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Thread: A7rII - sharpening for large prints - some simple tests

  1. #1
    Senior Member ErikKaffehr's Avatar
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    A7rII - sharpening for large prints - some simple tests

    Hi,

    Now that I have the Sony A7rII it would be a good thing to find adequate sharpening settings. The aims were:

    • Avoid/limit haloing
    • Sharpening that allows large prints
    • Having a reasonable starting point


    The method I used was to shot a test chart and analyse with Imatest and tune parameters until I got a good level of sharpening, without MTF going excessively high (say below 105% on the sharpened image), little haloing and high SQF.

    I came up with three methods that show good promise:

    • Using "scene/landscape" sharpening in Lightroom. (Keeps parametric workflow)
    • Not doing any sharpening in Lightroom and do all sharpening in FocusMagic. Default parameters and 75% sharpening, in order of avoiding oversharpening on low frequencies. (Breaks parametric workflow)
    • Not doing any sharpening in Capture One and doing all sharpening in FocusMagic. (Breaks parametric workflow)


    These candidates remained after some "math based" evaluation. From the three candidates I made small crops printed on A4 size paper, corresponding to 95x145 cm prints. That is around 37"x57". These prints were pretty similar. I would say that the C1/FocusMagic combo was probably the best, doing pixel peeping on those cropped prints.

    The lens I used here was the Sony 90/2.8G at f/4. Results may vary.

    So what I have found was that the "scene" sharpening in Lightroom is pretty OK with the A7rII. Capture One had a small benefit, I was able to pick it from the other two.

    Using the scene setting in LR didn't break the parametric workflow, no TIFFS and no Photoshop involved.

    All images has shown some colour demosaic artefacts, just a fact of life with non OLP-filtered images. These artefacts were definitively visible in prints. The lens needed to be stopped down to f/16 to remove all artefacts. I did not test moiré removal tools. These normally are quite good at reducing colour moiré but don't really help with monochrome artefacts.

    So what is my take? I guess that I am quite happy with the "landscape/scenic" setting in LR 6. It has been developed by Jeff Schewe. It is truly parametric. The other methods give marginally better results.

    This is all for now.

    Best regards
    Erik

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    Senior Member ErikKaffehr's Avatar
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    Re: A7rII - sharpening for large prints - some graphs

    Hi,

    Here are the SQF data (*):
    LR Scenic
    Click image for larger version. 

Name:	best_20151109-_DSC3191_LR_LRSCENIC_YR4_01_sqf.jpg 
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ID:	114092
    LR no sharpen + FM
    Click image for larger version. 

Name:	best_20151109-_DSC3191_LR_NOSHARP_FMDF_075_YR4_01_sqf.jpg 
Views:	28 
Size:	18.6 KB 
ID:	114090
    C1 no sharpen + FM
    Click image for larger version. 

Name:	20151109-_DSC3191_C1_NS_FMDF_075_YR4_01_sqf.jpg 
Views:	27 
Size:	18.4 KB 
ID:	114091

    Best regards
    Erik

    (*) SQF is based on research made by Ed Granger who worked at Kodak. SQF (Subjective Quality Factor) approximates perceived sharpness at different viewing distances in prints of different sizes. It is essentially the integral of he MTF weighted with the Contrast Sensitivity Function, normalised to 100 for some small print size.

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    Senior Member Joe Colson's Avatar
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    Re: A7rII - sharpening for large prints - some simple tests

    Erik, thanks for the information and analysis. I have been using a formula presented in these forums by Tim Ashley some time ago for sharpening in LR. The settings are 60, 0.7, 70, 20 for Amount, Radius, Detail, and Masking respectively. I've never tried the LR preset and assume you're referring to the Lightroom General Presets>Sharpen-Scenic preset. If not, point me in the right direction.

    The Sony 90mm is definitely a sharp lens and may not need the amount of sharpening I've been applying when using other Sony lenses.

    Joe
    _________________________________
    Joe Colson Photography

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    Senior Member ErikKaffehr's Avatar
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    Re: A7rII - sharpening for large prints - some simple tests

    Hi Joe,

    Thanks for input. This thread is intended to be a series of experiments. Next up may be a lens degraded by diffraction or a less excellent lens.

    One of my concerns is that we may sharpen a bit to much for pixel peeping on screen and ignore lower frequency detail that may play an important role when looking at prints.

    Just to say, I am familiar with Tim's sharpening. But I sort of feel that a less aggressive sharpening may be more optimal. What I have seen is that intensive sharpening enhances noise. Uisng masking hides that noise but yields artefacts on the edges of the applied mask.

    I actually think that some of the "orange peel" artefacts are coming from that kind of sharpening rather than raw compression. Extensive sharpening enhances shot noise. So using less intensive sharpening may give us very good prints with less artefacts.

    I would also add that pixel peeping is a bit odd. In real life we never look at pixels at actual size. We either show downscaled images. Even full HD is just 2-3 MP and 4K may be around 10 MP. 8K will be a good match for high end 135 of today, but than we need a large screen and look close.

    With prints it is quite similar. I would say that an A2-size print (16"x23") is very forgiving compared to an actual pixels view.

    Best regards
    Erik


    Quote Originally Posted by Joe Colson View Post
    Erik, thanks for the information and analysis. I have been using a formula presented in these forums by Tim Ashley some time ago for sharpening in LR. The settings are 60, 0.7, 70, 20 for Amount, Radius, Detail, and Masking respectively. I've never tried the LR preset and assume you're referring to the Lightroom General Presets>Sharpen-Scenic preset. If not, point me in the right direction.

    The Sony 90mm is definitely a sharp lens and may not need the amount of sharpening I've been applying when using other Sony lenses.

    Joe

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