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06-07-2012, 10:35 AM   #1
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DA 40/2.8 XS reviewed by dxomark

Looks somewhat worse in resolution, and chromatic aberration, although it improves on light transmission.

DxOMark - Pentax?s new pancake lens falls flat

06-07-2012, 11:25 AM   #2
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Wow, I'm kind of surprised it got such a bad review. I have the XS and I love this little lens. Sure I only have a couple zooms in my gear to compare to but I have not had any problems with CA and the little XS seems sharp to me! I say this review falls flat for having no photos!
06-07-2012, 02:51 PM   #3
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What do their resolution figures mean, anyway?

Presumably 50% contrast,
but at what aperture (fully open, stopped down 2 stops, . . . ),
where in the image field (center, edge, corner),
and at what focus distance?

A quick perusal of their site did not reveal
any description of their test procedure.

But giving a single figure like they do,
and then factoring it in to some weighting,
does not seem to be a very meaningful procedure.
06-07-2012, 03:04 PM   #4
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QuoteOriginally posted by lytrytyr Quote
A quick perusal of their site did not reveal
any description of their test procedure.
Must have been really quick. Here you go:

DxOMark - Lens scores

Resolution scores are discussed here:

DxOMark - Metric Scores

06-07-2012, 03:10 PM   #5
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QuoteOriginally posted by Laurentiu Cristofor Quote
Here you go:

DxOMark - Lens scores

Resolution scores are discussed here:

DxOMark - Metric Scores
Thanks. I'd expected that to be in the lens section, not the "About."
Most of the information you need to know for using a lens seems to get lost in that averaging.
Many good lenses reach maximum edge resolution at different apertures from where the center is best.
06-07-2012, 03:11 PM   #6
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PhotoZone tests jibe more with my experience with lenses than do DxO's. I'm looking at images, though, not shooting test charts.
06-07-2012, 03:16 PM   #7
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QuoteOriginally posted by lytrytyr Quote
Most of the information you need to know for using a lens seems to get lost in that averaging.

Yes. I use a lens for a purpose. Perhaps I want good IQ wide open. Sometimes I want good IQ at the smallest possible aperture. an average score is not very useful.

Last edited by civiletti; 06-07-2012 at 03:16 PM. Reason: forgot words
06-07-2012, 03:24 PM   #8
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Falls flat? I've made some amazingly sharp images with the XS and with the 40 Limited I had owned. Their standards must be astronomical and something I've never experienced with the various glass I've used in ~7 years of using DSLRs.

06-07-2012, 03:29 PM   #9
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One of the nice features of good pancakes is the evenness of their resolution,
across the image field and through a wide range of apertures.
I suspect that DxO's scoring method makes that virtue look like a vice.
06-07-2012, 03:32 PM   #10
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QuoteOriginally posted by sjwaldron Quote
Falls flat? I've made some amazingly sharp images with the XS and with the 40 Limited I had owned.
I too find that title a very poor representation of the lens or even the test results. It "ONLY" beat the da40/2.8 ltd. (a hugely popular lens) by a single point and shows improvements besides being ultra light.

So its better than the current beloved lens, costs half as much, weighs much less, yet "falls flat"? I think not.

btw, I own the the lens in question and find it more to my liking than the Ltd. version.
06-07-2012, 04:39 PM   #11
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While I like DxO, their lens testing procedure has always been a puzzle.

I remember being struck, for example, by a Lenstip.com article on colour rendering in lenses and binoculars as an aside praising the DA 40 as a great lense for light transmission ('The [light] transmission, reaching 97-98% in the big part of the visible spectrum with 8 surfaces, means on one air-to-glass surface we lose only 0.2-0.3%.')

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And then seeing DxO rate the Tstop of the DA 40 at 3.1, which is heading towards poor.

However in the same lenstip article they profile the light transmission of the Samyang 85 1.4, which doesn't appear to have any advantages over the DA40 in terms of light transmission:

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but DxO rate the SamYang much better than the DA40, with a Tstop of 1.7.

And to add insult to injury, DxO's Tstop value for the DA40 (3.1) is is even worse than (for example) the Tstop (3.0) of a complex zoom like the Sigma 24-70mm F2.8 IF EX DG HSM, which is also profiled in the same lenstip.com article.

So something seems amiss. Or maybe I am misunderstanding what they are doing here.

Last edited by rawr; 06-07-2012 at 04:49 PM.
06-07-2012, 04:45 PM   #12
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QuoteOriginally posted by rawr Quote

And then seeing DxO rate the Tstop of the DA 40 at 3.1, which is heading towards poor.

but DxO rate the SamYang much better than the DA40, with a Tstop of 1.7.

So something seems amiss here.
Not necessarily.

For the Samyang, 1.4 / 1.7 = 82%.

For the DA 40, 2.8 / 3.1 = 90%.
06-07-2012, 05:00 PM   #13
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QuoteOriginally posted by lytrytyr Quote
Not necessarily.
For the Samyang, 1.4 / 1.7 = 82%.
For the DA 40, 2.8 / 3.1 = 90%.
Maybe it's just the presentation of their results then. It simply gives the impression that the Tstop score goes from 'Poor to Excellent', without reference to transmission efficiency. When in fact the DA40 is a very bright piece of glass.
06-07-2012, 06:06 PM   #14
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QuoteOriginally posted by lytrytyr Quote
Most of the information you need to know for using a lens seems to get lost in that averaging.
Most of that information can be found in their charts. No scoring method will be perfect as there is no way to compress losslessly all the testing information into a single number. I think of scores as summaries, but I always check the graphs for the real picture. Here's the comparison between the old DA and the new XS.

Resolution differences don't seem that significant, but the CA seems more of an issue and, strangely, it looks like it worsens a lot on stopping down.
06-07-2012, 09:21 PM   #15
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Can't say I can believe a word of the linked review.
DA40XS certainly punches above its weight (by a lot)
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