This webpage was written to help students enrolled in SP.747. In thefilm-developing lab, all people realized that many photos wereover-exposed for some reason. Hopefully this will help you figure outwhat could go wrong. I assume you have read the Silly Camera Numbers page.
ISO is the film sensitivity. It's a number, more common ISOs are 100and 400. The higher the ISO, the higher the film sensitivity and thelarger the film-grain size. If you plan to shoot indoors in low lightconditions, film ISOs of 400, 800, or even 1600 are preferred. If youare shooting outside and you have lots of sunlight, try to use ISO 100film, or even slower (you can find films with ISO 50 or 25). The goodthing about low-ISO film is that the film-grain is very fine and youhave a lot of detail. If you are a diverse shooter, taking photos invarious conditions, stick to ISO400 film, such as Ilford HP5+, TMAX400,Ilford Delta 400 and others.
Every time you load film into your camera make sure you tell thecamera what ISO film you are using. New automatic cameras should beable to read the barcode on the film canister and know the ISO. If youare using an older one, find the dial or the wheel that sets theISO. Even if you are using a newer camera, double check to make surethat you and the camera agree on the ISO value:)
PS: Note about digital SLRs - the cool thing about Digital SLRs isthat you can change the ISO settings anytime. If you shoot film youare stuck with one ISO setting for 36 frames. With digital SLRs you cancrank up the ISO up to 1600 or 3200 if you are shooting at night (soyou get reasonable shutter speeds and minimal blur). You can also setthe ISO to 100 on your digital SLR if you are shooting in sunlight,such that you minimize noise and get maximum detail in the photos.
You have to control the shutter speed and the Fstop (aperture) on yourcamera in order to get the pictures that you want. In older camerasyou have to set the Aperture (f/2.8, f/5.6, etc) and then vary theshutter speed until the proper exposure is reached. Your light metershould tell you what the proper exposure is (you might have a needlelight meter, or a meter with a red dot and a green dot, or somethinglike that).
In newer cameras you can use semi-automatic modes such as AperturePriority (labeled "A" or "Av") or Shutter Priority (labeled "S" or"Tv"). In Shutter Priority mode you set the shutter speed (say 1/60sec) and the camera automatically adjusts the aperture on your lens toget the proper exposure. In Aperture Priority you set the Aperture andthen the camera uses the built-in light meter to adjust the shutterspeed in order to get the proper film exposure.
I almost always use Aperture Priority mode, and I recommend it toeveryone. It's easy if you know what you want. Suppose you want totake a nice portrait of a friend. Youwant a nice blurry background, therefore you want a low Fstop number,such as f/1.8, f/2.8, or whatever the lowest number on your lensis. You focus on the person's eyes, frame the photo, make sure thatthe shutter speed is reasonable and shoot.
We are coming back to thequestion, what is a reasonable shutter speed? It's something fasterthan 1/50th of a second for most lenses that you are going to use forthis class (remember the inverse rule). On the other hand, your camerahas some maximal shutter speed limit, for the older cameras it'saround 1/500-1/1000 sec, for the newer cameras it's around1/4000sec. Suppose you have your aperture wide-open and you areshooting ISO400 film outdoors. I am pretty sure your camera will saythat there is too much light and even at the maximal shutter speed thephoto will be over-exposed (different cameras tell you that indifferent ways, they blink, give you an error message, flash a red dotat you, etc.). In this case you would have to stop-down (i.e. decreasethe aperture, from f/2.8 to f/8 for example).
Now suppose you are shooting indoors and there is little lightavailable. Even though light from fluorescent lights looks bright toyou, it might not be enough for your lens/camera. Then you have toopen the aperture on your lens all the way and try to achieve that1/50 sec or 1/60 sec necessary for a steady shot (or use a tripod).
If you are able to understand what the Fstops and Shutter Speeds do,you should be able to squeeze the most out of your camera. Remember, a$100, 10 year old SLR camera can give you awesome pictures, and so caneven older/cheaper cameras. Ultimately it's all about you (having anice, auto-focus camera with a fast, sharp lens might help a bit though).
