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Author Topic: Optimal Capture Sharpening, a new tool  (Read 29678 times)
Hening Bettermann
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« Reply #80 on: December 06, 2012, 03:44:46 PM »
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Hi Bart

Thank you for your offer to check my file. Here is the download link:

http://rapidshare.com/files/1042777387/Sonnar_85_f%3A8_7074.CR2

In the meantime, here is my best effort with CS5, SmartSharpen Gaussian blur 100% r=0.4, viewed at 400%.
--edit: hm - it looks a deal better than RD...

Kind regards - Hening.

« Last Edit: December 06, 2012, 03:49:56 PM by Hening Bettermann » Logged

BartvanderWolf
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« Reply #81 on: December 06, 2012, 05:51:35 PM »
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Hi Bart

Thank you for your offer to check my file. Here is the download link:

http://rapidshare.com/files/1042777387/Sonnar_85_f%3A8_7074.CR2

In the meantime, here is my best effort with CS5, SmartSharpen Gaussian blur 100% r=0.4, viewed at 400%.
--edit: hm - it looks a deal better than RD...

Hi Hening,

The link doesn't lead to a file (or at least Rapidshare says it is not found). Anyway, the CS5 conversion + Smart Sharpening already looks a lot better. You can also try Lens blur instead of Gaussian.. Sharpening in ACR would offer some more possibilities (Radius/Amount/Detail, together with masking, and noise reduction if needed) to tweak the settings.

Cheers,
Bart
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Hening Bettermann
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« Reply #82 on: December 07, 2012, 04:50:53 AM »
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Hi Bart,

sorry for the download failure. They have changed some things since I last used them. I had to activate "Direct download"  and can now access the file. Please try again.

I have contacted a local print service asking to print and mount your target.

By the time I may have obtained it, also the announced new Mac version of Raw Therapee may be available, and the upgrade of Raw Developer, and I plan then to compare them and CS5 and C1.

Good light! - Hening.
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BartvanderWolf
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« Reply #83 on: December 07, 2012, 07:04:10 PM »
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Hi Bart,

sorry for the download failure. They have changed some things since I last used them. I had to activate "Direct download"  and can now access the file. Please try again.

Hi Hening,

Unfortunately the file is not available. I suppose the https:// suggests that it requires a userID/password to access the file with this URL.

Quote
I have contacted a local print service asking to print and mount your target.

This is interesting in its own right. Depending on the technology they use to produce prints, the resolution target may reveal a thing or two about their setup. A local service that I used for quick photochemical prints found out that the RGB laserbeams of their Fuji Frontier were not aligned as well as could be ...

You will be able to judge the actual on-paper-resolution, by measuring the diameter of the central blurred disk of the 'star', and adjust the PPI of print jobs you send them in the future accordingly.

Cheers,
Bart
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Les Sparks
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« Reply #84 on: December 08, 2012, 10:22:20 AM »
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Just a quick thanks for this useful tool. It's been a great help in improving my capture sharpening.
Les
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BartvanderWolf
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« Reply #85 on: December 08, 2012, 04:04:25 PM »
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Just a quick thanks for this useful tool. It's been a great help in improving my capture sharpening.

Hi Les,

Thank you. I'm glad it is of use for a lot of people, even though it's currently not as user friendly as I intend it to become.

Cheers.
Bart
« Last Edit: December 08, 2012, 04:20:56 PM by BartvanderWolf » Logged
Hening Bettermann
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« Reply #86 on: February 12, 2013, 02:21:17 PM »
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Hi Bart,

I have now received my target printed and mounted flat. How bright (in EVs) should it be illuminated for shooting? (I assume the exposure should be adjusted for the middle gray area).

Kind regards - Hening
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BartvanderWolf
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« Reply #87 on: February 12, 2013, 02:47:22 PM »
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Hi Bart,

I have now received my target printed and mounted flat. How bright (in EVs) should it be illuminated for shooting? (I assume the exposure should be adjusted for the middle gray area).

Hi Hening,

I usually aim for the white patch of the gray steps at the edge to land around RGB 235,235,235, but a bit darker is no problem.  I use as linear a tonecurve as possible during Raw conversion, because I also use a linear tone curve at the final Raw conversion of my images. I also use my regular (almost default) contrast and brightness settings. If you tend to use different settings you can use those, but do understand that contrast influences the final sharpening as well.

Cheers,
Bart
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Hening Bettermann
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« Reply #88 on: February 12, 2013, 03:57:21 PM »
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Hi Bart,

thanks for your fast reply. It seems that you don't reply to the first part of my question, which refers to illumination when shooting. I mean I can illuminate the middle gray of the target to different EV values, and I thought there might be a recommendable range. In fact it was not me who thought - the operator of my print service did.

Kind regards - Hening.
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BartvanderWolf
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« Reply #89 on: February 12, 2013, 05:36:27 PM »
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Hi Bart,

thanks for your fast reply. It seems that you don't reply to the first part of my question, which refers to illumination when shooting. I mean I can illuminate the middle gray of the target to different EV values, and I thought there might be a recommendable range. In fact it was not me who thought - the operator of my print service did.

Hi Hening,

I don't see how the absolute level of illumination could have an effect, since it's the ISO setting, and the aperture, and exposure time, that determine where on the tone curve the image of the target will be placed. We're not shooting film with an S-curve shaped response curve, but a digital sensor with a linear response curve, and the gamma pre-compensation that will be applied afterwards is to compensate for the human response and the display gamma.

Maybe I'm mis-interpreting what the operator was suggesting?

Cheers,
Bart
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Hening Bettermann
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« Reply #90 on: February 12, 2013, 06:20:37 PM »
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Hi Bart,

His thought - at least in my adaption - was: The performance of a lense depends on brightness of illumination of the subject, independent of post-processing. Say the target is illuminated to EV 6 or 10. I can compensate for the lower illumination by increasing the exposure time, achieving the same middle gray - but that will not help the lens to see lines. Or is it me who got it wrong?

Kind regards - Hening
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BartvanderWolf
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« Reply #91 on: February 13, 2013, 03:40:15 AM »
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Hi Bart,

His thought - at least in my adaption - was: The performance of a lense depends on brightness of illumination of the subject, independent of post-processing. Say the target is illuminated to EV 6 or 10. I can compensate for the lower illumination by increasing the exposure time, achieving the same middle gray - but that will not help the lens to see lines. Or is it me who got it wrong?

Hi Hening,

The level of illumination makes no difference to the lens, it's purpose is just a matter of refracting photons. Their quantity doesn't really matter, their wavelength does.

What his thoughts might have been, is that ideally one would do the deconvolution sharpening while in linear gamma space. When we do our Capture Sharpening however, we usually are already in an approx. gamma 1/2.2 space which stretches shadows, and compresses highlights. Therefore it does matter where on the gamma curve we measure contrast, and thus exposure level (not illumination level) does matter.

I've taken two precautions to work around that. One is the grayscale stepwedge which, when properly exposed, spans a large range from reflected black to reflected white. It would be quite easy to already see if the exposure level was correct, otherwise we'd lose shadow or highlight detail. When properly exposed, like I assume one's regular images are, then the white patch should land around [235,235,235], the medium gray around [128,128,128], and black somewhere around [10,10,10], but these are not absolute goals because different Raw converters produce different tonalities. The point is that there is a good spread of brightness levels with visible details from dark to light. The second precaution I took was to evaluate that entire range (whatever it happens to be) as it also forms at the sub-pixel edge transitions, and fit a curve to it. I do not measure contrast, but a contrast transition curve shape.

And as that curve shape shows, the transition is usually very well balanced and symmetrical along the brightness range, and almost perfectly follows a symmetrical differential Gaussian curve. The only deviation that can pop-up is some lens glare which raises the response of the shadows and lowers contrast. It is taken into account when fitting the curve, but it won't dominate the outcome.

Cheers,
Bart
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Hening Bettermann
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« Reply #92 on: February 13, 2013, 06:52:14 AM »
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Hi Bart,

thank you for your detailed reply. There is no end to surprises in these matters, for the ignorant. That the brightness of illumination made a difference sounded right to me because in MTF curves, resolution and contrast are mutually dependent. (If I got THAT right...)

Kind regards - Hening
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BartvanderWolf
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« Reply #93 on: February 13, 2013, 07:06:03 AM »
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Hi Bart,

thank you for your detailed reply. There is no end to surprises in these matters, for the ignorant. That the brightness of illumination made a difference sounded right to me because in MTF curves, resolution and contrast are mutually dependent. (If I got THAT right...)

Hi Hening,

Almost right, and that perhaps explains the confusion. It's actually the 'transfer of contrast' (=modulation) and resolution that are dependent. The function describes how an input modulation (100%, even if it has modest absolute contrast) and a given resolution is reduced to an output modulation, as a function of resolution. It doesn't describe, at least not directly, total scene contrast. It's the deterioration of modulation of the specific spatial frequency component that is described.

Cheers,
Bart
« Last Edit: February 13, 2013, 12:42:03 PM by BartvanderWolf » Logged
Hening Bettermann
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« Reply #94 on: February 13, 2013, 12:26:30 PM »
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Thanks again!
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