on" that body.

The look list

Once you have fitted looks, the list is grouped:

• None;
• the open frame's body, open and marked "this camera";
• every other body with a fitted look, folded, with a count;
• General: film looks and any other .cube or .png look you added.

Click a heading to fold or open it.

One table per display curve

A fitted look is learned under one Display curve (in the LIGHT section), Per channel or AgX, and applies only to a picture on that curve. A look can hold one table for each.

Each fitted look's row names the curves it has ("per channel · AgX"). A look with nothing for the open picture's curve is dimmed. If you pick it, the section says it is off for this picture and offers Refit under AgX… (or under per channel). That opens the sheet for just that look's group, and the run adds a table for the picture's curve beside the one the look has.

A refit needs the look's frames in the scope. If none are there, the sheet says so and Fit stays off.

Removing a look

Pick the look and press Remove this look…. The sheet lists its files and says how many pictures in this folder (or the library) use it. Move to the trash removes every table of the look together.

Pictures that used it show the look as "(missing)" and render without it. Their edits are not changed, so putting the files back brings the look back.

Where looks are kept

In a greycard/looks folder under your data folder: ~/.local/share on Linux, ~/Library/Application Support on a Mac, %APPDATA% on Windows. A fitted look is a .cube file, and a table for AgX sits beside it with .agx before the extension. Copy them along with the look to use it on another machine.

Limits

• Picture styles are read from Canon CR3, Fujifilm RAF, Nikon NEF, Sony ARW and Panasonic RW2.
• Canon's per-style contrast, saturation and color tone settings, Fujifilm's Color, Color Chrome and Clarity, a Nikon Picture Control's sharpening, contrast, saturation and hue steps, Sony's contrast, saturation and Creative Look settings, and a Panasonic Photo Style's own adjustments are not read, so a group may mix frames shot with different settings.
• Panasonic writes the same code for Standard and for its custom styles, so they share one group, "Standard or Custom", and a fit may mix them; a high held-out error on that group is the sign. Photo styles the camera writes that greycard has no name for (some newer ones, such as the Leica looks and the cine styles) are not fitted.
• Sony's Picture Profiles are not read, so a frame shot under one may still group under its Creative Style.
• A look fitted under AgX lands a little further from the camera than one fitted under per channel, since the camera's own tone is closer to per channel.
• A fit that would tint greys is not written, and its line says "refused: the fit would tint greys it never saw". Fitting from more shoots, with neutral things in them, is the way past it.
• While a run is going, the sheet stays open.

For how the camera match was measured, see camera-match.md.