 BetterPhoto Member |
The ASA (or ISO) Switch My photography teacher told me never to mess with the ASA switch. I asked why and he said 'just because', so my question is what is the ASA and what does it do?
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BetterPhotoJim.com - Jim Miotke  Contact Jim Miotke Jim Miotke's Gallery |
The ASA switch syncs up your camera's exposure meter with the speed of the film speed you use. It is very important that you do mess with it on occasion; unless you are experimenting or getting fancy, you always want to set the ASA to the film speed (or one stop less, if you want to saturate the film). Hope this helps.
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John A. Lind |
Be careful with advice on adjusting the ASA setting like this. This will work for color negative films and should increase contrast with B/W negative. This advice is OK for the majority of your readers who use color negative. However, with reversal films (a.k.a. slides) this could be disastrous! Deliberate over exposure (by setting the ASA lower than the film speed) On the other hand, slide film will do just the opposite. Over exposure will leave the emulsion very thin! This will also have the opposite effect with the saturation of the image. It will look washed out with little saturation. Furthermore, slide films are far less forgiving of exposure error (in this case deliberate) and you will undoubtedly lose highlight details under nearly all will make the emulsion "thicker" on negative films. In printing you "bore a hole" through it by leaving the enlarger lamp on longer when making the print. A thicker emulsion on color negative will saturate color in the print paper. Negative films are also more forgiving of doing something like this and will still contain highlight and shadow details under all but the highest contrast conditions. You will also increase grain with most films. On the other hand, slide film will do just the opposite. Over exposure will leave the emulsion very thin! This will also have the opposite effect with the saturation of the image. It will look washed out with little saturation. Furthermore, slide films are far less forgiving of exposure error (in this case deliberate) and you will undoubtedly lose highlight details under nearly all conditions. A "thin" emulsion slide image with loss of highlight detail is almost impossible to extract a decent print from.
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BetterPhotoJim.com - Jim Miotke Contact Jim Miotke Jim Miotke's Gallery |
Thanks, John - you are very right to catch me on that assumption. Thanks for making it clear to our slide users.
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