CIE L*a*b* Photo Editor

Split tone from colour.

In RGB, brightness is baked into every channel — turn down red and the picture gets darker as well as less red. Lab pulls them apart. One channel carries all the tone. Two carry all the colour. Change one without disturbing the other.

Now available for iPhone and iPad See what it does

iPhone and iPad, iOS 17 or later. No account. No ads. Your photos never leave the device.

Lab Channels?
Original Invert a
LabLightnessab
LightnessInvert
aInvert
bInvert
ExclusionInverted a against the original Linear LightInverted Lightness, driven hard
LAYERS
Layer 1Exclusion · 100%
BackgroundBackground
Save to Photos
What it does

Three channels, edited separately.

Lightness holds every bit of tone in the photograph. The a channel runs green to magenta. The b channel runs blue to yellow. Neither colour channel knows anything about brightness, which is exactly why they are useful.

See any channel alone

Tap Lightness, a, or b to view that channel by itself as greyscale — the fastest way to tell whether an edit has anything to work with.

Invert, brighten, push

Each channel gets its own invert, brightness, and contrast. Invert the tone channel and clouds go black while grass stays green.

Swap the colour axes

Trade a and b to rotate every hue in the frame at once, leaving the tone completely untouched.

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Layers and blending

Duplicate the photo, edit the copy's channels, and blend the two. All 24 blend modes, including Luminosity and Colour.

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Out-of-range colour

Pushing a colour channel sends much of the frame beyond what a screen can show. Choose whether it eases back or clips hard.

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Full-resolution export

Editing happens on a preview so it stays immediate. Saving re-runs everything against your original full-size photo.

Workflow

Four minutes to understand it.

01

Open a photo with sky and greenery. Landscapes show the effect most clearly.

02

Tap through Lightness, a, and b. Watch what disappears each time.

03

Invert the a channel. Foliage turns rust while the sky barely moves.

04

Duplicate the layer, blend the copy, then save at full resolution.

Questions

FAQ

What is Lab, in one sentence?
A way of describing colour that keeps brightness in its own channel, so tone and colour can be edited independently rather than tangled together as they are in RGB.
Which channel should I reach for?
Move the channel the colour you care about actually sits on. Greens and skin live on a. Skies and warm light live on b. Anything about brightness is Lightness. Inverting a transforms grass and leaves a blue sky almost untouched, because sky is a b-channel colour.
Does it change my original photo?
No. The original stays in your library untouched. Saving writes a new image.
Why does the app ask about out-of-range colour?
The colour channels are unbounded but your screen is not, so editing one pushes a large share of the frame outside what can be displayed. Preserve eases saturation back until the colour fits, holding brightness and hue. Clip cuts at the boundary, which flattens detail into solid blocks — useful when you want the poster look on purpose.
Does it work on iPad?
Yes. iPhone and iPad, iOS 17 or later.
Does the app upload my photos?
No. The app has no network access at all. Photos are read when you pick them and written back only when you ask. See the Privacy Policy.
Get it

Available on the App Store.

iPhone and iPad, iOS 17 or later. Questions and bug reports welcome.

Now available on the App Store Get Support