DA 21 focus issues

Started Nov 23, 2006 | Discussions thread
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Greg Vaughan Regular Member • Posts: 459
DA 21 focus issues

I got my DA 21 lens a couple days ago. In playing with it, I noticed some out of focus test shots. I did a search and read a couple of the DA 21 back focus threads and the various theories. I decided to run some tests and definitely feel at least my lens has an issue. Now it's true that I primarily plan to use this lens for landscape pictures, and it focuses to infinity in a short distance, so I'm not going to worry too much about it. However, if I'm taking indoor wide angle pictures, I'll use the kit lens, and I think it's bad that a more expensive lens like this doesn't do better.

I decided that I didn't like the angled focus chart method, since you have to trust that the person really had the focus point at the right place. So I made my own focus test as follows (I trust the idea is pretty self evident).

My test methodology was to focus on various things (some closer and some more distant), and then take a picture focusing on the center card.

Since the controversy also centered around whether the fault could possibly lie with the lens, or if this is just the way everything works when you get to that degree of wide angle, I tested the lens against the kit lens, shooting each at 21mm (obviously) and f4. This is shot from about 3 feet, which I'll freely admit is probably closer than I'd ever use this lens, but the results are still very interesting. I tried setting up a more distant test, but I'm having trouble getting clear results (I think I need to make similar test targets with larger text).

DA 21 limited at f4 (4 tries and the interesting bits copied into the following picture):

18-55 "kit" lens. 21mm at f4:

Focusing manually with the DA 21 got me a perfect result.

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