Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
02-02-2008, 07:45 PM   #1
Senior Member




Join Date: Jan 2008
Location: Boston
Posts: 142
New to Pentax - CA, PF

I'm really surprised at how badly the 31mm Limited controls CA. The lens is everything it's talked up to be, as far as sharpness and build quality, but in situations where my old Nikon D70+Sigma 30mm f/1.4 shows very little chromatic aberrations (but is otherwise unappealing), the K10D and 31mm has rather noticeable color fringes.

I've searched the forums, and apparently CA affects all Pentax lenses to some degree, but how much is too much? Has anyone bough a 31mm Limited, thought the CA was excessive, exchanged it and got a new one that was better? The really unhappy thing is that I also have a 77mm Limited, but I'm afraid to open the box...

-T

02-02-2008, 07:58 PM   #2
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,400
QuoteOriginally posted by twinda1 Quote
I'm really surprised at how badly the 31mm Limited controls CA. The lens is everything it's talked up to be, as far as sharpness and build quality, but in situations where my old Nikon D70+Sigma 30mm f/1.4 shows very little chromatic aberrations (but is otherwise unappealing), the K10D and 31mm has rather noticeable color fringes.

I've searched the forums, and apparently CA affects all Pentax lenses to some degree, but how much is too much? Has anyone bough a 31mm Limited, thought the CA was excessive, exchanged it and got a new one that was better? The really unhappy thing is that I also have a 77mm Limited, but I'm afraid to open the box...

-T
How about an example?

Show us what you think is unacceptable.

BTW all lenses will have fringing in out of focus areas. it is not limited to pentax
02-02-2008, 08:20 PM   #3
Ole
Administrator
Ole's Avatar

Join Date: Sep 2006
Location: Copenhagen, Denmark
Photos: Gallery | Albums
Posts: 3,881
I haven't noticed any color fringing in the several hundreds of shots I have made with my 31mm.
02-02-2008, 09:33 PM   #4
Senior Member




Join Date: Jan 2008
Location: Boston
Posts: 142
Original Poster
Example attached

Hi, thanks for the quick replies. I've attached a 100% crop -- the fringing is definitely in the out of focus area in the eye and also along the face. Shot wide open. I'm pretty sure I haven't noticed this type of fringing on the Sigma 30mm and D70 combo. It's possibly the K10D too though -- reidreviews.com has noted CA for the 3 or so lens tested so far with the K10D.

-T

Attached Images
View Picture EXIF
PENTAX K10D  Photo 

Last edited by twinda1; 02-02-2008 at 09:52 PM.
02-02-2008, 11:19 PM   #5
Veteran Member
aegisphan's Avatar

Join Date: Nov 2007
Location: New Mexico
Posts: 815
That's not too excessive. You can correct it quite easy. Anyway, from my personal experience and reviews from other sites (e.g. 16-9.net on the 85mm comparison), Pentax does have more CA issue than other brands. I recently did a comparison between the 31 and the Distagon 28. The 28 had very minimal amount of CA even at wide open, while the 31 at 2.8 still had more CA. This was in extreme condition (sunlight directly on white surface). I found that if i stopped my 31 down to f5.6, the CA was gone. CA is not a major problem to me since i can somewhat control it with post processing.

By the way, that's a lovely picture. I like it.
02-03-2008, 09:16 PM   #6
Senior Member




Join Date: Jan 2008
Location: Boston
Posts: 142
Original Poster
QuoteOriginally posted by aegisphan Quote
...

By the way, that's a lovely picture. I like it.
Thanks, even with the fringes, I'm liking my results so far. I highly doubt they're visible on smaller prints.
02-04-2008, 01:48 PM   #7
TKH
Veteran Member
TKH's Avatar

Join Date: Aug 2007
Location: Germany
Posts: 371
QuoteOriginally posted by Ole Quote
I haven't noticed any color fringing in the several hundreds of shots I have made with my 31mm.
I have noticed a lot of color fringing in the several hundreds of shots I have made with my 31mm. This was one reason to change my lenses from FA to DA. Now Im very happy.

See also this thread: lose your respect

My personal look of view is:

On my K10D the three DAs are

- quicker AF
- smaller
- lighter
- exposing is correct
- mutch less CAs
- have quick shift

I really know that a mutch better photgraph than me will perhaps take mutch better pics from using the FAs instead of using the DAs. But with my little photographic scills, the DA will work better.

Rainer
02-04-2008, 09:30 PM   #8
Senior Member




Join Date: Jan 2008
Location: Boston
Posts: 142
Original Poster
Now this a little excessive, no? It's a pretty high contrast situation, so if it fringes, so be it. I'm trying to determine if I have a bad sample of either the 31 or K10D -- unfortunately both are new. What do you all think?

Attached Images
View Picture EXIF
PENTAX K10D  Photo 
02-04-2008, 09:47 PM   #9
Site Supporter
SpecialK's Avatar

Join Date: Dec 2006
Location: So California
Photos: Gallery
Posts: 14,903
QuoteOriginally posted by twinda1 Quote
Now this a little excessive, no? It's a pretty high contrast situation, so if it fringes, so be it. I'm trying to determine if I have a bad sample of either the 31 or K10D -- unfortunately both are new. What do you all think?

Looks like my old Opteka conversion lens :-(

And also like a used 300mm f/4 Pentax I had for a week and returned (but that was only $99).
02-05-2008, 03:59 AM   #10
Veteran Member




Join Date: Jan 2008
Location: Seattle, Washington, USA
Photos: Gallery
Posts: 813
QuoteOriginally posted by twinda1 Quote
Now this a little excessive, no? It's a pretty high contrast situation, so if it fringes, so be it. I'm trying to determine if I have a bad sample of either the 31 or K10D -- unfortunately both are new. What do you all think?
The CA on the edge of that ear is rather bad. However, the outer lobe of the ear is/is just about totally blown out. That's pretty provocative to a shorter focal length (if my experience with the SMC Takumar 35mm is anything to go by). If you shot that in RAW, I'd try a bit of exposure compensation, maybe on just the ear (process twice, once for less exposure, then a layer mask in Photoshop). The CA green fringe can be reduced in pp in several ways, as well (I like the selective color/color replacement trick). Good luck, and watch out for those blown highlights!

Last edited by christinelandon; 02-05-2008 at 04:02 AM. Reason: clarification and comparison
02-05-2008, 05:05 AM   #11
Inactive Account




Join Date: Mar 2007
Photos: Gallery
Posts: 3,675
Chromatic Aberrations (CAs)

Lateral chromatic aberrations (color shadows at harsh contrast transitions) are very low for a wide angle lens. The issue shouldn't be really field relevant with an average pixel width of 0.4px to 0.6px at the image borders. You can force the lens to produce some mild purple fringing (color blooming) at large aperture settings and in extreme contrast situations. (Emphasis added)


the EXIF shows the first picture is shot at f1.8 and the second at f2.

Courtesy of Pentax Lens Tests

Last edited by J.Scott; 03-30-2009 at 03:27 AM.
02-05-2008, 05:10 AM   #12
Veteran Member
wlachan's Avatar

Join Date: Sep 2006
Location: Canada
Photos: Albums
Posts: 2,626
QuoteOriginally posted by twinda1 Quote
Now this a little excessive, no? It's a pretty high contrast situation, so if it fringes, so be it. I'm trying to determine if I have a bad sample of either the 31 or K10D -- unfortunately both are new. What do you all think?
I think it's normal for this lens. I have noticed the same green CA even on film. However, I have found it happens only on OOF areas. Recently I took 3 identical shots on tripod and 2 were with this same green CA, but surprisingly the 3rd one was free of it. I have no explanation of it however.
02-05-2008, 05:30 AM   #13
Veteran Member
blende8's Avatar

Join Date: Feb 2007
Location: Bremen, Germany
Photos: Albums
Posts: 1,484
QuoteOriginally posted by twinda1 Quote
Now this a little excessive, no? It's a pretty high contrast situation, so if it fringes, so be it. I'm trying to determine if I have a bad sample of either the 31 or K10D -- unfortunately both are new. What do you all think?
This is longitudinal CA (aka "fringing") and it looks pretty normal to me.
I think you have to live with that.
Or you have to buy the very expensive Leica lenses, which are known for their outstanding chromatic correction.

You may want to look at my recent test of the Voigtlander 40/2:
Voigtlnder Ultron 40/2.0 vs Pentax FA 35/2.0
If you scroll down a bit, you will see some CA examples from this lens.
The FA31 will very probably look similar.
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!
31mm, k-mount, pentax, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search



All times are GMT -7. The time now is 01:33 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