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Images & Audio

Changing one thing at a time is the only way to learn what an image prompt does

Image prompts accumulate untested words because everything is edited at once, and a habit that costs a few extra generations turns guesswork into something you can actually build on.

By Adrian Novak4 min read

Editorial note. Independent reporting and analysis. Nothing here is sponsored or paid for. How we work.

Prompt soup and where it comes from

Look at any long-lived image prompt and you will find a tail of terms nobody can account for. Something about volumetric lighting, a couple of quality words, a resolution that means nothing here, an aspect instruction contradicted by another one. Each was added during a session where several things changed at once and the result improved.

The improvement was then attributed to all of the changes together, because there was no way to tell which one did the work. Over a few weeks a prompt accumulates a dozen of these, most of them inert, some actively fighting each other, all of them consuming influence that could have gone to the parts that matter.

The cost is not just clutter. A prompt you do not understand cannot be adapted, so the next task starts from copying and hoping rather than from anything you learned.

One variable, then look

The discipline is unglamorous and it works. Change one element, generate, compare against the previous result, keep or discard. With whatever mechanism the tool offers for holding the random element fixed, the comparison becomes genuinely clean and you can see exactly what the word did.

Without that mechanism you need two or three generations per variant, because a single image tells you about that image rather than about the change. This is more work than most people want to do, and it is the difference between having a technique and having a superstition.

What you are building is a small personal vocabulary of terms whose effect you have actually observed. Ten reliable words are worth more than a hundred inherited from someone else’s screenshot, and they transfer to new subjects because you know what they are doing.

Order and weight are part of the prompt

Position matters in most of these tools, generally in the direction of earlier terms carrying more influence. That means moving a word without changing it is itself an experiment, and one worth running before you conclude that a term does nothing. It may simply have been buried.

Where the tool exposes explicit weighting, the same discipline applies: change one weight, look, decide. Weighting is more precise than adding synonyms, which is the usual improvised alternative and which tends to produce a blurred average of several related ideas rather than more of one.

The related habit is subtraction. Once a prompt is working, remove terms one at a time and see whether anything changes. Most long prompts lose a third of their length with no visible effect, and every term removed makes the remainder easier to reason about.

Subtraction has a second use when you inherit a prompt from somebody else. Strip it back to the terms you understand, generate, then add the rest one at a time until something visibly changes. Most of the time you finish with a shorter prompt and a clearer idea of what the original author was actually relying on.

Keep the record, because you will not remember

A prompt without its output is close to useless six weeks later, and an output without its prompt is entirely useless. Saving the pair, plus whatever the tool provides for reproducing the random element, is the difference between a body of work and a folder of pictures you cannot recreate.

The most valuable thing in that record is not the successes. It is the failed variants with a note on what went wrong, because those are what stop you from spending an afternoon rediscovering that a particular combination never works.

This applies with more force than it does in text work, since image results are harder to describe and much harder to reconstruct from memory. What seemed obvious at the time will not be obvious later.

When to stop refining and start editing

Iteration converges for a while and then stops. The usual sign is that changes produce a different image of similar quality rather than a closer approach to what you wanted. At that point you are sampling rather than steering, and further generations are a lottery with a slowly falling expected value.

The right response is usually to leave the prompt alone. Take the closest result into an editing step — masking a region for regeneration, compositing two outputs, or fixing the problem area by hand — because a local problem is much better solved locally than by re-rolling the entire image and losing everything that was already right.

There is a version of this failure that costs whole days. Someone has a result at ninety per cent, keeps generating in the hope of a perfect one, and finishes with two hundred images and nothing better than the fourth. Recognising a plateau is a skill, and it is mostly a matter of admitting it early.

Common questions

How many images should I generate per variant?

Enough to see past the randomness, which in practice means two or three if you cannot fix the random element and one if you can. A single image from a single variant is a weak signal, and drawing conclusions from it is how untested terms get into prompts in the first place.

Are quality-boosting keywords worth including?

Test them the same way you would test anything else, and expect the answer to vary by tool and to change between versions. Some of these terms had a real effect in earlier systems where captions carried them; in others they do nothing measurable. Inherited lists are the least reliable part of any prompt.

Does the aspect ratio change more than the shape?

Yes, often substantially. Composition adapts to the frame, so a portrait and a landscape version of the same prompt can differ in what is included, how close the subject is and how the background is arranged. Decide the ratio early rather than treating it as a final crop.

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Adrian Novak
Deputy editor, Prompt After Prompt

Adrian has written about prompt craft, writing with ai, images & audio for most of the last decade and prefers a plain explanation to a clever one.