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05-06-2010, 02:50 PM   #1
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DA15mm limited vs DA14mm

I just got a new DA15mm limited from B&H for my newly acquired K7 and I also picked up a used used FA31mm Limited and a also got the 20mm Voigtlander manual focus lens.
So far I am very pleased with the FA31mm tack sharp and also the 20mm Voigtlander,
but when I tried my DA 15mm limited, results not so good, very soft corners at all apertures f8-f16 some very noticeable CA which I can correct in post, but I can't fix soft corners. So I am not sure if I have a bad copy of the lens or should I be looking at the DA14mm lens, I know it's much bigger but I am not sure about the performance..

Thanks
Steven

05-06-2010, 03:22 PM   #2
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If you have not already read... try this thread

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/86234-15mm-lim...s-my-mind.html


cheers
05-06-2010, 04:23 PM   #3
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The DA 14 will not give you noticeable improvement in your results, and is a heavier and bulkier ultrawide prime than the 15 ltd.

You may need to take your 15 ltd back for review by your vendor if you're not getting good images, but posting examples with intact EXIF would help us help you more.
05-06-2010, 04:34 PM   #4
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Thanks Ash
Yeah I just don't know if I have a bad copy. I am sending it back to B&H I will try another one.
All the reviews I have read have not been so great with this lens especially wide open but stopping down usually helps, but for me on my copy stopping down even to F16 which I really don'w want to shoot at is still soft on the edges.

Steven

05-06-2010, 06:36 PM   #5
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I'd post some sample images. But most likely, you're simply seeing the same two thng as anyone else: it's almost impossible to get the corners in focus on a 15mm lens, especially at f/4 or f/5.6, and even if do, the *extreme* corners are indeed not quite as sharp as some lenses at those apertures. The DA14 won't be an improvement, though.
05-06-2010, 06:54 PM   #6
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If you are considering the DA14, you may as well look at the DA 12-24. It is not that much bigger and heavier than the DA14. I think it is even the same price. The only drawback is the minimum focusing distance.

I know, the DA 12-24 is 1 stop slower but at this range of focal length and thus the possible low handheld shutter speed, that may not matter to you (it does not to me).
05-06-2010, 06:56 PM   #7
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How's your 20mm Voigtlander? I just received my 40mm and like it so far, thinking of the 20mm and 58mm to complete the trinity.
05-06-2010, 07:00 PM   #8
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Marc,
I guess my expectations are a "little" high especially on a crop sensor. If this were FF then I would understand.
Oh well I was hopping for a little better result but even at f8-f11 did not improve things to much.
I am also trying the 20mm Voigtlander which is working quite well. Very impressed.

Steven

05-06-2010, 08:55 PM   #9
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At f/8 - f11, the DA15 is the sharpest lens out there, even n the corners, as measured by photozone - again, assuming you manage to actually have the corners in focus. That's why I'm suggesting you post samples, to see if your copy actually might be defective, or if you just have unreasonably high expectations.
05-06-2010, 09:03 PM   #10
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Its good that you post some images and exifs that you said are soft on corners @f8-f11..
@ f4 it may be soft on corners but @ f8, you must be expecting too much or you have a bad copy.
05-06-2010, 09:24 PM   #11
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Here is an image but I can't seem to upload a larger version of it
steven
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05-07-2010, 02:14 AM   #12
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Steven, this is not an image that will show us the apparent softness you are talking about. Indeed, it looks sharp at this resolution, even at the corners from what I can see, but a 100% crop would tell us more. Correct focusing at f/8 should give you results comparable to the best of lenses.
05-07-2010, 03:17 AM   #13
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QuoteOriginally posted by Ash Quote
Steven, this is not an image that will show us the apparent softness you are talking about. Indeed, it looks sharp at this resolution, even at the corners from what I can see, but a 100% crop would tell us more. Correct focusing at f/8 should give you results comparable to the best of lenses.
Thought the same and would be happy with that image just looking at it as is
05-07-2010, 07:50 AM   #14
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QuoteOriginally posted by Ash Quote
Steven, this is not an image that will show us the apparent softness you are talking about. Indeed, it looks sharp at this resolution, even at the corners from what I can see, but a 100% crop would tell us more. Correct focusing at f/8 should give you results comparable to the best of lenses.
And to synthesize what you and Mark have said, correct focus does not mean letting the AF lock on the middle of the photo, which usually sets the lens at infinity. The difference in distance between the corners and the center on an ultrawide lens can be so great that the depth of field scale and manual focus are often required if you really want the corners sharp. This has really come home to me since I started using the M20/4 on film. On that lens, I get reasonably sharp corners in many scenes only by putting the infinity mark just inside the DOF mark for my aperture.

The only thing I can see on the photo Steven uploaded is that the roof on the left edge may not be as sharp as the roof as it moves toward center. All of that roof would appear to be at infinity (which on this lens begins at about 4 feet), so this would not be a focus issue. It is still not a badly resolved photo.
05-07-2010, 08:04 AM   #15
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Look at the far upper-right corner, where that little house is. (Well, it looks little in the picture.)

What's the funky stuff happening along the top edges of the roof? Is that background clouds or hills, or is something weird going on? It looks pixelated.
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