Rings within bokeh lights??

RollsUp · 12-26-2008, 05:04 AM

Sorry about the title, I don't know the exact words to describe it.
I'm wondering if this is normal shooting at F2.8 ISO 1600 1/10 with a Tamron 28-75 @75mm on a K20D. It's the circles within the red light bokeh I'm referring to. And why is there little spots in there too?

Marc Sabatella · 12-26-2008, 06:38 AM

JPEG compression artifacts?

alohadave · 12-26-2008, 06:39 AM

It has to do with how that particular lens renders bokeh. It's going to vary based on how far away the background is and which aperture you are at.

mattdm · 12-26-2008, 07:10 AM

Since they can be so attention-getting, rings like that are often considered to be a factor in "bad bokeh".

Isaac314 · 12-26-2008, 07:36 AM

I find this in the bokeh on my pentax-m 50mm 1.4. I think it is related in some way to the surfaces of the lens elements, but i cant work out how. Generally, your bokeh doesn't look too bad.

creampuff · 12-26-2008, 07:37 AM

The rings in the out of focus circles are characteristic of lenses that have aspherical lens elements. The aspheric lens element has subtle changes of the lens curvature where the edges are flatter to correct spherical aberration.

soccerjoe5 · 12-26-2008, 07:56 AM

I like it

ivoire · 12-26-2008, 08:20 AM

Agree with creampuff and alohadave. i ran into this once in a while with the sigma 10-20mm and used photoshop to smudge or blur the 'artifacts'.

heliphoto · 12-26-2008, 08:48 AM

My DA* 16-50 does this. I assumed the rings were an interference pattern of some sort.

Here's an example (also xmas lights)...

50mm, f/4, lens near close focus limit and lights about six feet away...

**Kerrowdown** · 12-26-2008, 05:58 PM

If you don't like 'em or can't live with them, it's time to get Photoshopping.

creampuff · 12-26-2008, 07:24 PM

I tend to feel primes typically show better bokeh rings because they don't have that many elements when compared to zooms.

yeedub · 12-26-2008, 07:40 PM

My DA* 16-50mm does that too. I can see rings inside my bokeh circles. At first I thought it might be a defect too

borno · 12-26-2008, 07:49 PM

Here's some good reading from an old thread by carpents, I think creampuff's right about the aspherical elements

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/17970-bokeh-sp...ng-result.html

rfortson · 12-26-2008, 08:19 PM

Originally posted by Marc Sabatella

JPEG compression artifacts?

I agree with Marc. Looks like a compression artifact to me.

I'll have to go back and look at some of my shots and see if I've gotten this before.

RollsUp · 12-27-2008, 03:24 PM

Thanks everybody. I'll take it that it as it being the normal characteristics for this lens since it shows up in the RAW file also.
Thanks for the link borno. I haven't read through it yet, I will go back and read it when I have more time.

12-26-2008, 05:04 AM	#1
RollsUp Veteran Member Join Date: Apr 2008 Location: AK USA Photos: Gallery Posts: 1,766	Rings within bokeh lights?? Sorry about the title, I don't know the exact words to describe it. I'm wondering if this is normal shooting at F2.8 ISO 1600 1/10 with a Tamron 28-75 @75mm on a K20D. It's the circles within the red light bokeh I'm referring to. And why is there little spots in there too?

12-26-2008, 07:40 PM	#12
yeedub Forum Member Join Date: Jan 2008 Location: Vancouver BC Canada Posts: 78	*DA 16-50mm** My DA* 16-50mm does that too. I can see rings inside my bokeh circles. At first I thought it might be a defect too

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
Different rings in 1,4/50	estudleon	Pentax SLR Lens Discussion	8	01-22-2010 09:13 AM
People Portrait, Christmas Lights, Octagon Bokeh	skyoftexas	Post Your Photos!	4	12-26-2009 02:33 PM
Step-up rings	MrTea	Pentax Camera and Field Accessories	3	05-26-2008 12:43 PM
Two apature rings?	regken	Pentax SLR Lens Discussion	9	01-02-2007 09:40 PM

12-26-2008, 06:38 AM	#2
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	JPEG compression artifacts?

12-26-2008, 06:39 AM	#3
alohadave Veteran Member Join Date: Jan 2008 Location: Quincy, MA Photos: Gallery \| Albums Posts: 2,024	It has to do with how that particular lens renders bokeh. It's going to vary based on how far away the background is and which aperture you are at.

12-26-2008, 07:10 AM	#4
mattdm Veteran Member Join Date: Feb 2007 Location: Boston, MA Photos: Gallery Posts: 2,948	Since they can be so attention-getting, rings like that are often considered to be a factor in "bad bokeh".

12-26-2008, 07:36 AM	#5
Isaac314 Veteran Member Join Date: Aug 2008 Location: London Photos: Gallery Posts: 417	I find this in the bokeh on my pentax-m 50mm 1.4. I think it is related in some way to the surfaces of the lens elements, but i cant work out how. Generally, your bokeh doesn't look too bad.

12-26-2008, 07:37 AM	#6
creampuff Veteran Member Join Date: May 2007 Location: Singapore Photos: Gallery Posts: 3,953	The rings in the out of focus circles are characteristic of lenses that have aspherical lens elements. The aspheric lens element has subtle changes of the lens curvature where the edges are flatter to correct spherical aberration.

12-26-2008, 07:56 AM	#7
soccerjoe5 Veteran Member Join Date: May 2008 Location: Philippines Photos: Gallery Posts: 1,343	I like it

12-26-2008, 08:20 AM	#8
ivoire Veteran Member Join Date: Mar 2007 Photos: Gallery Posts: 3,381	Agree with creampuff and alohadave. i ran into this once in a while with the sigma 10-20mm and used photoshop to smudge or blur the 'artifacts'.

12-26-2008, 08:48 AM	#9
heliphoto Veteran Member Join Date: May 2008 Location: Region 5 Photos: Gallery Posts: 2,539	My DA* 16-50 does this. I assumed the rings were an interference pattern of some sort. Here's an example (also xmas lights)... 50mm, f/4, lens near close focus limit and lights about six feet away...

12-26-2008, 05:58 PM	#10
Kerrowdown PEG Moderator Join Date: Aug 2008 Location: Highlands of Scotland... "Hold Infinity in the palm of your hand" - William Blake Photos: Gallery Posts: 57,819	If you don't like 'em or can't live with them, it's time to get Photoshopping.

12-26-2008, 07:24 PM	#11
creampuff Veteran Member Join Date: May 2007 Location: Singapore Photos: Gallery Posts: 3,953	I tend to feel primes typically show better bokeh rings because they don't have that many elements when compared to zooms.

12-26-2008, 07:49 PM	#13
borno Veteran Member Join Date: Nov 2006 Location: md-usa Photos: Gallery \| Albums Posts: 2,580	Here's some good reading from an old thread by carpents, I think creampuff's right about the aspherical elements https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/17970-bokeh-sp...ng-result.html

12-26-2008, 08:19 PM	#14
rfortson Veteran Member Join Date: Sep 2006 Location: Houston TX Photos: Gallery Posts: 2,129	Originally posted by Marc Sabatella JPEG compression artifacts? I agree with Marc. Looks like a compression artifact to me. I'll have to go back and look at some of my shots and see if I've gotten this before.

12-27-2008, 03:24 PM	#15
RollsUp Veteran Member Join Date: Apr 2008 Location: AK USA Photos: Gallery Posts: 1,766 Original Poster	Thanks everybody. I'll take it that it as it being the normal characteristics for this lens since it shows up in the RAW file also. Thanks for the link borno. I haven't read through it yet, I will go back and read it when I have more time.