Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-10-2018, 09:11 PM   #1
Pentaxian




Join Date: May 2016
Photos: Albums
Posts: 2,136
Can you check this DFA 15-30 sequence and compare to yours?

Hi all. Would be a great favor if other 15-30 owners can have a look at the full res sequence and let me know if it looks about right, or worse than yours.
I'm on a 3rd copy of this lens, first two purchased from Adorama were not good, this one from Kenmore Camera seems better, but maybe a bit worse than I expected it to be being such an expensive piece of gear,
and reading stellar reviews for Tamron 15-30 as well as the Pentax version.

Full-res sequence: Update your browser to use Google Drive - Google Drive Help

Pics are a bit processed, mainly to make details easier to see (raised shadows), and added a bit of sharpness to emulate a closer look to my usual working files.
Center is very good at all apertures, sides however are weaker, which is to be expected I guess.

What i've noticed is that with af I cannot nail focus spot on, and if it's off even by a tiny bit the sides go very soft. I don't know if this is my camera's issue at this point. I might have to send the lens together with the camera
for tune ups, which is pretty annoying since shipping such heavy items, and insuring them would cost quite a bit. Hand holding shooting does not work for me, I will to calibrate the af with a target within next couple of days,
see if that does anything for me. I took the lens on a trip yesterday, and majority of the hand held shots had soft sides due to focus being off by a hair. I tried single center point, 9 point, afc, afs and about every combination
I could think of lol, but I can't achieve consistent results yet.

Pretty tired of the process, my enjoyment of the purchase is spoiled, hopefully it comes back after few more shoots with current lowered expectations)

If anyone's interested - my previous 2 threads about the other 2 copies I had are here:
How to test Pentax 15-30 for decentering? - PentaxForums.com
Wanted - DFA 15-30 hand-held shots - PentaxForums.com

01-10-2018, 10:31 PM   #2
Site Supporter
Site Supporter




Join Date: Feb 2015
Photos: Gallery | Albums
Posts: 5,441
QuoteOriginally posted by awscreo Quote
I'm on a 3rd copy of this lens, first two purchased from Adorama were not good, this one from Kenmore Camera seems better, but maybe a bit worse than I expected it to be being such an expensive piece of gear, and reading stellar reviews for Tamron 15-30 as well as the Pentax version.
Everything is relative, including the review, relative for wide angle lenses. I guess your expectations of corner sharpness are set too high for WA lenses.Have you compared with the Nikon 14-24?
With regards to auto-focus with K1 and 15-30, the K1 is not that precise around the hyperfocal distance especially with short focal length. Downsample images to 24Mp and all of a sudden realize everything is good.

Last edited by biz-engineer; 01-10-2018 at 10:49 PM.
01-11-2018, 01:36 AM   #3
Pentaxian




Join Date: Dec 2011
Posts: 2,066
QuoteOriginally posted by awscreo Quote
Hi all. Would be a great favor if other 15-30 owners can have a look at the full res sequence
Run the decentering test exactly as described in the article here from a tripod and post the full res results.
Run it again with the next widest lens you have and post the results to see if the same corners are weakest.

The lower right corner on 15/2.8 looks different than the rest.

In addition I suggest to take two shots at 15/2.8 of the exact same subject handheld and manual focus (so the focus distance cant change), only that for the second shot you turn the camera upside down (yes, pushing the trigger is a little awkward then, but not impossible). Compare them.

But with uwa's it can also be that the camera mount is not super exactly the way it is intended, which might happen if camera/lens combo ever receives a hit in a bag or elsewhere.
Actually even minor force to the lens barrel can influence corner sharpness on uwas.

Most uwa's including this one have a field curvature where the focus "plane" on the edges is different from the center. So AF will be correct for one part only (center OR edges) on perfectly flat subjects. If the AF is miscalibrated a little bit into the wrong direction that will exarcerbate the effect.
01-11-2018, 06:43 AM   #4
Pentaxian




Join Date: May 2016
Photos: Albums
Posts: 2,136
Original Poster
Thanks for replies guys. I haven thought that maybe my mount is not aligned properly, doubt it's something I can fix myself, or even test properly. Don't think my other lenses show any signs of that. Next day off I'll take 15-30 and rokinon for another round of tests. I guess I'm going to keep this copy, just because I'm tired of sending them back and waiting for refunds. I was planning to send camera to Precision camera again this winter, will send the lens with it and ask them to test it with their equipment.

What do you think of f8-16 at 15mm? Do my samples look similar to yours? I mostly use those values for landscapes, so that would be the most important for me.

Downsampling things to make my feelings go away is not an options since I was planning to sell prints taken with this lens, I'd need all the resolution I can have in case someone wants a big one.

01-11-2018, 06:58 AM   #5
Site Supporter
Site Supporter




Join Date: Mar 2009
Location: Gladys, Virginia
Photos: Gallery
Posts: 19,122
I think it looks pretty good from f5.6 and 15mm on and all of the photos at 30mm look pretty good to me. The right lower corner at 15mm is the only place I see some softness and that goes away stopped down a couple of stops. I would probably keep it, but I guess it depends on how perfect you want it to be and how often you plan to shoot at 15mm and f2.8.
01-11-2018, 11:18 AM   #6
Pentaxian




Join Date: May 2016
Photos: Albums
Posts: 2,136
Original Poster
QuoteOriginally posted by Rondec Quote
I think it looks pretty good from f5.6 and 15mm on and all of the photos at 30mm look pretty good to me. The right lower corner at 15mm is the only place I see some softness and that goes away stopped down a couple of stops. I would probably keep it, but I guess it depends on how perfect you want it to be and how often you plan to shoot at 15mm and f2.8.
This copy seems better than previous two I tried, so I will probably end up keeping it. It gives me hope that with a tune up from Pentax it'll be pretty close to excellent. I shoot stars quite a bit so I do need the 2.8 often enough, with the 15-30 I wanted to have a one in all tool for astro, Landscapes and interior stuff, I took a plunge and bought my first pro zoom, maybe I was expecting too much, I have nothing to compare it to except my rokinon 14 2.8 which seems more consistent and just as sharp, and af being what it is it seems manual focus is not a massive negative point.

Last edited by awscreo; 01-11-2018 at 11:27 AM.
01-11-2018, 07:00 PM   #7
Loyal Site Supporter
Loyal Site Supporter
Mikesul's Avatar

Join Date: Sep 2009
Location: Phoenix, AZ
Posts: 5,179
Is what the OP is finding much different from the mild distortion reported in the Pentax Forum review of the lens?
HD Pentax-D FA 15-30mm F2.8 ED SDM WR Review - Distortions | PentaxForums.com Reviews
01-12-2018, 06:53 PM   #8
Pentaxian




Join Date: May 2016
Photos: Albums
Posts: 2,136
Original Poster
actually, I went back through my Rokinon 14 files and compared them directly to 15-30, seems I was mistaken, 15-30 resolves more fine detail for sure, and sides of the frame are also sharper with the DFA. I guess it didn't matter to me on a $300 lens, but I expected way too much from the pro zoom.

01-26-2018, 10:39 AM   #9
Pentaxian




Join Date: May 2016
Photos: Albums
Posts: 2,136
Original Poster
So I finally had time to take some astro stuff, and I think I can see some things out of order here. The top left corner definitely shows more coma. The photo seems out of focus, but the same exact settings with astrotracer gave me pinpoint stars, so I guess my exposure time was too long for such high res sensor (I was at 20s iso 3200). I will definitely be sending the combo to repairs after I'm back from holidays. Pity I don't have time to fix it now, I am planning to visit few places with good potential for astro photography..

Full res jpeg: _TIM3720.JPG - Google Drive
01-27-2018, 05:47 PM   #10
Pentaxian




Join Date: Apr 2007
Location: Oklahoma USA
Posts: 1,600
QuoteOriginally posted by awscreo Quote
So I finally had time to take some astro stuff, and I think I can see some things out of order here. The top left corner definitely shows more coma. The photo seems out of focus, but the same exact settings with astrotracer gave me pinpoint stars, so I guess my exposure time was too long for such high res sensor (I was at 20s iso 3200). I will definitely be sending the combo to repairs after I'm back from holidays. Pity I don't have time to fix it now, I am planning to visit few places with good potential for astro photography..

Full res jpeg: _TIM3720.JPG - Google Drive
Please report back when you have your lens repaired (or not repaired, as the case may be.)
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!
af, bit, check this dfa, dfa 15-30 sequence, focus, google, hand, k-mount, lens, pentax lens, sequence, shots, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: (all sold) K-1 body, DFA 15-30, FA77, DFA 28-105, Zeiss ZK 35 f/2 kaspy Sold Items 16 10-14-2017 09:31 PM
DFA 24-70 or DFA 15-30 for the K-1? Hattifnatt Pentax SLR Lens Discussion 42 10-25-2016 08:03 AM
Compare DA 70 with DFA* 70-200 @ 70 Paul the Sunman Pentax SLR Lens Discussion 20 10-06-2016 05:54 AM
K5 II - Check FA77 - Check FA31 - Check: Now should I keep my 16-50 2.8 Borislav Pentax SLR Lens Discussion 8 08-06-2013 08:14 AM
Suggestion Camera comparison chart within reviews section / compare check boxes ElStellino Site Suggestions and Help 4 02-22-2012 02:19 PM



All times are GMT -7. The time now is 02:01 PM. | See also: NikonForums.com, CanonForums.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