Author Topic: Pixel-Shifting Vs. Larger Sensors  (Read 30722 times)

Michael Erlewine

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Re: Pixel-Shifting Vs. Larger Sensors
« Reply #15 on: October 28, 2017, 16:26:13 »
look at the video I linked to understand that you need a 12.5 MP sensor with huge 8 micron pixels and  16 shot with full native color information fo every pixel.

The point is to also work on the lighting setup to get a better color response and contrast. You are already in the highend, so better lighting will cost you.

Another question is, which company will deliver such a camera that is better than the superb D850? Look at my natural light shots from the botanical gardens with no stacking...

What video is that, please?  And I am talking here about the pixels in the D850 and sifting them, not some other sensor.

I'm referring to pixel-shift stacking and not no stacking at all. Let's talk about that please.
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Les Olson

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Re: Pixel-Shifting Vs. Larger Sensors
« Reply #16 on: October 28, 2017, 16:49:46 »
I mean what I wrote, the four-shot technique of Red, Green, Blue (withtwo Greens) compared to the Bayer interpolated, nothing more and nothing less. What is hard to understand about that?

What is hard to understand is what avoiding interpolation - if, indeed the pixel shift procedure does - has to do with "more RGB pure" colours ("more" or "pure" in what possible sense?).  I realise Sony has talked about "unprecedented colour accuracy", but that is BS for psychophysical reasons. 

A few years ago Sony had another sensor that avoided interpolation, which they called Active Pixel Color Sampling - APCS.  The micro-lenses were on tiny wheels, and could be moved so that each sensor successively captured blue, red and green images.  Apart from the obvious problem with exposure duration, the micro-lenses were no more perfectly wavelength selective than the current ones are, so there was nothing pure about the channels then and there will be nothing pure about the channels with pixel shift. 

Bruno Schroder

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Re: Pixel-Shifting Vs. Larger Sensors
« Reply #17 on: October 28, 2017, 16:55:19 »
I guess it is hard to be understood. ²

Obviously but I remember how you said, several years ago, that your had to learn patience. This is a test :)

I think you are right to think you will get more resolution and better colours. From a pure data acquisition standpoint, replacing an interpolation by a direct measure will, by definition, provide a better result, unless in the practically unfeasible case where the result of the interpolation is equal to the measured value.

Your style is the perfect use case for this technique.

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Michael Erlewine

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Re: Pixel-Shifting Vs. Larger Sensors
« Reply #18 on: October 28, 2017, 16:58:19 »
Obviously but I remember how you said, several years ago, that your had to learn patience. This is a test :)

I think you are right to think you will get more resolution and better colours. From a pure data acquisition standpoint, replacing an interpolation by a direct measure will, by definition, provide a better result, unless in the practically unfeasible case where the result of the interpolation is equal to the measured value.

Your style is the perfect use case for this technique.

At last, a response I can understand and that addressed my question. Perhaps I used the wrong terms, but if you go and read about pixel-shifting, they show a red, blue, and two greens results that are more "pure" (use your own words) than the familiar Bayer interpolation schemes, which are just that: interpolations. That's it.
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Frank Fremerey

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Re: Pixel-Shifting Vs. Larger Sensors
« Reply #19 on: October 28, 2017, 19:21:48 »
What video is that, please?  And I am talking here about the pixels in the D850 and sifting them, not some other sensor.

I'm referring to pixel-shift stacking and not no stacking at all. Let's talk about that please.

the video I linked in answer #7
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Michael Erlewine

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Re: Pixel-Shifting Vs. Larger Sensors
« Reply #20 on: October 29, 2017, 12:27:35 »
the video I linked in answer #7

OK, thanks. So we are getting in the Sony pixel-shift double the resolution of the sensor without enlarging the sensor, correct? And the colors are actual or "true", and not hypothetical. Is that correct?
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Les Olson

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Re: Pixel-Shifting Vs. Larger Sensors
« Reply #21 on: October 29, 2017, 12:52:30 »
From a pure data acquisition standpoint, replacing an interpolation by a direct measure will, by definition, provide a better result, unless in the practically unfeasible case where the result of the interpolation is equal to the measured value.

There is another case where it won't make any difference: where there isn't any data. 

The idea that the world has "real" colours, which you can capture data about, which can be more or less accurate, is just wrong.  The colour we see does not exist outside our heads: it is purely subjective.  There is no such thing as objectively "better colour" or "more accurate colour", only subjectively better or more accurate colour.   

Of course, although there is no "colour" in the real world there is light of different wavelengths, and the wavelengths are data. But a silicon-based detector can't measure wavelength: we have no access to that data.  We can use an RGB system and, by experiment, develop an algorithm that reproduces the effect of light of a particular wavelength on the RGB system in our retina.  The catch is that the micro-lenses do not transmit light of only one colour.  The micro-lens means that the quantum efficiency of a pixel with a (say) green lens is less for red and blue light than for green light, but it is not zero.  The same number of captured photons could result from pure green light, or from less intense green light plus some blue and/or red light.  You have to find a way of working out, or guessing what it probably was. 

If you had a measured RGB value for every pixel you could calculate it directly, since you know the spectral transmission of the micro-lens.  That would get rid of interpolation.  That is not what you get with pixel shift. With pixel shift you get a value from the pixel's neighbour with a different coloured micro-lens when it looked (you hope) at the same part of the image.  You are still interpolating: assigning the pixel a value for the colours it did not measure based on its neighbours which did measure those colours.  That is no different to the Bayer mosaic for detail bigger than four pixels, so for detail on that scale pixel shift won't change the RGB values.  Detail smaller than two pixels is not resolved in either case.  So there is a window where you might get some benefit, if the sensor shift is precise enough, and you have really good tripod and a lens with no lateral colour. 

It is reasonable to ask whether you get different answers by looking at a pixel's neighbours compared to pixel shift.  We will have to wait and see, although you certainly won't where the detail is either larger than eight pixels or smaller than two pixels. 

Frank Fremerey

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Re: Pixel-Shifting Vs. Larger Sensors
« Reply #22 on: October 29, 2017, 12:54:33 »
a 12 Megapixel sensor with 16 Multishot will deliver 48 Megapixels and the collected photon events will be 16 times the amount of a single shot accumulated. The color fidelity should be significantly higher though.

BUT

this is currently a theoretical piece of hardware. Quality is also dependent on implementation details

An A7S2 with 16 shot pixel shift multishot would be your dream come true...  write a letter to Sony. would be great for all table top shooters!
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Michael Erlewine

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Re: Pixel-Shifting Vs. Larger Sensors
« Reply #23 on: October 29, 2017, 13:20:38 »
I can follow what Les Olson points out, that ultimately it is subjective and in our minds. However....

Having actually used pixel-shifting a lot, in both the K3 and K1 Pentax cameras, you can say what you think, but seeing is believing. And I have SEEN the difference between Bayer interpolation and pixel-system, over and over.

So, we can talk until the cows come home or we can agree they are two different takes or kinds of interpolation, but to me, this just muddies the waters. And it is not why I started this thread, to litigate out of discussion the difference.

The pixel-shifted colors, however you spell it, are IMO (which is all that I have) quite a bit better than the standard Bayer interpolation scheme we are used to. My original question had to do with the value of going after ever-larger sensors as opposed to getting better color/resolution of the existing sized sensors as in the A7R3. And Pixel-Shifting, to my eyes, seems to offer this.



 
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Ilkka Nissilä

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Re: Pixel-Shifting Vs. Larger Sensors
« Reply #24 on: October 29, 2017, 15:47:48 »
How does use of flash work with pixel-shift technology? What about the effects of flickering artificial lights (100/120Hz)?

Michael Erlewine

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Re: Pixel-Shifting Vs. Larger Sensors
« Reply #25 on: October 29, 2017, 15:58:48 »
How does use of flash work with pixel-shift technology? What about the effects of flickering artificial lights (100/120Hz)?

Any change of light is not good. I can't remember, but I thought I saw somewhere that there is a box you can check to equalize the light, but not sure for what camera.

It fits my regime, but when I used the Pentax cameras outside, light was real problem. It is a first step.
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Frank Fremerey

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Re: Pixel-Shifting Vs. Larger Sensors
« Reply #26 on: October 29, 2017, 16:35:06 »
natural light on an overcast day or sunny day behind a huge diffusor shade gives the best light for your kind of work. Artists light, northern light.
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Michael Erlewine

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Re: Pixel-Shifting Vs. Larger Sensors
« Reply #27 on: October 29, 2017, 16:41:03 »
natural light on an overcast day or sunny day behind a huge diffusor shade gives the best light for your kind of work. Artists light, northern light.

It is the variability of the light that is the problem with pixel-shifting, not the kind.
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Bruno Schroder

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Re: Pixel-Shifting Vs. Larger Sensors
« Reply #28 on: October 29, 2017, 17:26:26 »
Think data acquisition. If you change a parameter during sampling, your data loses coherency and can not be correctly aggregated.

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Frank Fremerey

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Re: Pixel-Shifting Vs. Larger Sensors
« Reply #29 on: October 29, 2017, 19:09:53 »
It is the variability of the light that is the problem with pixel-shifting, not the kind.

the variability of the light is smallest in the named lighting.

With Kinoflo style lighting the color changes over time.

With professional strobes you need 16 flash cycles for one picture????
You are out there. You and your camera. You can shoot or not shoot as you please. Discover the world, Your world. Show it to us. Or we might never see it.

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