Why higher ISO means more grain
Faster films need to catch more light, and they do it with larger light-sensitive crystals. Larger crystals mean larger, more visible grain, and a rougher overall texture. Slow films use smaller crystals, so they look smooth but need more light.
In FilmGrainLab one ISO slider from 160 to 3200 moves grain amount, particle size and roughness together, so each step looks like a different film speed instead of the same noise turned up.
What each step looks like
These are approximate descriptions. The slider is calibrated against how real film behaves, but it is a starting point and not an exact copy of any one stock.
| ISO | Look | Good for |
|---|---|---|
| 160 | Very fine. Visible only when zoomed in, adds a gentle texture. | Portraits and landscapes where you want a soft analog feel |
| 400 | Fine and even. Noticeable at 100%, subtle at normal viewing size. | An all-round default for most photos |
| 800 | Clearly visible. The classic look of fast color film. | Street photography, indoor and evening scenes |
| 1600 | Coarse and rough, with bigger clumps of grain. | Moody, gritty or low-light looks |
| 3200 | Heavy and dominant. Similar to strongly pushed black and white film. | Deliberate, stylized results |
How to choose
- Match the scene. A bright daylight portrait rarely needs more than ISO 400. A night street scene can carry ISO 1600 without looking out of place.
- Match the destination. Photos viewed small on a phone can take a higher ISO than a photo you plan to print large, where coarse grain becomes very obvious.
- Check at 100%. The overall view hides grain structure. Zoom in before settling on a value.
Grain size scales with your photo on export, so a 9-megapixel image and a 60-megapixel image get the same relative look at the same ISO, with no need to re-tune the slider for each file.