im going up the mountains tonight and all i have is 800 speed film. i don't plan on taking movement shots so the speed is kinda wasted. i want to avoid noise and im just wondering what will happen if i set my rebel to 200 iso with 800 film?
This is an old trick that film shooters have been using for decades. Some cameras have the ability to rewind the roll without pushing the leader all the way inside the canister. 1) Set option not to rewind the leader and take note of frame number 2) rewind 3) remove the canister (with the leader hanging). 4) use a perm. marker and write down the frame number on the canister 5) place the roll in the plastic container 6) load the other roll of 200 iso when you are ready to shoot the rest of the partially exposed roll, 1) remove from plastic container 2) load roll as usual 3) Place cap on lens or remove lens and install the body cap. 4) set the shutter to the highest 1/1000 5) trip the shutter until your are at your recorded frame. 6) trip the shutter a couple times more to make sure you don't double expose the last frame 7) shoot the rest of the roll.
I am not sure what camera you have but if you are shooting with an older manual camera, when you rewind the partially exposed roll, you'll need to listen carefully (press your ear to the back of the camera). You can hear the leader release from the take up spool and feel the tension on the rewind change.
if he has 800 speed film and he is rating it at 200 then why couldn't he just stop down 2 stops? If nobody mentioned this than maybe it doesn't quite work like that? wouldn't it work like pull processing?
Setting the iso down and/or stopping down is essentially the same. What doesn't change is the appropriate exposure. So it buys you nothing... he is concerned about grain (noise?) which necessitates swapping out the film to a lower than 800 iso... stopping down won't improve that either. Pull processing which attempts to compensate over-exposed negatives in development rarely works too well. Its a whole lot easier just to do a mid-roll change... I do it all the time with no issues.
Manual rewind cameras usually have a release button on the bottom, which you can watch as it rotates. What it and when it stops, the film has disengaged from the take-up spool. No you can't shoot half a roll at 800 and half at 200, over exposing all the photos, and get anything but a royal mess. Rewind the film all the way in, and go to a photo store, where someone will have a leader retriever. Most of the time, they are happy to get your leader back out, or if you plan on doing this more times, just buy one.
If it is colour neg then a couple of stops of 'overexposure' usually doesn't matter - in fact it lowers the graininess. I use Portra 800 in my carry-all-the-time camera because I know that I can set the meter to anywhere between 200 and 800 on the same roll and get good results. I usually set the meter to 400 to get good, low graininess results. Remember that the ISO speed of colour film is based on the minimum exposure that the film needs, and that there is plenty of dynamic range over that. It's easy enough to switch films, as already explained, so that is preferable if you know that you want to shoot a lower speed film. Best, Helen
Really I think fim is chep enough that you can just rewind. As has already been stated if you have only shot a few frames on the roll you can rewind it and then go to any lab and have them pull the leader out for you. All you need to remember is whatever frame you stopped at I would advance your camera at least 3.4 frames beyond to avoind any over-exposure problems caused by mis-alignmnt. There is no real way to precisely load and reload your film so you will start at a diferent position every time. Whatever you do though make sure you remember what frame you left off on as there is nothing more frustrating than having a mystery roll of film floating around.
