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TP: How to do useful lens comparisons

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steem21 View Drop Down
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Post Options Post Options   Quote steem21 Quote  Post ReplyReply Direct Link To This Post Topic: TP: How to do useful lens comparisons
    Posted: 14 April 2007 at 20:01
I was thinking about doing a test between the CZ and my Sigma 17-70 (and possibly between the 35/2 and 35/1.4, and Sigma 70-200 and Sony 70-200). I was wondering if anyone has good pointers as to how to go about doing relevant and useful comparison test between lenses? I've seen a few good suggestions in that thread and others but what's the best way to do them?



What subjects to photograph?

What apertures to use? How to keep exposure the same (technical aspects for newbies e.g. using M mode etc.).

How best to host/post the images for viewing?



Any suggestions will be welcome.



Thanks,

Steve



Edited by rovhazman - 16 September 2013 at 01:52
A900 | CZ 16-35 | CZ 24-70 | Sony 70-200 SSM | Sony 1.4x TC | Sony 100M
 



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binbald View Drop Down
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Post Options Post Options   Quote binbald Quote  Post ReplyReply Direct Link To This Post Posted: 14 April 2007 at 20:20
First I recommend this introduction. Here many good hints can be found and you can start with that.
Regards, Michael

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Turerkan View Drop Down
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Post Options Post Options   Quote Turerkan Quote  Post ReplyReply Direct Link To This Post Posted: 14 April 2007 at 20:36
i'll try to put down what i have in my mind about lens testing:)

things to be tested:
sharpness
contrast
aberrations
color
bokeh

sharpness:
you need a target with high frequency details, with both high micro contrast and low micro contrast. Your target should include varieties of different sized details. You should have some micro details which are well beyond what the sensor can resolve, renditition of such reveal a lot about the lens. Good targets are: anything crowded with small details

contrast: a target with a dynamic range a bit larger than the camera can handle. Anything with harsh lights would make a good target

aberrations: CA will show up well in sharpness test. However you need some over exposure for testing purple fringing. Flare will also show up in over exposure occassions

color: you need subjects with varieties of colors.. not really hard to get, as anywhere you may point the camera at, there will be colors. It will go nice combined with the contrast test.

bokeh: you need a composition with a busy background.. easy to find everywhere.


those tests can be done in groups, for example the color, contrast and aberrations can be tested in a single subject. get one shot from each lens, a landscape in bright sun light with some tree branches or sharp edges around the corners of the frame will be great.

sharpness test will be the longest one to do. you better don't spend your time on useless samples. The important information about lenses will be obtained from large aperture shots (no point of taking F16 comparison shots). If i were you i'd get samples at 17mm, 28mm, 50mm and 70mm. At each focal length get two shots from each lens, one wide open, one stopped down by 2 stops ( only 1 stop as these lenses are already slow (ofc you want to use equal apertures on both lenses))

thats all what comes to my mind.. hope it helps:)
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colmo View Drop Down
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Post Options Post Options   Quote colmo Quote  Post ReplyReply Direct Link To This Post Posted: 14 April 2007 at 21:12
What comes to mind for me is Phil Askey's still life of assorted objects on dpreview. He uses it to demonstrate the ability of the camera to render detail (therefore meeting the requirements on Turerkan's sharpness test). He also uses resolution and colour charts, amongst other things.

My own suggestion would be to stick to the scientific method - this includes:
1) eliminating all variables except the lens (use a tripod and manual exposure settings, constant lighting, same focus point, ISO and focal lengths etc.), and
2) using a control - a 'neutral' third lens (or lenses); this is harder - ideally, one would use primes or high quality zooms of equivalent focal lengths, but you could go the other way and use a kit lens, as it will demonstrate what improvements folks can expect when they upgrade their standard lens for the first time. You have a good assortment of lenses covering the focal lengths of the CZ and Sigma anyway, so you could use them.
3) Reproducibility is another desired attribute of any test - I believe this is why Phil Askey uses a still life, as he can use it again and again - he probably never even moves the tripod he mounts his test cameras on to shoot it.
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omerbey View Drop Down
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Post Options Post Options   Quote omerbey Quote  Post ReplyReply Direct Link To This Post Posted: 14 April 2007 at 22:00
I always find tin foil test nice.
Shows both the bokeh characteristics and color aberrations.
For contrast test, I'd recommend shooting a not contrasty scene.

At any rate, please don't just shoot infinity, or walls. I think they tell little about lenses.
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David_S View Drop Down
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Post Options Post Options   Quote David_S Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2007 at 00:05
I know it's boring but a brick wall can be useful for checking vignetting or corner softness.

DS
 



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brettania View Drop Down
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Post Options Post Options   Quote brettania Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2007 at 10:32

An interesting recent thread started by keith h consists of what he admits is an unscientific test of five lenses at around 70mm or the cropped equivalent.

Included are a couple of kit lenses, the beercan, a 50mm prime, and the 28-75 D.

The thread is here and you can read the guesses.

Edited by brettania - 16 April 2007 at 07:11
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dogears View Drop Down
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Post Options Post Options   Quote dogears Quote  Post ReplyReply Direct Link To This Post Posted: 27 April 2007 at 17:55
Nice read. I should apply these when I post test shots in the future :P Hopefully when I get that Min35-70/4 :)
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Post Options Post Options   Quote Dorset Mike Quote  Post ReplyReply Direct Link To This Post Posted: 28 April 2007 at 00:59
One thing that occurs to me is finding something which is easy for most people to find, could text on a news paper or magazine page serve for judging sharpness among other things. May need to figure out distances for focal lengths to give some consistency to the size of print in the image.
Alternatively is there any sort of test sheet which can be downloaded and printed out.
Cheers MIKE,



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Bob J View Drop Down
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Post Options Post Options   Quote Bob J Quote  Post ReplyReply Direct Link To This Post Posted: 28 April 2007 at 01:25
Assessing relative sharpness isn't too difficult - simply print out a range of different text sizes and shoot at an equivalent magnification: I've done this in the past by pinning two sheets with similar text on with corners adjoining



you focus on the middle of the bottom sheet and adjust camera-to-subject distance until the top left of the upper sheet is in the top left of the viewfinder - you can then compare the sharpness of the different sized texts to get an idea of sharpness at the centre and the top left corner... Of course this only tells you about how the combination of sharpness and contrast combine to give an image - with some lines visible you can get an idea of distortion, but colour rendition CA and bokeh, now that's a whole different thing! I was trying to work out a test for bokeh, maybe involving taking a picture of city lights deliberately out of foucus, but the key would be to get the same degree of OoF for different lenses of differing focal lengths....

Be interested to see what sort of tests people can think of for that...

BOb
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Post Options Post Options   Quote Sanjuro Quote  Post ReplyReply Direct Link To This Post Posted: 24 July 2007 at 13:25
I think also the image should be a RAW one, in that way you can use the same settings by SW (if there are diff cameras) and bypass the "in camera raw processor".
Just an idea, at least I would have use a RAW with the a WB grey card, black and white and greay for color corrections and that it is.
Rgds
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