If I push 160iso film by 2 stops, and shoot a scene at 1/500 @ f16 as if I would have shot it with 400iso film at 1/500 @ f16, will I get a similar exposure by pushing the 160iso film?

Basically, if I push film can I keep all other settings such as aperture and shutter speed the same or do I have to change them as well in some way?


When you push an ISO 160 film in camera to 400, you are under exposing it by about 1.5 stops. When underexposed, pushing the film in developing is usually pretty forgiving so long as you don't overdo it.

What you're effectively doing is telling your meter that the film is more sensitive to light than it really is.

When pushed in the developer, the grain will become more apparent and although the contrast will be greater, the change in contrast isn't uniform across the light and dark areas of the image so the end result won't be the same as exposing it as ISO 160, although it could well look excellent.

If you're looking to experiment with it to see what effects you can create, then you have nothing to lose by giving it a try.

I know a few photographers who routinely push their film for more contrast simply because they like it, however when they need the results to be consistent (such as when they're doing a shoot for a client), they tend to favour a more sensitive film and expose it at the recommended ISO.

One big advantage of pushing an ISO 160 is that with it not being a particularly sensitive film, the grain will potentially be pretty tight which will mitigate the effect of the more apparent grain when pushed in the developer.

That is of course a massive generalisation. Some films are much more tolerant of being under/over exposed than others, so it might be worthwhile doing a little research on the specific film you're using to see if you can find some images which have been pushed.

Personally, I'd give it a try just to have a point of reference, but it's dependant on what you're shooting and who the images are for.

If its your own project, just go for it and see what you think.

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When you underexpose film and compensate by pushing it in development, you will typically see more grain in the highlights, increased contrast, and reduced shadow detail -- all of this heavily dependent on lighting conditions, film and developer. Lots of variables.

So yes, if you intend to push your ISO 100 film two stops, you would expose it as if it were an ISO 400 film.

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The reason you need to "push process" ISO 160 film metered at ISO 400 is because you "pulled exposure" by 1 1/3 stops when you shot it. That is, you underexposed your film by metering at ISO 400 when your film is only ISO 160. So you then need to overdevelop the film by 1 1/3 stops to compensate.

The language can be confusing because many photographers say they "pushed the film" when they shot it when they really mean they "pulled" exposure (intentionally underexposed the film) and now need to "push" the processing to compensate for the underexposure.

You can also do the opposite: You can push exposure when shooting and then pull in development. That is, you can use metering for ISO 160 when you have ISO 320 film in the camera. However, in that case you'll probably have some blown highlights if the scene is very high contrast.

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  • Thanks this helps me understand better the concept. Indeed it’s quite confusing to a novice ! – MFJC Apr 4 '18 at 22:08

If I push 160iso film by 2 stops, and shoot a scene at 1/500 @ f16 as if I would have shot it with 400iso film at 1/500 @ f16, will I get a similar exposure by pushing the 160iso film?

If your proper exposure using 100 speed film metered at 1/500 @ f16, and you wanted to push the film to 400 - then you need to change the exposure settings to what would be a proper meter using 400 speed film. In this case, 1/2000 @f16 (2 stops faster) changed the question to use 100 ISO to make the math easier

Obviously, this is under-exposing your film by 2 stops. You need to compensate for this by over-developing.

For example, Ilford Delta 100 shot at ISO 100 and processed in 1+4 DDX needs 12 minutes of development.

Delta 100 shot at ISO 400, also processed in 1+4 DDX needs 23 minutes of development.

This process, of intentionally underexposing film and overdeveloping, is push-processing.

The reverse can also be done (pull-processing).

Film and developer combos already have unique characteristics, and those change again when pushing or pulling, and more so depending on how much you push or pull a film. Some handle it well, others not so much. So, experiment away.

I would not develop myself unfortunately for the moment but it’s something I want to try with B&W in the future. Just got to find a good way to scan the negatives.

I would strongly encourage you to invest in some development supplies. All you really need is a Patterson tank and a change bag and you're set. Film/developer combos is a part of the fun of shooting B&W film. But, it's understandable that this isn't feasible all the time.

When using a lab, make sure you are absolutely clear that you need push processing done by X stops. Pro photo labs can do this easily. The local drug store, not so much.

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  • I’m still confused regarding the pushing. Do you have an article you would recommend ? For the development, I’d love to do it but then I need a scanner for the negatives. Do you recommend a cheap and good one ? – MFJC Apr 4 '18 at 18:25
  • @MFJC - I don't have a favorite article for you - I'd recommend reading a lot of material by googling and post clarifying question here on Photo.SE. RE: Scanning - good scanners are super expensive and cheap ones super crappy. You'll get better results by getting a lab to do the scans. My scanner is an Epson v850 - and while I like it and it does a good job - it is very time consuming to use. It's definitely a labor of love that is NOT for everyone. – OnBreak. Apr 4 '18 at 18:50

If you're shooting with 160 ISO film, two-stop push processing would normally mean you exposed the film as if it were ISO 640. But, in short answer to your question, "yes". And some films work better for push/pull processing than others, so if you plan to do much of this, I'd suggest doing some research (look at the results from others people's experiments with the pushability of the films you normally like), then experiment with what looks most promising.

I self-loaded my 35mm film spools and in medium format, I only owned older cameras with no sensors for DX codes or anything, so I have to confess that the only times I ever had film "push processed", aside from maybe one or two experiments, was if I noticed I'd accidentally underexposed a roll (or three). Then push processing might help make up for my mistake. But if you want to shoot at ISO 400, you'll almost always have better results with film made for that, than with ISO 100 film pushed two stops. (And if you're not doing your own "push-processing", labs often charge extra for it, which makes it even less "worth it"). The only other reason you might want to push process film would be for those times when you're ready to shoot, but don't have the right film for the situation. IMHO, it's better to be prepared and have the right film in your bag. But otherwise, it's good to know what to expect from the film you use, so go ahead and push a roll one stop and another roll two stops and compare the results to similar exposures taken with faster film, and see if "push processing" is the solution you want to fall back on when you "need" greater light sensitivity.

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  • Thanks for your feedback. So iso 100 isn’t good to push ? What iso is better? For when you said “yes” to my question are you referring to the original post ? – MFJC Apr 9 '18 at 20:13
  • You’re right I’ll check which films are more suited. At the moment I’m planning to push ilford 100iso delta at 500 so 5 stops right ? I know hat pushed 2/3 times it’s nice based on reviews I saw. – MFJC Apr 9 '18 at 20:15

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