Help! Soft wide angle shot?

Irminsul · Jul 13, 2007

I just got my first wide angle lens, a Sigma 10-20mm F4-5.6 EX DC HSM. I plan to use it with my Rebel XTi (400D) and my original DRebel (300D). Well, I tried it with the 300D and made this test shot from my balcony. Although I've heard that these lenses tend to be a bit soft, I think the Sigma I got may be really soft. But maybe I'm doing something wrong, perhaps I should have used a tripod with this type of lens, or my computer is not calibrated correctly, etc. I took the shot at 1/500 f/16, ISO 800. I identified the main focus area by drawing a yellow circle around it. Any ideas, opinions or views on this test shot? Sorry, even though this is I crop, I had to insert a large copy to show you what I'm taking about. Your help is appreciated. :hail:

Don Simon · Jul 13, 2007

I can't really say for sure, but it looks to me like the main focus area you pointed out was not actually the main focus area... maybe it's just me or my screen, but it seems more like you were focusing on the plants in the immediate foreground... Was the camera on fully-auto AF point, or did you focus it by selecting a focus point or focusing manually?

Since you were using a shutter speed of 1/500 with a wide-angle lens, I don't think a tripod would have made much difference.

TBaraki · Jul 13, 2007

Shooting at ISO 800 isn't helping the situation either. I'd agree with the above poster that the foreground trees seem to be what the camera focused on.

Irminsul · Jul 13, 2007

It was in full-auto focus, with manual exposure. My EOS Viewer program confirmed that the circled area was the point of focus (i.e., that's where the program superimposed the red square marker). I was thinking that the fact that the plants are the ones that are in focus may mean the the lens's focus is de-centered or something. I agree, I should have checked the ISO before shooting, but to what extent does that affect sharpness of focus?

Don Simon · Jul 13, 2007

ISO won't affect the focus at all... however at higher ISOs the image may not be quite so clear... at ISO 800 the camera may be applying some noise reduction when it processes the Jpegs, which will result in some softening.

As for whether there is a problem with the lens... it's possible, but I would take a lot of shots in order to try and confirm it. Try selecting the focus points yourself; it may not make a difference but it's worth a try.