Ineffective, large and expensive

- No practical use lockable
- Enormous mounted outside diameter requires large amount of space to stow
- Expensive

in practice:
After approximately 500 images with the EF-S 10-22 (oh. Filters, oh. Geli), then approximately 1,000 images with slim filter (Hoya Pro1) and then again for about 500 images with filters and these Geli I can say that Geli subjective allows no advantage in terms of the general. image quality, lens flares or other light error.

I think in any case that the 10-22er is backlit strong Lensflares occur actually only in frontal and strong backlight on, they remain then usually still quite small and can be subsequently easily removed from the image.

The angle of 10-22er is anyway so great that in any case (with or oh. Geli) scattered light falls on the lenses. For that reason alone the actual benefits of these Geli is already questionable. The picture angle of Geli must be greater than the 10mm lens just adds and reduces the effectiveness of virtually zero.

Very practical is the enormous outer diameter, thus I bring my camera with mounted Geli (no matter how rum) is no longer in my Bereitschaftstaschen (Lowepro Zoom AW45 and AW55). The only advantage is the additional protection of the lens and the Frontlise.

Conclusion: Practical benefits can not be determined, do not actually possible. Those who still like to get accustomed to good Canon quality and a little more protection for the front lens.