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06-09-2016, 11:07 PM   #1
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Question about Pentax's version of Pixel Shift Resolution

Just have some questions about it. I looked online to find some more info about a specific question but one site would say "Yes it does" & another site would say "No it doesn't", so I figured here would be the best place to ask.

I know that the color accuracy will be better & there will be less noise, but everything else I've read (even the review on here) kinda left me like "wha... O.o?"

1.) Does the MP go up like Oly's & Hasselblad's PSR version? (Some sites say the MP count doubles/triples)

2.) Does the Resolution increase at all? If so, how much?

3.) Is it similar to HDR/a HDR variant?

4) Related to #3: Does the Dynamic Range increase? By how much?

5.) Would it be a good option to use to digitize B&W film?


Last edited by Nass; 06-09-2016 at 11:12 PM. Reason: unfortunate spelling error in title (no f in shift)
06-10-2016, 12:03 AM   #2
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QuoteOriginally posted by disconnekt Quote
Just have some questions about it. I looked online to find some more info about a specific question but one site would say "Yes it does" & another site would say "No it doesn't", so I figured here would be the best place to ask.

I know that the color accuracy will be better & there will be less noise, but everything else I've read (even the review on here) kinda left me like "wha... O.o?"

1.) Does the MP go up like Oly's & Hasselblad's PSR version? (Some sites say the MP count doubles/triples)

2.) Does the Resolution increase at all? If so, how much?

3.) Is it similar to HDR/a HDR variant?

4) Related to #3: Does the Dynamic Range increase? By how much?

5.) Would it be a good option to use to digitize B&W film?
#1 No.
#2 No.
#3 No.
#4 I think so, but I don't know how much.
#5 Probably.


Cheers,
Terry
06-10-2016, 12:27 AM   #3
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QuoteOriginally posted by disconnekt Quote
Just have some questions about it. I looked online to find some more info about a specific question but one site would say "Yes it does" & another site would say "No it doesn't", so I figured here would be the best place to ask.

I know that the color accuracy will be better & there will be less noise, but everything else I've read (even the review on here) kinda left me like "wha... O.o?"

1.) Does the MP go up like Oly's & Hasselblad's PSR version? (Some sites say the MP count doubles/triples)

2.) Does the Resolution increase at all? If so, how much?

3.) Is it similar to HDR/a HDR variant?

4) Related to #3: Does the Dynamic Range increase? By how much?

5.) Would it be a good option to use to digitize B&W film?
The theory:
How Pentax Pixel Shifting Works - Articles and Tips | PentaxForums.com

The tests:
Pentax K-3 II Pixel Shift Resolution Tests - Hands-On Tests | PentaxForums.com

In practice:
Pentax K-1 Review - Super Resolution and AA Filter | PentaxForums.com Reviews

QuoteOriginally posted by disconnekt Quote
3.) Is it similar to HDR/a HDR variant?
Kind of, except that an electronic shutter is used for the four exposures. The mirror stays up for the duration.

QuoteOriginally posted by disconnekt Quote
4) Related to #3: Does the Dynamic Range increase? By how much?
Dynamic range isn't affected, though you might get more detail in otherwise dark portions of the image. Color accuracy is also improved, and noise is greatly reduced.

QuoteOriginally posted by disconnekt Quote
5.) Would it be a good option to use to digitize B&W film?
Yes it would, as it would increase the overall resolution of each image and practically eliminate noise if you shoot at base ISO.

Adam
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06-10-2016, 04:36 AM   #4
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QuoteOriginally posted by disconnekt Quote
3.) Is it similar to HDR/a HDR variant?
Only in the sense that multiple shots are taken. With HDR the shots are all different (ie different shutter times) then merged, whereas the PS exposures are identical (but moved by 1 pixel) and merged

06-10-2016, 07:14 AM   #5
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QuoteOriginally posted by disconnekt Quote
4) Related to #3: Does the Dynamic Range increase? By how much?

5.) Would it be a good option to use to digitize B&W film?
Adam's and Nass' answers to these last too points are quite good, though I figured I could add a few more words

QuoteOriginally posted by Adam Quote
Dynamic range isn't affected, though you might get more detail in otherwise dark portions of the image. Color accuracy is also improved, and noise is greatly reduced.
DPReview would consider the noise reduction to be increased dynamic range and perhaps it is. The term "dynamic range" seems to be evolving. In the traditional sense it was defined simply as the range of subject luminance over which the sensor or film is able to capture usable detail. The enhanced shadow detail capture would definitely qualify, even though it is a side effect of retaining detail normally lost to Bayer interpolation and to noise. The range of light over which the sensor responds without clipping remains the same. Increasing that would require higher bit-depth at the sensor.

QuoteOriginally posted by Adam Quote
Yes it would, as it would increase the overall resolution of each image and practically eliminate noise if you shoot at base ISO.
The implications for B&W intrigue me as well. It seems to me that pixel shift should be able to offer tonality on a par with the Leica monochrom. Lloyd Chambers (diglloyd.com) has made strong assertions in that direction and his B&W examples seem to back up the claim. The proof of the pudding will be in tasting full bit-depth output on a wide gamut high resolution display or a fine art print.


Steve

Last edited by stevebrot; 06-10-2016 at 07:20 AM.
06-10-2016, 11:58 AM   #6
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I think a good way to think about it is that chroma resolution is increased (full color at each pixel) and luma noise is decreased (4x averaging luminance values). So for both color and B&W you should see improvements, which fits with my experience on a K3-ii. Fine detail is enhanced due to the chroma improvements (even though MP count isn't changing) and noise is decreased and makes the sensor look ~1.4-1.7x bigger as far as noise is concerned (not 2x because it's not a perfect process). B&W shot with pixel shift on my K3-ii looks great, I look forward to seeing what people here do with the K-1! (And maybe if when I convince myself to get one...)
06-10-2016, 01:56 PM   #7
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I was thinking how Medium Format Film would look if someone used the K-1's PSR on it.
06-10-2016, 02:38 PM   #8
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I could have sworn that I had some 125mp shots with the pixel shift. Mind you, SD cards are so big now, who cares?


Last edited by pentasonic49; 06-10-2016 at 02:39 PM. Reason: spelling mistake
06-10-2016, 03:46 PM   #9
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QuoteOriginally posted by disconnekt Quote
I was thinking how Medium Format Film would look if someone used the K-1's PSR on it.
Thanks! Why did'nt I think of that? Brilliant!
06-10-2016, 03:58 PM - 1 Like   #10
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QuoteOriginally posted by stevebrot Quote
The implications for B&W intrigue me as well. It seems to me that pixel shift should be able to offer tonality on a par with the Leica monochrom. Lloyd Chambers (diglloyd.com) has made strong assertions in that direction and his B&W examples seem to back up the claim. The proof of the pudding will be in tasting full bit-depth output on a wide gamut high resolution display or a fine art print.
While I'm not a B&W aficionado, because you get a full color image I'd argue that the dynamic range could potentially be much wider than the Leica's, plus the higher sensor resolution seals the deal.

QuoteOriginally posted by stevebrot Quote
DPReview would consider the noise reduction to be increased dynamic range and perhaps it is. The term "dynamic range" seems to be evolving. In the traditional sense it was defined simply as the range of subject luminance over which the sensor or film is able to capture usable detail. The enhanced shadow detail capture would definitely qualify, even though it is a side effect of retaining detail normally lost to Bayer interpolation and to noise. The range of light over which the sensor responds without clipping remains the same. Increasing that would require higher bit-depth at the sensor.
Yes, the term certainly does seem to be evolving in everyday use. In practice I think you are right on. From my more theoretical point of view, and as you hinted at, pixel shift doesn't add information, but rather corrects artifacts that result from the bayer filter. Hence no improvement as far as clipping is concerned.

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06-11-2016, 04:41 PM   #11
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Huh? The definition of dynamic range is not "evolving" at all. It is a technical term, set in stone, and in the realm of imaging simply applies to the distance between maximum and minimum values of light intensity that can be recorded without clipping (i.e. blowout or maxed out black). HDR photo merging refers to combining separate staggered exposures to push the clipping boundaries further into the darks and lights. There are a number of different algorithms you can use to choose which tones to emphasize at any point along the overall tone curve, but that is not what makes an image HDR or not.

Many (most?) people on photo forums can't even tell whether a photo really is HDR or not, since they simply key in on the garish tonemapping that most HDR plugins default to rather than the actual range of tones present in an image.

The Leica M Monochroms, particularly the older ones, which tended to blow highlights horribly, don't even have particularly great dynamic range. What they do have is tonal accuracy, since 1) they don't interpolate luminance intensity, and 2) they since they don't have to assign separate values for each color channel they can instead allocate them to a more finely divided range of luminance values on a single gray scale gradient.

What SR does for the Pentax isn't increasing dynamic range, it is increasing the accuracy of Color tones (i.e. the R, G, and B luminance values) recorded for each pixel. Color tones are recorded by taking a black and white image through a colored filter (RGB) at each photosite. By shifting the sensor around, the SR gets an i intensity value at each photosite for light filtered at R, G, and B frequencies rather than taking a single color intensity at each photosite and interpolating the other two values using measurements from adjacent photosites in the Bayer color array (interpolation that is dispensed with by the monochrom models, since it is measuring single discrete intensities at each photosite and converting them directly into grayscale values). So what you are gaining is more accurate color information, NOT more range. This is the same reason it helps to reduce luminance noise, since it averages the luminosities of the R+G+B channels, which though somewhat different for each color, tend to produce an overall more correct luminance per pixel value when averaged together.

When taking pictures of a monochrome image, this might give some overall accuracy advantages when compared to an unshifted Bayer array sensor, all other things being equal, it's still not going to be superior to a dedicated B+W platform for reproducing B+W images, since the color filters will introduce some minor discrepancies into the luminance intensity measurements that won't be entirely averaged out. The degree of this influence might be trivial, but there's no way it will improve upon the performance of a non-filtered sensor. In fact, the best way to get accurate tonality on a purely monochrome image would likely be to use a non-filtered sensor to overlay several images taken in succession with as little shift as possible, since chroma accuracy is irrelevant, and you'd be getting a very accurate averaged value for each photosite corresponding to an identical location on the film emulsion.




QuoteOriginally posted by Adam Quote
While I'm not a B&W aficionado, because you get a full color image I'd argue that the dynamic range could potentially be much wider than the Leica's, plus the higher sensor resolution seals the deal.



Yes, the term certainly does seem to be evolving in everyday use. In practice I think you are right on. From my more theoretical point of view, and as you hinted at, pixel shift doesn't add information, but rather corrects artifacts that result from the bayer filter. Hence no improvement as far as clipping is concerned.
06-11-2016, 08:47 PM   #12
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QuoteOriginally posted by dcshooter Quote
Huh? The definition of dynamic range is not "evolving" at all.
I believe he referred to the term and not its definition. At this time, the term is being applied in several different and related senses. With time the definition may shift as well, though at present, I am content with the general form as summarized in the Wikipedia article on the subject.
QuoteQuote:
Dynamic range is the difference between the smallest and largest usable signal through a transmission or processing chain or storage medium. (emphasis supplied)
https://en.wikipedia.org/wiki/Dynamic_range

The article rightly frames the concept in terms of usability where "usable" means different things according to discipline. In photography, usable has generally been defined by the ability to record detail. As a result, the range of luminance resulting in values from clipped low (black) to clipped high (white) is somewhat wider than the actual dynamic range for the system. A camera may be capable of accurately capturing a 14-stop exposure wedge, but fail at retaining detail in a swatch of black velvet at 1/2 stop or even 1 1/2 stops above the clipping point.* Tonal sensitivity at the extremes counts and is often difficult to attain.

The failure is often, though not always**, related to replacement of signal-derived values with random sensor noise. That is why discussions of dynamic range and sensor performance are increasingly being framed in terms of noise as if S/N ratio directly translates into tonal sensitivity. Yes, the usage of the term is evolving as is addition of additional concepts such as ISO invariance. I am not sure I like the shift, because I don't believe it is meaningful nor do I think there is predictive value, but that is just my opinion.


Steve

* This may be demonstrated in PP by shifting the low values upward using the exposure or curve controls. What usually emerges is a muddy, low-contrast mess of non-data that cannot be resolved by changing contrast or applying noise reduction and/or sharpening.

** Linearity for low-end sensitivity is often suspect, though is often assumed.
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