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**pentagor** · 04-03-2008, 04:52 AM

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?

Harald · 04-03-2008, 07:07 AM

I have to admit that bokeh seems not to be very beautiful....

**pentagor** · 04-03-2008, 10:43 AM

Thanks Harald!
Anyone else?? Any ideas?

Peter Zack · 04-03-2008, 10:55 AM

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.

Peter Zack · 04-03-2008, 10:58 AM

You can see the same thing with the Tamron in this shot:

**pentagor** · 04-03-2008, 12:07 PM

Thanks Peter. You must be right. On this one, the bokeh is really creamy.

hudsong · 04-03-2008, 12:14 PM

That lens just doesn't have good bokeh
If you want good bokeh, get a 50 1.4
Oneshotmeuk :: Becca & Nick
Oneshotmeuk :: Dreams&Dreamers

**pentagor** · 04-03-2008, 12:17 PM

Originally posted by hudsong

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.

hudsong · 04-03-2008, 12:55 PM

Yes! By the way, do you know of Ciril Jazbec? He's from Slovenia as well...
Ciril Jazbec Photography

deejjjaaaa · 04-03-2008, 01:24 PM

Bokeh

"...nisen-bokeh..."

also : About Bokeh

**pentagor** · 04-03-2008, 10:40 PM

Originally posted by hudsong

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.

lithos · 04-04-2008, 04:22 AM

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.

**pentagor** · 04-04-2008, 05:07 AM

Originally posted by lithos

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.

Peter Zack · 04-04-2008, 11:29 AM

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?

04-03-2008, 04:52 AM	#1
pentagor Site Supporter Join Date: Dec 2007 Location: Ljubljana, Slovenia Posts: 495	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, 10:58 AM	#5
Peter Zack Pentaxian Moderator Emeritus Join Date: May 2007 Location: Edmonton Alberta, Canada Photos: Gallery \| Albums Posts: 10,643	You can see the same thing with the Tamron in this shot: Last edited by Peter Zack; 06-14-2008 at 06:22 AM.

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04-03-2008, 07:07 AM	#2
Harald 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
pentagor Site Supporter Join Date: Dec 2007 Location: Ljubljana, Slovenia Posts: 495 Original Poster	Thanks Harald! Anyone else?? Any ideas?

04-03-2008, 10:55 AM	#4
Peter Zack Pentaxian Moderator Emeritus Join Date: May 2007 Location: Edmonton Alberta, Canada Photos: Gallery \| Albums Posts: 10,643	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, 12:07 PM	#6
pentagor Site Supporter Join Date: Dec 2007 Location: Ljubljana, Slovenia Posts: 495 Original Poster	Thanks Peter. You must be right. On this one, the bokeh is really creamy.

04-03-2008, 12:14 PM	#7
hudsong 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
pentagor Site Supporter Join Date: Dec 2007 Location: Ljubljana, Slovenia Posts: 495 Original Poster	Originally posted by hudsong 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
hudsong 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
deejjjaaaa Veteran Member Join Date: May 2007 Location: steel city / rust belt Posts: 2,043	Bokeh "...nisen-bokeh..." also : About Bokeh

04-03-2008, 10:40 PM	#11
pentagor Site Supporter Join Date: Dec 2007 Location: Ljubljana, Slovenia Posts: 495 Original Poster	Originally posted by hudsong 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
lithos Inactive Account Join Date: Oct 2007 Location: Brisbane, QLD, AUS Posts: 3,261	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
pentagor Site Supporter Join Date: Dec 2007 Location: Ljubljana, Slovenia Posts: 495 Original Poster	Originally posted by lithos 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
Peter Zack Pentaxian Moderator Emeritus Join Date: May 2007 Location: Edmonton Alberta, Canada Photos: Gallery \| Albums Posts: 10,643	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?

Sigma 17-70... strange bokeh?

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