Back to Basics
May 29th, 2009 Rob Sheppard
For many of you, I know this is way basic. But several questions in recent classes have made me rethink what new photographers know. This is very basic information about f-stops and ISO settings, but it is critical to know, and not everyone knows this.
Aperture priority is a fine way to use auto exposure. Many pros do exactly that (including me). I know some photographers would have you always do manual exposure. I used to feel that way years ago, but having worked with so many great camera models over my years at Outdoor Photographer magazine, I don’t feel that way at all. You can use auto exposure just as effectively as manual exposure if you pay attention to such things as highlight warnings and histograms. You can be just as accurate as manual exposure and faster in many cases. This is not a case for quitting using manual exposure if that works for you, but for feeling guilt-free if you don’t use manual exposure.
The challenge is in what apertures to use and how to balance ISO settings for the best shutter speeds and image quality. Here are some ideas:
ISO settings:
- 100-400 good for all around use, lower number for bright daylight, higher number for lower light.
- 800-1600 (depending on camera) good for low light and higher shutter speeds when some noise is not bad
- above 1600 for really dark situations only when this is the only way to get a shot.
And some ideas for choosing and using f-stops:
- f/5.6 and larger (such as f/4, f/2.8) — used when limited depth of field is needed, i.e., to make a subject stand out from background or when faster shutter speeds are needed.
- f/8-f/11 — mid-range f-stops used when depth of field or shutter speed is not critical as this is usually the sharpest range for a lens. Distant scenes can always be shot at these f-stops.
- f/16-f/22 — small f-stops used for maximum depth of field or sharpness from foreground to background; limitation is slower shutter speed is often needed.
- smaller than f/22 — avoid if possible as these are usually not as sharp; you may find that some lenses, especially wide-angle lenses, have a distinct drop in sharpness at even f/22
The photo shown here is of a flowering yucca in the chaparral north of Los Angeles California in the amazing Santa Monica Mountains. A wide-angle lens and a small f-stop were used for max depth of field, plus a low ISO of 100 was used for best image quality. Olympus E-3, 8mm full-frame fisheye.
