Working on a laptop that cannot hold the job

Four separate causes of a slow document

“It has got slow” is four different problems, and the fix differs for each. Diagnose before you start deleting work.

1. Pixel count. A 50-megapixel image in 16-bit is 300 MB per full-resolution layer before anything else. Every operation touches all of it.

2. Layer count and re-compositing. Change one layer and the application re-composites everything above it. Twenty adjustment layers means twenty operations per brushstroke.

3. Smart filters re-rendering. Each smart filter re-runs on every change to its smart object. A Gaussian blur at radius 200 on a large smart object is seconds of work, repeated constantly.

4. Scratch thrashing. The previous lesson’s problem. Watch the efficiency indicator: Photoshop shows it at the bottom of the window if you set the status bar to Efficiency. Below 100 per cent means it is using disk; below 60 per cent means it is mostly using disk and you will feel it.

The five fixes, from cheapest to most drastic

Turn off what you are not looking at. Hide the groups you are not working on. Hidden layers still take memory but are not composited, which addresses cause 2 immediately.

Rasterise finished smart objects. Once the retouch inside a smart object is done and the transform settled, rasterising removes the re-render cost permanently. Save a version first.

Stamp a checkpoint. Ctrl/Cmd+Alt+Shift+E to flatten the visible result onto one layer, then hide everything below it and carry on above. The stack is preserved for a revision and costs nothing to composite while hidden. Name it with the date.

Split the job. Do the retouching in one document at full resolution and save a flattened TIFF. Do the compositing in a second document that places that TIFF. Two 400 MB documents open one at a time beat one 900 MB document open all the time.

Work at reduced size, apply at full. For work that is about placement rather than detail (a rough composite, deciding a crop, testing a grade) do it on a half-size copy. Curves, Levels, Hue/Saturation and most adjustment settings copy across to the full-size file unchanged, because they are functions of tone rather than of pixels. Masks and brushwork do not; those have to be done at full size.

Photopea’s ceiling, stated plainly

Photopea runs in a browser tab, so it lives inside that tab’s memory allocation. In practice this is around 2 to 4 GB depending on the browser and the machine, and there is no scratch disk to overflow into. When it runs out, the tab does not slow down gracefully: it stops or reloads.

What that means in practice: Photopea handles a 24-megapixel photograph with fifteen layers comfortably and will not handle a 100-megapixel poster with forty. Save often, and for large documents use a desktop application. This is not a criticism of Photopea; it is the architecture.

GIMP and Krita both have real tile-based memory management and swap to disk, so they degrade gradually instead. On a machine with 8 GB of RAM, GIMP on a large file will be slow and will keep working, which is often the more useful behaviour.

Working on low-end hardware

A large part of this readership is on a laptop with 4 to 8 GB of RAM, integrated graphics, and a nearly full drive. That is a real constraint and it is workable.

• Downsize at the start, deliberately. If the delivery is a 2,000-pixel web image, working on a 24-megapixel original is not producing quality, it is producing lag. Resize to 3,000 pixels on the long edge before you begin and you have ample margin.
• 8-bit unless the job needs 16. Tonal stretching on a gradient needs 16; a product cut-out with modest adjustments does not.
• Use GIMP or Krita rather than a browser tool for anything large, for the memory reason above.
• Close the browser. Thirty tabs is two gigabytes.
• An external SSD over USB 3 for scratch and files costs about £30 for 500 GB and is the single best value upgrade for this work. More RAM is better and is often soldered on modern laptops; a fast external drive is never soldered.

On a phone

Entirely viable for a real class of work, and worth knowing the limits. Snapseed keeps an editable stack and is free with no ads. Lightroom mobile’s free tier develops raw and DNG parametrically, which is non-destructive. Photopea runs in a mobile browser and is painful to use on a small screen but works. Krita has an Android build.

What a phone does not do: precise masking at 100 per cent zoom, colour-managed print work, or anything with a deep layer stack. What it does well: developing a raw file, straightening, cropping, global tone and colour, and a quick cut-out. For a market trader photographing stock, that covers most of the job.

The limit worth accepting

Some jobs need hardware you do not have. A 200-megapixel architectural composite with sixty layers is not going to happen on an eight-gigabyte laptop, and no amount of technique changes that.

When you meet one, the answer is to reduce the scope of what is open at once (split the document, work in sections, flatten aggressively with versions saved) or to rent time on a better machine. What does not work is spending the day fighting an application and delivering late. Recognising the ceiling early is a professional skill, and telling the client on day one rather than day five is the part that matters.