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Thread: Graduated sharpening

  1. #1
    Ndukes's Avatar
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    Neville Dukes

    Graduated sharpening

    Low to mid priced lenses in general for APS-C cameras tend to have a more significant sharness fall-off towards the edges than full frame specific mid-priced lenses. Having used both full frame and APS-C cameras concurrently I wanted to develop a simple process to graduate sharpening across my APS-C images which would counteract, at least to an acceptable degree, this resolution fall-off towards the frame edges.
    I do all of my post-processing in Photoshop (CS6) and to streamline things I develop ‘Actions’ to condense most common processes into single steps.
    I thought I would share this graduated sharpening process with other APS-C camera owners who use Photoshop CS?. It’s a bit cumbersome but once your preferred settings can be established an ‘Action’ can be recorded to streamline the process into a single step. Seperate actions need to be set up for horizontal and vertical format files and would be specific to sensor size (Megapixel count) but they are not suitable for cropped or resized files.

    This example is for horizontal format files.

    1. Using the Eliptical Marqee tool, set to fixed ratio, select a perfect circle the full height of the frame and centred (as near as possible) across the width.
    2. Set ‘Refine Edge’. This depends on sensor size (Megapixel count) and you will need to experiment here. For a Nikon D5200 or D7100 a setting of 400 is about right.
    3. Use USM or Smart Sharpen (your preferred method) to sharpen the selection, in this case the image centre. In USM try Amount = 75, Radius = 0.8, Threshold = 1
    4. Invert the selection (Select > Inverse)
    5. Use the USM or Smart Sharpen to sharpen the image edges. In USM try Amount = 150, Radius = 1.2, Threshold = 1
    6. De-select the selection

    This might apply to some full frame lenses also but not so far in my experience.

    Hope some find this useful.

  2. #2
    dje's Avatar
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    Dave Ellis

    Re: Graduated sharpening

    Hi Neville

    Thanks for posting this. Interestingly, I was thinking about the concept of graduated sharpening myself just the other day (for the reasons you mention). I must have a play with your technique.

    I prefer to do my capture sharpening in ACR and was thinking it might be possible to do graduated sharpening using the selection brush but at this point I haven't been able to do anything worthwhile with that. When the adjustment brush is invoked, it seems to have limited sharpening options.

    Dave

  3. #3

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    Re: Graduated sharpening

    I prefer to sharpen what needs to be sharpened rather than a pre-set which suits little or nothing. Often the fall off in sharpness is a bonus feature anyway.

  4. #4
    Moderator Dave Humphries's Avatar
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    Re: Graduated sharpening

    Hi Neville,

    It is an interesting concept.

    John has a fair point, unless you're photographing artwork, documents, or similar, where having sharpness fall off to the edges is a bad thing.

    Personally, I prefer to sharpen after I have down sized for web display, by which time my images have been inevitably cropped, making the centre not the centre, if you see what I mean (and as you acknowledge).

    I guess ideally you'd want most aspects of the sharpening to gradually increase towards the edge of the lens circle, not just the amount, but also the radius (not the threshold though, since that's a sensor thing). Rather than the step change you have inside and outside of a given circle.

    It therefore occurs to me that this might be a technique that camera manufacturers might apply in camera to their jpgs, much as these days, CA (Chromatic Aberration) and vignetting corrections are.
    Similarly, it could be (optionally) available in LR and ACR, where the whole image is available.

    Now there's a thought

    Cheers, Dave

  5. #5
    rpcrowe's Avatar
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    Re: Graduated sharpening

    When sharpening with NIK the two sharpening tools (RAW Presharpener and Adaptive Output Sharpener) you can easily adjust the areas and amount of sharpening in those areas chosen using the NIK Control Point System...
    https://www.youtube.com/watch?v=s_RvXCLzHDA

    You also "can increase apparent sharpness locally or globally using the structure slider in NIK Viveza. The structure slider increases the localized contrast around the details in the image to make them stand out more clearly, and it’s the secret weapon across the whole of the Google Nik Collection – it helps make this adjusted area look ‘punchier’ and more natural."
    see:
    Life After Photoshop
    http://www.lifeafterphotoshop.com/ne...ontrol-points/

    The structure slider is one of my favorite tools among the many neat tools in the NIK Software "toolbox"...

    I have mentioned this earlier but, IMO, if Adobe had purchased NIK and incorporated the NIK tools into Photoshop; people would be singing the praises of the new improved Photoshop as the greatest thing since sliced bread.
    Last edited by rpcrowe; 10th October 2014 at 10:09 PM.

  6. #6
    davidedric's Avatar
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    Re: Graduated sharpening

    Not a perfect solution by any means, but if one is using Lightroom it is possible to draw out a circular /oval filter with an appropriate feather and use the sharpening control within that. There is only a single sharpness slider. This can also be used to dial in negative sharpness, which introduces a kind of gaussian blur to help separate the main subject from the background if you haven't managed it with dof.

    Dave
    Last edited by davidedric; 11th October 2014 at 08:44 AM.

  7. #7
    The Blue Boy's Avatar
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    Re: Graduated sharpening

    An interesting concept.

    I think the same technique would be better suited to creating a mask, then sharpening through that for greater control, i.e. Opacity.

  8. #8

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    Re: Graduated sharpening

    One of the delightful aspects of the editing programme is its ability to reduce any action to the area selected.

  9. #9

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    wm c boyer

    Re: Graduated sharpening

    Dave, the sharpening method that you mentioned...is it the same algorhym that is used on the
    whole image in the LR sharpening section?

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