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02-01-2009, 06:41 PM   #1
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4x50 lens game

I thought I would take a shot today using 4 of my lenses to see if I could see an obvious difference in lens quality. I thought it might be fun to see if anyone else could guess what picture goes with what lens. There is not a lot of color around here this time of year, so I made up my own subject that had color, detail, and contrast.

All pictures are jpeg right out of the camera all at 50mm. Exposures are identical: ISO100, 1/350s, f/4.5. I chose f/4.5 since that was wide open for the 18-250. Here are the four lens choices (obviously written out of order):

Pentax FA 50 f/1.4
Pentax DA 18-250 f/3.5-6.3
Pentax DA* 50-135 f/2.8
Tamron 17-50 f/2.8

Here they are in the "Large" format. I can go to the 100% size if it is not obvious which is which. Can you place the picture with the lens?






Last edited by PentaxPoke; 02-01-2009 at 06:48 PM.
02-01-2009, 10:54 PM   #2
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I think the last one is the DA 18-250, because it seems softest (that lens is wide open) and the framing is a bit more zoomed in than the other 3, easy to do with a super zoom. The other 3 pictures are much closer. The first one seems to have more contrast, so I'm going to guess that's the FA50/1.4. I can't tell any difference between 2 and 3 besides framing.
02-02-2009, 01:05 AM   #3
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This is a trick question. They were all done with a Holga.

But seriously, I have no idea.
02-02-2009, 02:50 AM   #4
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I agree, the last one seems to be the 18-250, but the others show no significant differences at this resolution.

02-02-2009, 11:01 AM   #5
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No others want to play? I was sure I would get comments from people who can see differences in the "rendering," "color," and "contrast," of different lenses as figures of merit.

Thanks to Dave, asdf, and drerka for trying.

Well here is the answer. The results may surprise you. In order from top to bottom:

Pentax DA 18-250 f/3.5-6.3
Pentax FA 50 f/1.4
Tamron 17-50 f/2.8
Pentax DA* 50-135 f/2.8

Yup, that is correct; the last picture is the DA*, not the "megazoom."
02-02-2009, 12:02 PM   #6
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QuoteOriginally posted by PentaxPoke Quote
No others want to play? I was sure I would get comments from people who can see differences in the "rendering," "color," and "contrast," of different lenses as figures of merit.
I started to write something up before you posted this, but backed up. Here's what I was going to say, and I swear, I am saying this *before* looking at the answers below:

While #4 is the least sharp, it's hard to be sure if that is really the lens or if it is just focus error or shake of some sort. So while I'm not saying it isn't the 18-250, I'm going to put that aside and concentrate on the distortion visible in the wall.

#1 and #3 distort one way (based on the curvature of the top line), #2 and #4 the other. #2 and #3 are better than #1 and #4.

Not know much about the physics of things, I'd say that one end of a zoom would be likely to distort one way the other end the other way. So if the 17-50 is #1 or #3, the 50-135 is #2 or #4, and vice versa. I'm also taking it on faith that the 50-135 and FA50 are the best. So either #2 is FA50 and #3 is 50-135, or the other way around. #1 is the only one I'd call "bad" with respect to distortion, so it's either the 18-250 or the 17-50 which I know little about. I'll bow to the fact that #4 *is* noticeable less sharp and call it the 18-250.

Doing the math, the works out to:

1) 17-50
2) 50-135
3) 50
4) 18-250

Looking at the answers, obviously, I'm quite wrong :-). I wasn't really believing for a minute that apparent lack in sharpness in #4 was significant. Truth be told, I really *wanted* to call #1 the 18-250 because as I said, it had the worst distortion. It appears I might have guessed right about the direction of the distortion between the 17-50 and 50-135. But I think I still would have assumed the 50-135 was #2 or #3, and that the other was the 50. So at best, if not for the sharpness issue, the best I probably would have done would be the get #1 & #2 correct but reverse #3 and #4.

Oh, another thing I noticed but didn't mention: the view in #4 seems slightly narrower than the others. That would have made me assume it was either the 50 or the 50-135, which of course are the ones in which you'd have had no choice. Again, the lack of sharpness threw me off that scent.
02-02-2009, 12:07 PM   #7
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QuoteOriginally posted by PentaxPoke Quote
No others want to play? I was sure I would get comments from people who can see differences in the "rendering," "color," and "contrast," of different lenses as figures of merit.

Thanks to Dave, asdf, and drerka for trying.

Well here is the answer. The results may surprise you. In order from top to bottom:

Pentax DA 18-250 f/3.5-6.3
Pentax FA 50 f/1.4
Tamron 17-50 f/2.8
Pentax DA* 50-135 f/2.8

Yup, that is correct; the last picture is the DA*, not the "megazoom."
thats the order i had them in actually...

you can tell from the first photo, because the barrel distortion is so significant

the second shot is the best overall

altho the last two could have went either way, i would have put the tamron last though, surpsised why the DA* is so soft...

it might have been mis focused compared to the other lenses, since the balls are all tac sharp, would indicate the depth of field corridor was shifted closer to you.
02-02-2009, 12:16 PM   #8
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Nice job Marc,
You are the first one to pic up on the distortion. That is where the mortar lines in the bricks were nice to have. All 3 zooms had more noticeable distortion compared to the prime.

The sharpness and the framing of the DA* surprised me though. It is very sharp in the center though. At 100%, it is just as sharp if not sharper than the others. It is just softer at the borders. The other 3 lenses are indistinguishable in sharpness from the borders to the center. I am also at a loss to explain why the framing at 50mm on the DA* is not the same as the others. It almost appears that 50mm on that lens is not exactly 50mm. I wonder if it has anything to do with the IF changing the effective focal length? The EXIF and the camera said 50mm though.


Last edited by PentaxPoke; 02-02-2009 at 12:26 PM.
02-02-2009, 12:17 PM   #9
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QuoteOriginally posted by Gooshin Quote
thats the order i had them in actually...
Nice job Gooshin, way to swoop in after the answer is posted!

Hmmm, still no comments from anyone about rendering, color, or contrast...
02-02-2009, 01:56 PM   #10
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This might convince some people that the SMC is the most imporant factor in determining a lens's contrast and colour characteristics, because I see little difference.

Poke, I'd like you to post a comparison between the FA 50 and the DA* 50-135, but this time focusing near/at infinity. I've been test-driving a DA* 50-135 these past few days and the focal length change is very apparent at close-focus distances, but not so much beyond 2-3m.
02-02-2009, 02:11 PM   #11
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QuoteOriginally posted by PentaxPoke Quote
...Hmmm, still no comments from anyone about rendering, color, or contrast...
I did mention contrast, but it sure didn't help me get the right answer.

You can always learn something from a lens test. Sometimes it's not what you wanted to learn.
02-02-2009, 02:27 PM   #12
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QuoteOriginally posted by PentaxPoke Quote
Nice job Gooshin, way to swoop in after the answer is posted!

Hmmm, still no comments from anyone about rendering, color, or contrast...
you are shooting round objects very close to a wall at a high F stop at the same focal length, the rendering is almost identical, since nothing is OOF and there are no specular highlights

talking about the colour reproduction of a lens on a digital camera is rather moot, ditto for contrast, since all that is just a slider away from adjustment.
02-02-2009, 10:03 PM   #13
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QuoteOriginally posted by Gooshin Quote

talking about the colour reproduction of a lens on a digital camera is rather moot, ditto for contrast, since all that is just a slider away from adjustment.
I am in complete agreement! I can't tell you how many times I have seen people make lens recommendations however, based on the nebulous qualities of color and contrast. That is why I was being facetious. These things are much more dependent upon camera settings, camera (or software) processing, and sensor.

BTW, I selected a shallow field in the test on purpose to assess distortion and sharpness from edge to edge.

QuoteOriginally posted by Miserere Quote
Poke, I'd like you to post a comparison between the FA 50 and the DA* 50-135, but this time focusing near/at infinity. I've been test-driving a DA* 50-135 these past few days and the focal length change is very apparent at close-focus distances, but not so much beyond 2-3m.
Interesting, so it probably is the IF then? If I get a chance tomorrow, I'll try to do the test you requested.

Last edited by PentaxPoke; 02-02-2009 at 10:16 PM.
02-03-2009, 06:54 PM   #14
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QuoteOriginally posted by Miserere Quote
Poke, I'd like you to post a comparison between the FA 50 and the DA* 50-135, but this time focusing near/at infinity. I've been test-driving a DA* 50-135 these past few days and the focal length change is very apparent at close-focus distances, but not so much beyond 2-3m.
I ran the test you suggested, and you are correct that the difference is much smaller at infinity focus.
02-04-2009, 01:49 PM   #15
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QuoteOriginally posted by PentaxPoke Quote
I ran the test you suggested, and you are correct that the difference is much smaller at infinity focus.
Thanks Poke! I'll try to run my own test when I have some time and figure out what the real focal length is at close-focus distance.
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