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Is it sharp ?

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    Is it sharp ?

    Since I went Digital , some years ago now , it has always bugged me to what we consider and how we decide what is sharp . The general rule seems to be to enlarge the image 100% and see how it looks . Some images in a sequence should have the same amount of sharpness but often don`t though they may all be " Sharp enough " , some lenses are definitely sharper than others , full frame cameras seem to have cleaner sharper images than bridge or cropped sensor bodies . Does what looks sharp to me look sharp to you , definitely not always , so how can you actually define sharp ?

    #2
    Re: Is it sharp ?

    Now that is a brilliant question.

    In the days of film that was an easy question to answer. Within reason, it was either sharp, or it wasn't. With digital we have an Anti-Aliasing filter in front of the sensor and that is to prevent the Moire Silk effect over the image. Definitely needed when resolution was 3, 6, or 10MP, probably still needed at 15MP, but do we still need it with resolutions greater than 15MP? Nikon don't seem to think so and most of their latest releases are without AA filters. The downside of an AA filter is that it slightly softens the image, so some extra sharpening is needed in camera, or post capture to restore the original sharpness.

    Easy enough to add some sharpening in your editing program, but there are those that think if a little sharpening is good, a lot of sharpening has to be better. I have always been an advocate of doing what you need to in Photoshop (etc), not what you can and my two biggest bugbears are over sharpened and over saturated images. Vastly over sharpened images end up with the halo effect, but careful use of the sliders can bring you up to where the halo would be just starting and even though no halo, still obviously too sharp. If we are comparing our images against something too sharp, then our images may seem soft, when in fact they are just right with a little sharpening.

    I think at the end of the day we have to use some common sense. You are the photographer, you saw the subject and if the sharpness compares favourably with what you saw, then it's right. If it is sharper than what you saw, then you have moved the sliders a little too much.
    Colin

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      #3
      Re: Is it sharp ?

      I agree that what one person considers sharp enough someone else may not - so 'sharp enough' is a variable amongst people. What is constant is that if you put two images side by side with different sharpness then everyone will agree on the relative sharpness, i.e. which is sharper and which is less sharp.
      Its like.....'You can please all of the people some of the time and some of the people all of the time but you cant please all of the people all of the time'.....I'm quoting Bob Dylan quoting Abraham Lincoln.
      I tend view at 50% and if it looks sharp then that's good enough....should be able to print to A2 or bigger and the print will still look sharp....unless of course you get too close.
      Brian Vickers LRPS

      brianvickersphotography.com

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        #4
        Re: Is it sharp ?

        Like Brian I generally assess sharpness at 50%, if it looks right then then it will look right in print. I normally only assess sharpness at 100% for images intended for electronic display where the image size will be that of the device be it monitor, TV or digital projector. I might monitor full size images at 100% if I am having an issue with halos but even then I prefer to give the final assessment at 50% - I've found you can sharpen at actual pixel level just stopping shot of halos and yet at real world sizes. eg prints or 50% on a monitor the image looks hyper-sharp and a touch unnatural.

        With subjects that have clearly defined edges you can generally expect crisper edges than those that or softer or more rounded. I often find that people tend to look a touch soft even when their surroundings are nicely sharp - even though the person is in the same focal plane - and this seems to extend to quite a few other natural objects as well.

        Overall I work to the principle of if it looks right then it is right. Softness cause by camera shake or mis-focusing will never look right no matter how much USM you apply so it never looks right.
        Nigel

        You may know me from Another Place....

        The new ElSid Photogallery...

        Equipment: Far too much to list - including lots of Nikon...

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          #5
          Re: Is it sharp ?

          It all depends on what you mean by "sharp" which is a rather poorly defined concept and is often used rather loosely. What you get from your lens and sensor combination is a certain level of resolution. A "sharper" lens will give a higher resolution than a "softer" one, which means fine detail will be resolved better, and of course the aperture setting can also have a considerable effect on resolution. No amount of processing can increase the resolution of the image once it has been taken.

          "Sharpening" an image only increases the acutance, the contrast at edges, which makes the image appear sharper to human perception, but does not actually increase the resolution. With a tool like the Unsharp Mask, there are three things you can change radius (fineness), amount and threshold which each have different effects. Where an image appears to be "oversharpened", e.g. with the halo effect, it seems to be most often due to too high a value for radius/fineness. I reckon it's a good idea to start with a low level for this and increase it little by little until you are happy, which of course means using the Unsharp Mask tool, not the simple Sharpness. There is a good short article on the subject in the Oct - Dec 2016 magazine, "DPP sharpening".

          I've also found that the Fine Detail picture style available on the newer cameras gives much better results for out of camera jpegs, because of the low setting of Fineness, and you can alter all three controls to make your own user defined style, while with the older models you can only change Sharpness, which gives little control. You can apply the Fine Detail settings to all Raw images using DPP, which generally gives good results.

          This Wikipedia definition sums it up "Perceived sharpness is a combination of both resolution and acutance: it is thus a combination of the captured resolution, which cannot be changed in processing, and of acutance, which can be so changed."
          EOS 6D, 6D Mk II, 80D, 70D, 100D, 200D, M50, M100. Canon 10-18, 18 - 55, 55 - 250 IS STM lenses, Canon 16 - 35 mm F4L, 35 mm EF-S macro, 50 mm F1.8 STM, 60 mm EF-S macro, MPE-65 macro, 85 mm F1.8, 200 mm F2.8 L II, M 15 - 45 mm, M 22mm F2, M 32mm F1.4. Sigma 24 - 35 F2 Art, 135 mm F1.8 Art, 17 - 50 F2.8 DC, 105 mm OS macro, 100 - 400 C, 150 - 600 C.

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