[K5 Guy]

Hi guys,

Thinking about adding a wide angle (for landscape) lens to my K5 system.I understand that this has a crop factor of 1.5x...so what I'm curious about is how low can I go before I hit 'fish eye territory'? Don't know what I should be looking for in terms of keeping my shots in perspective and accounting for the crop factor:

eg. 10mm @ 1.5x= 15mm (16mm)

What I'm trying to say is will I have to go lower than a 10mm lens (considering crop factor) to keep everything in perspective or is that 5 or 6mm difference not worth worrying about?

Thanks for your advice!

edit: Sorry if I've got lens sizes wrong, just started in photography!

[newmikey]

Obvious UWA zoom options without the fisheye effect would be the Sigma 8-16 and both 10-20's as well as the Tamron 10-24, Pentax and Sigma 12-24
Prime options would include 14mm lenses from Sigma and Samyang, not sure if there are any other primes worth looking at at the UWA side.

[Clavius]

Obvious UWA zoom options without the fisheye effect would be the Sigma 8-16 and both 10-20's as well as the Tamron 10-24, Pentax and Sigma 12-24
Prime options would include 14mm lenses from Sigma and Samyang, not sure if there are any other primes worth looking at at the UWA side.

What about the DA 15 ltd?

I'm going to tag along in this thread, as I'm interested in adding a UWA myself. The opinions on the 15 ltd are very diverse! Some say it has ultra miracle sharpness, whilst others complain about the disappointing resolution. One thing I'm sure about though, is that I love a lot of the pictures in the "DA 15 controls my mind."-thread.

Very briefly, I owned two copies of the 8-16. Which was very disappointing to me. The borders and corners were so soft, that I ended up cropping all the pictures taken with that lens. What good is a 8mm picture if you end up cropping it back to a 20mm focal lenght?? I thought it was copy-variance, so I traded it for another copy, which had the same issues.

That's why I'm now looking at the 15mm.

[lytrytyr]

how low can I go before I hit 'fish eye territory'?

People talk about wide angle lenses as being "rectilinear" to mean that they are not designed as fisheye lenses.
As newmikey mentioned, there's a rectilinear Sigma zoom that starts as wide as 8mm.
But as Clavius mentioned, there may be problems with that lens,
depending on your luck in getting a good copy, or how critical you are.

Samyang (also available as "Bower," "Vivitar," "Rokinon," and other names)
have recently announced a rectilinear 10mm prime wide angle lens,
due probably some time in 2013, which may or may not work out better than the Sigma zoom.

Don't know what I should be looking for in terms of keeping my shots in perspective

What I'm trying to say is will I have to go lower than a 10mm lens (considering crop factor) to keep everything in perspective

I'm not quite sure what you mean by "keeping everything in perspective."
Unless you stick your nose really close to an extreme wide angle photo,
you may get a sense that the perspective looks distorted.
The wider the angle (so the shorter the focal length), the more extreme this effect will be.

The widest angle lens I have at the moment is the DA 15.
If you're careful about the composition with that lens,
you shouldn't get a sense of distorted perspective with it.
Personally, I like it both for landscape and for general reportage,
although some people are really picky about sharpness with landscape,
while others already have a problem with its perspective. YMMV.

[K5 Guy]

I have noticed in some landscape photos (and architecture) a kind of 'bending' at either end of the shot. I had always attributed that to the lens and so automatically thought 'fish eye' lens for some reason, that was the point behind the 'keeping everything in perspective' comment. I would just like to go out and take a nice shot of the coast, beach, mountains etc without the bending effect. I'm not sure if it was me or maybe PP editing?Maybe me lol!

[Clavius]

The widest angle lens I have at the moment is the DA 15.
If you're careful about the composition with that lens,
you shouldn't get a sense of distorted perspective with it.
Personally, I like it both for landscape and for general reportage,
although some people are really picky about sharpness with landscape,
while others already have a problem with its perspective. YMMV.

What's your opinion about the resolution of the DA15ltd?

I very much prefer user-opinions then resolution figures from charts.

[lytrytyr]

I have noticed in some landscape photos (and architecture) a kind of 'bending' at either end of the shot. I had always attributed that to the lens and so automatically thought 'fish eye' lens for some reason, that was the point behind the 'keeping everything in perspective' comment. I would just like to go out and take a nice shot of the coast, beach, mountains etc without the bending effect. I'm not sure if it was me or maybe PP editing?Maybe me lol!

OK, it sounds as you're referring to the "barrel distortion"
that affects most rectilinear wide angle lenses to a greater or lesser extent.
That distortion can usually be corrected fairly easily in PP,
for example using the Pentax Digital Camera Utility that is bundled with the K-5.
A more evil form is "mustache distortion,"
like with the M20/4 on full frame,
which is trickier to correct.

[lytrytyr]

What's your opinion about the resolution of the DA15ltd?

I very much prefer user-opinions then resolution figures from charts.

I'm very satisfied with it,
although in the interest of full disclosure,
I'm not printing landscapes at 20x30 inches
and taking a magnifying glass to the print.
(Frankly, for that, you'd do better with a view camera.)

To me, its big advantage over the zooms is its compactness.
You can use it on the street without scaring people.

One thing to bear in mind with that lens,
as with many wide angles, is the field curvature.
So the sharp focus at the edges
will be closer than the sharp focus in the center.
The trick is to match that to your subject.

[newmikey]

I've always been quite satisfied with the corner sharpness of my 8-16mm but maybe I got lucky. Now that things around your "fisheye" remark have been cleared up and it is obvious we're talking about barrel distortion, a few comments.

1. Many wide lenses have some barrel distortion - it is almost unavoidable by nature of the laws of optics.
2. Prime lenses will (and I'm willing to be corrected on this) exhibit less of this because the single focal length allows the manufacturer to avoid compromises in correcting it.
3. Eventually though, both correction in the lens design as well as correction in post-processing will introduce some unwanted corner effects. The former in the way shapes are distorted the further they are near an edge or corner of the image, the latter because existing pixels are "smeared out" over a larger area.

If you are really into architecturally correct images without any distortion and with corner to corner sharpness and detail, think about shooting multi-row panorama shots using a lens of average focal length with measured minimal or non-existing edge/corner issues. A good 35mm lens would be a nice candidate there.

[lytrytyr]

2. Prime lenses will (and I'm willing to be corrected on this) exhibit less of this because the single focal length allows the manufacturer to avoid compromises in correcting it.

Quite often, a zoom lens will transition
from barrel distortion at one end (usually the wider)
to pincushion distortion at the other,
so you can get a sweet spot somewhere in between
where there is very little geometric distortion.
My Tamron 17-50/2.8 (A16P) is like that at 24mm.
I don't have any UWA zooms, so I can't speak to those.

[Sandy Hancock]

DA15. Feels like a gem. Built like a tank. Remarkably sharp and incredibly flare resistant. Renders skies like it has a built in polarising filter. Did I mention starbursts?
That is all.

[johnyates]

One thing to bear in mind with that lens,
as with many wide angles, is the field curvature.

That's why I sold mine. If you're shooting landscapes, you're better off with the 12-24.

[lytrytyr]

That's why I sold mine. If you're shooting landscapes, you're better off with the 12-24.

With a lot of landscapes, field curvature can work in your favor.
A close foreground in the lower edges, and a more distant scene in the center.
The sky at the top being less sharp isn't a problem.

For street use, on the other hand, the zoom would be too large,
especially with the petal hood that the bulbous front element needs.
My Tamron 17-50/2.8 is not really discreet enough for street use,
and the 12-24/4 is comparable in size.

[Transit]

+1 sigma 8-16...my copy is beautifully sharp

[normhead]

I had my own thread similar to this one a while ago. My conclusion was Sigma 8-16, and the reason wasn't as much the lens quality, which was excellent, but the DA 15 ltd, I have to say, is unmatchable @ 5.6 for center sharpness, though it falls off at the edges, but at F8 it's excellent center and edge... to a degree I don't think you're going to match with any other lens. But the 8-16 has better control of CA. The DA 15 is no slouch, but the Sigma is outstanding for a lens of this focal length.

Toss into that that the Tamron 28-75 is quite simply one of the best lenses you can get on Canon and Nikon, and is availble in a Pentax mount. It's just one of those lenses you might buy a camera, just to get. (As is the 15 ltd.) If you're going with that lens, you might want to get the Tamron 10-24, as it's a much more compatible zoom range leaving only a gap of 24 to 28.

One other consideration... I have a shot that was by ruined purple fringing by my 10-17 fisheye that I want to take over again with a better corrected lens. The image was taken @ 15 mm. Which means, it is composed the way I want it (because I had the zoom which meant I could have gone longer or shorter had I desired). With the SIgma and Tamron 10-24 are rectilinear, and rectilinears don't give you the exact same field of view as fisheye. People say that but no one has ventured a guess how much difference it might be? 1mm, 2mm? Who knows. So I'm guessing the 15 ltd won't give me as much FoV as I want for this image. 15 mm fisheye is not the same as 15mm rectilinear. So my temptation is to go with the 8-16 SIgma, just to give me a bit of latitude in my framing. The spot I took the image from was hanging off a steep embankment with a creek in front of me and steep slope with no place to set up behind me, I took it with myself and the tripod supported against a small tree to keep from falling into the water, so lets not even speculate about moving forward or backwards, with my feet.