Subject:	Red x's
Author:	whaletale
Date:	4/14/2002 9:05:15 AM
Message:

Your WA images aren't showing. I'll give a rambling non-specific half-ass answer.

Is the problem fuzzy distortion (e.g. stretching of lines) or barrel distortion. An example of barrel distortion is your shot of the Aquafina bottle. Notice the bowing out of the wall, background door, and stair railing. This is common for zooms and poorly designed wide angle lenses. The opposite effect is called pin cushion distortion when zooms are at longest focal length. As the lens elements are shifted to change focal length, they are no longer optimized for a given focal length, hence the distortion at the extremes.

Wide angles mean you are receiving reflected light from as much as 100 degrees. This light must be straightened out as it passes through the lens so that it hits the film straight on. Digital photocytes or whatever they are called require even straighter delivery because they actually have depth versus almost flat piece of film. Distortion in the wide angle range of digital zooms is a common problem.

It is normal for the wide angle image to be sharpest in the center. Each lens has an optimal f-stop (at least for real lenses, not digital) usually in the mid-range of f/8 or f/11.

You can experiment by taking the same image, only changing the f-stop to see if the distortion changes or not. Just run the series of shots in Aperture priority so you get the same overall exposure. Set up your shot with subjects on the outer edges that will produce detail (e.g. don't use a white wall).

I can't comment specifically on the Inon lens. I don't know enough about it. I know it can be used topside, which surprised me a bit. I'm clueless as to whether the specific distortion will be improved underwater.

There's a guy on this board who knows more about optics and actually remembers what he learned. One day I leaned to my left and all my technical knowledge fell out my ear. I now have to look up everything.

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