Barrel distortion on DSLR

Hi,

I'm looking for a Wide Angle lens to use with my EOS20D. I saw a lot of articles in the internet speaking about Sigma 15mm FE and Canon 15mm FE, some guys presents Sigma as the better choice than Canon, other spoke that Canon is the best. The price diference is not big.

Does anybody knows which lenses will give me less barrel distortion underwater on DSLR 1.6x crop sensor ? Any pratical test published on the internet ?

Regards

Fabio Amorim

Hi,

barrel distortion values are used to describe very little lens errors for normal (non fisheye) lenses.

fisheye lenses have a completely different image projection in comparison to a rectilinear wideangle.

The distortion is super huge but no lens error. It is exactly the kind of projection a fisheye lens is designed for.

No matter if Canon or Sigma, both are fisheye lenses and completely different to rectilinear wideangles.

In terms of image quality some state the Sigma is better, some others do state the Canon is better.

I've done some shots with both before buying. Couldn't notice any significant difference.

However I think both lenses deliver about the same very high quality.

Beside the "distortion" fisheyes have some advantages:

- no vignetting compared to wideangles

- fisheyes focus on a curved image which the dome produces

- superb minimum focus distance

Personally I bought the Sigma for it's better minimum focus distance of 15cm (from sensor plane). Canon = 20cm.

Julian

Fabio,

You can correct for the barrel distortion with software. However, just because you can correct for distortion doesn't mean you have to or even should. In some cases, particularly with marine life and people, I like the fisheye effect because it makes the subjects appear closer.

For more see the following.

http://www.splashdowndivers.com/photo_gall..._wide_angle.htm

You're right Peter, some times the barrel distortion do great efects and there are some good PS plugins and softwares to correct it.

I am newbie on digital underwater and I saw that both sigma and canon FE when used with DSLR (1.5x or 1.6x) looks like a WA lenses, probably due the crop. I am looking for a lens to cover the same field of a 20mm in a full frame camera to my DSLR with the similar result of a WA lens.

The price is very similar and my concerns are about the lens sharpness and wich lenses give more distortion.

Thank you.

Fabio

The 14mm Sigma (or Canon if you have the money) may be a good choice if you want a 20mm Equiv. WA Lense.

Simon