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Thread: Interesting lens Test Data

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    Senior Member barjohn's Avatar
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    Cool Interesting lens Test Data

    I used Bob Atkins 4x6 test image chart used to test lens resolution to see how a few lens I have compare. I used his test setup and I printed 3 4x6 test images on 1 13x19 page with one in the upper left corner, one in the middle and one in the lower right corner. A multiplier of 25 times the sensor size works out to 17.21" x 13.28" so it was close enough for my purposes to use a multiplier of 25. I was particularly interested in the wide open performance of the Minolta 40/2, the Nikon 28/2.8 and the Nikon 50/1.8 in comparison to the kit 14-45 lens.

    There is a high contrast set of test images and a low contrast set of test images. Since several of these lenses are full frame (35mm) lenses one would expect the edges to be very near the center.

    Here are my results:
    Minolta 40/2
    F stop Location High Contrast Low Contrast
    2.0 C 90 lpm 70 lpm
    2.0 U 80 lpm 50 lpm
    2.0 L 70 lpm 45 lpm
    2.8 C 100 lpm 70 lpm
    2.8 U 80 lpm 55 lpm
    2.8 L 80 lpm 55 lpm

    Nikor 28/2.8
    2.8 C 90 lpm 70 lpm
    2.8 U 80 lpm 62.5 lpm
    2.8 L 80 lpm 55 lpm

    Nikor 50/1.8
    1.8 C 90 lpm 62.5 lpm
    1.8 U 70 lpm 55 lpm
    1.8 L 70 lpm 45 lpm

    14-45 @45
    5.6 C 90 lpm 80 lpm
    5.6 U 90 lpm 70 lpm
    5.6 L 90 lpm 70 lpm
    @14
    3.5 C 90 lpm 62.5 lpm
    3.5 U 90 lpm 62.5 lpm
    3.5 L 90 lpm 70 lpm

    C = CENTER
    U = UPPER CORNER
    L = LOWER CORNER
    lpm = Lines Per Millimeter

    The Kit lens has a very consistent image across the frame

    The surprise to me was the fall off on the full frame lenses. Anyone have any guesses as to why?
    V/r John

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    Senior Member barjohn's Avatar
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    Re: Interesting lens Test Data

    I know several of you have seen this so why no help in understanding these results. Below is an image of my 13 x 19 test chart. I am going to retry the tests again using better controls and lighting to see if I made errors while doing this the first time.
    Last edited by barjohn; 23rd August 2009 at 20:55.
    V/r John

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    Senior Member Per Ofverbeck's Avatar
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    Re: Interesting lens Test Data

    Quote Originally Posted by barjohn View Post
    I know several of you have seen this so why no help in understanding these results....
    Well, John, please don´t feel ignored and neglected....

    We´ve seen your results and find them quite interesting. They seem to confirm the excellence of the kit lens, and that´s good to know.

    So, certainly you deserve some kind of feedback for your effort. Speaking for myself, however, I don´t have the expertise needed to even guess at the question you posed, i e why those old lenses show lots of falloff. And I suppose that goes for many other forum members, too.

    Possible explanations might include either different design goals, or the absence of aspherical components (which are used in the kit lens), or differences between film and sensors in handling oblique light rays. Only, for me it would be just a wild guess to choose between these.

    We´ll be quite interested to see the results of your further tests. Even if the cause is unknown, knowing the effects quantitatively is quite valuable for anyone contmplating any of these lenses.

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    Senior Member Brian Mosley's Avatar
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    Re: Interesting lens Test Data

    John, thanks for taking the time to share your results - but why have you tested the lenses at different apertures?

    Kind Regards

    Brian

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    Senior Member barjohn's Avatar
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    Re: Interesting lens Test Data

    I wanted to see the effects of stopping down on the lens. I actually tested from wide open to f8.
    V/r John

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    Senior Member barjohn's Avatar
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    Re: Interesting lens Test Data

    I just subscribed to digilloyd's and I was amazed at the effect of mirror slap on image sharpness. Even high shutter speeds and OIS could not compensate for the mirror slap. Since the G1 has no mirror it should be capable of producing sharper images than many DSLRs unless mirror lock up is used. Since it has the same maximum shutter speed as the M8.2 this may imply that it can compete with the M8.2 in image sharpness.
    V/r John

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    Senior Member Brian Mosley's Avatar
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    Re: Interesting lens Test Data

    John, have you got the test results at f3.5 across the board?

    Kind Regards

    Brian

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    Senior Member barjohn's Avatar
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    Re: Interesting lens Test Data

    No because several of the lenses don't have a 3.5 setting but rather a 4.0. I was only testing complete f stops.
    V/r John

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    Senior Member Brian Mosley's Avatar
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    Re: Interesting lens Test Data

    OK f4 then, just so that you're comparing at the same aperture?

    I suspect the results may be quite different?

    Cheers

    Brian

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    Re: Interesting lens Test Data

    Quote Originally Posted by barjohn View Post
    I know several of you have seen this so why no help in understanding these results.
    I don't see anything wrong with the way you set it up, but flat-chart testing is only meaningful for lenses that are going to be used exclusively for photographing flat subjects (process-camera and copy lenses, for example.)

    Chart testing exaggerates the importance of field flatness, a mild degree of which isn't really harmful in most real-world photography. Most everyday photo subjects have depth, making a flat field not necessarily the best fit -- so lens designers don't give top priority to achieving it. ('Back in the day,' Minolta even made a lens with adjustable field curvature -- you could change it from convex through flat to concave, allowing you to choose the "plane" of best focus that fitted the subject most closely.)

    I know it would be tedious, but if you really wanted to get a handle on this, you could do a focus-through test on each lens: making your test images at a variety of focus settings from nearer through farther. Then examine them to find the sharpest center, edge and corner image from each set.

    This would give you an idea of how edge sharpness compared to central sharpness for an in-focus image, and also of whether the field was flat, convex, or concave and by how much. Knowing all this might be helpful in choosing which lends would give you the sharpest picture in various real-world photo situations (although not necessarily helpful enough to be worth all the bother!)

    Historica: The limitations of flat-chart testing had become obvious by the late '60s, so that testing organizations gradually de-emphasized them (for example, you finally stopped seeing the beloved but misleading "lp/mm" charts in Modern Photography magazine.)

    But now in the Age of the Internet the test charts seem to be rearing their deceptive heads again. It's oh so tempting to believe that an easy-to-do test will yield impressively quantitative numerical results that will tell you definitively "how good a lens really is"... but for everyday photography, the reality is still a lot more complicated.

    Not the kind of response you wanted to hear, I'm sure... sorry...

  11. #11
    Senior Member Brian Mosley's Avatar
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    Re: Interesting lens Test Data

    Well, I'm glad John posted - if only to learn from your response... now who's going to tell dpreview?

    Kind Regards

    Brian

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    Senior Member barjohn's Avatar
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    Re: Interesting lens Test Data

    I think, if nothing else it helps me to know which lens will give me a sharper and greater contrast image. In particular the difference between a lenses ability to display sharp images that are low in contrast as well as those imsges with high contrast. The test chart also has fields of grass and waves and it really illustrates what the numbers are telling you.
    V/r John

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    Re: Interesting lens Test Data

    ... now who's going to tell dpreview?
    Oh, they know... they just don't want to face it. They've got too much invested in generating their spiffy animated performance graphs to concede that when it comes to real-world photography, they're taking the p*ss...

  14. #14
    Senior Member Brian Mosley's Avatar
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    Re: Interesting lens Test Data

    Good to know, thanks Ranger.

    Kind Regards

    Brian

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    Senior Member barjohn's Avatar
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    Re: Interesting lens Test Data

    While Ranger may be technically correct, I think it helps to have visual aids whether they are calibrated measurement charts or newspaper clippings and carefully arranged inanimate items the way Sean uses them to display what the lens is doing and how it draws.
    V/r John

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    Re: Interesting lens Test Data

    HI John
    Whilst I absolutely concur with Ranger about the 'flat field' issue, I think the results really do show how far lens design has come in the last few years. Very few companies are really putting resources into fixed focal length lenses.
    The fact that the Olympus kit lens is a cheap plastic lens, doesn't detract from the fact that it's an absolutely modern design.

    I've had real frustrations using old Nikon and Minolta lenses with the D3 and A900 respectively - both company's modern 24-70 f2.8 lenses seem to perform better than any of the primes of equivalent lengths.

    Your results really don't surprise me in the least.

    Just this guy you know

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    Senior Member barjohn's Avatar
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    Re: Interesting lens Test Data

    Tonight I decided to do a simple test with each of the following 4 lenses:
    1. Minolta 40/2 Rokkor
    2. 14-45 Panasonic kit lens
    3. Nikon Nikor AF 50/1.8 D
    4. Nikon Nikor AF 28/2.8 D
    5. 45-200 Panasonic Kit lens

    I shot the same subject in the same incandescent lighting and processed in LR 2.2 at all default settings. No tweaks and no sharpening. All were shot at ISO 400 at the widest aperture for each lens.

    Because shutter speed were low, 1/60, 1/8, 1/80, 1/40, & 1/13 there is some loss of sharpness due to motion blur (my shaky hands). The important thing to note is the difference in the way each lens paints its image. I would like your thoughts on each lens and the way it draws its image. The crops shown were taken from the center focus area of each image. Images are shown in the order listed above for each lens.
    Last edited by barjohn; 23rd August 2009 at 20:55.
    V/r John

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    Senior Member barjohn's Avatar
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    Re: Interesting lens Test Data

    By, the way, since I made each crop the same size, you will see more noise where the magnification is greatest since a lens like the 28 is much more enlarged in the crop than the 50 or 40. Note the difference in contrast and tone between the Rokkor 40/2 and the two kit lenses. The Nikons appear to be of lower contrast to me too.
    V/r John

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    Senior Member Brian Mosley's Avatar
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    Re: Interesting lens Test Data

    John,

    my thoughts are, use a tripod and the same aperture for the whole series... I'm afraid I can't really tell anything from this, which is why I'm speaking up - I don't want you to waste your time.

    Kind Regards

    Brian

    p.s. just in case the above sounds harsh and unfriendly - here's an emoticon which genuinely expresses my feelings

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    Senior Member barjohn's Avatar
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    Re: Interesting lens Test Data

    Brian,
    I can certainly add the use of a tripod but since I am looking to see the way the lenses paint an image and each lens has a different maximum aperture I can't use the same unless I use like 5.6 for all but then I am using a portion of the fast lenses that will provide a sharper image than the same f stop on a slower lens. I will do both to see if it makes any difference. What I see is that both kit lenses seem to be much more contrasty than the Rokkor or the nikons. I can see using the Rokkor where I have a very contrasty seen and I want to have the lens help me tame it.
    V/r John

  21. #21
    Senior Member Brian Mosley's Avatar
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    Re: Interesting lens Test Data

    Quote Originally Posted by barjohn View Post
    Brian,
    I can certainly add the use of a tripod but since I am looking to see the way the lenses paint an image and each lens has a different maximum aperture I can't use the same unless I use like 5.6 for all but then I am using a portion of the fast lenses that will provide a sharper image than the same f stop on a slower lens.
    This is why I had a problem with the resolution test you did at the top of this thread - you were loading the test heavily in favour of the 14-45 imho... I'd genuinely like to see the lpm figures of the 14-45 vs, say the nikon 50mm f1.8 at the same aperture.

    Cheers

    Brian

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    Re: Interesting lens Test Data

    Quote Originally Posted by barjohn View Post
    Tonight I decided to do a simple test with each of the following 4 lenses:
    Re the sample photos: Nyah-hah-hah, now we know what number to dial to open your gate!

  23. #23
    Senior Member barjohn's Avatar
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    Re: Interesting lens Test Data

    Brian,
    I guess I don't understand what you are getting at. My goal was to measure the lenses at the aperture I want to use them. No point in having fast lenses to use them stopped down. Therefore I was measuring performance at the widest aperture to try and determine the performance where I intended to sue it, not to compare in the sense of whether one lens is really better than another. My real question is whether it is good enough and under what circumstances. If I don't like the way a lens paints wide open and that is why I am using it (i.e. for speed), then why bother. It is easier to use the kit lens at f5.6, f8, etc. What was surprising to me was the visibly higher contrast of the kit lenses which some will like and some won't and the consistent level of performance. As I said, I actually tested over F-widest to f8 for each lesn. I just didn't post up all of the values. The other surprise to me was the fall off toward the edges of lenses designed for full frame when only the sweet spot of the center was being used due to the crop factor. I wasn't expecting that.
    V/r John

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