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Author Topic: C1 12 Diffraction Correction  (Read 599 times)

Kevin_Sink

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C1 12 Diffraction Correction
« on: August 26, 2019, 10:22:02 pm »

Hey Doug Peterson or some other high tech Capture One guru out there, how does Capture One perform diffraction correction?  Is it a type of sharpening?  Does Phase have tons of lens optical performance profiles and makes some algorithm for each one?  It doesn't quite look like sharpening.  I want to avoid that because in very large prints sharpening can create ugly halos.  Would diffraction correction degrade image quality in a 30' wide mural print?  I'll do some testing but thought I'd ask first. 
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Bart_van_der_Wolf

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Re: C1 12 Diffraction Correction
« Reply #1 on: August 27, 2019, 08:34:13 am »

Hey Doug Peterson or some other high tech Capture One guru out there, how does Capture One perform diffraction correction?  Is it a type of sharpening?  Does Phase have tons of lens optical performance profiles and makes some algorithm for each one?  It doesn't quite look like sharpening.  I want to avoid that because in very large prints sharpening can create ugly halos.  Would diffraction correction degrade image quality in a 30' wide mural print?  I'll do some testing but thought I'd ask first.

Hi Kevin,

I'm not a Capture One guru, but I've been involved in all sorts of (deconvolution) sharpening for many years already. All I can say, the Diffraction correction is very good, and will in general not lead to visible artifacts. However, as a rule, always be careful when applying further postprocessing to adjusted images. The additional processing may 'enhance' otherwise invisible artifacts.

I wouldn't hesitate using Diffraction correction on final conversions that require little or no postprocessing or upscaling.

I have noticed that only in exceptional(!) cases, when using novel AI methods for upscaling (e.g. TopazLabs' Gigapixel AI) there may be (normally invisible) traces of edge halo (or edge specular reflections) that get amplified. But that's more due to the upscaling algorithm/model which is extremely sensitive to faint traces of detail when creating new detail at a larger size with enhanced resolution.

To reduce the risk, Capture One also allows to manually override the aperture number (from the EXIF metadata) that dictates the Diffraction correction. When one uses/enters a wider aperture value than was actually used, the diffraction correction is also lessened/undercorrected.

Cheers,
Bart
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