Almost no photograph you see in a magazine, an ad or a portfolio is exactly what came out of the camera. Exposure is corrected, colours balanced, dust removed, sometimes whole skies replaced. The skill is not just knowing which tool does what; it is working so that every change can be undone or adjusted tomorrow, when the client asks for 'a bit less'. And because editing is now so easy and so convincing, every editor also has to know when a change stops being a correction and becomes a lie.
Layers and non-destructive editing
A layer is a separate sheet stacked over the image. Editing directly on the photograph's pixels is destructive: once you brighten, erase or paint and then save, the original pixels are gone. Non-destructive editing keeps the original untouched and stores each change as something you can switch off, weaken or redo. In practice that means three habits: corrections go on adjustment layers, hiding goes on layer masks, and retouching goes on a new empty layer above the photo.
- Brightness applied straight to the pixels
- Eraser used to remove a background
- Clone stamp painted onto the original photo
- One version; every change is permanent after saving
- A Levels or Curves adjustment layer, adjustable at any time
- A layer mask that hides the background and can be repainted
- Cloning onto an empty layer set to sample all layers
- The original survives; any step can be changed or removed
Selections and masks
| Selection tool | How it decides | Best for |
|---|---|---|
| Marquee | A rectangle or ellipse you draw | Simple geometric areas |
| Lasso / polygonal lasso | The outline you trace by hand | Rough selections and straight-edged objects |
| Magic wand / colour range | Pixels similar in colour to the one you click | Plain skies or backdrops |
| Quick selection / select subject | Edge detection, increasingly with machine learning | A clear subject against a different background |
| Pen tool path | A vector outline you build with anchors | Hard-edged products, where a crisp edge matters most |
A selection is temporary; a layer mask turns it into something permanent but editable. A mask is a greyscale image attached to a layer: white reveals, black conceals, and grey partly shows. Because it is just paint, you can fix a bad edge by painting with a soft black or white brush instead of starting the selection again. Hair and fur are the hard cases, which is why programs have a 'refine edge' or 'select and mask' step that detects fine strands, and why a slightly feathered (softened) edge usually looks more natural than a razor-sharp cut-out.
Reading a histogram: Levels and Curves
A histogram is a bar graph of the image's tones. In an 8-bit image the horizontal axis runs from 0 (pure black) on the left to 255 (pure white) on the right, and the height at each value is how many pixels have that brightness. A histogram bunched to the left means a dark, underexposed image; bunched to the right, overexposed; squeezed into the middle, flat and low in contrast. A tall spike against either edge is clipping: detail lost to pure black or white, which no adjustment can bring back. The Levels adjustment moves the black point and white point inward to the edges of the data, stretching the tones to fill the full range.
Retouching: clone and heal
| Tool | How it works | Use it for |
|---|---|---|
| Clone stamp | Copies pixels exactly from a sampled source point | Rebuilding edges and patterns, where texture and colour must match exactly |
| Healing brush | Copies texture from the source, then blends it into the colour and brightness around the target | Blemishes, wrinkles in fabric, marks on skin |
| Spot healing | Like the healing brush, but picks the source automatically | Dust spots and small specks |
| Content-aware fill | Analyses the surroundings and synthesises new pixels | Removing larger objects from varied backgrounds |
The ethics of retouching
Whether an edit is acceptable depends on what the viewer has been promised. News and documentary photographs promise that this is what happened. Major news agencies such as The Canadian Press and the Associated Press allow normal adjustments of exposure, colour and cropping, but forbid adding, removing or moving anything in the frame. Advertising and fashion images are understood to be constructed, so retouching is normal, but there are limits. Canada's Competition Act prohibits materially false or misleading advertising, so an ad that digitally exaggerates what a product does, such as lashes lengthened in editing for a mascara, risks breaking it. Since 2017, France has required commercial photos in which a model's body shape was altered to carry the label 'photographie retouchée'. Dove's 2006 'Evolution' campaign, made in Toronto, became famous for showing exactly how much a billboard face is changed.