Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
04-03-2008, 04:52 AM   #1
Veteran Member
pentagor's Avatar

Join Date: Dec 2007
Location: Ljubljana, Slovenia
Photos: Gallery
Posts: 473
Sigma 17-70... strange bokeh?

Hi!

I was testing my new Sigma 17-70 with some macro shots. I have two images to show to you.
I'm concerned about the bokeh on those two pics. It seems to me, as if it would be doubled if you know what I mean. What do you think? Is it just me, not used to such lens or is it something wrong with this lens?





04-03-2008, 07:07 AM   #2
Senior Member




Join Date: Sep 2006
Posts: 259
I have to admit that bokeh seems not to be very beautiful....
04-03-2008, 10:43 AM   #3
Veteran Member
pentagor's Avatar

Join Date: Dec 2007
Location: Ljubljana, Slovenia
Photos: Gallery
Posts: 473
Original Poster
Thanks Harald!
Anyone else?? Any ideas?
04-03-2008, 10:55 AM   #4
Pentaxian
Moderator Emeritus




Join Date: May 2007
Location: Edmonton Alberta, Canada
Photos: Gallery | Albums
Posts: 10,648
My guess would be that this is what you will come to expect with the lens in the close up (macro) mode. I have the Tamron 28-75 f2.8 Di and notice almost the exact same thing with my copy when the background is busy or there are highlights/high contrast colours in the background. If the image has a smoother colour like mostly a green or something else then the bokeh looks quite even and creamy.

This is one of the weaknesses of a zoom vs a prime. They just can't render the background as well. Even the much heralded DA*50-135 doesn't render a background nearly as well as the FA50 f1.4 or even a Tak 135 f2.5.

04-03-2008, 10:58 AM   #5
Pentaxian
Moderator Emeritus




Join Date: May 2007
Location: Edmonton Alberta, Canada
Photos: Gallery | Albums
Posts: 10,648
You can see the same thing with the Tamron in this shot:

Last edited by Peter Zack; 06-14-2008 at 06:22 AM.
04-03-2008, 12:07 PM   #6
Veteran Member
pentagor's Avatar

Join Date: Dec 2007
Location: Ljubljana, Slovenia
Photos: Gallery
Posts: 473
Original Poster
Thanks Peter. You must be right. On this one, the bokeh is really creamy.

04-03-2008, 12:14 PM   #7
Inactive Account




Join Date: Jan 2008
Location: Midwest
Photos: Gallery
Posts: 59
That lens just doesn't have good bokeh
If you want good bokeh, get a 50 1.4
Oneshotmeuk :: Becca & Nick
Oneshotmeuk :: Dreams&Dreamers
04-03-2008, 12:17 PM   #8
Veteran Member
pentagor's Avatar

Join Date: Dec 2007
Location: Ljubljana, Slovenia
Photos: Gallery
Posts: 473
Original Poster
QuoteOriginally posted by hudsong Quote
That lens just doesn't have good bokeh
If you want good bokeh, get a 50 1.4
Oneshotmeuk :: Becca & Nick
Oneshotmeuk :: Dreams&Dreamers
Thanks!
I didn't get it for a bokeh, but it is a good info anyway.

04-03-2008, 12:55 PM   #9
Inactive Account




Join Date: Jan 2008
Location: Midwest
Photos: Gallery
Posts: 59
Yes! By the way, do you know of Ciril Jazbec? He's from Slovenia as well...
Ciril Jazbec Photography
04-03-2008, 01:24 PM   #10
Veteran Member
deejjjaaaa's Avatar

Join Date: May 2007
Location: steel city / rust belt
Posts: 2,046
Bokeh

"...nisen-bokeh..."


also : About Bokeh
04-03-2008, 10:40 PM   #11
Veteran Member
pentagor's Avatar

Join Date: Dec 2007
Location: Ljubljana, Slovenia
Photos: Gallery
Posts: 473
Original Poster
QuoteOriginally posted by hudsong Quote
Yes! By the way, do you know of Ciril Jazbec? He's from Slovenia as well...
Ciril Jazbec Photography
No sorry, I don't know him, but he seems to be pretty good. Thanks for pointing out.
04-04-2008, 04:22 AM   #12
Inactive Account




Join Date: Oct 2007
Location: Brisbane, QLD, AUS
Posts: 3,262
How many aperture blades does it have? Are they evenly spaced?

Remember, odd-numbers of aperture blades act as if there are twice as many blades than there really are - five blades would act like a ten bladed aperture.

Either that, or it is just bad bokeh.
04-04-2008, 05:07 AM   #13
Veteran Member
pentagor's Avatar

Join Date: Dec 2007
Location: Ljubljana, Slovenia
Photos: Gallery
Posts: 473
Original Poster
QuoteOriginally posted by lithos Quote
How many aperture blades does it have? Are they evenly spaced?

Remember, odd-numbers of aperture blades act as if there are twice as many blades than there really are - five blades would act like a ten bladed aperture.

Either that, or it is just bad bokeh.
It has 7 blades.
04-04-2008, 11:29 AM   #14
Pentaxian
Moderator Emeritus




Join Date: May 2007
Location: Edmonton Alberta, Canada
Photos: Gallery | Albums
Posts: 10,648
The number of aperture blades doesn't entirely control the OOF bokeh in a picture. If the lens had say 20 blades (yeah I have a bellows macro lens that has that many) then the aperture hole will be almost perfectly round and the highlights in the background will look like circles. A lens with 5 or 6 blades will create hexagonal shaped highlights. Curved aperture blades will create smoother looking highlights than staright blades.

Proof that aperture blades are not the only factor is when you shoot any lens wide open. A lens wide open with poor optical design (in terms of bokeh) has a round image circle and still creates poor bokeh. A lens with good optical design and shot wide open will still create good bokeh. In both the blades are fully retracted and the bokeh is still the same respective to each lens.

I've never heard of this 5=10 thing. What exactly do you mean Lithos?
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!
k-mount, lens, pentax lens, sigma, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Bokina versus Bokeh Monster, which bokeh you prefer? Pentaxor Pentax SLR Lens Discussion 3 04-21-2010 01:50 AM
strange circular light bokeh? platinum Pentax SLR Lens Discussion 15 12-02-2008 03:29 AM
Very Strange benjikan General Talk 9 01-29-2008 07:44 AM
Strange Ducks thomasjmpark Post Your Photos! 13 01-19-2008 06:30 PM



All times are GMT -7. The time now is 04:04 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