The whole question of lens sharpness...

Started Jun 12, 2013 | Discussions thread
Detail Man
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Re: DxO Labs' "Lens Softness" Corrections
In reply to GaryW, Jun 22, 2013

GaryW wrote:

Detail Man wrote:

GaryW wrote:

I have less luck with countering poor focus, but for slight diffraction, it seems to work fine.

In addition, it's what DxO uses (I think) for their "lens sharpness", to counteract the effects of unsharp lenses, particularly in the corners where they use more intensity to counter the greater softness. This seems to work to a large extent.

...You may be familiar with these concepts if you are familiar with MTF (Modulation Transfer Function) curves. DxO Labs has developed a unique unit called the BxU (Blur eXperience Unit) which is a mathematical way of describing this 'blur'. Reducing the ‘lens softness’ or 'blur' or 'lack of sharpness' means performing local, color-channel dependent and anisotropic deconvolution of the image produced by the camera.

Furthermore, DxO deblurring uses a complex contextual approach taking into account both local noise and local detail level in the image. As a result, deblurring will be automatically reduced in uniform areas (like a pure blue sky.), but increased in a detailed zone....

...

As the DxO RAW Optics Correction Modules for a given camera-lens combination appear (to me) to in general to be significantly more effective than the DxO JPG Optics Correction Modules (for the same camera-lens combination), I think that it (may) be the case that some of the related processes may proceed on a RAW-level prior to de-mosaicing of the RAW image-data.

The "lens sharpness" option does not appear for unsupported lenses. I am not sure what happens for RAW vs. JPEG.

When processing OOC JPG from supported camera-lens combinations (using the accompanying JPG DxO Optical Corrections Module), the "Lens Softness" tool works - but is less dramatic than the RAW-mode version (with my LX3, have not checked with my GH2). Part of that is that even if adjusted to minimum using on-camera controls, the applied in-camera JPG Sharpening and NR limit how much can be done after the fact of in-camera JPG encoding.

This approach is distinct from the deconvolution-deblurring that occurs in the sharpening tools of Adobe Lightroom, Camera RAW, Photoshop, the PS/LR plugin Topaz Infocus, as well as RAW Therapee's R-L DD - all of which appear operate on what is already de-mosaiced image-data.

Whatever DxO is doing, they've really got it figured out. Typical deconvolution tends to produce artifacts if overdone, so they are definitely doing something to control the noise.

I think where DxO has done a good job overall is making their program deceptively simple. You could probably get good results with RAW Therapee, but RT requires more fiddling. My thought is that at lower ISO, I liked RT just fine, but at higher ISO, the NR is not the best, and the deconvolution will increase the noise. I can get pretty good results with DxO at any ISO.

Regarding RT's Richardson-Lucy DD and Lightroom / Camera RAWs DD incorporated into their Sharpening tool. RT's seems perhaps just a bit better, but I rather loathe Adobe's tool. Both can create some "gritty" and ugly processing artifacts.

DxO Optics Pro silently adjusts and increases their NR (and/or a separate related similar functionality) when higher ISO Sensitivities are used (or perhaps actual image-noise detected) - at least in the case of some cameras - as a measure to reduce the visiblity of DD artifatcs. See what "falconeye" reports in conversing with me on this thread at Pentax Forums dot com (which for some silly reason is a domain that DPReview still blocks the URLs of):

/forums/digital-processing-software-printing/88315-dxo-pentax-k-7-now-available.html

The "Bokeh" control (Versions 7.x on) - which appears to be some sort of variable corner-frequency low-pass filter(?) - has not seemed to do that much for me when adjusted above the default setting of 50 when I have tried to use it to reduce artifacts - but it seems to manage to increase artifacts when I have tried to lower to levels of around 40. As a result, I generally keep it parked at the default setting of 50, and sometimes use a bit more NR than I would otherwise. Artifacting seems most common in OOF areas where color contrasts exist.

Here is an example in a shot that I took the other day (note the "grittiness" in the upper-right OOF areas). Upping the "Bokeh" control does not help much, and I have to increase the NR all the way up to the automatically set NR values to quash it (neither of which were done in the example below) - whereas I am used to only having to select a fraction of the automatic NR setting values in all but higher ISO cases.

I usually can use only around 1/2 of the automatic NR setting values in such a case as below (which does here manage the shadows and the Red/Blue channel noise in the flower petals). One contributing factor is that the Gamma in the DxO Lighting tools is set fairly high (upwards towards 2.0, which is usually the very most that I use).

DMC-LX3 RAW, F=5.6, T=1/30, ISO=200, DxO Optics Pro 7.23

Note: It look like the Quantization data compression (QF~90%) that DPR is performing these days in all view modes of their Image Viewer interface is low-pass filtering out some of what I am describing above out. To see the artifacts better, download and view the Original loss-less JPG here:

http://www.dpreview.com/galleries/4464732135/download/2594948

DM ...

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