Weird Bokeh with 40mm Limited vs. XS

Outis · 07-08-2015, 11:41 AM

Off and on, I consider buying one of the 40mm pancakes, either the 40mm XS or the 40mm Limited. One of the things that bothers me, though, is the weird bokeh I see in reviews of the 40mm Limited (e.g. this and this), stuff like this and this. How prevalent is it? Is it just an issue for the 40mm Limited, or does the 40mm XS produce it as well?

shaolen · 07-08-2015, 11:58 AM

I have had three 40mm xs' before and never noticed this but then again I haven't been paying particular attention. Since these lenses are basically the exact same lens in different housings I would imagine it happens on xs

Na Horuk · 07-08-2015, 12:10 PM

I never noticed that odd bokeh effect, and it doesn't really bother me. I quite like the bokeh of my DA 40mm XS, which has nice round bokeh even if stopped down. I like to use the 40mm for flower photography with relatively wide aperture just because of this (I posted some photos on my 500px page and around these forums, but they might be difficult to find). You can look for the "flat wonder" thread on these forums, which is dedicated to the DA 40mm. You can also look at the sample photo gallery and search for the DA 40mm, see how often that bokeh effect appears.

The DA 40mm comes in three versions:
SMC DA Ltd: This is the first one. Has hood, distance scales. Was not advertised as having "rounded aperture blades", though some say its blades are just as rounded as the later versions.
SMC DA XS: This one originally bundled only with K-. Cheaper, flatter, no distance scales, no hood, and a silly 27mm filter ring. Optically it should be the same as the SMC, but it was advertised as having rounded aperture blades, so it might have smoother bokeh when stopped down. This is the smallest one, I think it was even the smallest DSLR lens ever, at least back when it was introduced. But I doubt some other brand beat this (ignoring pinhole lens covers).
HD DA Ltd: This is the latest version, with red ring. Same as SMC, but newer lens coatings and also advertised as rounded aperture blades. I guess this is optically the best one, though, by how much? I dunno. The Pentax Forums did a SMC vs HD test some time ago, so you can look there to see comparisons.

**hyyz** · 07-08-2015, 02:00 PM

I have noticed the same with my 40mm XS. I shot the plastic base of a table lamp. The highlight showed up like that, I recall.

photodesignch · 07-08-2015, 03:41 PM

Originally posted by Na Horuk

I never noticed that odd bokeh effect, and it doesn't really bother me. I quite like the bokeh of my DA 40mm XS, which has nice round bokeh even if stopped down. I like to use the 40mm for flower photography with relatively wide aperture just because of this (I posted some photos on my 500px page and around these forums, but they might be difficult to find). You can look for the "flat wonder" thread on these forums, which is dedicated to the DA 40mm. You can also look at the sample photo gallery and search for the DA 40mm, see how often that bokeh effect appears.

The DA 40mm comes in three versions:
SMC DA Ltd: This is the first one. Has hood, distance scales. Was not advertised as having "rounded aperture blades", though some say its blades are just as rounded as the later versions.
SMC DA XS: This one originally bundled only with K-. Cheaper, flatter, no distance scales, no hood, and a silly 27mm filter ring. Optically it should be the same as the SMC, but it was advertised as having rounded aperture blades, so it might have smoother bokeh when stopped down. This is the smallest one, I think it was even the smallest DSLR lens ever, at least back when it was introduced. But I doubt some other brand beat this (ignoring pinhole lens covers).
HD DA Ltd: This is the latest version, with red ring. Same as SMC, but newer lens coatings and also advertised as rounded aperture blades. I guess this is optically the best one, though, by how much? I dunno. The Pentax Forums did a SMC vs HD test some time ago, so you can look there to see comparisons.

=_=; You totally missed the original Pentax-M 40mm F2.8.. the actual "father" of all 40mm.....

Na Horuk · 07-08-2015, 03:53 PM

Originally posted by photodesignch

=_=; You totally missed the original Pentax-M 40mm F2.8.. the actual "father" of all 40mm.....

Are they the same optical design? Because what I read is the M 40mm is not as good as the DA versions so I assumed it is different design, but I guess you are right. If OP wants an affordable MF version

**reduno** · 07-08-2015, 07:07 PM

Now I'm going to have to look closely at some of my photos to see if I can see anything. I did get some odd reflections using a filter on the XS, possibly as the small size places it very close to the lens. In night shots, I got mirror images of light points on the opposite side of the picture (almost like they were reflected around the center point of the lens).

Mistlefoot · 07-08-2015, 07:41 PM

https://www.flickr.com/groups/1945188@N23/pool/

519 photos here should give you a pretty good idea of the XS. It's a lens that never leaves my bag (it fits in a filter pocket) but I still seem to prefer to use my 35mm 2.4.
I am sure with a flickr search you could find a good number of photo's with the DA's as well.

ZombieArmy · 07-08-2015, 07:47 PM

The 40mm's Bokeh isn't what I'd call bad. I'd call it "hard to tame". I've gotten some lovely bokeh and some not so lovely.

macTak · 07-09-2015, 04:27 AM - **1 Like**

That Bokeh is the result of over-corrected spherical aberration. Both the Ltd and XS versions have the same optical formula and should therefore be the same in this regard. From my experience with lenses that have some over-corrected spherical aberration (e.g., M35/2), it only occurs (or at least is noticeable) in a certain range of circumstances--for instance wide open when focusing to within 2ft and then with a background that is significantly behind the plane of focus. Based on the samples of the DA40 you link to, the range of circumstances seems pretty similar. Depending on your shooting habits, it may or may not be prevalent, but generally is not catastrophic even when it occurs as only very tight crops/very large prints will make it visible.

shaolen · 07-09-2015, 07:09 AM

so looking at optical design of the m40 and seems to be same

macTak · 07-09-2015, 07:54 AM

Originally posted by shaolen

so looking at optical design of the m40 and seems to be same

They are both 5/4 (Unar Elmar hybrid) designs, but there are definite differences in the shapes of the elements that would unquestionably affect their characteristics.

07-08-2015, 11:41 AM	#1
Outis Veteran Member Join Date: Apr 2014 Location: Cambridge, MA Posts: 935	Weird Bokeh with 40mm Limited vs. XS Off and on, I consider buying one of the 40mm pancakes, either the 40mm XS or the 40mm Limited. One of the things that bothers me, though, is the weird bokeh I see in reviews of the 40mm Limited (e.g. this and this), stuff like this and this. How prevalent is it? Is it just an issue for the 40mm Limited, or does the 40mm XS produce it as well?

07-09-2015, 04:27 AM - 1 Like	#10
macTak Veteran Member Join Date: Apr 2010 Photos: Gallery Posts: 759	That Bokeh is the result of over-corrected spherical aberration. Both the Ltd and XS versions have the same optical formula and should therefore be the same in this regard. From my experience with lenses that have some over-corrected spherical aberration (e.g., M35/2), it only occurs (or at least is noticeable) in a certain range of circumstances--for instance wide open when focusing to within 2ft and then with a background that is significantly behind the plane of focus. Based on the samples of the DA40 you link to, the range of circumstances seems pretty similar. Depending on your shooting habits, it may or may not be prevalent, but generally is not catastrophic even when it occurs as only very tight crops/very large prints will make it visible. Last edited by macTak; 07-09-2015 at 07:55 AM. Reason: Over-, not under-

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07-08-2015, 11:58 AM	#2
shaolen Veteran Member Join Date: May 2012 Location: Phoenix AZ Posts: 1,047	I have had three 40mm xs' before and never noticed this but then again I haven't been paying particular attention. Since these lenses are basically the exact same lens in different housings I would imagine it happens on xs

07-08-2015, 12:10 PM	#3
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	I never noticed that odd bokeh effect, and it doesn't really bother me. I quite like the bokeh of my DA 40mm XS, which has nice round bokeh even if stopped down. I like to use the 40mm for flower photography with relatively wide aperture just because of this (I posted some photos on my 500px page and around these forums, but they might be difficult to find). You can look for the "flat wonder" thread on these forums, which is dedicated to the DA 40mm. You can also look at the sample photo gallery and search for the DA 40mm, see how often that bokeh effect appears. The DA 40mm comes in three versions: SMC DA Ltd: This is the first one. Has hood, distance scales. Was not advertised as having "rounded aperture blades", though some say its blades are just as rounded as the later versions. SMC DA XS: This one originally bundled only with K-. Cheaper, flatter, no distance scales, no hood, and a silly 27mm filter ring. Optically it should be the same as the SMC, but it was advertised as having rounded aperture blades, so it might have smoother bokeh when stopped down. This is the smallest one, I think it was even the smallest DSLR lens ever, at least back when it was introduced. But I doubt some other brand beat this (ignoring pinhole lens covers). HD DA Ltd: This is the latest version, with red ring. Same as SMC, but newer lens coatings and also advertised as rounded aperture blades. I guess this is optically the best one, though, by how much? I dunno. The Pentax Forums did a SMC vs HD test some time ago, so you can look there to see comparisons.

07-08-2015, 02:00 PM	#4
hyyz Site Supporter Join Date: Jan 2008 Location: Michigan Posts: 478	I have noticed the same with my 40mm XS. I shot the plastic base of a table lamp. The highlight showed up like that, I recall.

07-08-2015, 03:41 PM	#5
photodesignch Senior Member Join Date: Feb 2014 Photos: Albums Posts: 133	Originally posted by Na Horuk I never noticed that odd bokeh effect, and it doesn't really bother me. I quite like the bokeh of my DA 40mm XS, which has nice round bokeh even if stopped down. I like to use the 40mm for flower photography with relatively wide aperture just because of this (I posted some photos on my 500px page and around these forums, but they might be difficult to find). You can look for the "flat wonder" thread on these forums, which is dedicated to the DA 40mm. You can also look at the sample photo gallery and search for the DA 40mm, see how often that bokeh effect appears. The DA 40mm comes in three versions: SMC DA Ltd: This is the first one. Has hood, distance scales. Was not advertised as having "rounded aperture blades", though some say its blades are just as rounded as the later versions. SMC DA XS: This one originally bundled only with K-. Cheaper, flatter, no distance scales, no hood, and a silly 27mm filter ring. Optically it should be the same as the SMC, but it was advertised as having rounded aperture blades, so it might have smoother bokeh when stopped down. This is the smallest one, I think it was even the smallest DSLR lens ever, at least back when it was introduced. But I doubt some other brand beat this (ignoring pinhole lens covers). HD DA Ltd: This is the latest version, with red ring. Same as SMC, but newer lens coatings and also advertised as rounded aperture blades. I guess this is optically the best one, though, by how much? I dunno. The Pentax Forums did a SMC vs HD test some time ago, so you can look there to see comparisons. =_=; You totally missed the original Pentax-M 40mm F2.8.. the actual "father" of all 40mm.....

07-08-2015, 03:53 PM	#6
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	Originally posted by photodesignch =_=; You totally missed the original Pentax-M 40mm F2.8.. the actual "father" of all 40mm..... Are they the same optical design? Because what I read is the M 40mm is not as good as the DA versions so I assumed it is different design, but I guess you are right. If OP wants an affordable MF version

07-08-2015, 07:07 PM	#7
reduno Loyal Site Supporter Join Date: Apr 2008 Location: Central NY, USA Posts: 965	Now I'm going to have to look closely at some of my photos to see if I can see anything. I did get some odd reflections using a filter on the XS, possibly as the small size places it very close to the lens. In night shots, I got mirror images of light points on the opposite side of the picture (almost like they were reflected around the center point of the lens).

07-08-2015, 07:41 PM	#8
Mistlefoot Veteran Member Join Date: Jan 2013 Location: Nanaimo, British Columbia Photos: Albums Posts: 328	https://www.flickr.com/groups/1945188@N23/pool/ 519 photos here should give you a pretty good idea of the XS. It's a lens that never leaves my bag (it fits in a filter pocket) but I still seem to prefer to use my 35mm 2.4. I am sure with a flickr search you could find a good number of photo's with the DA's as well.

07-08-2015, 07:47 PM	#9
ZombieArmy Pentaxian Join Date: Jun 2014 Location: Florida Posts: 3,210	The 40mm's Bokeh isn't what I'd call bad. I'd call it "hard to tame". I've gotten some lovely bokeh and some not so lovely.

07-09-2015, 07:09 AM	#11
shaolen Veteran Member Join Date: May 2012 Location: Phoenix AZ Posts: 1,047	so looking at optical design of the m40 and seems to be same

07-09-2015, 07:54 AM	#12
macTak Veteran Member Join Date: Apr 2010 Photos: Gallery Posts: 759	Originally posted by shaolen so looking at optical design of the m40 and seems to be same They are both 5/4 (Unar Elmar hybrid) designs, but there are definite differences in the shapes of the elements that would unquestionably affect their characteristics.

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