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Thread: 14-54 circular aperture - Ian eats humble pie!

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    Red face 14-54 circular aperture - Ian eats humble pie!

    I have been asked a few times about the circular aperture 'feature' of the new Mark II Digital Zuiko 14-54 f/2.8-3.5, as changes to the optics comparared to the original we all know and love.

    I contacted Japan and the answer was that the optics were unchanged. It made sense and so I assumed that the old and new lenses also had the same aperture iris designs. This is what I have been telling people, but I was WRONG! Here's the evidence:


    At full aperture (f/3.5 @54mm) the iris shape is circular for both. This is because the iris blades don't come in to play when the lens is wide open.

    But in the lower pair of images, you can see that the Mark I lens, at f/5, definitely has a hexagonal outline, while the Marek II is still almost circular.

    So I apologise for my mistake and thank you to Kuifje and geohsia for prompting me to test the lens again in this thread:

    http://www.fourthirds-user.com/forum...ead.php?t=2886

    Ian (stuffed with humble pie - yum)
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    Re: 14-54 circular aperture - Ian eats humble pie!

    Interesting factoid, Ian, and explains a technical advance so that even I can understand it.
    Question, though, why are the images @ f5 so much brighter than those at f3.5?
    I would not expect any difference.


    The picture is the story, it is your history. dw.

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    Re: 14-54 circular aperture - Ian eats humble pie!

    Quote Originally Posted by Imageryone View Post
    Interesting factoid, Ian, and explains a technical advance so that even I can understand it.
    Question, though, why are the images @ f5 so much brighter than those at f3.5?
    I would not expect any difference.
    Operator error (me!) I didn't use manual exposure. Sorry (again!)

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    Re: 14-54 circular aperture - Ian eats humble pie!

    or simply kinda logical guessing here... Assuming taken in A mode and figure the camera meter and set the shutter speed accordingly

    the lights in the F5 circular bokeh is more concentrated, and thus brighter?

    the light source emit costant amount of light, with wide open Aperture, those lights need to be spread through a bigger area, thus dimmer and more diffuse, vs the stopped down more concentrated and bigger?

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    Re: 14-54 circular aperture - Ian eats humble pie!

    I can see a logic in your reply, bitslizer, but on the flagship camera of the range and all other factors being exactly the same in both sets of images. I would have expected the camera to automaticaly compensate to the same brightness.So I don't actually see how Ian could be at fault.
    You have to remember, I still use an old E-300 for certain types of image, so am very well used to slight deviations in exposures.
    It would be of interest to me to see the shutter timings for a comparison, Ian.


    The picture is the story, it is your history. dw.

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    Re: 14-54 circular aperture - Ian eats humble pie!

    Quote Originally Posted by Imageryone View Post
    I can see a logic in your reply, bitslizer, but on the flagship camera of the range and all other factors being exactly the same in both sets of images. I would have expected the camera to automaticaly compensate to the same brightness.So I don't actually see how Ian could be at fault.
    You have to remember, I still use an old E-300 for certain types of image, so am very well used to slight deviations in exposures.
    It would be of interest to me to see the shutter timings for a comparison, Ian.
    Mk1 14-54 - f/3.5 @54mm, 0.6 sec
    Mk1 14-54 - f/5 @54mm, 1.3 sec
    Mk2 14-54 - f/3.5 @54mm, 1 sec
    Mk2 14-54 - f/5 @54mm, 2 sec

    My reason for being self-critical, is that both sets of exposures should have been identical. But I subscribe to the light concentration theory to explain why the smaller aperture discs appear brighter than the larger ones.

    Ian
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    Re: 14-54 circular aperture - Ian eats humble pie!

    Thanks for the information, Ian, I in no way disagree with the theory, just thought the electronics should compensate.
    Very interesting to note, however, that in both tests, the Mk11 required a slower shutter speed than the Mk1 to obtain the same image.
    .4 @ f3.5
    .7 @ f5.0

    With .7 delay, I would expect the light emitted to the sensor would be enough to round the iris anyway, so is it a technical advance, or a little bit of flim-flam?
    So, on that note. if you were to reset the test using the same apertures and shutter speeds on both lenses, what would be the comparison then?.


    The picture is the story, it is your history. dw.

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    Re: 14-54 circular aperture - Ian eats humble pie!

    Quote Originally Posted by Imageryone View Post
    Thanks for the information, Ian, I in no way disagree with the theory, just thought the electronics should compensate.
    Very interesting to note, however, that in both tests, the Mk11 required a slower shutter speed than the Mk1 to obtain the same image.
    .4 @ f3.5
    .7 @ f5.0

    With .7 delay, I would expect the light emitted to the sensor would be enough to round the iris anyway, so is it a technical advance, or a little bit of flim-flam?
    So, on that note. if you were to reset the test using the same apertures and shutter speeds on both lenses, what would be the comparison then?.
    OK, I will re-do the test under better controlled conditions, over the weekend.

    Ian
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    Re: 14-54 circular aperture - Ian eats humble pie!

    Maybe also good to note that there seems te be a difference in maximum apperture in respect to focal length. The MK II seems to hold its brightness longer then the MK I.

    Looking forward to the result (and ofcourse of it bests the PL 14-50 .. )

    Martin

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    Re: 14-54 circular aperture - Ian eats humble pie!

    Quote Originally Posted by Kuifje View Post
    Maybe also good to note that there seems te be a difference in maximum apperture in respect to focal length. The MK II seems to hold its brightness longer then the MK I.

    Looking forward to the result (and ofcourse of it bests the PL 14-50 .. )

    Martin
    I've decided to expand the scope a bit and to test defocussed aperture disc shapes for a range of lenses:

    DZ 14-42
    DZ 14-45
    DZ 17.5-45
    DZ 14-54 I & II
    DZ 14-35
    DZ 12-60
    DZ 50-200 (old and new versions)
    Panasonic Leica 14-50 f/3.5-5.6

    I'd like to include the old and new versions of the DZ 40-150, but I don't have either at the moment. If anyone reasonably local to me can help, do let me know.

    The idea is to test at full aperture and f/8 at as close to 50mm focal length as possible.

    Hopefully I can get this done by the end of the coming week.

    Ian
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