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04-12-2015, 07:11 PM   #1
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16 Bit On The 645z?

I've noticed my DNG files are registering as 14 bit in Adobe Bridge (not Camera Raw) and the PEF are registering as 16 bit. I'm sure others have noticed this, but has anyone done an actual 1 to 1 comparison? I'll certainly have to do this comparison for myself, but would like the input from those who've been there.

It'd be nice if the PEFs are true 16 bit for the smoother transition in tones it can provide.

04-12-2015, 07:47 PM   #2
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The image data should be 14 bits per channel for both. Didn't observe any difference between PEF and DNG while I was using the 645Z.

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04-12-2015, 10:15 PM   #3
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QuoteOriginally posted by 72ndPoolShark Quote
I've noticed my DNG files are registering as 14 bit in Adobe Bridge (not Camera Raw) and the PEF are registering as 16 bit. I'm sure others have noticed this, but has anyone done an actual 1 to 1 comparison? I'll certainly have to do this comparison for myself, but would like the input from those who've been there.

It'd be nice if the PEFs are true 16 bit for the smoother transition in tones it can provide.
smallest addressable unit on computers = 1 byte = 8 bit => to store 14 bit you need 2 bytes = 16 bit. the 14 bit are the bits per RGB color channel for one color pixel. the 16 bit are the storage needed to store data for each RGB channel of one color pixel within a pef- or dng-file.

Last edited by acoufap; 04-12-2015 at 10:23 PM.
04-13-2015, 02:29 AM   #4
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QuoteOriginally posted by 72ndPoolShark Quote
It'd be nice if the PEFs are true 16 bit for the smoother transition in tones it can provide.
Currently, there do not seem to exist any cameras that can register true 16-bits because there are no analog to digital converters that output in that bit depth, so even if the camera writes 16 bits, it's just padding. This has been known for a while now, even the $40k Phase and Hasselblad backs use 14-bit ADCs.

Also, almost all sensors are monochrome by design and colors are derived through demosaicing, so you have one 14-bit channel from which you may eventually derive three 16-bit channels, so needless to say a lot of data is "made up" along the way using complex math trickery. What I'm saying is don't pay too much to the science behind this, 14-bits are easily enough for the Z to flex it's muscles, and it would take quite a bit of a technological breakthrough before 16-bit even starts to make sense.

Shooting in DNG is simply more future-proof because it's an open format that there will likely always be support for, while PEF is not.

04-13-2015, 04:03 AM   #5
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There are analog to digital converters up to 24 bits... even the old K10D had 22 bits converter. The limitation is caused by dynamic range. Above 14 bits, additional bits only quantify noise...
From a computer science aspect, the simpler is to use 16 bits words (2 bytes), let 2 bits to zero, and use a compression algorithm -huffman tree like in zip - to reduce file size.
04-13-2015, 07:40 AM - 1 Like   #6
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QuoteOriginally posted by goubejp Quote
There are analog to digital converters up to 24 bits... even the old K10D had 22 bits converter. The limitation is caused by dynamic range. Above 14 bits, additional bits only quantify noise...
From a computer science aspect, the simpler is to use 16 bits words (2 bytes), let 2 bits to zero, and use a compression algorithm -huffman tree like in zip - to reduce file size.
A higher-bit converter may not useful for every task, 24-bit is very much possible and desirable for audio recording, but not so much for imaging.

If one refers to this article: The Secrets of the K10D (Part 2 of 3) - The Bridge: A to D Convertor, you'll find that this ADC unit is actually a combination converter + image processor, which explains the 22-bit figure - there are image processors that can easily go to 32bits because of the complex operations involved in manipulating image data and sensor operation. In the case of the K10D, the actual conversion is done at 12-bits and a 22-bit processor handles the color balance and such, which is actually fairly tame by today's standards.

The designers of the world's most expensive "cost-no-object" cameras have the luxury of picking parts that only fit two goals: performance and optimal interoperability with the other components, and these cameras "still" have 14-bit ADCs. The RED Dragon camera might have a 16-bit ADC, but it also can't really be compared to regular cameras because it also applies a lot of techniques suitable for motion video, like temporal image stacking, lossy Raw compression (3:1 at minimum) and it only ever shoots at base ISO (in-camera ISO250, measured ISO104), so your ISO exposure range is limited to the DR of the camera. This might sound weird to a photographer, but most high-end video cameras actually work this way since they are designed to be used under ideal shooting conditions.
04-13-2015, 08:13 AM   #7
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The maximum for each RGB channel seems to be 15 bit when using 2 bytes. The reason is that one bit is used for the sign of number - so I read. I think PhaseOne in some backs uses 15 bit per channel. By the way - it's really a huge amount of colors you get out of 3 x 14 or 15 bit! Write down the number in decimal and you'll understand. Our eyes cannot distinguish so many colors and printers cannot print them. The more bits per channel you have in processing the images the better because rounding errors are mimimized. So 14/15 bit per RGB channel are very good for input and processing/post processing. This is why 16-bit tiff is often used as intermediate format. 8 bit for each RGB channel as used in jpeg are sufficient for the output of images in most of the cases.

Last edited by acoufap; 04-13-2015 at 08:49 AM.
04-13-2015, 09:14 AM   #8
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QuoteOriginally posted by acoufap Quote
seems to be 15 bit when using 2 bytes.
I think the 16 bit tiff uses UInt16, as there are no negative brightness values
Here is the enumeration of the last 5 pixels on a tiff 16 of 1951 by 1159 pixels

1947,1159: (18.3932%,22.1637%,25.7801%) #2F1638BD41FF srgb(18.3932%,22.1637%,25.7801%)
1948,1159: (19.5941%,20.6256%,26.3325%) #322934CD4369 srgb(19.5941%,20.6256%,26.3325%)
1949,1159: (18.2467%,20.3326%,23.209%) #2EB6340D3B6A srgb(18.2467%,20.3326%,23.209%)
1950,1159: (19.1653%,20.9827%,24.1566%) #311035B73DD7 srgb(19.1653%,20.9827%,24.1566%)
1951,1159: (18.4756%,20.0793%,26.4927%) #2F4C336743D2 srgb(18.4756%,20.0793%,26.4927%)

04-13-2015, 09:24 AM   #9
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QuoteOriginally posted by wombat2go Quote
I think the 16 bit tiff uses UInt16, as there are no negative brightness values
Here is the enumeration of the last 5 pixels on a tiff 16 of 1951 by 1159 pixels

1947,1159: (18.3932%,22.1637%,25.7801%) #2F1638BD41FF srgb(18.3932%,22.1637%,25.7801%)
1948,1159: (19.5941%,20.6256%,26.3325%) #322934CD4369 srgb(19.5941%,20.6256%,26.3325%)
1949,1159: (18.2467%,20.3326%,23.209%) #2EB6340D3B6A srgb(18.2467%,20.3326%,23.209%)
1950,1159: (19.1653%,20.9827%,24.1566%) #311035B73DD7 srgb(19.1653%,20.9827%,24.1566%)
1951,1159: (18.4756%,20.0793%,26.4927%) #2F4C336743D2 srgb(18.4756%,20.0793%,26.4927%)
I think you're right. My scanner is said to deliver 48 bit = 3 x 16 bit for color and the basic format is 16 bit tiff RGB. So there should be even more "headroom" and PhaseOne hasn't reached the ceiling yet . Pentax can get there first - to be serious - I don't think we must get there.
04-13-2015, 11:06 AM   #10
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With some further reading about this on Imagemagick site:
Imagemagick uses dcraw as a delegate to read Bayer camera files.
dcraw will convert ( with the -4 flag) the RGGB camera files and de-mosaic into a 16 bit tiff.
Common Formats -- IM v6 Examples

I checked the resulting tiff with a file from the Pentax K-01 (K-01 is specified with a 12 bit resolution.)
The resulting 16 bit tiff is at full 16 bit resolution.
I have not found reference to how the 12 bit depth ends up as 16 bit after the Bayer de-mosaicing, I suppose it does not matter much.

I assume other post processing software will also use dcraw or something similar.
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