Changing Film Speed (Mid Roll)

[hojamohoho]

I thought i just better check a few things, I just purschased my first role of infrared film, and am planning to use it tommorow (assuming the weather is as marvellous as today) and was just wondering about a few things reguarding film speed.

I've read up on the topic and think i know what i'm doing, but i want to use this as a test roll, so i basically want to try everything. This means i'll be using a R72 and 25A filter and try a variety of shots.

Now my question comes because i was just wondering what peoples thoughts are on changing the film speed for successive shots on the same roll of film. It's been suggested to shoot the R72 filter at ISO 25 with the 25A filter at ISO400 this would mean if i wanted to try a few shots with each i must adjust the film speed.

Can anyone advise me if this will be ok, i'm thinking from all perspectives here, including development. And if you do feel there may be a problem could you expain why and perhaps suggest another way if there is one...

Thanks,

Luke.

 

[chris]

Ordinarily changing film speed mid-roll is not a good idea as the development times for each speed are likely to different. However, with infra red the exposure is already a bit hit and miss - Kodak recommend bracketing in one stop intervals from +2 stops to -2 stops - so just bracket everything and see how it comes out.
If you do want to vary the development on one film then you would have to cut the film and process the pieces separately hoping that you haven't cut through the only good frame on the film. This used to done to process a few frames from the start of a film if the exposure was particularly tricky, or if a film had been grossly over or under exposed, so that the processing could be adjusted if necessary for the rest of the film but with the advent of DX coding and more accurate exposure meters the need for this has diminished.

 

[chris]

Ordinarily changing film speed mid-roll is not a good idea as the development times for each speed are likely to different. However, with infra red the exposure is already a bit hit and miss - Kodak recommend bracketing in one stop intervals from +2 stops to -2 stops - so just bracket everything and see how it comes out.
If you do want to vary the development on one film then you would have to cut the film and process the pieces separately hoping that you haven't cut through the only good frame on the film. This used to done to process a few frames from the start of a film if the exposure was particularly tricky, or if a film had been grossly over or under exposed, so that the processing could be adjusted if necessary for the rest of the film but with the advent of DX coding and more accurate exposure meters the need for this has diminished.

 

[motcon]

i've shot hundreds of rolls with infrared film. if you are using kodak hie, i highly recommend you change the ei to see what you can get with the film. i shoot with a #25 filter, ttl and shoot at anywhere from 100 to 400 (again, ttl).

have fun; it's a great film.