Iso Digital Photography

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What is the ISO and FSTOP on my digital camera do?

I am in a photography class and I have to learn how to adjust my ISO and my FSTOP, but I have no idea what those are and how to use them and manuever them to make the best picture. Does any one know what they are and how to work them?

First of all, talk to your instructor. If you're instructor can't explain the concepts to you, then get your money back and take a different class.

ISO stands for International Organization for Standardization (http://www.iso.org/iso/home.htm ). As this relates to photography, it deals with film speed. ISO film speeds are standard for the industry, so that a film make by Kodak, Agfa, Ilford, Fuji, etc, that's rated ISO 100 will perform similarly in all cameras. ISO 100 defines the degree of light sensativity of the film. The higher the ISO value, the faster the film. The faster the film, the lower the level of lighting need for a proper exposure.

ISO 200 requires half the light of ISO 100, or it is twice as sensitivity. There is a trade off. The higher the ISO, the coarser the grain of the emulsion, but that's the subject of another post.

With film, once you load a certain ISO into the camera, you set the film speed dial to what ever ISO number on the film and leave it.

With digital, you aren't using film speed per se, but rather a film speed equivilent. When you adjust the ISO number on a digital camera, what you're doing is changing the sensitivity of your digital sensor. You want to set you're ISO as low as possible because you start getting digital noise above a certain ISO everl. Basically the pixels start showing additional colors.

F/ stop or f/ number is a ratio that is figured by dividing the focal length of the lens (again another discussion) by the effective diameter of the lens. The effective diameter is controlled by the aperture (or lens opening).

If you have a 50mm lens with a lens opening of 10mm your f/ number (or f/ stop) would be 50/10=5, which would be written f/5. On the same lens, an aperture (lens opening) of 25mm would be 50/25=2, written f/2. An aperture of 5mm would be f/10 (50/5=10)

As you can see, the wider the aperture or lens opening, the small the f/ number.

As for adjusting your f/ stop, you will find either a ring on the lens with numbers, such as 2.8 / 4 / 5.6 / 8 / 11 / 16 / 22 etc. This ring will snap as each of the number aligns with a mark on the top of the lens, these are your f/ stops -- f/2.8 / f/4 / f/5.6 etc. You adjust these buy turning the ring.

On some electronic cameras, film and digital, you will find there is no aperture adjustment ring. This is because you adjust the lens opening with the camera's controls. How you do this will depend on the individual model. On my Nikon D200, there are two dials on the upper right side of the camera, one in front; one in back. The rear dial adjusts shutter spead and the front one adjusts aperture.

We could be more specific if you let us know exactly what camera you're using for your class.

Photography Tips: ISO (part 3 of 4)


iso digital photography5
iso digital photography5
iso digital photography5