: My Pentax ZX-7 35 mm SLR says you can push up the ISO. Example. I have a 400 speed film in the camera, but have a great low-light oppurtunity. I manually push up the ISO to 1600 for one or two shots. How does this work, and does it work well? I haven't used it. Will it turn out? If anyone has done this before , please post your comments.It works, but not that way. You'll have to do that for the entire roll and then have it processed at 1600. The results should be ok. If you only set it for 1600 for two shots and then back to 400 and develop them at 400, the two at 1600 will be underexposed.