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Author Topic: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range  (Read 11991 times)

EinstStein

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42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« on: November 05, 2015, 05:22:58 am »

Practically, is there IQ difference between a digital camera with 42MP x 12-bit dynamic range and one with 20MP x 14-bit dynamic range? Which one would be likely to be more useful?
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hjulenissen

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #1 on: November 05, 2015, 06:21:16 am »

I am not sure that it is productive to specify dynamic range as "bits". Sure the raw file will use a number of bits per pixel and that will be an upper bound, but in practice, raw files seems to be limited to maximum unsaturated signal level (may well be less than the maximum integer value possible for N bits) and some noise floor >1/2 lsb.

42 is (obviously) more than 20. If you need large spatial precision and have sufficient light, 42 is probably the answer.

If you have a choice between (optimal) 20 MP 14-bit files and (optimal) 40 MP 13-bit files, the answer would perhaps be more clear cut, as the 40 MP file could always be filtered to produce something equivalent to a 20 MP 14-bit file.
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AlterEgo

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #2 on: November 05, 2015, 08:55:13 am »

but in practice, raw files seems to be limited to maximum unsaturated signal level (may well be less than the maximum integer value possible for N bits) and some noise floor >1/2 lsb.
some people here allude that flare/glare/etc in lens to camera chamber to sensor assembly surface and layers on top of the silicon itself will limit that even more - so in fact you never get the engineering DR out there...
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hjulenissen

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #3 on: November 05, 2015, 09:19:00 am »

some people here allude that flare/glare/etc in lens to camera chamber to sensor assembly surface and layers on top of the silicon itself will limit that even more - so in fact you never get the engineering DR out there...
Jim Kasson pointed to this paper in another discussion:
https://graphics.stanford.edu/papers/glare_removal/glare_removal.pdf
"Based on simulations, the Canon 20D can record nearly 20 stops of dynamic range using HDR imaging if only a point light source is present. If half of the field of view is covered by an extended source, then only 9 stops of dynamic range can be recorded by the 20D..."
It seems that flare can plausibly either restrict DR significantly or insignificantly, depending on the scene.

There is always the possibility that one is underexposing the shot (i.e. there are no bright parts in the scene to cause much flare). Brightness could be restored by upping the camera ISO or pushing a slider in you raw developer. I would still want the pushed image to look as good as possible.

-h
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razrblck

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #4 on: November 05, 2015, 11:43:54 am »

Working with both 12bit and 14bit cameras I can tell you that I've never had to push my files so much as to notice issues. Under normal conditions, if you make the right exposure for the result you need/want, you won't feel limited either way.

Here are two pictures shot last weekend, one comes from a 16MP 14bit camera (D7000) and the other from a 10MP 12bit camera (D200). If you can tell which is which then you probably need a 14bit sensor because your eyes are too good! :P
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Bart_van_der_Wolf

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #5 on: November 05, 2015, 11:59:16 am »

Just to mention something that apparently gets misinterpreted, 12 or 14 bit ADC conversions provide for more accurate smooth transitions and subtle color differences, not DR.

Dynamic range only depends on well depth and read noise, as a ratio. The read noise is a characteristic of all (supporting) electronics.

Cheers,
Bart
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EinstStein

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #6 on: November 05, 2015, 12:36:35 pm »

Bit depth and MP are the maximun possible performance of two of th impotant imaging quality. The actual image is affected by noise and the interference.

Unless the vendor purposely lying, a sensor with more bits will perform better in terms of coloring or dynamic range, while a sensor with more MP will perform better in terms of resolution. assume all else are equal, such as same optical system, etc.

The question is, quantitatively, at these level, 42mp&12b vs. 20mp&14b, which one would be more practically preferred.

All the argument in this thread seems suggest no difference.

Of course, the judge must based on noncrappy, well exposed picture on sensible objects.


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ErikKaffehr

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #7 on: November 05, 2015, 12:51:57 pm »

Hi,

I would mostly go with a camera having 42 MP, especially as I have a camera with 42 MP and it gives stunning image quality. With the DR stuff, you either need it or you don't need it. Mostly you don't need it. AFAIK 42MP at 12-bit DR would correspond to about 12.5 EV when downsized to 20 MP.

There are quite a few situations where high DR is useful, but I still feel DR is a bit overrated. Twelve stops is sort of plenty.

Best regards
Erik


Practically, is there IQ difference between a digital camera with 42MP x 12-bit dynamic range and one with 20MP x 14-bit dynamic range? Which one would be likely to be more useful?
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Erik Kaffehr
 

ErikKaffehr

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #8 on: November 05, 2015, 01:19:20 pm »

Hi,

Your question in not possible to answer as all parameters are not known.

Anyway, high DR is essentially the same thing as clean shadows. So with a camera with higher DR you can pull out better shadow detail. At least as long as you expose optimally. But if you don't need that deep shadow detail the DR simply does not matter. Also, as pointed out on the thread, lens flare often limits DR anyway.

If you have high DR, you can opt your exposure to protect highlights, as you can still get good shadow detail. That will lower your image quality by increasing noise level. But again modern sensors are so good that noise is seldom an issue at low ISO numbers and small to moderate print sizes. If you print really large those pixels may be beneficial and you want to maximise your exposure to keep noise down.

So, depending on your exposure and scene illumination ratio DR may be beneficial for image quality.

This article discussed the issues in great detail: http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/

Best regards
Erik


Bit depth and MP are the maximun possible performance of two of th impotant imaging quality. The actual image is affected by noise and the interference.

Unless the vendor purposely lying, a sensor with more bits will perform better in terms of coloring or dynamic range, while a sensor with more MP will perform better in terms of resolution. assume all else are equal, such as same optical system, etc.

The question is, quantitatively, at these level, 42mp&12b vs. 20mp&14b, which one would be more practically preferred.

All the argument in this thread seems suggest no difference.

Of course, the judge must based on noncrappy, well exposed picture on sensible objects.
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Erik Kaffehr
 

EricV

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #9 on: November 05, 2015, 03:04:57 pm »

You can (more than) make up for the resolution difference by shooting with a longer lens and stitching images.  You can (more than) make up for the dynamic range difference by shooting multiple exposures and combining images.  Excluding these options, the question is which is more important for your style of photography, resolution or shadow noise?  If you do a lot of shooting in low light, if you find yourself using high ISO frequently, or if you lift dark shadows quite a bit in post processing and are bothered by noise, then pick the higher DR sensor.  Otherwise pick the higher resolution sensor.
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hjulenissen

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #10 on: November 06, 2015, 02:15:39 am »

Bit depth and MP are the maximun possible performance of two of th impotant imaging quality. The actual image is affected by noise and the interference.

Unless the vendor purposely lying, a sensor with more bits will perform better in terms of coloring or dynamic range
Providing a 16-bit file is not in any way "lying". But there is a distinct possibility that the same image-forming information could be stored in a 14-bit file. Thus using file size as an indicator of image quality is naiive in my view, especially as there are knowledgeable people out there who offers more relevant measures of image quality.
Quote
, while a sensor with more MP will perform better in terms of resolution. assume all else are equal, such as same optical system, etc.

The question is, quantitatively, at these level, 42mp&12b vs. 20mp&14b, which one would be more practically preferred.
If Eric Fossum is right and able to deliver, his single-bit sensor will provide more resolution and more DR than any current technology and mainly be limited by the physics of light.

-k
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Dave Ellis

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #11 on: November 06, 2015, 02:43:48 am »

Just to mention something that apparently gets misinterpreted, 12 or 14 bit ADC conversions provide for more accurate smooth transitions and subtle color differences, not DR.

Dynamic range only depends on well depth and read noise, as a ratio. The read noise is a characteristic of all (supporting) electronics.

Cheers,
Bart

+1

Dynamic Range is a ratio of analogue values expressed in logarithmic units (exposure stops in photography). To use the bit depth used in the digital processing of the image to describe Dynamic Range is meaningless and also confusing as some cameras have the option of recording the raw file in either 12 bits or 14 bits. But this has nothing to do with Dynamic Range, rather the precision of the processing. You can process a capture with a DR of 14 stops with a bit depth of 8 but you won't get the most out of it doing that.

Dave
« Last Edit: November 06, 2015, 04:34:22 am by Dave Ellis »
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EinstStein

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #12 on: November 06, 2015, 05:55:17 am »

The dynamic range of a ADC (or DAC) is the ratio bentween the largest expressible value vs. the smallest expressible value. It's is that simple.
If a sensor/ADC is speced to capture 14bit bit depth, than it should make sure the (internal) noise figure is within the half bit range, unless the engineers or the marketing guys lie. Rarely happen for reputable.

Whether the signal it captures has that much of dynalic range is another issue.

Flare, interference, lens distortion, and optical system resolution etc., would affect the final captured image and will affect the effective usable dynamic range and resolution. Both MP and bit depth can suffer the deteriorating.

If you want to fool yourself, you are welcome.


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hjulenissen

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #13 on: November 06, 2015, 07:12:11 am »

If you want to fool yourself, you are welcome.
What are you saying here? If you want to depend on specs like "16 bits" as a proxy for DR instead of directly measured DR, is it not you who are fooling yourself?

-h
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bjanes

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #14 on: November 06, 2015, 08:51:29 am »

Dynamic Range is a ratio of analogue values expressed in logarithmic units (exposure stops in photography). To use the bit depth used in the digital processing of the image to describe Dynamic Range is meaningless and also confusing as some cameras have the option of recording the raw file in either 12 bits or 14 bits. But this has nothing to do with Dynamic Range, rather the precision of the processing. You can process a capture with a DR of 14 stops with a bit depth of 8 but you won't get the most out of it doing that.

What you say is not the case for a linearly encoded raw file, where the bit depth places an upper limit on the DR, which is equal in stops to the bit depth. If you are dealing with a gamma or log encoded file, then your statement is correct. However almost all digital cameras use linear encoding for the raw file.

Bill
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ErikKaffehr

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #15 on: November 06, 2015, 02:20:39 pm »

Hi,

DR is actually defined as full well capacity divided by readout noise. As pointed out by BJanes, the width of the ADC sets a limitation on the DR as long as linear representation is used. Sensor vendors sometimes specify the dynamic range of the chip, say for instance 76 dB. You can convert that 76 dB to EV by dividing by 6. So 76 dB -> 12.6 EV. DxO-mark measures DR for cameras and they came up with a DR 12.34 EV. Pretty close. The camera in question was the Leica M (typ 240). It is a 14-bit device, achieving 12.34 EV in DR.

Now, another device has been measured by DxO-mark, and it came in at 11.89 EV. That camera is a 16-bit device known as the Phase One IQ-180.

Which is the best camera regarding DR according DxO-mark? It is the Nikon D810 at 13.67 EV. It is a 14 bit device.

Now, of all these cameras the Phase One IQ-180 has the lowest DR, actually meaning it utilises 12 bits out of the 16 bits it is claimed to have. But, it has quite a lot of pixels. Now, if we make a small print, those pixels would be packed and yield a higher DR. This is simple math, and I don't go into that for now. DxO-mark does this calculation using a small 8MP print as a base, in this print mode we get:

Leica M (typ 240) 13.13 EV
Phase One IQ-180 13.56 EV
Nikon D810 14.76 EV

It seems that the Nikon can transfer more than 14 EV trough it's 14 bit data path, but this is not the case. It is a result of normalisation.

Let's check out Canon's latest creation, the 5DSR. In screen mode it reaches just 11.05EV, in spite of having a 14 bit data path. In the normalised mode it reaches 12.39 EV, a bit shy of the Leica M (typ 240).

Now, we may go up in ISO, somewhere around 1200 ISO the Canon is just as good in DR as the Nikon. At high ISO the signal of the sensor is amplified and noise in ADC is thus reduced.

Best regards
Erik






The dynamic range of a ADC (or DAC) is the ratio bentween the largest expressible value vs. the smallest expressible value. It's is that simple.
If a sensor/ADC is speced to capture 14bit bit depth, than it should make sure the (internal) noise figure is within the half bit range, unless the engineers or the marketing guys lie. Rarely happen for reputable.

Whether the signal it captures has that much of dynalic range is another issue.

Flare, interference, lens distortion, and optical system resolution etc., would affect the final captured image and will affect the effective usable dynamic range and resolution. Both MP and bit depth can suffer the deteriorating.

If you want to fool yourself, you are welcome.
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Dave Ellis

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #16 on: November 06, 2015, 02:51:42 pm »

I think we are probably all on the same page here, just focusing on different aspects. The point I was trying to make is that DR should be referred to in stops not bit depth. The DR represents the widest possible useful range of light values that can be recorded by the camera. I agree that the bit depth used in the adc limits this range. So if the analogue part of the sensor has a dynamic range of say 13 stops, you should be using an adc bit depth of 14 rather than 12 to take full advantage of the sensor's dynamic range.

Dave
« Last Edit: November 06, 2015, 03:24:03 pm by Dave Ellis »
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GrahamBy

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #17 on: November 06, 2015, 04:50:39 pm »

Pretty much anything quoted in log-base-2 values can be given the unit of "bit". It's used very often as a unit of entropy, for example. So bits=stops and a preference one way or the other is really just aesthetic.
The fact that the data is then stored in 12, 14 or whatever bit-length memory locations is another matter.
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EinstStein

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #18 on: November 07, 2015, 01:21:29 pm »

One of a digital camera vendor is desperately trying to release the firmware to fix this problem to boost the 12-bit bit-depth to 14-bit.
Now you can relax and stop defending for it for this short-come. I will be entertained to see you change your tone to swear how important the bit-depth is.

Whether the firmware can really fix the problem is yet to be seen.  It won't be easy, since tbe original problem is not a firmware/software bug, it's the generic problem in the hardware.
« Last Edit: November 07, 2015, 01:25:33 pm by EinstStein »
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hjulenissen

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Re: 42MP x 12-bit dynamic range vs. 20MP x 14-bit dynamic range
« Reply #19 on: November 09, 2015, 01:08:10 am »

One of a digital camera vendor is desperately trying to release the firmware to fix this problem to boost the 12-bit bit-depth to 14-bit.
Now you can relax and stop defending for it for this short-come. I will be entertained to see you change your tone to swear how important the bit-depth is.
...
For a moment I thought that your original post was sincere, and my answers were attempts to contribute.

This last post makes me doubt that you really have any questions. I have nothing further to add.

-h
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