Can depth of field be controlled by user on digital cameras?

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I would like to know if the phoitographer can control the depth of field on digital cameras, or are all subject and background images given sharp focus, as with videocams?

-- Dean M. Chambers (elmogibb@inetw.net), July 23, 1999

Answers

There are only a few ways to control depth of field:

- Smaller F Stop
- Focal Length of lens

If you have no exposure control then changing the F stop is not an option. You might exert some minor control by adjusting the amount of light on the image - but depending on the camera it might changes shutter speed instead of F stop leaving you with the same depth of field.
Changing the focal length may be an option, or perhaps not. You'll notice less depth of field at longer focal lengths unless you only have a digital zoom (then the focal length doesn't really change).
If you are unlucky enough to have a camera with no exposure control, and only a digital zoom - then you are out of luck.

Des

-- Dan Desjardins (dan.desjardins@avstarnews.com), July 23, 1999.

Most consumer digicams pick both shutter speed and aperture for you. Some (like the Nikon CoolPix 950, Olympus C-2000 Zoom, or Canon Pro70) give you an option that lets you specify the aperture, and the camera picks the shutter speed. This is called "aperture priority". With it, you can select either a larger aperture for less depth of field, or a smaller one for more. Due to fairly slow equivalent ISO ratings, digicams will generally give you shallower depth of field, all other things being equal (lens focal length, etc).

-- Dave Etchells (detchells@imaging-resource.com), July 25, 1999.

Even if depth of field cannot be controlled in the camera, you can simulate the effect later with an editing program such as Adobe Photoshop, or -- my favorite -- Micrografx Picture Publisher.

In MGX Picture Publisher version 8, there is a simulation built right in. You click where you want the focus to be sharp, and it gradually softens the focus, apparently in a circlular shape, as the radius increases away from that point. The strength of the defocussing vs. distance is adjustable. Of course this is only an approximation as your subject that youu want sharp is probably not going to always be circular.

For better results, simply lassoo (also known as select) the irregular shaped subject that you want sharp, then invert the selection so everything BUT the subject is selected, and then apply a blur filter. You can do this in any decent image manipulation program.

-Bruce

-- bruce komusin (bkomusin@bigfoot.com), July 25, 1999.


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