Why Pull instead of Push?

danalec99 · Jan 9, 2005

While I was browsing through Bambi Cantrell's work in her book, I noticed that in most of the images, she pulled her 3200 film to 1600

-Why not 400 pushed to 1600?
-What difference does both the action make?
-Is 1600 in both the process same?

Thanks,
Daniel

photobug · Jan 9, 2005

Push processing increases the grain, pull processing would decrease the grain.

So 400 pushed to 1600 would be grainier than 3200 pulled to 1600. Theoretically anyway. If this is actually true I can't say.

danalec99 · Jan 9, 2005

photobug said:
Push processing increases the grain, pull processing would decrease the grain.

So 400 pushed to 1600 would be grainier than 3200 pulled to 1600. Theoretically anyway. If this is actually true I can't say.

Thanks photobug. This is an interesting piece of information.

walter23 · Jan 9, 2005

photobug said:
So 400 pushed to 1600 would be grainier than 3200 pulled to 1600. Theoretically anyway. If this is actually true I can't say.

That makes sense. I'm still not sure I understand what pushing or pulling actually is - is it a processing thing (like temperature or timing during development), or an exposure thing? If it's an exposure thing, for me it's easier to just think of it in terms of underexposing or overexposing.. in which case pushing (underexposure) would give flatter images with more grain, and pulling (overexposing) would give high contrast and color saturation.

oriecat · Jan 9, 2005

It's both. You expose at the other ISO, then you have to compensate the development.

Unimaxium · Jan 9, 2005

It's both exposing and processing; you use variations in processing time to compensate for under/over exposure. So for pushing you underexpose and then overdevelop, and for pulling you overexpose and then underdevelop. That way the picture on the negative essentially comes out as if it were exposed normally and developed normally (not counting things like graininess, etc.).

photobug · Jan 9, 2005

Yes, it's exposure. Either in-camera, or in the darkroom (accidently or purposely).

I think it's the other-way-round, but I'm reaching the edges of my knowledge base since I've never set foot in a darkroom in my life.

I think Kodak had some info about this on their site, which is probably where I got the info.

Perhaps one of our subject-knowledgeable esteemed forumites will bail my butt out here?

Unimaxium · Jan 9, 2005

I don't think it's the other way around. Because when you push (increase ISO), you're increasing the ISO setting on the camera, which means the camera thinks the film is more sensitive than it really is, which means the camera thinks the film takes less light to expose correctly, which means it is underexposing. And then you overdevelop to compensate. And pulling is the opposite.

Jamie R · Jan 9, 2005

"While I was browsing through Bambi Cantrell's work in her book, I noticed that in most of the images, she pulled her 3200 film to 1600"

Bambi like many other photographers, recognise that the nominal ISO of Ilford Delta 3200 or even Kodak TMax 3200 is not ISO 3200. Ilford Delta's ISO according to densitometry scales indicate it is closer to ISO 1000.

That means that to develop Delta 3200 at ISO 3200, it requires "push-processing'. Arguably then Delta 3200 is only considered normally exposed at 1000 and photographers all rely on the developer to add the extra speed to make it up to 3200. This is possible because Delta 3200 film 'pushes well'.

-Why not 400 pushed to 1600?

Good question. This question has been asked around other forums (usually in winters where the nights are long). Tri-X, HP5+ can be pushed to 1600. The results are not just 'grainier', but the tonal scale loses out the middle-values and becomes mostly 'blocked up' shadows' and 'white lights'. It can look 'too gritty' for some people's tastes.

If film is developed in a lab according to instructions (or equally as well in a home darkroom), then underexposing film and extending development times [push-processing] or over-exposing film and cutting development times [pull processing] is straight-forward. This is more commonly practiced on black and white film. It's possible to do on colour negative and colour slide film too.

ksmattfish · Jan 10, 2005

A "push" is a deliberate under exposure with the intention of increasing development time to compensate. Results vary from film to film, but it usually increases contrast.

A "pull" is a deliberate over exposure with the intention of reducing development time to compensate. It tends to decrease contrast.

On an overcast day (low contrast) I like to underexpose and overdevelop to increase my contrast, while on a bright, sunny day (high contrast) I overexpose and underdevelop to decrease contrast.

I would say that shooting film labeled ISO 3200 at ISO 1600 is not really a pull, because, as has been mentioned, it's not really ISO 3200 in the first place. For instance notice that Tmax 3200 is really Tmax 3200p. That little "p" stands for "push". Depending on the developer you use Tmax 3200p is actually only ISO 800 to 1000. So shooting it at ISO 1600 is still a push. Read the small print in the tech pubs for Kodak, Ilford, or Fuji high speed films, and you'll find that to get the ISO on the label, it's a push.