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Old Oct 26, 2006, 9:50 PM   #1
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I've noticed the barrel distortion on my S3 IS (normal lens, 35 - 432 mm) near the widest setting. I've also noticed this with other cameras (Canon A540 and three non-Canons) -- which is every digicam I've ever worked with.

If a billboard fills the picture, or there is an archway near the edge of the picture, barrel problem is really noticable. I don't want to sound like a picky person, but I do notice it....

And the barrel distortion doesn't go away as soon as you leave the widest setting, either. Would getting a wide angle lens solve this? If I zoomed in with the Canon (say, 50-110mm?) enough to stop the distortion, and then the wide angle multiplied that by .7 or .66, I could have general (in this case, 35-77 mm) free of distortion.

I can't tell the focal length when I'm shooting in the field, but at some point experience would tell me when I'm zooming in enough to take the wide-angle off.

Would this be an okay (though expensive) idea, or

(a) would the wide angle introduce imperfections of its own, possibly including its own barrel distortion, or

(b) can the barreling be treated in software post-processing?

(I'm not *_really_* interested in focal length below 35 mm at this time, though it would be nice. I'm just interested in barrel problems below 110 or wherever it dimishes).

If I had a lot of money (won the lottery, whatever), would this be a decent idea? Or can software save the day?


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Old Oct 26, 2006, 10:22 PM   #2
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Barrel distortion can be fixed in software post-processing.

(sorry, Linux locked up -- [there's a phrase you rarely hear!] before I could finish this post.)

Let's change this thread into a technical discussion. Why does barrel distortion happen? Is it reduced at the wider end of higher-end zoom lenses, film or digital?
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Old Oct 27, 2006, 6:46 AM   #3
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It's probably not too hard to "design out" distortions from a fixed focal length lens, but when you have to accommodate a range of focal lengths (especially with a range like that of the S3IS and other "super-zooms"), it's harder. As far as I know, barrel distortion (sides bow outward) is more prevalent at telephoto settings and should flatten out as you zoom back to normal/wide angle (would that be "unzooming?"), but as you go toward the wide angle end, you may see some pincushion distortion (sides bow inward).

Zoom lens design is always kind of a compromise. If you add elements and/or make more of them move to reduce distortion, you add complexity, weight, and cost.
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