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04-08-2010, 03:12 PM   #1
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Help me see the differences

A while ago i read this review of a lens I have had for several years:

Pentax Lens Review and Specification Database - 28-80mm F3.5-4.5

As i found the rating a bit on the high side i decided that i had to revise my opinion with a test on my k100d. I decided to take a few shots with the tamron 28-75 f2.8, Pentax FA 50 f1.4, A50 1,7, the DA 18-55 and the above mentioned lens. The shots where done at 400 iso f5.6 at 50mm.

This is my first actual comparison of lenses, and my first mistake was to take pictures of an object that was to close for the pentax A-zoom. I might redo it and if anyone has a suggestion for a better object to photograph don`t hesitate to suggest any.

Tamron:


FA 50 f1.4:


A50 1,7:


DA 18-55


Pentax A-zoom 28-80



You find the album here


Last edited by Aanund; 04-08-2010 at 10:51 PM. Reason: small pics
04-08-2010, 05:06 PM   #2
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You may want to try and resize these to something we can look at. I can't squint that well.
04-08-2010, 11:08 PM   #3
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FA 50 1,4 vs A 50 1,7

Thanks for the input timestone.

Basically what I notice with this subject is that its difficult to see a difference in the end result.

I was surprised that the 28-80 zoom performed so well, i was expecting alot of purple fringing as i have seen before. I may have to use it some more. past 80mm it also has macro zoom.

I used the A-zoom on a pentax p30, wich was given to me in my youth. at the time i didn`t know how to use my old m42 takumars so it was my only lens for some time and it nearly killed the joy of photography. I mainly had problems with focus and exposure. the p30 with M 40mm 2,8 and A 50mm 1,7 focus and meter much better so i still blame the lens.
04-08-2010, 11:13 PM   #4
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Other than the focal range differences, I don't really see any differences in the photos. And I mean literally nothing. I don't even see any real difference in image quality.

04-08-2010, 11:18 PM   #5
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I was a bit curios about the FA 50 f1,4 and the A 50 f1,7 since there has been some post about them in the past days. For my use it seems autofocus is the difference.
04-08-2010, 11:37 PM   #6
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You are shooting at close range & you are displaying very small pics. These are 2 factors which will equalize lens performance in a big way.

Try shooting at longer subject distances, with links to full size shots--then the differences will be apparent.

But you do make a good point: the biggest difference between most of these lenses is in their price tags. Something along the lines of the Emperor's New Clothes is acting out on photography forums if you ask me.
04-08-2010, 11:40 PM   #7
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Thank you for the tip Jewelltrail. I will try with a longer distance.

Best regards
04-08-2010, 11:49 PM   #8
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Yes its hard to tell the difference on these aside form the focal lenghts. Maybe re do them with a different subject or maybe even a landscape type of pic will show more difference's?

04-09-2010, 12:57 AM   #9
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i suggest zooming in on say the leaves of a plant more and to take identical shots =)
04-09-2010, 12:59 AM   #10
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Next time you try the test, set all of the lenses to 50mm and use the same aperture (I suppose that would have to be fairly small due to the kit lens being in the mix, which will also make the other lenses much sharper) and make sure the lighting conditions are the same for each one.
04-09-2010, 01:34 AM   #11
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All the lenses were set at 50mm actually, the variation you see is me not staying in the same spot.. Point taken about precision in my method.

They were also all done at f5,6. due to lighting conditions.

I appreciate the input here. Next time i will try a land/cityscape, with a smaller aperture.

Thank you!

Last edited by Aanund; 04-09-2010 at 01:35 AM. Reason: typo
04-09-2010, 01:54 AM   #12
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What I've found helpful is to set up a test scene that is in a place out of the way so that it doesn't change. Set up a small tripod or something and mark where it is in case it moves, if you really want to get very precise tests (like they do at DPreview or DCresource), but otherwise your current method works fairly well, just sometimes not fair to some of the lenses in it.
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