Filter question

[E.B.West]

I asked this over at dpreview and haven't gotten much response, mostly that I need a better lens.

After I got the Rebel, and a Sigma 70-300mm 4/5.6 lens (I know, it aint a Canon L) I went to the local Ritz and got two UV filters. Went on a little camping trip this weekend to try everything out and nothing was in focus. With either lens.

I tried ISO 800 and down, everything was on a very sturdy tripod and still nothing was in focus, everything was soft. When I got home I thought I'd try a few other things and it struck me that the only difference was the filters. I took them off and everything was sharp, well as sharp as it's going to get until I get a *real* lens.

Has anyone else had any focus problems as a result of filters? I know I need a circular polarizing filter but I didn't think that counted on UV's.

Any thoughts?


I know that the Sigma is not as sharp as a canon lens on a side by side comparison but the same thing was true with the 18-55 kit lens, everything soft until I took the filter off.

[[email protected]]

For best results, try to get the super multi-coated filter from Hoya or the B+W filters, any cheap filter will degrade the quality of the lens. At F/5.6 maximum aperture, sometimes you will have problem with AF anyway in the not-well lit area. An good UV filter shouldn't interfere with the AF operation..., you will anticipate more problem with AF if you attach the polarizer filter on this lens since it will reduce the light up to 2 f-stops, the best way to handle this is to focus the subject manually and shoot...

Cheers

[E.B.West]

Thanks for your reply. I got Canon filters thinking they would be good ones. Live and learn.

[E.B.West]

Read this: http://forums.dpreview.com/forums/re...essage=6166467

It may shed some light on the subject.

[Mathilde uP]

Thanks both of you, this confirmed my suspicion about my film slr blurr.

With my new camera and lense the shops gave an UV filter B+W f-pro. Is that any good? What uv filter would be best choice for 50mm f1.8 prime lense?

[E.B.West]

I wish i could help, until I find out more, I'm leaving the filters off and being very careful.

I placed my multi-coated Quantaray UV filters on both my Canon 50mm/f1.8 & 28-105mm USM zooms (2 different filters for 2 different sized lenses). I shot off a tripod (using the timer) using Halogen Hot lights with exactly the same lighting, f stop & all other variables. I could NOT see (nor could Photoshops color profiles) ANY difference in either image with or without the filter. I tried several different f stops & shutter speeds to verify that it wasn't a fluke. I also verified all camera variables in Breeze Browser & had Zero differences. I plan on doing the same test tomorrow in sunlight but I'm convinced that my filters are ok for my work!

YMMV, but I am happy with keeping the filters I have on my lenses...


Everybody ready for Halloween?