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Thread: Judging image sharpness

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    Judging image sharpness

    I'd like to ask the great folk on this forum how they judge image sharpness.

    What with front/back focus, AF adjustments, camera shake and shake reduction, image resolution, the use and strength of AA filters - all of which doesn't even take account of the lens qualities - how do you conclude that the image is sharp enough from the K5?

    Do you judge from the image in preview mode, 50% magnification or 100%?

    Do you apply some sharpening beyond the default LR defaults before judging?

    Do you actually make a print to decide on how sharp the shot is?

    It seems to me that K5 shots that are in focus and do not have (much) camera shake clearly sharpen up nicely with 80-100% sharpening amount. If they don't look sharp with that setting then they are not in focus or suffer from shake.

    Shots from other cameras, such as Leica, M4/3 etc may appear to be sharper without much fiddling in LR. But it is the same question - how do you ultimately make the sharpness judgment?

    Thanks

    Lee

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    Re: Judging image sharpness

    Quote Originally Posted by Sapphie View Post
    I'd like to ask the great folk on this forum how they judge image sharpness.

    What with front/back focus, AF adjustments, camera shake and shake reduction, image resolution, the use and strength of AA filters - all of which doesn't even take account of the lens qualities - how do you conclude that the image is sharp enough from the K5?

    Do you judge from the image in preview mode, 50% magnification or 100%?

    Do you apply some sharpening beyond the default LR defaults before judging?

    Do you actually make a print to decide on how sharp the shot is?

    It seems to me that K5 shots that are in focus and do not have (much) camera shake clearly sharpen up nicely with 80-100% sharpening amount. If they don't look sharp with that setting then they are not in focus or suffer from shake.

    Shots from other cameras, such as Leica, M4/3 etc may appear to be sharper without much fiddling in LR. But it is the same question - how do you ultimately make the sharpness judgment?

    Thanks

    Lee
    Lee, lots of excellent questions, I'm afraid I don't have all the answers though , but I simply check at 100% (C1) first.
    If it's good I'll leave it as is (obvious), otherwise I'll try a little sharpening and perhaps a little more and if it's then still not to my liking: too bad and I dispose off the image.
    But saying that for street and candids it's more about the content and a little blur or unsharpness is no problem IMO.
    Not sure if this helps you, hopefully more knowledgeable people will chime in and eventually you'll get your answers.

    Kind regards.
    Bart ...

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    Re: Judging image sharpness

    Quite frankly i look at the picture as others would look at it. Not blown up to see every pixcel, just normal viewing. If it looks good, fine. If any out of focus area is not what was intended, then i look more for reasons why, and do the shot again and see what is going on.

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    Re: Judging image sharpness

    If you use a good lens and if you nail focus (and avoid shake) it is possible to get very sharp images with the K5 without much post processing.
    In my case most of the images which are not sharp are caused by front/backfocus. My lenses are still not fine tuned enough to get good results.
    So I would first check if the "unsharp" look could be caused by front or backfocus and if so try to get rid of that problem.

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    Re: Judging image sharpness

    Quote Originally Posted by Sapphie View Post
    What with front/back focus, AF adjustments
    I highly recommend Lens Align MkII, here http://www.whibalhost.com/lensalign/

    Lens align is to my knowledge the only complete "black and white" means to determined front and rear focus of a camera system, one that will be difficult to a camera brand to argue against.

    The other part is what adjustment tolerance is acceptable. Phase One for medium format cameras recommends a tolerance of +/-3.5mm within the focus plane when using an 80mm lens @ f/2.8 and 800mm focal distance. If the lens used is 150mm it should be @ f/2,8 and instead 1500mm and similar multiplier of distance for each focal (if I got it correct). No idea how that tolerance relates to smaller formats, but at least it can give you an idea.

    I hope above helps.

    Regards
    Anders

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    Re: Judging image sharpness

    My focus test check 50-135 at 135mm f2.8
    It would be better if the pot was cylindrical, but it does the job and it was there.
    Last edited by DavidL; 27th February 2014 at 02:35.

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    Re: Judging image sharpness

    Quote Originally Posted by DavidL View Post
    My focus test check 50-135 at 135mm f2.8
    It would be better if the pot was cylindrical, but it does the job and it was there.
    By putting three of them at slight different focus distance you can also determine which one of three appears as sharpest...

    ... albeit same as with one pot you cannot determine with any accuracy that your system is at its optimum sharpest focus adjustment. Hence lens align to accurate determine front or rear focusing of your system, and black on white to bring to your service center / agent (or programme focus adjustment on camera if it has such feature).

    Also of course lens align has focus target perpendicular to lens axis, thus at plane of focus, and which rules out any misshap of you not focusing exact where actual focus sensor is for your system.

    Above is brief summary of what I go through now with Mamiya with Leaf's help, thanks to Lens align...


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    Re: Judging image sharpness

    Hi Anders
    Didn't think I needed to put 3 in a line as the text on the pot drifts out of focus and I'm happy with that. I'm an easily pleased guy.
    One benefit of my test is you get the see the Bokeh
    I've just changed from Nikon, as my pro days are coming to an end, the Pentax af system isn't a patch on the Nikon one, IMHO. But I'm learning to live with it thanks to my tomato plants pot. You'll be pleased to hear that the plants have now been potted and are growing well.
    David.

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