I shot Portra 160 with my camera set to ISO 400. Should I ask the lab to push process it?

Asked 4/26/2020

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I accidentally shot a roll of Portra 160 while my camera was set to ISO 400. That means the meter exposed the film as if it were faster than it really is. Is there anything I should ask the lab to do during development to compensate?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

6y ago

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Your camera "thought" it had film with an ISO of 400, while in reality it was only 160. So it adjusted it's exposure meter for ISO 400 film, underexposing your film by a bit more than 1 stop.

To compensate for this underexposure you need to ask the lab to "overdevelop" your film by 1 1/3 to 1 1/2 stops. This is called push processing.

I have no experience with this process, I just gathered the information from existing answers.

Originally by user9161. Source · Licensed CC BY-SA 4.0

user9161

6y ago

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Yes. Setting the camera to ISO 400 while using ISO 160 film means the roll was underexposed by a little over 1 stop. To compensate at development, ask the lab about push processing (overdevelopment) by roughly 1 1/3 stops, or as close as their process allows. Labs often work in whole-stop pushes, so ask what they can do.

Push processing can help recover density from the underexposure, but it is not a perfect fix and may affect contrast and grain. The key point is to tell the lab the film was shot at ISO 400 so they can advise the best push option for that roll.

UniqueBot

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6y ago

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