Compare

The Compare page measures how close the scene is to a reference and tells you what to change. It looks at the things that make a frame read like its concept, values and colour, not at the details.

Run a comparison

1. Show a reference over the viewport: double-click it on the board, or look through a camera it is linked to.
2. Open the Compare page and click Compare viewport.

Or choose Compare with viewport in an image’s … menu on the board: it shows the image over the viewport if needed, opens the page and compares.

Limner renders the viewport clean (game view, without icons, the overlay or a view filter), lets exposure, temporal anti-aliasing and Lumen settle for Warm Up Frames frames (12 by default), and compares the result with the reference. Lighting, exposure and post process count; editor icons don’t.

Which part is compared depends on the reference’s Fit: with Fit, only the part of the viewport the reference covers; with Fill, only the part of the reference you can see; with Stretch, everything. When a camera constrains the aspect ratio, only the camera frame is used.

The scores

Card	Shows
Value structure	The share of the frame that falls in the same value band in both images. Both are compared on a coarse grid, band by band, so texture detail and small offsets don’t matter.
Palette	The share of the scene within Palette Tolerance of a palette colour (the key palette, or the reference’s own).
Mean value L*	The average lightness of the reference and of the scene (0 is black, 100 is white).
Contrast	The spread of lightness in both images, with the range from their darks to their lights.

The value and palette scores are coloured green from 75 %, amber from 50 % and red below.

Previews and charts

• Reference and Viewport side by side, as the compared crops. Switch both between Color, Values and Notan above the results.
• Lightness histogram: how much of each image is at each lightness, reference in orange, viewport in blue.
• Value bands: the area of each band in both images, lights on top. The bands are named by their number: with 3 bands, Shadows, Midtones and Highlights.
• Palette: the reference palette with each colour’s share, the share of the scene nearest to each palette colour, and the scene’s own main colours.

Add viewport capture to board puts the viewport as it looks now on the board, next to the references, for a before and after.

What to change

The hints at the bottom name the biggest differences, for example:

• “The scene is 9 L* darker than the reference on average.”
• “The scene is cooler than the reference.”
• “The scene has 62% of the reference’s value contrast. Push the darks down or the lights up.”
• “Shadows cover 48% of the scene but 30% of the reference.”
• “#E8956B covers 18% of the reference but only 3% of the scene.”
• “Only 41% of the scene is close to the palette. The Off-palette view shows where.”

When the scene matches well, the hints say so with a green check: “The value structure matches the reference (86%).” If nothing stands out, the list says “Nothing stands out.”

Hint	Appears when
Darker, brighter	The mean lightness differs by 6 L* or more.
Cooler, warmer	The colour cast of the near-neutral pixels differs by 4 or more on the blue to yellow axis (b*), measured the way Match colours measures it.
Low or high contrast	The scene has less than 75 % or more than 133 % of the reference’s contrast.
Band areas	A value band’s share differs by 15 points or more.
Missing colour	A palette colour covers at least 8 % of the reference, but the scene uses less than a quarter of that.
Off-palette	Less than 60 % of the scene is close to the palette.
Match	Value structure or palette score of 80 % or more.

The darker, brighter, cooler, warmer and contrast hints have a Match colours link: it solves the Match colours card right away, with suggested post-process values previewed in the viewport.

Match colours

The Match colours to the reference card on this page suggests the exposure, white balance, saturation and contrast that bring the viewport closer to the reference, previews them, and applies them to a camera or a Post Process Volume in one undoable step. See Match colours.

Tip

Compare after each lighting pass and keep the captures on the board. The value structure score is the one to watch first: a frame with the right big shapes of light and dark reads like its concept even before the colours are right.

Without a viewport

From Python, compare_image_files() compares two image files, for example a render and a concept, without a level or viewport, and compare_viewport() runs the comparison above. Both return the scores, statistics and hints. See Python.