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02-10-2010, 11:43 AM   #1
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Da 15mm F4

I got this lens a week ago and I like it a lot, but I want to comment on some elusive issues and hear what others think about it.
First, the lens doesn't seem extremely sharp at f/4. But I wonder if that has to do with focus accuracy. My k20d seems to produce some small variations on approaching focus from close or infinity positions, enough to impact on sharpness. May be the small maximum aperture in such a wide lens taxes autofocus as much as it does my eyes on manual focus. Some results appear very sharp, some not quite, things look good with a +5 focus adjustment at infinity, but that's the other issue, that amount of correction is completely off for close focus. All this at a very finicky level, because everything looks more or less in focus, but I think getting critical focus right makes this a great lens for landscape photography, for example.

02-10-2010, 11:47 AM   #2
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Here's a quote from photozone: "The DA 15mm f/4 is capable of producing very sharp images. This is certainly true for the center resolution which is already stunningly high at f/4. The border quality is only "good" here and also affected by some field curvature problems (a curved focus field rather than a flat one)." You can take it as a reference to know what you should expect.
02-10-2010, 12:21 PM   #3
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Remember that this is really wide so you hit hyperfocal before reaching infinity even when its wide open at f/4, try something closer to what your normally desired focus point is and go from there.
02-10-2010, 01:04 PM   #4
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Pretty much any lens will benefit from stopping down a bit. The DA15 is no exception. It is decent wide open, and much better at 5.6.

02-10-2010, 01:34 PM   #5
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QuoteOriginally posted by asdf Quote
Here's a quote from photozone: "The DA 15mm f/4 is capable of producing very sharp images. This is certainly true for the center resolution which is already stunningly high at f/4. The border quality is only "good" here and also affected by some field curvature problems (a curved focus field rather than a flat one)." You can take it as a reference to know what you should expect.
Fits my experience perfectly. Center at f/4 is already pretty amazing. Borders less so, butnot as bad as it might first appear once you taken into account the fact that the borders are rarely in focus in the sort of tests we tend to throw together quickly - both because of DOF but also field curvature issues. It's still perfectly useful for what it is - after all, who shoots a wide angle lens at f/4 and has any right to expect the entire scene to fit within the DOF in the first place? In real life situatins where you'd use f/4, you don't expect the corners to be in focus. In landscapes, you do - and you don't shoot f/4.
02-13-2010, 03:15 PM   #6
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Thanks for the answers and Mark, after some more focus adjustments i get pretty much what you describe, excelent center sharpness wide open and all over at f/8. At f/8, using a tripod and with everything in the frame more than 1 meter away the results are amazing. I can't wait to do some landscapes.
I'm impressed with the quality of these digital combos, the IQ starts to demand techniques closer to medium format than 35mm to squeeze every drop of image quality out of them. By the way, the 15mm is pretty close to another lens I used on MF.
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02-14-2010, 12:02 AM   #7
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QuoteOriginally posted by max889 Quote
By the way, the 15mm is pretty close to another lens I used on MF.
Wow, Max, I recognize this big 50mm! Nice to meet you here.

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02-14-2010, 06:15 AM   #8
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I had this lens for about two weeks in december. I am now waiting for a wide zoom from pentax either to lean to Sigma 10-20.

Why ?
It simply deceived me regarding the resolution. It is rather a consumer optics in a pro shell. For a wide lens to be acceptable (at least) means to have a constant definition throughout the entire field. A panoramic landscape is unacceptable to be "weak" on corners and margins. So it is this lens: sharp in center but very poor in margins, regardless the aperture

I really think this lens is much overrated just for is it a "Limited".
For me, Limited used to mean a superb optics firstly, a fine shell came secondly only.

02-14-2010, 09:00 AM   #9
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QuoteOriginally posted by huqedato Quote
I had this lens for about two weeks in december. I am now waiting for a wide zoom from pentax either to lean to Sigma 10-20.

Why ?
It simply deceived me regarding the resolution. It is rather a consumer optics in a pro shell. For a wide lens to be acceptable (at least) means to have a constant definition throughout the entire field. A panoramic landscape is unacceptable to be "weak" on corners and margins. So it is this lens: sharp in center but very poor in margins, regardless the aperture

I really think this lens is much overrated just for is it a "Limited".
For me, Limited used to mean a superb optics firstly, a fine shell came secondly only.
You should take some time to educate yourself on the realities of lens design. Extreme retrofocal designs such as the 15 are generally not going to stand up to scrutiny as well as longer lenses.
Make pictures instead of measurebations.
The 15 is fine when used for photography.
02-14-2010, 10:04 AM   #10
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QuoteOriginally posted by Wheatfield Quote
Extreme retrofocal designs such as the 15 are generally not going to stand up to scrutiny as well as longer lenses.
Make pictures instead of measurebations.
The 15 is fine when used for photography.
Absolutely correct.

As can be seen from the bottom of the first playground photo I just posted in a thread on using the DA lenses on film, even the extreme edge, outside of the APS-C crop, is usable in actual photos. The sand and the bar at the bottom might or might not stand up to pixel peeping, but it looks pretty good in the photo.
02-14-2010, 01:51 PM   #11
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QuoteOriginally posted by huqedato Quote
So it is this lens: sharp in center but very poor in margins, regardless the aperture
Either your copy of the lens or your testing metholody was defective, then. Objective tests show your conclusion to be wrong: at f/8 or f/11, it beats every comparable lens available. it is true the corners aren't as great at f/4, assumign you could manage to shoot something where the corners were even in focus at f/4. that's next to impossible, though, and in any case, who shoots at f/4 when they want the entire field in focus?
02-14-2010, 03:39 PM   #12
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QuoteOriginally posted by Marc Sabatella Quote
Either your copy of the lens or your testing metholody was defective, then. Objective tests show your conclusion to be wrong: at f/8 or f/11, it beats every comparable lens available. it is true the corners aren't as great at f/4, assuming you could manage to shoot something where the corners were even in focus at f/4. that's next to impossible, though, and in any case, who shoots at f/4 when they want the entire field in focus?

Uh oh!
Sabatella and Wheatfield agree with each other.

How did things come to this point?
02-15-2010, 12:28 PM   #13
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Been known to happen. Actually, I'm blessed with an incredibly short memory for this kind of stuff; I'm too forgetful to carry grudges.
02-15-2010, 02:27 PM   #14
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QuoteOriginally posted by Wheatfield Quote
Uh oh!
Sabatella and Wheatfield agree with each other.

How did things come to this point?

HAHA!!!!

I wondered where that thunderclap came from.
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