Check Push Processing Conditions Before You Shoot Tri-X 400 at EI 1600

This guide covers how many stops apart each speed is, how much longer development runs, and what to tell the lab.

How is push processing different from normal development?

Push processing means shooting at a higher speed number than the one on the box and making up for it with longer development. Kodak describes it for dim light, freezing fast action and shooting by available light. The trade-off is less shadow detail and coarser grain.

The 400 on the box is the film's speed. The number you actually set when shooting is called the EI (exposure index). If you shot a roll with the camera set to 1600, that roll is EI 1600.

Tri-X 400 comes in 135 and 120 formats. Kodak's product page lists 135 in 24 and 36 exposures and 120, and says the film can be used for push processing.

What changes when you raise the speed from 400?

Every doubling of the speed number is one stop. From 400, 800 is one stop, 1600 is two stops and 3200 is three stops higher.

Checked on 2026-10-23. The table is based on Kodak's Tri-X 320 and 400 technical data (F-4017, October 2021). EI 800 takes normal development. The film's wide exposure latitude lets you underexpose by one stop and still use the normal development time, according to Kodak's data. For two and three stops, Kodak tells you to find the right speed with test rolls.

How much longer does development take?

The values below are Kodak's for a small tank at 20°C (68°F) with agitation every 30 seconds. They are starting points for people who develop at home.

Even for the same roll, the times change with the developer, dilution, temperature and agitation method. In the small-tank table, T-MAX developer is marked NR (not recommended) at 18 to 22°C under EI 3200. A note beside the table says tank development shorter than 5 minutes can be uneven. The normal HC-110 (B) time falls in that range.

What should you check on the camera?

Look in the camera manual to see whether you can set the speed to 1600 or 3200 yourself. If the camera reads the speed from the film canister automatically, check whether exposure compensation can achieve the same result.

For a first try, shoot one roll at EI 800, have it developed normally and look at the shadow areas. Then test EI 1600 on the next roll so you can compare the same kind of scene. Keep each roll to a single speed, because the development time applies to the whole roll at once.

What should you tell the lab when you drop off the film?

Say these four things at drop-off or write them on the order note.

1. The film name and format, for example Tri-X 400, 135.
2. The EI you shot the whole roll at, as a number such as 800 or 1600.
3. Ask first whether they develop black-and-white film and accept push processing.
4. If they do push, ask how they choose the developer and time, and whether there is a separate way to submit pushed rolls.

The development times above are Kodak's starting points, so you can't assume a lab uses the same values. Ask whether the lab sets its own conditions, and submit rolls separately if their EI values differ. For color film the process is different, so read the C-41 lab checklist first. You can read how black-and-white, color and slide film differ in the film type comparison.

Write the EI number on the film canister too. With several rolls, it is easy to mix up which roll was shot at which speed.