Da 15mm F4

max889 · 02-10-2010, 11:43 AM

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.

asdf · 02-10-2010, 11:47 AM

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.

summonbaka · 02-10-2010, 12:21 PM

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.

Wheatfield · 02-10-2010, 01:04 PM

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.

Marc Sabatella · 02-10-2010, 01:34 PM

Originally posted by asdf

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.

max889 · 02-13-2010, 03:15 PM

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.

Abbazz · 02-14-2010, 12:02 AM

Originally posted by max889

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.

Abbazz

huqedato · 02-14-2010, 06:15 AM

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.

Wheatfield · 02-14-2010, 09:00 AM

Originally posted by huqedato

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.

GeneV · 02-14-2010, 10:04 AM

Originally posted by Wheatfield

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.

Marc Sabatella · 02-14-2010, 01:51 PM

Originally posted by huqedato

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?

Wheatfield · 02-14-2010, 03:39 PM

Originally posted by Marc Sabatella

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?

Marc Sabatella · 02-15-2010, 12:28 PM

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.

bimjo · 02-15-2010, 02:27 PM

Originally posted by Wheatfield

Uh oh!
Sabatella and Wheatfield agree with each other.

How did things come to this point?

HAHA!!!!

I wondered where that thunderclap came from.

02-10-2010, 11:43 AM	#1
max889 Inactive Account Join Date: Jun 2009 Photos: Gallery \| Albums Posts: 35	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.

02-13-2010, 03:15 PM	#6
max889 Inactive Account Join Date: Jun 2009 Photos: Gallery \| Albums Posts: 35 Original Poster	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. Attached Images

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02-10-2010, 11:47 AM	#2
asdf Veteran Member Join Date: Jan 2009 Location: Canada Posts: 1,252	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
summonbaka Senior Member Join Date: Dec 2009 Location: Kagoshima, Japan Photos: Gallery \| Albums Posts: 237	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
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,981	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
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Originally posted by asdf 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.

02-14-2010, 12:02 AM	#7
Abbazz Pentaxian Join Date: Nov 2006 Location: Jakarta Posts: 667	Originally posted by max889 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. Abbazz

02-14-2010, 06:15 AM	#8
huqedato Inactive Account Join Date: Mar 2008 Location: France, EU Posts: 97	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
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,981	Originally posted by huqedato 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
GeneV Veteran Member Join Date: Oct 2008 Location: Albuquerque NM Photos: Albums Posts: 9,830	Originally posted by Wheatfield 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
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Originally posted by huqedato 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
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,981	Originally posted by Marc Sabatella 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
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	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
bimjo Veteran Member Join Date: Jan 2008 Location: Pasco, WA Posts: 967	Originally posted by Wheatfield Uh oh! Sabatella and Wheatfield agree with each other. How did things come to this point? HAHA!!!! I wondered where that thunderclap came from.