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07-08-2013, 03:09 PM   #1
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DA 40mm Ltd. f2.8 vs. M-50mm f1.7

Hey there y'all. I received my K-5ii a couple days ago, then acquired a DA 40mm Ltd. 2.8. I've had an M-50mm 1.7 for a few years now. I wanted to pit them against each: one shot wide open (2.8 vs. 1.7 to see if there was a real difference in bokeh) and one shot at their smallest apertures, which happens to be f22 for both lenses.

Now, I'm busy teaching summer school, so I don't have much time to find great subjects. And the times I am on campus seem to be not conducive to great photos. I tried early this morning but the shade was too much. I tried at 3:00 this afternoon, which is not optimal. Ideally, I should go at the magic hours, but because I wanted to post results comparing apertures asap, and because I simply can't make it back onto campus at those times, this is what I got. Let me say this: I'm not looking for critiques on composition or lighting, simply notes on what you see here regarding sharpness and bokeh and colors. I tried to keep the shots as similar as possible in order to eliminate variables. The DA 40 2.8 is on the left in both shots, meaning the M 50 1.7 is on the right.

Here are the results:
1. f2.8 vs. f1.7


2. f22 vs. f22


I notice a pretty big difference in the background between the 40 at 2.8 and the 50 at 1.7. In fact, I was really surprised about how much more blur there was in the M-50mm. But I feel the DA 40mm is sharper, due perhaps to the autofocus.

What are your thoughts?

07-08-2013, 03:54 PM   #2
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QuoteOriginally posted by tele_pathic Quote
But I feel the DA 40mm is sharper, due perhaps to the autofocus.
It could also be thinner DOF on the 50 @1.7

Perhaps do another test with both lenses at f2.8 to compare?

The bokeh on the 50 is real nice, as it is on pretty much all Pentax 50 1.7's of any series.
07-08-2013, 03:55 PM   #3
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From the photos provided: the DA 40 wins hands down in my humble opinion
07-08-2013, 04:00 PM   #4
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QuoteOriginally posted by mdodrill Quote
From the photos provided: the DA 40 wins hands down in my humble opinion
That´s impossible to tell from these images, displayed like this.

07-08-2013, 04:00 PM   #5
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QuoteOriginally posted by mdodrill Quote
From the photos provided: the DA 40 wins hands down in my humble opinion
Agreed, definitely on the sharpness metric, from the photos provided the 40mm wins. I'd say that I'm surprised that the OP didn't get more bokeh from it, though.

Note, I do not know the 50/1.7, but the 40/2.8 is really a real deal: amazingly cheap for its quality.
07-08-2013, 04:23 PM   #6
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QuoteOriginally posted by crewl1 Quote
It could also be thinner DOF on the 50 @1.7

Perhaps do another test with both lenses at f2.8 to compare?

The bokeh on the 50 is real nice, as it is on pretty much all Pentax 50 1.7's of any series.
Dang it! It never even crossed my mind to set the 50 to 2.8. I'll do that soon. Not in the next few days, though, as its blazing hot. Maybe Friday. And maybe I'll go at 6:00 or 7:00 and try to get better light.

I will agree that it's difficult to choose a winner though.
07-08-2013, 04:29 PM   #7
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QuoteOriginally posted by tclausen Quote
Agreed, definitely on the sharpness metric.
Assuming the photo was taken arround 2 meters of the subject, the 40mm @ f/2.8 will give you 30cm DoF, while the 50mm @ f/1.7 allows 10cm...

Here´s the image in bigger dimensions:
http://i16.photobucket.com/albums/b34/tele_pathic/DA40mmLtd28vsM50mmf17_zps1...e.jpg~original

The 50/1.7 clearly missed focus on the face. Sharpness and aberrations seems similar on the focused areas in common between both pictures.
07-08-2013, 04:34 PM   #8
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QuoteOriginally posted by crewl1 Quote
Perhaps do another test with both lenses at f2.8 to compare?
That was my first thought. Could you also check what metering mode you used, as the overall brightness in the first two images is not the same

07-08-2013, 05:16 PM   #9
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QuoteOriginally posted by carrrlangas Quote
Assuming the photo was taken arround 2 meters of the subject, the 40mm @ f/2.8 will give you 30cm DoF, while the 50mm @ f/1.7 allows 10cm...

Here´s the image in bigger dimensions:
http://i16.photobucket.com/albums/b34/tele_pathic/DA40mmLtd28vsM50mmf17_zps1...e.jpg~original

The 50/1.7 clearly missed focus on the face. Sharpness and aberrations seems similar on the focused areas in common between both pictures.
Perfectly agree with you there, mate, on the DoF calculations and its impacts. As I said, on the sharpness metric, and judged on the photographic evidence presented.....it's hard to do anything other than give the 40/2.8 the edge. Alas, the comparison isn't really fair (different focal lengths, different apertures).

I think OP promised a new batch of tests, I'll be watching this space
07-09-2013, 10:10 AM   #10
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Found a new "subject" last night, but too late for acceptable light. So I may conduct a dof/sharpness test that eliminates the bokeh aspect. I also picked up an A 50mm 1.7 last night, which I'll add to the mix when I get it in the mail.

Cheers.
07-10-2013, 03:07 PM   #11
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QuoteOriginally posted by tclausen Quote
Perfectly agree with you there, mate, on the DoF calculations and its impacts. As I said, on the sharpness metric, and judged on the photographic evidence presented.....it's hard to do anything other than give the 40/2.8 the edge. Alas, the comparison isn't really fair (different focal lengths, different apertures).

I think OP promised a new batch of tests, I'll be watching this space
You should know that I bough a DA40XS here on the marketplace and I held you responsible because of the how much you praise it in every thread I read about it.
I was looking for the Limited version too but the price difference was too much for my pocket (got the XS for U$D140 shipped). I have the F28 and F50 and although they are small, the 40mm looks promising for street shots. I´ll see how it compares once I get it...
07-10-2013, 05:03 PM   #12
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QuoteOriginally posted by carrrlangas Quote
You should know that I bough a DA40XS here on the marketplace and I held you responsible because of the how much you praise it in every thread I read about it.
I was looking for the Limited version too but the price difference was too much for my pocket (got the XS for U$D140 shipped). I have the F28 and F50 and although they are small, the 40mm looks promising for street shots. I´ll see how it compares once I get it...
You know, that is one responsibility that I gladly assume - I think you will be very excited about the lens, and not just for street-shooting
07-10-2013, 06:06 PM   #13
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The 40XS was definitely on my radar. Nearly bought one instead of the limited. But I sold a Sigma 17-70 and figured since I had the scratch I might as well spring for the limited. And if I decide to sell it later, I'm sure I'd make my money back with the limited but not the XS.
07-10-2013, 06:39 PM   #14
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I have some comments on the test. It's not sufficient to test wide open vs. wide open. That's a useful test, but you have to test them at common apertures to make it fair. I don't see much point in testing at f22. I've used an aperture that small with a macro lens, but never with this kind of lens. Anything past f11 is going to be resolution-limited due to diffraction. When shooting manual focus, I always take at least three shots are each aperture to ensure I nailed focus. I usually shoot some manual focus shots with an auto-focus lens too, to ensure the AF is not off. I find print is particularly telling judging resolution. Lastly, consider using a tripod and auto-timer to improve consistency.
07-10-2013, 09:12 PM   #15
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One question, in the first sample set the M50mm version seems to have a lower contrast. My main use of the 50 is for portraiture but when I have tried using it outdoors, I have noticed a poor contrast. This was helped significantly with a cheap, after-market hood.

Did you have a hood on either/both of the lenses?

That bokeh on the M50 wins hands-down though. From my experience it's still OK at 2.8 but no longer round, there is a noticeable straight-edge that creeps in very early once you stop down.
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