800 and 1600 pushing

[pteppic]

Am I right in saying that 800 pushed by two stops gives it an EI of 3200?

And am I also right in saying that 1600 pushed by an additional stop

also gives it an EI of 3200?

 

I'm asking since my Minolta X-700 only goes upto ASA 1600, and I

require to set it to ASA 3200. So I'm guessing the easiest way is to

add an additional stop from the 1600 position on the +/- scale.

[steve_dunn2]

<p>More or less. Technically, pushing happens during development, not when shooting, so pushing doesn't change the EI; changing exposure does.</p>

 

<p>If you underexpose by one stop (e.g. exposing 800 film as if it were 1600), you'd want to push one stop during development; if you underexpose two stops (e.g. exposing 800 film as if it were 3200), you'd want to push two stops during development. However, not all films respond equally well to pushing; sometimes pushing two stops will result in less than two stops' worth of results.</p>

 

<p>If you wish to shoot 800 film as if it were 3200 on a camera which only has speeds marked up to 1600, you could set it to 1600 and then deliberately underexpose one stop. I'm not familiar with your camera, but generally, to underexpose you'd pick - on the ± scale.</p>

[helenbach]

In practice colour neg films don't always achieve their theoretical speeds when pushed - though 'speed' tends to lose its definition and become a personal preference when push processing is used.

 

For example, when I use NPZ pushed two stops I set my meter for 1250 or 1600 depending on how much (or should I say little) shadow detail I want. For Portra 800 pushed two stops I set my meter to 1600 or 2000. With either film there is little increase in speed in the shadows (toe speed) - maybe half a stop.

 

I don't think that it is worth pushing colour neg one stop. You may as well go straight to two stops. Colour transparency is a different matter.

 

Best, Helen

[nullfinder]

okay. it's a noob question but can someone explain "pushing" and "pulling" to me? :(

[James G. Dainis]

Pushing is when the film is given an extended development time over normal, usually to compensate for an uderexposed film. Pulling is giveng the film less development time than normal, usually to compensate for an overexposed film. If you expose a 1600 ISO film at 3200 ISO, you are not pushing the film, although many people call it that, you are underexposing the film by one stop. Then you would take it to the lab to have it push processed or "pushed".

[discpad]

Push processing film involves leaving it in the developer longer, to compensate for not enough light exposing the film. [A less commonly used method to push process film is to increase the temperature.]

 

With process E6 color transparency (slide) film, the apparent speed gain is in lockstep with the number of stops pushed, i.e. if you underexpose the film by 1 stop, it will be push processed one stop. This is done by extending the time in the first developer bath from 6:00 to 8:00; or increasing the temperature from 100.0F to 105F.

 

C41 process color negative film is a different matter, as you can see from Helen's post above: A one stop push only gives about a half stop apparent speed increase, i.e. with NPZ or Press 800 from 800 to 1250; while a two stop push gives a one stop speed increase, i.e. from 800 to 1600. This is done by increasing the time in the color developer from the normal 3:45 by 45 seconds for one stop and 90 seconds for two stops.

 

The scam in color print film processing is that many labs charge extra for push processing, but in fact they can't because they have a roller transport or leader card film processor. Instead, they cross their fingers and try to "dig it out" in the printing. Buyer beware!