Lens: 20-35 f/3.5-4.5 - sweet spot?

[fx]

I'm curious if anyone has done comprehensive testing on this lens

and could tell me which f-stop the sweet spot is at. Images shot at

5.6, 6.7, and 8.0 at 20mm still produce soft corners most of the

time.

 

Side question - regarding stacking 2 regular filters(not super thin

ones) at 20mm...has anyone gotten away with this without noticing

vignetting? I've got a Kenko R1 and will probably pick up a UV

later on.

[larry_lambert1]

6.7 from my experience, too much diffraction beyond that. Kenko R1, is that a red? If it is you won't need a uv at the same time, the red will cut it off. Never tried two at a time but my polarizer is effectively two rings deep, no problem there.

[yakim_peled1]

1. Try f/11 and f/16.

 

2. Different samples (of the same lens) may exhibit different behavior. Thus, it may not matter how other people find their lens' performance. Example, my 70-200/4 USM L was not sharp at all at f/4 and f/5.6. This is contrary to the general behavior of this lens. I have seen numerous reports of how it is sharp wide open. I guess it was a lemon.

 

3. The common wisdom is that once you go below 24mm, a thin filter is advisable. Stacking filters is almost never a good idea.

[bill j.]

For what it's worth. I haven't used this particular lens, but I have saved a copy of a post claiming to interpret CDI's test results for EOS lenses.

 

 

From a July, 2000 posting on the EOS mail group:

 

[CDI test results:legend:]

[lens name, max. aperture, color rendition

 

distortion,

 

aperture edge/center sharpness, vignetting]

 

 

20-35 3.5-4.5 USM Slightly warmish

 

at 20 1.6 barrel

 

3.5 7/11 0.7

 

5.6 11/16 0.4

 

8.0 12/16

 

 

at 24 0.7 barrel

 

4.0 7/12 0.6

 

5.6 11/17 0.3

 

8.0 12/15

 

at 28 0.4 barrel

 

4.0 9/12 0.5

 

5.6 12/17 0.3

 

8.0 13/15

 

 

at 35 0.3 barrel

 

4.5 8/12 0.3

 

5.6 9/15

 

8.0 11/13

[Ken Katz]

At f8 & f11, I have images that look very good printed 11" x 16". I doubt any 20mm SLR lens is absolutely stellar in the corners.

 

I would not stack filters with this lens, but the good news is that standard width filters don't seem to vignette.

[lee_shively]

I agree. Don't stack filters. Otherwise, the lens performs relatively well at all apertures. Exceptionally well considering it's low price.

[jay_.]

I use this lens for the odd landscape shot while shooting wildlife (that's basically all I use the EOS for)mostly at f/11 and find it quite acceptible as 35mm goes (I shoot landscapes with Hasselblad). I also use it as a more or less standard zoom with the D60 and there it is really good--as digital goes :>)