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11-14-2017, 04:11 PM   #1
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Pentax-DA 15mm F4 distortion vs Pentax HD Pentax DA 21mm f/3.2

Considering adding a wide angle prime.

1. Never purchasing a prime wide angle before, should I expect some image distortion with the 15mm?

2. Also, any general opinion on the above 15mm vs 21mm?

11-14-2017, 04:20 PM - 1 Like   #2
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Both the DA15 and DA21 are excellent, but very different lenses.

The DA15 has low distortion - so low that I've never really corrected for it, as far as I can remember. It's a superb rectilinear wide-angle, and rightly has a lot of fans. I don't shoot mine very often, but I'm always impressed when I do.

The DA21 has (of course) a much narrower field of view. It exhibits a certain amount of fairly mild and simple barrel distortion, which is easily corrected internally for JPEG, or in post-processing if you're shooting RAW. It's very popular, and one of my all-time-favourite lenses.

As I said, these lenses have very different fields of view, so they arguably suit quite different use-cases. It's down to what you intend to shoot, and how, as to which would be best - but they're both great
11-14-2017, 04:26 PM   #3
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Agree with the above. The one thing I miss from APS-C is the DA 15mm. It was my sunrise lens and did a superb job. Really wish Pentax would come out with a FF lens with similar size, field of view and flare resistance.
11-14-2017, 04:34 PM - 1 Like   #4
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In answer to your second question, I can state my experiences with the 15 vs. the 21 on my K-5.

I find the 21 to be the widest lens I would ever use when I had taking pictures of people as my main subjects in mind.

I have found the 15 to be of use in two specific instances - in the back lanes and alleyways of large cities (specifically Melbourne, Australia) to take in a large slice of life where milling throngs rather than individuals were the focus, and on museum ships, where the corridors and spaces are fairly narrow anyway and where the widest possible FOV is welcome (the new 11-18 should prove tempting in that regard, when it comes).

I have found the 21 to be useful as a general street photography lens, and at social gatherings where I wanted to take pictures of individuals or small groups of people placed firmly in the context of their surroundings.

By the time you are talking about taking portrait-like shots of individual people, you want something like the DA40/2.8 Limited and its roughly 60mm-equivalent FOV (similar to the classic old 58mm). And THAT, in my opinion, is why the DA20-40/2.8-4.0 WR was invented.

The alternative to that, if you could find one easily or it were still being made, is the FA20-35, which carries certain advantages if you also shoot film or a K-1 (or a DSLR that can't drive an SDM or DC motor), but 20mm on full frame is not that far off from the FOV of the 15mm on APS-C, and that comes back to the use cases I outlined above.

11-14-2017, 04:41 PM - 1 Like   #5
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What primes do you already have? I enjoy the DA 21mm very much, wonderful colours and contrasts, very compact, and good sharp rendering of details. The main downsides are its aperture and distortion. The aperture is not a big problem, at least for me, because most of the time I use the lens between f5.6 an f8 anyway (for DoF). Distortion is a bit of a problem, though. Definitely not a portrait lens imo. But it depends how you angle the lens. If the camera is level and parallel to the subject the distortion is not that annoying, but if you angle it, then the distortion is visible on straight lines. But overall a great lens.

Btw, I think both of these lenses have their own threads on the forum and lot of user reviews. I doubt either lens will disappoint you, just get the FoV that you don't have yet. 15mm is really wide, very very wide. 21mm is wide, but manageable and has a bigger range of uses
11-14-2017, 05:53 PM - 1 Like   #6
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I first get a DA15 and later a DA21.
I like both 15 and 21.They are the older version, green ring. I like starbursts effect on green ring version

As people mentioned on earlier answer, the field of view between the two are quite difference. I often go out with both of them.

21 get a lot more use day and night because I like its field of view. Don’t hesitate to use it wide-open if needed. I often us f3.2 for night street shooting.

For 15, I mainly use it for night long exposure. You have to keep the Lens curvature effect in mind when use 15 on infinity focus. [While center is super sharp, the rest of the frame is a bit soft though the extreme corners are moving back towards the sharp focus.] It’s more pronounced on higher density sense body like K-3. I didn’t have much problem on K-5. However, it is not a concern when use 21. (click the 2 links for sample images.)

A quick fix for 15; Make sure area 1/3 from a far corner is sharp. It will result in a little softer in the center but sharpness for the rest of the frame is much, much better. It works well for the frame as a whole when do landscape.

Last edited by pakinjapan; 11-14-2017 at 06:24 PM.
11-14-2017, 05:53 PM - 1 Like   #7
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I have the DA21 Limited and it is a great walk-around lens, street shooting lens, etc... I do not have a DA 15, but a DA 14mm and it is my goto lens for grand vistas, sunrise/sunset, etc....

11-14-2017, 07:18 PM - 3 Likes   #8
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QuoteOriginally posted by BigMackCam Quote
The DA15 has low distortion
I might have the wrong idea of what distortion is, but the windmills in the bottom right actually stand straight up in real life. If I was specializing in architectural photography I would get a different lens for this field of view. On the other hand, the DA 15's flare resistance is phenomenal and I don't mind the bent corners in my photos.

11-14-2017, 08:15 PM   #9
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Na Horuk

Actually moving from Canon to Pentax and do not yet have lenses for intended K70 purchase in December.

Plan was to fit the K70 in the order below:
1st- DA 35mm f/2.4

2nd- 100mm f/2.8 WR D FA smc Macro Lens

3rd- either the HD DA 15mm f/4 or DA 21mm f/3.2 (thus the original questions).

I thought the above may be a fair distribution of focal lengths.

I am clearly getting ahead of myself researching my 3rd purchase as that will be a bit down-the-road.


RGlasel

I may have been using incorrect terminology, but your wind farm picture is really what I was curious about. If the 15, or even the 21, would greatly cause the 'tipping' of objects in the lateral aspect of the frame, as your picture does. ...very nice pic by the way.
11-14-2017, 09:10 PM   #10
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Buy your lenses used here on the forums, save enough to also get bot the 15 and 21. For both the 21 and 15, get the green ring SMC versions and not the red ring HD version. The older SMC has nicer sunbursts.

IMO, get the 15. Exceptionally unique. Here is a 700 page thread on the joys of the 15mm: https://www.pentaxforums.com/forums/122-lens-clubs/86234-15mm-limited-contro...-club-712.html
11-14-2017, 09:21 PM - 4 Likes   #11
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QuoteOriginally posted by RGlasel Quote
I might have the wrong idea of what distortion is, but the windmills in the bottom right actually stand straight up in real life. If I was specializing in architectural photography I would get a different lens for this field of view. On the other hand, the DA 15's flare resistance is phenomenal and I don't mind the bent corners in my photos.
Your photo is demonstrating keystoning, due to your shooting upwards.
11-14-2017, 10:14 PM   #12
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Well given the choice go DA 15. The reason I say that is then once you give into LBA again and add the DA 20-40 to your kit and you will be set. It is like 2 Limited Primes in one PLUS the DA 15 on top of the 20-40 give you a great two lens kit.

I donít shoot with my DA 15 a ton BUT each time I do it impresses me!
11-15-2017, 01:23 AM - 2 Likes   #13
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QuoteOriginally posted by RGlasel Quote
I might have the wrong idea of what distortion is, but the windmills in the bottom right actually stand straight up in real life. If I was specializing in architectural photography I would get a different lens for this field of view. On the other hand, the DA 15's flare resistance is phenomenal and I don't mind the bent corners in my photos.
QuoteOriginally posted by luftfluss Quote
Your photo is demonstrating keystoning, due to your shooting upwards.
Exactly. This is perspective distortion, caused by shooting at an angle - rather than perpendicular - to the subject, and exacerbated by the wide field of view.

I was referring to barrel and/or pincushion distortion (see attached pic - barrel on the left, pincushion on the right). The DA15 exhibits just -1.41% distortion, which is very minor given the focal length. The DA21 exhibits -2.14%, which isn't bad at all but can be noticeable, and certainly benefits from correction in post-processing.
Attached Images
 

Last edited by BigMackCam; 11-15-2017 at 01:34 AM.
11-15-2017, 02:43 AM   #14
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QuoteOriginally posted by rptdc Quote
2. Also, any general opinion on the above 15mm vs 21mm?
The DA21 is a versatile lens, useable right from wide open, great for just about anything. The DA15 is wonderful if you are into shooting sunsetty skies. Don't try shooting groups of people with it. And you have to stop it right down or be very careful with focus to get acceptable edge sharpness.

DA15
DA21

Unless you are an exceptional person and can visualise the difference between 1.41 and 2.14 % barrel distortion I would not worry about that. The rectilinear projection of ultrawides - stretching of the frame edges - is what makes some shots look unnatural. Then again, it may be what you are after.
11-15-2017, 02:53 AM - 1 Like   #15
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QuoteOriginally posted by RGlasel Quote
I might have the wrong idea of what distortion is
You are quite correct. You have the wrong idea.

As others have said, this is perspective, not distortion. Ultra-wide lenses exaggerate it, but the only way to avoid it for this sort of shot is to climb a very tall ladder, process the bejeezus out of it, or get a tilt shift lens.

Different lens (considerably wider in fact), same problem:



Back on topic, I find the DA21 to be a really useful general purpose lens, with a very natural angle of view on crop. It definitely has some barrel distortion, but unless you're shooting brick walls it's not much of an issue. The DA15 is a wonderfully compact ultra-wide, but will always be a niche lens for me. The famous flare resistance of the 15 is almost matched by the 21, and the starbursts (I'm talking about the SMC variants here) are equal.

Last edited by Sandy Hancock; 11-15-2017 at 03:11 AM.
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