Something about film cameras i cant understand...

[timmyquest]

I keep seeing people refer to "pushing the ISO up" on film cameras. I dont understand how this would...work.

I tried to search it, but with digital photography becoming so popular i found very little.

[primoz]

In very very short explanation it works so that you have ISO 100 film, which you expose as ISO 50 (pull) or ISO 200 (push). If you would develop this film normaly you would get over/under exposed film, so you need to develop it differently. I have no idea how it's done with processing machines (since everything ends with pressing button :) ), but I guess it has to be same as home developing, where you need shorter or longer developing times for push or pull processing.

[Moppie]

I found a referance to setting the ISO one step up from the actual film used.
Apprently it helps stop over exposure in some situations.

But I have less than zero actual experiance.

[PacAce]

Most photographers have a favorite film that they use. And usually, it's a low ISO film, like 50 or 100 since the lower the ISO, the better the image quality. Now, if the only film they have is a low ISO film but they're caught in a situation where they need to shoot in low lighting situations where they can not (or don't want to) use flash, then their only alternative is to push the ISO up a stop or two. They may have an ISO 100 film in the camera but they'll set the ISO on the camera to 200 or even 400. This underexposes the film so the film has to be processed a little longer than normal to get out the details on the film. When you push a film, the whole roll has to be shot at the pushed ISO speed because you cannot selectively process individual frames in a roll for a specific ISO setting. There are several types of films that are push or pull friendly. However, most average rolls tend to produce degraded images and worse grains when pushed more than just slightly.

[timmyquest]

Most photographers have a favorite film that they use. And usually, it's a low ISO film, like 50 or 100 since the lower the ISO, the better the image quality. Now, if the only film they have is a low ISO film but they're caught in a situation where they need to shoot in low lighting situations where they can not (or don't want to) use flash, then their only alternative is to push the ISO up a stop or two. They may have an ISO 100 film in the camera but they'll set the ISO on the camera to 200 or even 400. This underexposes the film so the film has to be processed a little longer than normal to get out the details on the film. When you push a film, the whole roll has to be shot at the pushed ISO speed because you cannot selectively process individual frames in a roll for a specific ISO setting. There are several types of films that are push or pull friendly. However, most average rolls tend to produce degraded images and worse grains when pushed more than just slightly.

So really it's just a method to throw off the cameras metering system?

You may put the film in developer for 10 mins usually, but now you put it in for 20?

Kind of like shooting in RAW then just upping hte exposier?

[PacAce]

So really it's just a method to throw off the cameras metering system?

You may put the film in developer for 10 mins usually, but now you put it in for 20?

Kind of like shooting in RAW then just upping hte exposier?

Yup, it's something like that.

[jrobert]

So really it's just a method to throw off the cameras metering system?

You may put the film in developer for 10 mins usually, but now you put it in for 20?

Kind of like shooting in RAW then just upping hte exposier? I wouldn't call it throwing off the metering, any more than changing ISO in your digicam throws off the metering. Your meter or camera will still accurately measure or make an exposure, but for a more sensitive medium. The effective sensitivity of the medium has to include the knowledge of how the captured signal (exposed silver halide or the sensels' electrical outputs) will be processed. When you "push" a medium, you are processing it differently , and you'll get a different effective sensitivity. There may be trade-offs in doing so, and the manufacturer has chosen a set of trade-offs for you when they specified the sensitivity, but there's no reason why you can't make a different choice, if you have control of the necessary variables - e.g., the development time, or the signal processing, in these two cases.

-jeff-

[timmyquest]

I wouldn't call it throwing off the metering, any more than changing ISO in your digicam throws off the metering. Your meter or camera will still accurately measure or make an exposure, but for a more sensitive medium. The effective sensitivity of the medium has to include the knowledge of how the captured signal (exposed silver halide or the sensels' electrical outputs) will be processed. When you "push" a medium, you are processing it differently , and you'll get a different effective sensitivity. There may be trade-offs in doing so, and the manufacturer has chosen a set of trade-offs for you when they specified the sensitivity, but there's no reason why you can't make a different choice, if you have control of the necessary variables - e.g., the development time, or the signal processing, in these two cases.

-jeff-

Thats the cherry on top, makes plenty of sense to me now.

[Jon]

. . . or you could just think of it as a way of expanding the histogram in post-processing.

[CyberDyneSystems]

For years,.. many shooters of Velvia pushed it.. claiming to get better results than at the "stock" rated ASA.

[Tom W]

. . . or you could just think of it as a way of expanding the histogram in post-processing.
Or at least sliding it one way or another.