Two small things at the end of an AI prompt have an outsized effect on your results: the aspect ratio and the parameters. Get them right and your image fits its purpose perfectly; get them wrong and you waste half the frame or fight the model. Here's a plain-English guide.
What is an aspect ratio?
Aspect ratio is the shape of your image — the relationship between width and height. It's written as width:height. A 1:1 image is a square; 16:9 is a wide landscape; 9:16 is a tall portrait (like a phone screen). Choosing the right ratio before you generate saves you from cropping later, which loses resolution and often chops off your subject.
Which ratio to use where
Match the ratio to where the image will live:
- 1:1 (square) — social posts, avatars, product tiles, app icons.
- 16:9 (wide) — YouTube thumbnails, website heroes, presentation slides, video.
- 9:16 (tall) — Instagram Stories, TikTok, Reels, phone wallpapers.
- 4:5 (portrait) — Instagram feed portraits, which get more screen space than square.
- 3:2 / 2:3 — classic photography ratios, prints, editorial.
- 4:3 — traditional screens, some cameras, a balanced everyday shape.
A portrait subject in a wide frame leaves awkward empty sides; a landscape squeezed into a tall frame crops the scene. Think about the destination first.
Setting the ratio in each tool
- Midjourney: add
--ar 16:9(or any ratio) at the end of the prompt. - DALL·E 3: ask in words ("a wide 16:9 image") or choose the size in the interface.
- Stable Diffusion: set the width and height directly (e.g., 1344×768 for roughly 16:9).
What are parameters?
Parameters are settings — usually flags at the end of a Midjourney prompt — that control how the model generates, separate from what it draws. The most common:
- --ar — aspect ratio, as above.
- --v — the model version (e.g.,
--v 6). Newer versions generally look better and follow prompts more closely. - --stylize (or --s) — how much artistic interpretation the model applies. Low values stick close to your prompt; high values let the model be more creative and painterly.
- --no — exclude things (
--no text, watermark), the Midjourney equivalent of a negative prompt. - --chaos (or --c) — how varied the initial set of options is. Higher chaos gives you more different directions to choose from.
- --tile — generates seamless, repeating patterns, great for textures and backgrounds.
- --seed — fixes the random starting point so you can reproduce or vary a specific image.
You rarely need more than a couple. For most images, --ar and --v do the heavy lifting.
Stylize, chaos, and creative control
Two parameters shape how "free" the model is. --stylize controls artistic license: raise it for lush, painterly, opinionated results; lower it when you need the model to follow your prompt literally (useful for products and logos). --chaos controls variety in the first grid of options: raise it early in exploration to see many directions, then lower it once you know what you want. Together they let you dial between "surprise me" and "do exactly what I said."
Reproducibility with seeds
If you find an image you love and want variations of that specific one, note its seed and reuse it. Same seed plus same prompt yields nearly the same image; same seed plus a small prompt change yields a controlled variation. Seeds turn happy accidents into a repeatable base — invaluable for consistent characters, series, and A/B-style comparisons.
Common mistakes
- Wrong ratio for the platform. Generating square art for a 16:9 thumbnail wastes resolution.
- Piling on parameters. More flags isn't better; each one should have a reason.
- Ignoring version. An old model version fights you; use the current one.
- Cranking stylize for literal work. High stylize on a logo or product shot invents details you didn't want.
A simple default
For most people, a reliable default looks like this in Midjourney:
[your full prompt] --ar [ratio for your use] --v 6
Add --no if you keep getting unwanted elements, lower --stylize when you need literal accuracy, and reach for --seed only when you need reproducibility. That's genuinely all most projects require.
The takeaway
Aspect ratio decides whether your image fits its purpose; parameters decide how the model interprets your prompt. Choose the ratio for the destination, keep parameters minimal and intentional, and reserve the advanced flags for when you have a specific reason. Master these small settings and every prompt you already know how to write will land more precisely. Explore the image prompt library to see how ratios and parameters are set in real, working prompts.
Key takeaways
- Aspect ratio is the shape of your image; choose it for the destination before you generate.
- Use 1:1 for social and avatars, 16:9 for thumbnails and heroes, and 9:16 for Stories and Reels.
- Parameters control how the model generates — for most images, --ar and --v do the heavy lifting.
- Lower --stylize for literal work like logos and products; raise it for lush, painterly results.
- Reuse a --seed to reproduce a specific image or make controlled variations of it.
- Keep parameters minimal and intentional — more flags is not better; each should have a reason.
