Canon 20-35 soft image

[gchong]

Hello all,

Hope you guys out there can help me with this. I just purchase a used Canon 20-35 f2.8L http://www.canon.com/camera-museum/camera/lens/ef/data/ef_20~35_28l.html). By the way, I'm using 350D.

The picture I took with f2.8 is soft but it's sharp on f5.6. I even notice the focus range (the lens indicator) will be different when I focus on a stll object with a tripot. It will go from 0.5m to 0.6m. Is the lens having problem and can I send to Canon for calibration?

Thanks!

[DayHawk]

Can you post a picture for reference?

[gchong]

Hi Dayhawk,

Image_01411.jpg taken at f2.8
Image_01421.jpg taken at f5.6

I've try manual/program and other mode, and different type of focus mode in 350d, but the result is still the same. thanks

[Icecamp]

Looking at Photodo's http://www.photodo.com/index.html site with it's MTF data, it shows the 20-35 to be a bit on the soft side especially wide open. Their rating is 3.5 which is the same rating they give the 28-135 and one point higher than the consumer 20-35. That being said, I am surprised at how soft it is at f/2.8 in your example photos.

[wintoid]

I sold mine a while back. I felt it was not quite as sharp as the 17-40L but had better contrast. I was never unhappy with the sharpness though.

Here is an example image at 2.8 and a 100% crop which admittedly looks softer than I remember...

[ScottE]

You may be looking at the advancement in lens making technology. The 20-35/2.8 was introduced in 1989. It was replaced by the 17-35/2.8 which was in turn replaced by the 16-35/2.8.

The 20-35/2.8 had a great reputation at the time it was introduced, but zoom lens technology has advanced since that time. One of the most notable improvements for L lenses has been the performance wide open.

[garysblim]

Hi:

I did the a simple test on mine and it doesn't look as soft as gchong's. At 2.8, it's softer but not significant.

http://flickr.com/photos/garysblim/sets/1666593/

The pictures are cropped at the center (around 1:1).

gchong, did you use tripod and mirror lockup?

Gary

[rklepper]

Are these hand-held? Since it is sharper stopped down it might be camera shake. Try the same thing using a tripod.

[Denny G]

Look at the EXIF. In the first photo the exposure program was set to "Portrait Mode" (For close up photos with the background out of focus) The second photo was set to "Landscape Mode" (For landscape photos with the background in focus)

Does this make a difference?

[gchong]

Hi all,

Thanks for the reply, I did more test with the lens and tripod but the result is still the same. I've sent the lens and body to Canon service center and get them to check on it. Hopefully they can fix the problem

Does anyone know what could be the problem? The lens is clear when I take it out and check against the light. I've call some workshop and ask about the lens and some of them said it could due to the F-stop problem and some said recalibration. Hope it won't cost me a bomb to fix it.

Thanks

[garysblim]

One reason could be the camera is not focuing properly. At f2.8, the depth of view is much shallower. Having said that, I realize when I first did my test, the image was also softer at f2.8 but that was attributed to hand shake. Once I used tripod, the images look a lot better.
Having said that, there are a lot factors affecting the resolution of the image:

1) your focal length setting. (mine set it at 20mm)
2) focusing distance. (I think fotodo and factory spec. optimizes at infinity).
3) camera support
4) shutter speed
5) aperture
6) focus accuracy

If you have another camera or a friend who has a canon, I'd try to mount it on that and see. But since you've sent it in for service, I hope they can resolve the issue.

[Jon]

Originally Posted by rklepper

Are these hand-held? Since it is sharper stopped down it might be camera shake. Try the same thing using a tripod.

Huh? In the same lighting conditions, stopping down would require a slower shutter speed, so the stopped-down shot would be more vulnerable to camera shake.