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Photography Question 
Piper Lehman
BetterPhoto Member Since: 7/20/2001

Pulling Film

Oops! Just shot a roll of Portra 160 at ISO 50 by mistake. Had Velvia in there last, I guess. My camera (Nikon N90s) sometimes mis-captures the correct DX coding on my film, and I forgot to check it this time.

I know it's cool to push film on purpose and then have it processed at the push-rated ISO, but what will happen when I tell the lab to "pull" this roll back to 50 when processing? How many stops is this anyway?! Two stops? Two-1/2? Is it possible to get adequate results from pull-processing?

Thanks in advance.

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5/27/2002 10:54:25 PM

Piper Lehman
BetterPhoto Member Since: 7/20/2001
  You know, now that I think about it, I wonder if I accidentally changed the ISO mid roll when fumbling around for the exposure mode button. It's right beside the ISO button. What are my options here? Have the lab pull it like above and hope for the best? Or should I have it processed at 160 and try to fix any problems with PhotoShop?

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5/27/2002 11:01:45 PM

Jeff S. Kennedy   Piper, I wouldn't worry about it. That film can handle a bunch of overexposure. If your lab is worth their salt you probably won't even be able to see the difference in the prints. That's only a couple of stops. I've overexposed that stuff by 4 or 5 stops and didn't mention it to the lab and I couldn't tell the difference between the proofs.

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5/28/2002 1:36:25 AM

Carrie C. Brannon   Jeff,
I have been learning all I can about Photography lately, but this push/pull thing confuses me, I have a hard time keeping up with which one is which. Please let me know if I have this right or backwards; To Push or overexpose film would be to have say, 400 Speed film in you camera, and have the film speed on the camera set at 200 speed. To Pull or underexpose, you would set the camera to 800 speed with the 400 speed film in that correct? And one more thing, there are little places between the numbers, like this: 200 * * * 400 * * * 800 * * * on my Canon AE-1's film speed setting dial that you can set it to as well as the actual numbers, what are those? Is that the "stops" you are refering to? Forgive my ignorance on this subject, but I haven't gotten quite so far into my Photography studies that I have used this technique yet.
Your talking about this with Piper made me think to ask you about it.
Sorry to interupt Piper!

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1/16/2003 10:02:53 PM

Jeff S. Kennedy   Sorry Carrie, you still have it backwards. When you push film you underexpose it and over-develop it (IOW take 200 speed film and set your camera for 400). When you pull film you over expose it and underdevelop it (IOW take 200 speed film and set your camera for 100).

A stop is one unit of light. When you add a stop you are doubling the light. When you subtract a stop you are cutting the light in half. If you have an exposure of 1/125 @ f8 and you want to add a stop of exposure (double the light) you could shoot it at 1/60 @ f8 or you could shoot at 1/125 @ f5.6.

The spaces in between your ISO settings are just in between ISO numbers like 250, 320, etc. They're so close to each other that if you get in the neighborhood you shouldn't have a problem. That's why they didn't go to the trouble and space to number them.

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1/16/2003 10:27:51 PM

Carrie C. Brannon   Thanks Jeff! I told you I was confused! Thanks for clearing that up for me, I understand now! I still have so much to learn! Thanks for all your help!

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1/16/2003 10:57:04 PM

Jeff S. Kennedy   No problem. :-)))

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1/16/2003 10:58:31 PM

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