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Photography Question 
Patricia Arrance

Film Speeds

Hi, newcomer to photography. Comparing cameras digital and iso speed capabilities. Under what conditions would you use a 32 - 50 iso and under what conditions would you use upwards of 1000 to 3200 iso. I don't want to buy a camera and then find I can't do the things I want to be able to do.

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11/21/2002 1:21:18 PM

Michael F. Harrington   Patricia, your question is a little confusing since you tossed in the digital part. Are you asking about digital ISO settings, or film ISO's?

If it's about film then: Simply put, lower iso numbers require faster lenses, and slower shutter speeds, or higher flash output because more light is needed to burn the image into the film.

Conversly, higher ISO's require less light, therefore shutter speeds can be increased, and apertures can be decreased, as well as flash output.

But that's not the whole story. Different speed films are used for their distinct characteristics, IE, grain, color rendition, and contrast.

As for purchasing the "right" camera: most good slr's cover the ISO range.

I hope this has helped.

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11/24/2002 5:19:18 PM

John A. Lind
BetterPhoto Member Since: 9/27/2001
Some guidelines regarding film speeds for 35mm SLR's . . .

Regardless of lighting levels you want a film speed that gives you some flexibility with using a shutter speed fast enough to stop action if needed, and some flexibility to open up the lens for a shallower depth of field or stop it down for greater depth of field if either of these are desired. In general, grain increases with film speed. Most serious and professional phtoographers use the the slowest film that still allows their desired level of flexibility with shutter speed and lens aperture settings.

For general daytime photography outdoors in bright sun you should be able to use anything from ISO 25 to ISO 200. I routinely use Kodachrome 64 for this. This can become too slow shooting near sunset, sunrise, in deep shade or under very heavy overcast unless using a tripod is feasible. ISO 400 and faster films are often too fast with subject material illuminated by direct sunlight. On many cameras, the lens cannot stop down far enough and the shutter speed cannot be set fast enough to sufficiently limit the amount of light reaching the film.

For indoor work with flash, film speed depends how powerful the flash is and your working distance. Unless you have a very powerful flash, or are using powerful studio strobes the very slow film speeds in the ISO 25 to ISO 50 range are usually too slow. At longer working ranges beyond about 15 feet, a film speed in the 160 to 200 range usually works much better than ISO 64 to ISO 125. I use ISO 160 with a lens aperture of f/5.6 routinely for wedding receptions at which working distances average about 10 to 25 feet. To reach the longer end of this (over 15 feet) I have a fairly powerful flash, but its full power definitely isn't needed under 15 feet. For other work indoors that doesn't exceed 12-15 feet (family type stuff) I routinely use the same ISO 64 film as I use outdoors. With slower lenses, longer working distances and weaker flash units indoors, ISO 400 can be more appropriate.

Faster films are required for available light indoors. An ISO 400 works if it's a brightly lit area. ISO 800 may work better for normal household lighting (without any sun coming through windows).

Shooting available light outdoors at night is highly variable and depends on the environment, the subject material (how much you need to stop action) and whether your're working hand held or with a tripod. In urban areas brightly lit by street lights and building lighting, ISO 400 can be used with care. For night architecturals without moving objects, film as slow as Ektachrome 64T can be used if the camera is on a tripod.

The very high speed films used at EI 1600 and EI 3200 are primarily for hand held shooting in very low light, or when narrower aperture must be used for depth of field in lower light levels. Three of the four films I've used in this speed range have ISO ratings slower than this, but are intended to be "pushed" and shot at these speeds. Two are B/W ISO 800 films specifically designed to be shot at EI 1600 or EI 3200. The user decides what speed to shoot it at, but must use the entire roll at that speed. They require "push" processing that must be done by a professional, full-service lab. This changes the normal developing times and an extra processing fee of several dollars is assessed for the special developing. The third is a color ISO 400 slide film specifically designed to be pushed to EI 800 or EI 1600. As with the two B/W films, it also requires special push processing that modifies developing times. The fourth is a color negative (print) film made by Fuji. It is a true ISO 1600 film and can be developed by any lab using the standard C-41 process, including one-hour labs. I've used these films for shooting everything from wedding ceremonies without flash to blues bands performing in dimly lit small nightclubs.

For general hand-held work indoors and outdoors with a 35mm SLR, try using an ISO 100 film first. If you have slower lenses and/or a weaker flash (the built in ones are very weak), then you may need to bump up to an ISO 200 film. If you have fast lenses and a powerful flash unit, you can easily work with ISO 64 films indoors and out. Reserve the very slow films at ISO 50 and below for very brightly lit subjects or when you can use a tripod and long shutter speeds. Reserve the fast and very fast films for the special situations that cannot be done with something in the ISO 64 to ISO 200 range.

I remain mystified why Kodak's marketing continues to push its ISO 800 Zoom Max as a general purpose film suitable for any and all conditions. It's much too fast for daytime use outdoors, and faster than need be for indoor use with flash under most conditions.

-- John

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11/24/2002 11:50:46 PM

Deborah    I like to shoot park and forest scenes with natural light. I usually use focus free 35mm or my WOCA.

Is it feasible to use the built-in shutter speed and f stop with 3200 BW in a wooded scenery?


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7/28/2003 3:00:12 PM

Daniel Phirman   Very interesting footnote from John. I had come to believe that the more expensive 800 speed film was necessary for better photos. It's true that the film is more sensitive, but also results in many grainy photos. Now I understand why my enlarged and panoramic photos came out poorly. Thanks John!

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12/27/2004 12:48:35 PM

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