Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-02-2011, 04:46 PM   #16
Veteran Member
Christine Tham's Avatar

Join Date: Nov 2008
Location: Sydney, Australia
Photos: Gallery
Posts: 2,269
Original Poster
QuoteOriginally posted by Just1MoreDave Quote
I see something different: the same type of aberration I get from the Cosina 55mm f1.2 wide open, and an old Vivitar 24mm f2. An example I have on line shows it
Interesting. I am also inclined to believe the results wide open are due to lens aberration - whether that is normal for the lens or not I'll leave it for each to make their own mind, but I get exactly the same results on two different copies.

It's very hard to design a zoom that is as sharp as a prime on all focus lengths and all apertures, a practical impossibility I would suggest.

I think Pentax optimised the DA*50-135 to be extremely sharp when stopped down by at least 1-2 stops - that's the right decision I think as I normally shoot at f4 and above.

If I compare that to Sigma for example, I find the Sigma much sharper wide open, but doesn't gain sharpness as I stop down so end up not as good under normal shooting conditions (my opinion only - Sigma owners, don't bite me!)

05-02-2011, 08:58 PM   #17
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by Christine Tham Quote
If that was true, then the primes would have been also blurry.
Not necessarily. Sometimes you get lucky.

QuoteQuote:
Also, I deliberately included photos in that gallery taken at 1/750 and 1/1000 second that are also soft. Are you suggesting camera shake for those as well?
Which image at 135mm and f/2.8 that you also have shot with the A135 are you talking about? Tthe only direct comparison I saw was the teddy bear.

QuoteQuote:
Anyway, this is a rehash of an earlier thread where plenty of other people (including Adam) have chimed in to say those photos are normal for the lens.
Some of them might be, but not those two - the only ones that were relevant to the comparison.
05-02-2011, 09:04 PM   #18
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by Just1MoreDave Quote
I see something different: the same type of aberration I get from the Cosina 55mm f1.2 wide open, and an old Vivitar 24mm f2. An example I have on line shows it:
I don't know; it doesn't really look the same to me. Christine's samples look more irregular. The very different look between f/2.8 and f/4 kind of seals the deal for me. The shape of the distortion is different - round in one, straight in the other. The f/4 especially looks exactly like camera shake to me. Shutter speed was in the 1/6 range, so blur seems quite plausible. Certainly, there should be enough doubt to warrant re-running the test.
05-02-2011, 09:34 PM   #19
Pentaxian




Join Date: Jun 2009
Location: GMT +10
Photos: Albums
Posts: 10,600
Irrespective of the lens, what's with the current mania for shooting wide-open, in broad daylight no less? It just invites problems with razor thin DOF, especially with a 135 prime at any close distance.

It's not a sin to use smaller apertures. One shouldn't feel guilty about using f5.6 or above on a f2.8 lens.

05-02-2011, 09:40 PM   #20
Veteran Member




Join Date: Mar 2009
Location: Midwest
Photos: Gallery
Posts: 1,407
QuoteOriginally posted by rawr Quote
Irrespective of the lens, what's with the current mania for shooting wide-open, in broad daylight no less? It just invites problems with razor thin DOF, especially with a 135 prime at any close distance.

It's not a sin to use smaller apertures. One shouldn't feel guilty about using f5.6 or above on a f2.8 lens.
Wait... isn't shallow DOF the raison d'etre of photography? Isn't it half of what makes full frame absolutely necessary for professional photographers? Stop it, you're scaring me!

Well, it does look really cool when you get the focus right.
05-02-2011, 09:48 PM   #21
Pentaxian




Join Date: Jun 2009
Location: GMT +10
Photos: Albums
Posts: 10,600
QuoteOriginally posted by jstevewhite Quote
Wait... isn't shallow DOF the raison d'etre of photography?
hehe. Indeed. But I don't buy into that.

To paraphrase Bruce Barnbaum, 'a blurred distraction in the background is still a unacceptable distraction. Good bokeh doesn't trump good composition'.

Last edited by rawr; 05-02-2011 at 09:53 PM.
05-02-2011, 10:29 PM   #22
Veteran Member
Christine Tham's Avatar

Join Date: Nov 2008
Location: Sydney, Australia
Photos: Gallery
Posts: 2,269
Original Poster
QuoteOriginally posted by Marc Sabatella Quote
Not necessarily. Sometimes you get lucky.



Which image at 135mm and f/2.8 that you also have shot with the A135 are you talking about? Tthe only direct comparison I saw was the teddy bear.



Some of them might be, but not those two - the only ones that were relevant to the comparison.
Think about it. If there was camera shake, it would affect the photos with longer exposure time, ie. the ones at f8 rather than the ones at f2.8.

Given that none of the photos at f8 show any sign of camera shake, we can reasonably conclude camera shake is not present for shorter exposure times.

I'm not sure what you are asking for Marc - I shot the teddy bear in the same conditions with all lenses, so the one taken by the A135mm at f2.8 is directly comparable to the one taken by the DA*50-135mm at 135mm f2.8.

Similar for 50mm. The photos taken on the A50mm would be directly comparable to the ones taken on the DA* 50-135mm at 50mm.
05-02-2011, 10:37 PM   #23
Veteran Member
Christine Tham's Avatar

Join Date: Nov 2008
Location: Sydney, Australia
Photos: Gallery
Posts: 2,269
Original Poster
QuoteOriginally posted by rawr Quote
Irrespective of the lens, what's with the current mania for shooting wide-open, in broad daylight no less? It just invites problems with razor thin DOF, especially with a 135 prime at any close distance.

It's not a sin to use smaller apertures. One shouldn't feel guilty about using f5.6 or above on a f2.8 lens.
Actually, I agree. Most of the time I shoot at f4 to f8. I didn't even notice the DA* 50-135 was soft at first because I didn't even use it at f2.8.

And when I eventually noticed it, I blamed the softness on user error. It was only when I noticed the softness was ALWAYS there, even at 1/4000 s, that I started suspecting maybe it wasn't just me.

But in answer to your question, I'm not sure about the "mania" and I can't speak for others, but these photos were for me practising accurate manual focus on the A135.

In fact, my album on Facebook from which these photos were selected from is called "Manual Focusing on the A135mm at f2.8" - I basically name albums after a specific technique that I'm trying to work on on a particular day. I have albums called Macro, HDR, etc.

05-02-2011, 10:43 PM   #24
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by Christine Tham Quote
Think about it. If there was camera shake, it would affect the photos with longer exposure time, ie. the ones at f8 rather than the ones at f2.8.
Not necessarily. These things can be pretty random. All I knoew is what I see - that f/4 image looks *exactly* like camera shake to me. Doesn't it to you? The f/2.8 is less conclusive, but another test in better light so you can get better shutter speeds would lay the matter to rest.

QuoteQuote:
I'm not sure what you are asking for Marc - I shot the teddy bear in the same conditions with all lenses, so the one taken by the A135mm at f2.8 is directly comparable to the one taken by the DA*50-135mm at 135mm f2.8.
Right, but the only such images I saw were all shot at very slow shutter speeds. You mentioned shots at 1/1000" - if any of *those* are direct comparisons, then links to those images would be useful.
05-02-2011, 10:57 PM   #25
Veteran Member
Christine Tham's Avatar

Join Date: Nov 2008
Location: Sydney, Australia
Photos: Gallery
Posts: 2,269
Original Poster
QuoteOriginally posted by Marc Sabatella Quote
Not necessarily. These things can be pretty random. All I knoew is what I see - that f/4 image looks *exactly* like camera shake to me. Doesn't it to you? The f/2.8 is less conclusive, but another test in better light so you can get better shutter speeds would lay the matter to rest.



Right, but the only such images I saw were all shot at very slow shutter speeds. You mentioned shots at 1/1000" - if any of *those* are direct comparisons, then links to those images would be useful.
None of the images look like camera shake to me. And the results are certainly not random, every image taken on every lens at f8 are all sharp. If they were as random as you seem to think, then they would have shown up on at least one image taken at f8. Given the camera was mounted on a tripod on a concrete slab (with a false timber veneer flooring), I think camera shake is extremely unlikely (unless you think I was doing the test near Sendai in Japan).

No there's no direct comparison at higher shutter speeds with the A135mm, but the softness I see at f2.8 on this lens I see in every photo, regardless of shutter speed.
05-02-2011, 11:51 PM   #26
Pentaxian




Join Date: Jan 2010
Location: Vancouver, BC
Posts: 1,421
QuoteOriginally posted by Marc Sabatella Quote
Not necessarily. These things can be pretty random.
Christina used a set methodology to test her lenses exactly the same so as to minimize the random factors - as we all probably were taught in HS Chemistry - to say these things can be pretty random is to imply her tests are meaningless. Then every review of Pentax lenses by the forum members whether favourable or unfavourable is also rendered meaningless. If anyone so adamantly disputes her results, let him or her run a test of these same lenses using Christina's methods and present his/her results here. Otherwise, it all just hot air.

I don't know why A135/2.8 has such a poor reputation here in the forums. Some of the best lenses have been of simple constructions. CZJ Sonnar 135/3.5 and it's clone, Jupiter 37a are highly sought after for their sharpness and they consist of 4 elements in 3 groups. I would love to see a comparison test of Pentax A135/2.8, CZJ Sonnar 135/3.5 and Jupiter 37a. Someday I may run such a test, if and when I acquire the latter two lenses.

Thanks,
05-03-2011, 01:57 AM   #27
Veteran Member
creampuff's Avatar

Join Date: May 2007
Location: Singapore
Photos: Gallery
Posts: 3,955
I had a very good copy of the A 135mm f/2.8 and while it's optical quality was decent and sharpness was OK, it wasn't really that great when pitted alongside my FA 135mm f/2.8 or even the K 135mm f/2.5.
I personally think it was one of the poorer performing A series lenses, with obvious softness at the corners.
05-03-2011, 03:08 AM   #28
Veteran Member
Abbazz's Avatar

Join Date: Nov 2006
Location: Myanmar
Posts: 510
This "softness" at f/2.8 looks like coma to me. Apparently, there was a quality control issue with the Tokina 50-135 and Pentax 50-135 in some batches:

Discussion Forums @ Nikonians

Poor Tokina quality control: Pentax SLR Talk Forum: Digital Photography Review

Cheers!

Abbazz
05-03-2011, 03:46 AM   #29
Veteran Member
selar's Avatar

Join Date: Jul 2007
Location: Sydney, Australia
Photos: Gallery | Albums
Posts: 2,035
Here's what my copy of the 50-135 looks at 135/2.8:

SG102403.JPG - Windows Live
05-03-2011, 04:34 AM   #30
Veteran Member
Christine Tham's Avatar

Join Date: Nov 2008
Location: Sydney, Australia
Photos: Gallery
Posts: 2,269
Original Poster
QuoteOriginally posted by selar Quote
Here's what my copy of the 50-135 looks at 135/2.8:

SG102403.JPG - Windows Live
Thanks for posting this.

That image looks kind of soft to me, and suffers from similar issues to my lens. I would have expected a sharp lens to disclose texture on the rendered surfaces.

Be interesting if you have a version at f8 and compare the difference.
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!
f2.8, ferry, friend, k-mount, pentax lens, photos, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Nature Some wide open Tulips JeffJS Post Your Photos! 6 04-18-2010 07:37 AM
Landscape Wide Open Garden rustynail925 Post Your Photos! 2 03-09-2010 08:22 AM
77/1.8 wide open... igor Post Your Photos! 14 08-17-2009 05:36 AM
F- 50mm 1.7 Wide Open bwield Post Your Photos! 2 07-08-2009 12:46 PM
DA* 55mm 1.4 wide open samples!!! Nice Steelski Pentax SLR Lens Discussion 2 02-16-2009 04:27 AM



All times are GMT -7. The time now is 12:25 PM. | 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