Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-13-2013, 10:40 AM   #16
Pentaxian
kh1234567890's Avatar

Join Date: Sep 2010
Location: Manchester, UK
Photos: Gallery
Posts: 2,327
Back to the original poster : It would seem that this is what you get with this lens. I don't have it, so I'm not really qualified to comment.

You could try for a replacement sample, but Pentax QC being what it is (rubbish), you might end up with a worse one. At least this one is reasonably centered. It would be interesting to see if the softness goes away as you stop down or move away from the zoom extremes. But from a quick look through shots posted on Flickr it would seem that it is like this even stopped down.

I would agree that it would be reasonable to expect a 400 lens to be better. It is almost as if someone at Pentax got their sums wrong or that the marketing people won over the lens designers. All those people buying this as a kit with the K-5iis are bound to be disappointed

03-13-2013, 10:55 AM   #17
Pentaxian
VisualDarkness's Avatar

Join Date: Nov 2011
Location: Uppsala, Sweden
Photos: Gallery
Posts: 4,439
QuoteOriginally posted by kh1234567890 Quote
I would agree that it would be reasonable to expect a 400 lens to be better. It is almost as if someone at Pentax got their sums wrong or that the marketing people won over the lens designers. All those people buying this as a kit with the K-5iis are bound to be disappointed
Well as I said before, other manufacturers charge the same or more for similar lenses so it's fair to say "this is what you get". K-5IIs will get an outstanding center performance! Borders won't need any AA filter.
03-13-2013, 11:15 AM   #18
Pentaxian




Join Date: Jul 2010
Location: Oregon
Photos: Albums
Posts: 1,417
Critical sharpness at wide aperture and all focal lengths is not a reasonable expectation of a lens with greater than 3:1 zoom range.
03-14-2013, 01:06 AM   #19
Junior Member
tx0h's Avatar

Join Date: Oct 2011
Photos: Gallery
Posts: 35
Original Poster
hello,

thank you so much for the constructive comments.
i just like to show that i don't shot mosaics at flat walls all the time.
again, you can click the images and take the magnifier lens to
zoom in.







but i also like to explain that shooting this mosaic wall is one of
my tests with lenses, and i think it is a valid test.

my concerns about edge and corner sharpness are, that i get
limited in composing an image. with a lens which can't deliver
good quality on the edges and corners and is 'only' sharp
in the center, i need the subject in the center which may lead
to boring center subject images with less dynamic in the
image statement. please correct me on this so i can feel
more comfortable with this handicap.

sure, i mainly use manual prime lenses and this lens will
be one of the few AF zoom lenses i use. i choose it
because it covers a long range, is WR sealed and not
that big and heavy.

greetings,
tx0h


Last edited by tx0h; 03-14-2013 at 05:29 AM.
03-14-2013, 06:37 AM   #20
Site Supporter
cali92rs's Avatar

Join Date: May 2011
Location: Long Beach, CA
Posts: 3,203
I have this lens, and it is on my camera more than any other lens, by a good amount......
Buuuuuut, that is because most of the time I am lazy and don't want to carry other lenses. If IQ is your top priority, I would choose a different lens.

Having said that DXO really does a good job correcting a lot of this lens' flaws, if you are willing to make another financial investment. I would only do that though if you have other lenses which are supported by DXO.
03-14-2013, 06:50 AM   #21
Pentaxian
JinDesu's Avatar

Join Date: Jun 2011
Location: New York City
Photos: Gallery
Posts: 5,624
I've seen DXO do wonders with this lens. That being said, after seeing your explanation, I don't think this lens is so bad in the corners that it would hinder your composition (unless you print super large size, or like to post full size images and pixel peep). The normal web sized image would not show any softness when it comes to this lens. You'd be more worried about CA on the edges showing up, which is easy to correct (especially with DXO).
03-14-2013, 07:36 AM   #22
Pentaxian
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 23,772
QuoteOriginally posted by tx0h Quote
sure, i mainly use manual prime lenses and this lens will
be one of the few AF zoom lenses i use. i choose it
because it covers a long range, is WR sealed and not
that big and heavy.
Try it at 24mm, sharp edge to edge, probably better than your manual primes... from 22-40 it's probably not worth your while to take it off the camera for the small amount of improvement in IQ you might get, if everything is perfect. The CA is another issue. I'm not sure why, but sometimes it affects IQ and sometimes it doesn't. It's not always an issue. For my shooting style the issue with this lens is sometimes it's not fast enough.
03-14-2013, 09:13 AM   #23
Junior Member
tx0h's Avatar

Join Date: Oct 2011
Photos: Gallery
Posts: 35
Original Poster
well, a bit off-topic but hey:

i checked the dxo website but they don't support my
operating system. as you can read here,

QuoteQuote:
Pentax = Linux/Unix - the smart mans choice!
i run darktable with linux myself and hope i will find
some ways to solve the problems with the softness,
somehow. do you know how dxo does it? maybe you
can show me some extreme examples croped before
and after dxo?

and you all say my sample of the lens behaves like it
should. it's not better or worse than i could expect?
then i will keep it. it's my first and only sealed lens.

thanks again,

tx0h

03-14-2013, 09:24 AM   #24
Pentaxian
JinDesu's Avatar

Join Date: Jun 2011
Location: New York City
Photos: Gallery
Posts: 5,624
QuoteOriginally posted by tx0h Quote
well, a bit off-topic but hey:

i checked the dxo website but they don't support my
operating system. as you can read here,



i run darktable with linux myself and hope i will find
some ways to solve the problems with the softness,
somehow. do you know how dxo does it? maybe you
can show me some extreme examples croped before
and after dxo?

and you all say my sample of the lens behaves like it
should. it's not better or worse than i could expect?
then i will keep it. it's my first and only sealed lens.

thanks again,

tx0h
See: https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/175026-da-18-1...ml#post1822139

No idea how it's done, but it's pretty awesome.
03-14-2013, 11:02 AM   #25
Pentaxian
kh1234567890's Avatar

Join Date: Sep 2010
Location: Manchester, UK
Photos: Gallery
Posts: 2,327
Just a quick question : The EXIF data in your test shots shows the in-camera CA and lens distortion corrections as set to on.

If this is true, then the K-5 is not doing a very good job of correcting either
03-14-2013, 11:06 AM   #26
Pentaxian
kh1234567890's Avatar

Join Date: Sep 2010
Location: Manchester, UK
Photos: Gallery
Posts: 2,327
QuoteOriginally posted by JinDesu Quote
It is correcting CA, tweaking exposure and contrast and doing some sharpening. What's the big deal - doesn't everyone do that ?
03-14-2013, 11:19 AM   #27
Pentaxian




Join Date: Nov 2011
Photos: Gallery | Albums
Posts: 3,615
QuoteOriginally posted by tx0h Quote
do you know how dxo does it?
Technically, by deconvolution.

Deconvolution - Wikipedia, the free encyclopedia

"In practice, finding the true PSF is impossible, and usually an approximation of it is used, . . . based on some experimental estimation by using known probes."

So that would be a point where they would need to know the specific lens.
03-14-2013, 11:21 AM   #28
Junior Member
tx0h's Avatar

Join Date: Oct 2011
Photos: Gallery
Posts: 35
Original Poster
QuoteOriginally posted by kh1234567890 Quote
Just a quick question : The EXIF data in your test shots shows the in-camera CA and lens distortion corrections as set to on.

If this is true, then the K-5 is not doing a very good job of correcting either
thats true.
i switched it off yesterday. i think i can do it much better
on the desktop. it also delays the cam.

@JinDesu: thanks for the link. i'll try to find someone
who can 'heal' one of my test shots. the example in the
link didn't look so bad (the original) but i also can't
really guess the focal length, aperture and exposure.

greetings,
tx0h
03-14-2013, 11:41 AM   #29
Pentaxian
kh1234567890's Avatar

Join Date: Sep 2010
Location: Manchester, UK
Photos: Gallery
Posts: 2,327
QuoteOriginally posted by tx0h Quote
thats true.
i switched it off yesterday. i think i can do it much better
on the desktop. it also delays the cam.
Strange. It usually does a pretty good job, except that it slows down the camera too much. Any chance of snapping a couple of random shots with the correction on and off to see if it is actually working with this lens ?
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
corners, da 18-135mm wr, edges, images, iq, k-mount, lens, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
DA 18-135mm F3.5-5.6 WR and filter fit Wingincamera Pentax SLR Lens Discussion 5 12-01-2012 08:56 AM
If my choices are the DA 18-135mm WR and DA 18-250mm, can I go wrong? Codazzle Pentax SLR Lens Discussion 26 03-27-2012 10:24 PM
For Sale - Sold: Pentax DA 18-135mm WR and DA-L 55-300mm ED arm_jstp Sold Items 2 03-05-2012 12:35 AM
Concerns about DA 18-135mm corner IQ at 135mm bwDraco Pentax SLR Lens Discussion 6 06-13-2011 05:31 PM
For Sale - Sold: Pentax DA 18-135mm WR + CIR-PL and UV Filters (US) kbrede Sold Items 5 05-06-2011 06:15 AM



All times are GMT -7. The time now is 04:16 AM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top