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02-14-2011, 08:15 PM   #1
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How to do a lens comparison???

Soon I'll be having two 40mm lenses: the 40mm f/2 Voigtlander Ultron and the 40mm f/2.8 Pentax DA Limited

I thought it'd be fun to do a little lens comparison...but then I realized I didn't really know where to start.

For example, do you always compare their respective max apertures, even though they are different, or always compare at same f/stop even though the Ultron would be stopped down at f/2.8 and the LTD wide open? etc

I'm willing to put in some time and work, cause I think it would be a good skill to learn. But since is for fun after all, I don't want this to be a super scientific, precise, tedious excercise. Have enough of that in grad school

Any pointers, hints, guidelines, etc?

02-14-2011, 09:26 PM   #2
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Use a tripod, set camera to base ISO, 2 second timer. Choose targets at both close/medium range and infinity.

Test them at the same aperture at multiple common apertures. Say f/2.8, f/4, f/5.6 f/8. Lenses typically peak in performance somewhere in that range.

Wide open on the faster lens is a "bonus". The slower lens cannot match that so there simply is nothing to compare; the characteristics of the image fundamentally change, such as DOF, so they cannot be compared. Objectively decide on the faster lens' own terms whether wide open is something you like and would use. If so, then it is a bonus point in favor of the faster lens. If not, then it is irrelevant.
02-15-2011, 02:13 AM   #3
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newspaper is a good target for resolution test
02-15-2011, 12:55 PM   #4
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QuoteOriginally posted by dasuhu Quote
Soon I'll be having two 40mm lenses: the 40mm f/2 Voigtlander Ultron and the 40mm f/2.8 Pentax DA Limited

I thought it'd be fun to do a little lens comparison...but then I realized I didn't really know where to start.

For example, do you always compare their respective max apertures, even though they are different, or always compare at same f/stop even though the Ultron would be stopped down at f/2.8 and the LTD wide open? etc

I'm willing to put in some time and work, cause I think it would be a good skill to learn. But since is for fun after all, I don't want this to be a super scientific, precise, tedious excercise. Have enough of that in grad school

Any pointers, hints, guidelines, etc?
too bad. lens comparison tests are tedious and are done precisely inorder to get a fair and true assessment of the lens. any slight error in the tests are more than enough to have an impact on the image. anyway, since you are into investing your time into making comparisons, here are some of the pointers that are worth considering.

1.> set your test in a controlled environment - lighting setup should be fixed (whether the light source comes from lights or flashes. I recommend testing done with and without flash use. same subject and distance. close up focus distance, mid distance and infinity.

2.> use a tripod

3.> set exposure with consistency. meaning, adjustments or exposure compensation are made due to possibility of difference in light transmission or exposure between lenses at the same aperture opening. also, make a footnote regarding lens transmission if one lens is brighter than the other by how many stops.

3.> tests are done from wide open comparisons andsame aperture openings.

4.> optimal focus is a necessity. any slight misfocus can make a big difference between sharpness, CA and bokeh.

5> shoot in RAW. make sure the settings are all set to "0".

02-15-2011, 12:59 PM   #5
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btw, as far as resolution tests are concerned, as already mentioned, a newspaper is a good measure. as far as other test parameters are concerned, refer to this test method >>> https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/130864-pentax-...0mm-1-2-a.html
02-15-2011, 01:04 PM   #6
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QuoteOriginally posted by Pentaxor Quote
too bad. lens comparison tests are tedious and are done precisely inorder to get a fair and true assessment of the lens. any slight error in the tests are more than enough to have an impact on the image. anyway, since you are into investing your time into making comparisons, here are some of the pointers that are worth considering.

1.> set your test in a controlled environment - lighting setup should be fixed (whether the light source comes from lights or flashes. I recommend testing done with and without flash use. same subject and distance. close up focus distance, mid distance and infinity.

2.> use a tripod

3.> set exposure with consistency. meaning, adjustments or exposure compensation are made due to possibility of difference in light transmission or exposure between lenses at the same aperture opening. also, make a footnote regarding lens transmission if one lens is brighter than the other by how many stops.

3.> tests are done from wide open comparisons andsame aperture openings.

4.> optimal focus is a necessity. any slight misfocus can make a big difference between sharpness, CA and bokeh.

5> shoot in RAW. make sure the settings are all set to "0".
for a close focus target, I have often thought of building a LEGO city, since I could shoot the same subject over and over again.

On top of your points, I would suggest taking at least 3 shots, one focusing as you would normally, one starting at infinity and one at closest focus, and then take the best shot.

The series of tests for each focus distance should be wide open, F2.8 (which is wide open in one lens case) F5.6 and F11.

Comparison of both bokeh and color should be made. Use identical settings for one series, keeping the shutter consistent with aperture and for a second set, let the camera meter through the lens. After all, this is as much a system test, one lens may have considerably lower light transmission than the other. I discovered this comparing 2 different 135 F2.8's where one was a stop faster.

At least one test should look for distortion, brick walls are good, and another look for CA especially in the corners.

ALso a blue sky test or uniformly lit surface test, wide open, and at each stop to F5.6 minimum should be done to check vignetting.,
02-15-2011, 05:14 PM   #7
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I've done a test comparison of those two lenses. I'll be interested how the OP's test comes out.

This is probably the most tedious and annoying thing I do in photography, and every time I do it I tell myself I won't do it again. As someone else said, you need multiple exposures of some kind of flat detail, like print and perfect focus as well as a tripod and a cable or remote. Flash is a must, and there should not be enough ambient light to add enough significant exposure to the flash. My best tests are just taking lenses out and taking photos and comparing them.
02-15-2011, 05:37 PM   #8
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QuoteOriginally posted by GeneV Quote
I've done a test comparison of those two lenses. I'll be interested how the OP's test comes out.
Care to share your findings?

02-16-2011, 07:16 AM   #9
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QuoteOriginally posted by les3547 Quote
Care to share your findings?
I'll see if I can find them and I am proud enough to post them. I only run the tests to see if I have a defective lens. I know I deleted one whole set. I did get the general impression that in amateur testing, I would be hard pressed to show any significant sharpness differences. I use the VL almost exclusively on film right now.
02-16-2011, 08:45 AM   #10
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I did a comparison between my Vivitar 28/2.8 and Tamron 28/2.5 a year or so ago and posted the results on this site. My approach was simple:
  • Shoot the same subjects from the same tripod and/or location in the same light
  • Include at least one series designed to test resolution/contrast
  • Include at least one series as a flare challenge
  • Consider usability as part of the comparison, particularly manual focus and auto focus functionality
  • Throw the 18-55 kit zoom on for at least one shot to lend some "perspective" to the contest
Here is the link to the big contest:
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/90340-vivitar-...m-2-5-02b.html

Steve
02-16-2011, 09:08 AM   #11
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A factor I consider when comparing lenses along with all that's been mentioned is the minimum focusing distance (though the DA 40 and VL 40 appear to be about the same at around 15 inches).
02-16-2011, 09:27 AM   #12
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QuoteOriginally posted by dasuhu Quote
Soon I'll be having two 40mm lenses: the 40mm f/2 Voigtlander Ultron and the 40mm f/2.8 Pentax DA Limited

I thought it'd be fun to do a little lens comparison...but then I realized I didn't really know where to start.

For example, do you always compare their respective max apertures, even though they are different, or always compare at same f/stop even though the Ultron would be stopped down at f/2.8 and the LTD wide open? etc

I'm willing to put in some time and work, cause I think it would be a good skill to learn. But since is for fun after all, I don't want this to be a super scientific, precise, tedious excercise. Have enough of that in grad school

Any pointers, hints, guidelines, etc?
This is probably heresy but I do lens comparisons the same way I normally shoot. I'm sure this is horribly unscientific, but then again I'm not doing this for anyone but me. What I do is go out shooting as I normally do, but I switch the lenses back and forth. I'll do close focus, wide open (if the lenses have two different max apertures I use the smallest (for instance I did a comparison between the FA 35mm F/2.0 and the DA 35mm F/2.4 so I shot both lenses at 2.4) I don't usually bother with smallest aperture because I very rarely shoot at small apertures. The shots are almost always hand held because that's the way I shoot. Like you I want this as fun as possible. I don't do tripods, I don't do walls etc. For CA I shoot something that will usually give me CA as in bare tree braches against a bright sky. I do shoot manual so I can get the same aperture and shutter speed.

NaCl(hobbies should be fun)H2O
02-16-2011, 12:32 PM   #13
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QuoteOriginally posted by GeneV Quote
I've done a test comparison of those two lenses. I'll be interested how the OP's test comes out.

Flash is a must, and there should not be enough ambient light to add enough significant exposure to the flash. My best tests are just taking lenses out and taking photos and comparing them.
I hope flash is not too important . Don't have one besides the on-board one on the K7. Do have the tripod and a shutter release cord.

QuoteOriginally posted by akanarya Quote
newspaper is a good target for resolution test
Ha, I knew keeping those NYTs from months ago when my neighbor was on vacation would come in handy

QuoteOriginally posted by stevebrot Quote
I did a comparison between my Vivitar 28/2.8 and Tamron 28/2.5 a year or so ago and posted the results on this site. My approach was simple:[LIST][*]Shoot the same subjects from the same tripod and/or location in the same light[*]Include at least one series designed to test resolution/contrast[*]Include at least one series as a flare challenge[*]Consider usability as part of the comparison, particularly manual focus and auto focus functionality[*]Throw the 18-55 kit zoom on for at least one shot to lend some "perspective" to the contest
Flare challenge? Does that mean shoot towards the sun? That's something I never do in real life, personally, but if people are interested...

I think manual focus using the DA40 is a pain. It's the only lens I AF exclusively with. Maybe the functionality would be how well AF works on the Ltd, versus how well I can MF on the Ultron.

I don't have a kit zoom unfortunately. I do have a 16-45 though.

~~~
Can't wait for the Ultron to arrive...slowly making its way from NYC to me.
02-16-2011, 02:01 PM   #14
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QuoteOriginally posted by dasuhu Quote
Flare challenge? Does that mean shoot towards the sun? That's something I never do in real life, personally, but if people are interested...
I've both shot straight into the sun and let the sun hit the lens from the side with the VL 40mm, it's a champ. Gives great stars in the right conditions, and so far I have not been able to make it show any flare whatsoever.
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