Contrast, black point, white point, and gamma

Summary

Four sliders in Adjust — Contrast, Black point, White point, and Gamma — tune an image layer's tonal range. All four are non-destructive: they're recomputed live from the original pixel data every time, so returning a slider to its default restores the image exactly.

Use it when

• The source image is flat or low-contrast and needs more punch.
• Shadows or highlights need to be pulled in or opened up.
• The midtones need to look brighter or darker without clipping the extremes.

Before you begin

Select a single placed image layer — these four controls are in Adjust alongside Crop, and are not available for shape, path, text, or template layers.

Steps

1. Select an image layer, then open Adjust.
2. Drag Contrast to increase (right of center) or decrease (left of center) the difference between light and dark areas.
3. Drag Black point up to force darker tones toward pure black, clipping shadow detail.
4. Drag White point down to force lighter tones toward pure white, clipping highlight detail.
5. Drag Gamma above 1.00 to brighten midtones, or below 1.00 to darken them, without moving pure black or pure white.
6. Return any slider to its default (Contrast 0%, Black point 0%, White point 100%, Gamma 1.00) to remove that adjustment exactly.

What changes

• All four adjustments apply to the selected image layer only, live, and are recomputed from the original image data every time — confirmed by sampling the same pixel before an adjustment, after several different slider values, and after returning to default: the pixel's color returned to its exact original value (within 1 unit of rounding) every time.
• Contrast pushes tones away from (positive values) or toward (negative values) the midpoint. A dark-mid-tone pixel at RGB(91, 91, 93) went to pure black at Contrast 80% and to RGB(123, 123, 124) — closer to neutral gray — at Contrast −80%.
• Black point and White point clip and stretch the tonal range from either end. Raising Black point to 30% took that same pixel from 91 to 21 (crushed toward black); lowering White point to 50% took it from 91 to 183 (stretched toward white).
• Gamma brightens or darkens midtones without affecting the extremes. Gamma 2.00 took the sample pixel from 91 to 152; Gamma 0.50 took it from 91 to 33.

Print note

These four adjustments change the actual pixel values used for export, not just an on-screen preview — the sampled RGB changes above are real data changes, confirmed by reading them directly off the rendered canvas. This article does not verify how these adjustments interact with the placeholder color profile noted in RGB, CMYK & print color.

Warnings and limits

• Pushing Contrast, Black point, or White point far enough clips tonal detail to pure black or pure white — that detail is not recoverable by adjusting the same slider back, though since the adjustment is recomputed from the original image each time, returning the slider to default does restore the original detail. The loss is only "live" while the extreme value is set, not permanent.
• These sliders affect only the selected image layer. Multiple image layers each need adjusting individually — there is no artboard-wide version of these controls (contrast with Filter scope: Artboard belongs to Creative presets, and is a different feature).

Desktop and mobile

Contrast, Black point, White point, and Gamma are reachable the same way on desktop (inline in Adjust) and mobile (the Adjust sheet from the bottom bar) — all four were confirmed present in the mobile sheet once an image layer was selected.

Troubleshooting

Related topics

• Crop and framing
• Effective DPI and resolution warnings
• RGB, CMYK & print color
• Creative presets and Pointillism

Verification note

Verified against Blotter Builder on 2026-07-20.

Source notes

Primary observations — all from the live application at https://blotterbuilder.tdl.fyi, 2026-07-20, using the built-in demo artwork placed via Fill canvas. Effects were measured by reading getImageData directly from the rendered lower-canvas at a fixed pixel coordinate before and after each slider change, rather than by eye — this gives exact before/after values rather than an approximate visual impression.

• Observed — slider ranges: Contrast −100% to 100% (input range −1 to 1), Black point 0% to 100%, White point 0% to 100% (default 100%), Gamma 0.20 to 3.00 (default 1.00).
• Observed — at a fixed sample pixel starting at RGB(91, 91, 93): Contrast 80% → RGB(0, 0, 0); Contrast −80% → RGB(123, 123, 124); reset to Contrast 0% → RGB(91, 91, 92) (original, within rounding).
• Observed — same pixel: Black point 30% → RGB(21, 21, 23); reset, then White point 50% → RGB(183, 183, 185); reset to White point 100% → RGB(91, 91, 92).
• Observed — same pixel: Gamma 2.00 → RGB(152, 152, 154); Gamma 0.50 → RGB(33, 33, 34); reset to Gamma 1.00 → RGB(91, 91, 92).
• Observed — the measured Black point and White point results matched a standard linear remap to within rounding — e.g. Black point 0.3 on an input of 91/255 ≈ 0.357 predicts (0.357 − 0.3) / (1 − 0.3) × 255 ≈ 20.8, matching the observed 21 — and the Gamma results matched input^(1/gamma) (e.g. Gamma 2.0: 0.357^0.5 × 255 ≈ 152.3, matching the observed 152). Noted here as a technical confirmation, not as documented product behavior the app guarantees.
• Observed — at 390 × 844, opening Adjust with an image layer selected showed all four sliders present in the mobile sheet.

Verification log