Thanks Moose. Always good to have someone do some leg work I don't have time
for. Great insights and analysis.
I admit I am not familiar with deconvolution sharpening. Someone pointed to the
Point Spread Function (similiar to impulse response). How this PSF is
determined for the sharpening I don't know and wonder if some optical
assumptions are involved or if it is derived from the actual image?
At the deep end.
donning my scuba gear now...
Wayne S
At 2/20/2019 01:07 PM, you wrote:
>On 2/20/2019 8:50 AM, Wayne Shumaker wrote:
>>Moire is when the pattern and the sensor sampling approach the Nyquist rate
>>combined with the fact the color pixels are not spatially on top of each
>>other. As such slight angle shifts, such as when you re-taped Thomas, may
>>affect the intensity of the color shift. Also the pixel density of different
>>cameras are sampling differently,
>
>Exactly the point of comparing 16 and 20 MP bodies, with ~50 MP,
>non-demosaiced version to show what's really there.
>
>>not to mention the degree of filtering in the anti-alias filter in front of
>>the sensor.
>
>No AA/OLPF filter in either camera. There is a definite trade-off of moire
>suppression and detail resolution in using AA filters. Here's an example from
>someone who replaced the filter in a Nikon D200 with flat glass.
><http://www.moosemystic.net/Gallery/tech/AA_Filter/D200_AA.htm>
>Nikon choose not to use one in the D810, which increased resolution of detail
>- and - produced some really awful moire and demosaicing artifacts with some
>subjects. <http://www.moosemystic.net/Gallery/tech/X-T1_E-M1_D750/FON.htm>
>Look esp. at D750 vs. D810.
>
>>There are so many factors, I'm impressed with and applaud your detailed
>>investigation.
>
>Thanks! I can be dogged on occasion, when I think the knowledge gained may
>improve the technical aspects of my photography.
>
>>A near impossible task to find nirvana.
>
>:-)Â Nirvana is in the photo, not the camera.
>
>>The Siemens star image used in
>>https://blog.kasson.com/the-last-word/adobe-camera-raw-11-2-enhance-details/
>>would eliminate differences in pixel density and orientation, to some degree.
>
>I'm not interested in test subjects that I can't relate to actual use. It may
>be a failure of my imagination, but when I look at those test images, they
>don't relate in my mind to how to use the camera and process the results.
>
>>Reminds me that film, with randomness in the grain sampling, does not have
>>this problem of uniform sampling. The randomness of grain in film vs
>>randomness in a scene for digital sensors is the tradeoff.
>
>And yet, it makes, from my perspective, in my straightforward mode, crappier
>images. ;-) So what's the point?
>
>>In signal processing, the sharper the cutoff of a low pass filter, the more
>>there is overshoot in the step response. This is what creates the halos with
>>over-sharpening. https://en.wikipedia.org/wiki/Ringing_artifacts A Bessel and
>>Gaussian filters, for instance, have a much smoother filter roll-off and no
>>overshoot. I spent many years designing filters where managers never
>>understood that you cannot have smooth time response with sharp filters.
>
>Again, no filters involved in this test. I wonder if you may be confabulating
>pure sensor pitch, subject frequency, moire effects with the effects of
>demosaicing?
>
>>If you know the subject matter is going to have moire issues, then perhaps
>>the best approach is to shoot taking that into account?
>>https://www.nikonusa.com/en/learn-and-explore/a/products-and-innovation/moir%C3%A9-false-color.html
>> I like Kasson's comment on ACR enhanced detail: "The good news was that it
>>appeared to do no harm. The bad news is that it didn't do much good."
>
>And that's good news for me. I don't need it, AND it's not useful with my
>computers.
>
>>I'm not familiar with all the terms. By HR do you mean higher resolution mode
>>using sensor shift technology? Seems like the best way to compensate for
>>moire, is that what <4,3> E-M5 II HR=>4640 is doing?
>
>Although others are doing versions now, Oly pioneered this with the E-M5 II.
>Oly shifts the sensor in half pixel pitch increments to take eight exposures.
>This accomplishes two intentional things and one nice byproduct:
>
>1. Higher resolution in the combined image. Although limited to tripod an
>static subjects on that body, it's still very useful for things like this
>comparison, lens tests, etc. It reveals that most µ4/3 lenses considerably
>out resolve the sensors.
>
>2. No demosaicing of an array of different colors. Each pixel location is
>sampled with sensels of all three colors. In this sense, it's analogous to the
>Foveon sensor.
>
>3. It acts as highly effective noise reduction.
>
>This review of the E-M5 II compares the 40 MP JPEGs of its HR mode to the 36
>MP Nikon 810 and then the 64 MP Raw files to the 51 MP Pentax 645Z. There
>are some excellent sample subjects and brief, but useful tech piece at the end.
>
>Note that they used the Oly ACR plug-in to process the Raw files, which
>compromises the HR results. They had to choose between the clumsy USM used in
>the plug-in, with the resultant halos, vs. detail resolution. Obviously, Oly
>were concerned that simply opening the files in ACR initially showed a very
>soft image. Unfortunately, they chose a non-optimal solution. This little test
>I did shows that using deconvolution, rather than USM, gives much more fine
>detail resolution without the halos.
><http://www.moosemystic.net/Gallery/tech/Focus_Magic/_B003950fpACRvsPlugin.htm>
> You can see that in my first two samples.
>
>Soooo, when reading the review, keep in mind that the Raw HR files in the
>Pentax comparison are actually a bit better than what they show. A piece of
>big news with the E-M1X is faster processor(s) that allow HR shots sans
>tripod, @ exposure speeds for all eight exposures up to 1/60 sec.
>
>>I wonder if sensor shift could be done in some sort of random way to simulate
>>grain?
>
>Not a clue, and perhaps not necessary, as there are no demosaicing artifacts.
>
>>going off the deep end
>
>Have a nice swim!
>
>Detail Oriented Moose
>
>--
>What if the Hokey Pokey *IS* what it's all about?
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