15mm f4 - soft copy?

hello,
i got the 15mm limited last month, and i've just come back from a wkd in barcelona where i tried it a little. I had high expectations as it's my first limited lens. Of course i have read every review on the pentax forum (9.26 score), and i am aware it needs to be stopped down to f8 or even f11 to get sharpness and even then it has mixed reviews on sharpness. i am not someone who is craving for sharpness, but i have to say it does look very soft, even in the middle.

i do love its size, and the colours/contrast are very good, it needs very little post processing, I also tested the flare which is indeed very well controlled. but i found that the close up shots are usually very good, but the landscape with little foreground are super soft across the frame. i am used to the sigma 10-20mm and it is clearly in much higher league.

i tried to shoot everything i could at f8+, i didnt do some proper "testing", but overall i am not that impressed, which brings 3 questions:

- am I too new at this and will learn how to use it? i didnt play with the AF points.. I use the newly acquired K-S2
- is it possible the lens is either front/back focusing when the focus is far away (i.e landscape), the focus definitely looks fine on close objects
- is it not the right lens for me? i was hoping to use it for city breaks and landscape as it's easy to carry around
- is my copy soft?

thanks

I guess posting a sample will help people to help you You can have a look at the samples in http://www.pentaxforums.com/forums/122-lens-clubs/86234-15mm-limited-controls-my... ; try to find images with similar subjects as yours and compare.

thanks - i will try to post some pics -

not very impressed by most of the pics on the forum, it's quite similar to my experience = filled foreground look good, but the landscapes look soft for most.

here are two shots,. it's not bad in the center - the ones that are bad everywhere are the ones taking trees from far away, i.e assuming it didnt focus right.
this is all acceptable of course, but nothing amazing

They look good in my opinion.

With regards to trees far away, I have a feeling your expectations are wrong. UWAs will not give you detail in subjects far away; the magnification is too small for that. You will be able to see the outlines, you will be able to recognize colors (and as a result perceive a little more detail) but you will not be able to recognize individual leaves ; looking at your first image that's already the case for the the tree/bush at the right and for the second image for the trees at the left of the building.

The theory is simple. At 50 meters you have a horizontal FOV of 80 meters. 1 pixel on your sensor represents roughly 80/5500 equals about 1.6 cm of the real life scene at 50 meters.

thanks for your comments, sadly i sold the 10-20mm so cant compare at 15mm like for like, but from memory it felt like sharper across the frame, even at f5.6.

I will also try to stop it down to f11 (which i rarely do but will need to break this habit) as it seems to be the sweet spot for this lens, i did compare it to the sigma 20mm f1.8 closed down to f8, and the latter was noticeably sharper, although it's 20mm so as you said the distance makes a difference.

i guess i will hold onto it for a little while as it's nice to use (tiny/light), and 15mm is a nice focal lens (i think 13mm would be the best though).

Don't the leaves on trees move in the wind, which as you're using a wide-angle lens and the size of he leaves make them look soft.

yes and no, i dont have the exif data in front of me but for instance the two pics above are shot probably around 1/125sec or 1/250sec, for 15mm focal lens I would expect that despite the small wind it would lock any movement, also if that was the case in the leaves in the middle would also be blurry - in the first picture there is a big difference between the leaves in the middle which appear sharp and the ones on the far right of the image, comparing the ones that are at the same distance from the camera.

i realise the website re-sizes the pic so you can't see the full resolution :/

It's definitely a quirky little lens. I think as a professional, I'll have to keep the 12-24, but I really prefer the 15 Ltd. The 15 produces beautiful rich, warm images and I think the softness (which is indeed a trait) adds to this 'film like' quality. So I will keep both, but if someone's paying, I'll lug the 12-24 to the shoot
I hoped it would make a good star lens, but it's way to soft for such exacting work.
If I get a chance I will compare it to the 17-50 Tamron and the DA12-24 wide open, and stopped down to around f11.

the main difference is indeed the size, the 17-50mm is amazing, i've never tried the 12-24mm although was tempted, but too bulky and pricey. 15mm is a good compromise!
i look forward to seeing some tests, i have no doubt the sigma at 17mm will be much sharper

I've just done a test with the 15 Ltd, the Tamron 17-50, the DA12-24 and the Fisheye. All as close as poss to 15, wide open and at f11.
The Tamron had a slight advantage in reach but lost that advantage by being f2.8.
All the lenses were sharp in the middle two thirds at f11 with the 15Ltd being noticeably softer at the edges. The 12-24 was sharp right across the frame and easily wins that contest.
Wide open, the Tamron wins by a comfortable margin despite being the only f2.8 - very useable and sharp.
all the others are quite soft, but still perfectly useable. They all suffer from CA wide open at the edges but the Ltd has the least.
My own comments about rendering nicely are not apparent in this test; they all look pretty much identical. Maybe I just take the Ltd to nicer places
The fisheye stands out as a incredibly versatile lens, capable of minimal distortion as well as dramatic distortion (fab for skies) and on my reason trip to Morocco, was one of my most used lenses.
I wouldn't dismiss any of these lenses.
For stars and dark venues it's the Tamron
For paid work (with enough light) it's the 12-24
For personal work it's the 15 or fishy, not least because they will go in your pocket!
I think Pentax create lenses with definite character; sharpness, especially at the edges, is not always important and can lead to other benefits.

thanks - very true, you are talking about the fish eye 10-17? i love this lens, so much fun and often very good results, although the subject needs to be quite centered.

i am keeping the 15mm for now, as you said sharpness is not the most important thing!

now i need to find an excuse to go outside and shoot!

Yep, the 10-17.
When I bought my K10D in 2007 I bought one lens - the fisheye
Never regretted it; always come home with an interesting photo.
I later bought the 16-45 but it was a bit meh, so I sold it.
Here's the 15 f4 shot. Focused on the white house, centre.