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11-05-2011, 07:16 AM   #1
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Pentax 28s reversed comparison

Hello,

This is a quick comparison I've done of 3 reversed Pentax 28s all on 75mm or so of tubes, using 1/4 power 540 flash, ISO 100. All stacked images of 15 exposures in Zerene Stacker using (approx) 10 μm steps. I did this just to see if any of the cheap reversing options are especially better than others. Note the exposure of these is a little different on each (I think moved the diffuser by a few mm hence the difference) so don't read anything into that.

Also I just used a small 2m jpg size for these processing speed. No sharpening, NR, just upped exposure a bit so I could see what's going on so they're a little rough but I invite anyone to draw up some conclusions, see what people think.

To me there's not a great amount of difference in any of them except that the -M seems a tad rougher on fringing than the Takumar which rather surprised me. Detail, sharpness, more or less similar as far as I can see. Will post shots in following posts so I know which is which when attaching posts.

11-05-2011, 07:18 AM   #2
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Takumar 28

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11-05-2011, 07:19 AM   #3
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m28

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11-05-2011, 07:21 AM   #4
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a28


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11-05-2011, 07:28 AM   #5
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Interesting - as you said, there is little diffference to be seen. How about comparing to some other FL as well. Like 24 or even 20mm. Or throw the kit lens into the comparison. I personally even prefer the kit lens sometimes, as zooming allows me to change the magnification ratio easily.
11-05-2011, 08:56 AM   #6
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Oooops forum resized them, so here's a 1:1 comparison

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11-06-2011, 02:34 PM   #7
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Here are some 50s, quite interesting. All 100% crops of reversed@5.6 on 65mm of tubes. Originally the -K was above the 1.7s but when I rescaled it to be the same it came out softer on other parts of the shot. Major surprise was just how good the -m 50 macro is reversed, very very close to the winner, the el-nikkor 50 f/2.8.

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11-06-2011, 02:36 PM   #8
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Just to repeat, these tests are all a little rough - the stacking steps wern't exactly the same nor was the angle. As close as I could manage whilst fighting wife and child for computer and desk time.

11-06-2011, 03:36 PM   #9
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Interesting. So which is your favorite lens for reversed use, overall?
11-07-2011, 12:58 AM   #10
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The el-nikkor, although I want to give the m50 macro another closer look because it does half stops which the nikkor doesn't. In terms of 28s I have a schneider 28 on the way and I'm hoping it'll be as much of an improvement as the nikkor is over the other non macro 50s.
11-07-2011, 07:07 AM   #11
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QuoteOriginally posted by Nass Quote
The el-nikkor, although I want to give the m50 macro another closer look because it does half stops which the nikkor doesn't. In terms of 28s I have a schneider 28 on the way and I'm hoping it'll be as much of an improvement as the nikkor is over the other non macro 50s.
It looks like a toss-up between the m50:4 and the el-nikkor 50:2.8. - they both seem to give excellent results.

Please tell us more about these lenses: is the el-nikkor an enlarger lens - which one? Is the m50:4 a pentax macro lens - which one? Are they reversed?
11-07-2011, 09:36 AM   #12
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Yes, reversing the macro m50 f/4 at 5.6 on tubes worked really really well, it was the major find. Backs up what I think you found a few weeks back that it's as good reversed as it is normal way round (or is my memory failing here?). The lack of CA really surprises me when I compare it to the CA on the -m 28s, but I guess it's a specialty macro lens so maybe it has stronger coating or something? The el-nikkor is the 50 f/2.8 enlarging lens reversed, it's well known to be an excellent little reverse lens for macro without getting into three figure sums or exotic expensive stuff. Do bear in mind the caveat that these tests are not as exact as I'd like. I need to do them with repeatable 1 micrometer steps and although I now have a stage to do that I need to have some bespoke metal plates cut first to fit the stage onto my setup, bah
11-07-2011, 09:56 AM   #13
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QuoteOriginally posted by Nass Quote
Yes, reversing the macro m50 f/4 at 5.6 on tubes worked really really well, it was the major find. Backs up what I think you found a few weeks back that it's as good reversed as it is normal way round (or is my memory failing here?). The lack of CA really surprises me when I compare it to the CA on the -m 28s, but I guess it's a specialty macro lens so maybe it has stronger coating or something?
Is the lens the Macro-Takumar (1:1) version or a later 1:2 version? - I don't know if there are actual lens design changes between versions.

QuoteQuote:
The el-nikkor is the 50 f/2.8 enlarging lens reversed, it's well known to be an excellent little reverse lens for macro without getting into three figure sums or exotic expensive stuff. Do bear in mind the caveat that these tests are not as exact as I'd like. I need to do them with repeatable 1 micrometer steps and although I now have a stage to do that I need to have some bespoke metal plates cut first to fit the stage onto my setup, bah
As I recall there are two basic versions of el-nikkors, 4 lens elements and 7 lens elements, that's why I ask - in case somebody wants to buy one.

Oh, and thanks for the tests!
11-07-2011, 10:04 AM   #14
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QuoteOriginally posted by newarts Quote
Please tell us more about these lenses: is the el-nikkor an enlarger lens - which one?
EL in EL-Nikkor means enlarging lens. We commonly see the EL-Nikkor 50/2.8 (40.5mm front thread) and 50/4 (34.5mm), usually very cheap, like under US$20 for the f/2.8 and under US$10 for the f/4. I have both. I'll someday get the 75mm and 105mm maybe. The f/2.8 reversed is one of Yeatzee's favorites. I haven't tried reversing ELs yet. Soon...
11-07-2011, 10:15 AM   #15
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Yes tanner is using this as well nowadays. The el nikkor 2.8 comes in an older metal ringed scalloped version and a newer plastic one. I have the plastic one - no idea about the # of elements sorry. The el nikkor 4 is (apparently) highly avoidable, it's the budget version of the 2.8 and in the tests I saw the quality just wasn't quite there.

In terms of the m 50 macro it's the 1:2 one at Pentax-M 50mm F4 Macro Reviews - M Prime Lenses - Pentax Lens Reviews & Lens Database - it's the only m50 macro I know of, sorry wasnt aware of a 1:1 m 50, which one did you mean?
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