Film ISO Guide for Beginners: Which Speed Should You Buy?

If you're new to film photography, ISO is one of the first things you'll need to understand. It's printed on every box of film, it affects how your photos look, and choosing the wrong ISO for your situation can mean underexposed, unusable frames.

The good news is that it's simpler than it sounds. Here's everything you need to know.

What is ISO?

ISO measures how sensitive a film is to light. A lower ISO number means the film is less sensitive and needs more light to produce a correct exposure. A higher ISO number means the film is more sensitive and can work in lower light conditions.

The trade-off is grain. Higher ISO films produce more visible grain. Lower ISO films produce finer, smoother images. This isn't necessarily a bad thing. Grain is part of the aesthetic of film photography, but it's worth understanding before you buy.

ISO 100: bright light, fine grain

ISO 100 films are the slowest and finest-grained option. They're designed for shooting in bright, even light. Sunny days, studio setups with plenty of artificial light, or any situation where you have full control over your exposure.

Kodak Ektar 100 is a great example: hyper-saturated, ultra-fine grain, and stunning in good light. The limitation is that in shade, indoors, or on overcast days, you'll struggle to get a correct exposure without a tripod or very wide aperture.

Best for: Landscapes, architecture, studio photography, bright sunny days.

ISO 200: the versatile middle ground

ISO 200 is a step up in sensitivity with a modest increase in grain. It's a good all-rounder for outdoor shooting in mixed light. Bright shade, partly cloudy days, or situations where the light is good but not perfect.

Kodak Gold 200 is the classic choice here. It's warm, punchy, and performs beautifully in daylight. It's also more affordable than professional stocks, making it a great option for everyday shooting and travel.

Best for: Outdoor shooting in good light, travel, everyday photography.

ISO 400: the everyday workhorse

ISO 400 is the most versatile speed for most photographers. It's fast enough to shoot in open shade, indoors with window light, or on overcast days without flash. It's also fine-grained enough to produce excellent results in bright conditions.

Kodak Portra 400 is the gold standard at this speed. It's the film that professional photographers reach for when they need reliability across a wide range of conditions. If you're only going to keep one film in your bag, ISO 400 is the right choice.

Best for: Everything. Portraits, events, travel, street photography, indoors, outdoors.

ISO 800 and above: low light and push processing

ISO 800 films are designed for low-light situations where you need every bit of sensitivity you can get. Kodak Portra 800 is the most refined option at this speed. It retains good skin tones and manageable grain even in challenging conditions.

Beyond ISO 800, most photographers push their film rather than buying a higher-speed stock. Pushing means rating your ISO 400 film at 800 or 1600 and asking your lab to develop it accordingly. The result is increased contrast and grain, which can be a desirable aesthetic choice.

Best for: Indoor events, evening shooting, concerts, any situation with limited light.

The simple rule

When in doubt, buy ISO 400. It's the most forgiving, the most versatile, and the most widely used speed for a reason. As you get more experience, you'll develop a feel for when to reach for something slower or faster.

Start with Kodak Portra 400 or Kodak Gold 200 and go from there.