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Author Topic: Why not 16bit?  (Read 8330 times)

LifeAfter

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Why not 16bit?
« on: December 14, 2011, 07:22:45 AM »
Why not 16 bit?

Shouldn't it contribute to a better DR?
There were some cameras that had 16 bit RAW files (so it is possible)

While the Digital SLR's are replacing the gelatine 35 mm SLR's
wich had astounding Dynamic Range (especially Black & White Film)
they are relatively matching the resolution,
and surpassing the noise/grain (ISO),

The only thing they develope sooo slowly is the DYNAMIC RANGE.
If it continues with this rythm, we are too far away of matching the film

I don't think that there is someone who wouldn't want this,
and i think that at the stage of the digital photography that we are now,
the DR should be the priority of developing instead of resolution and ISO.

Thank you for sharing with me a word weather you agree
with my opinion or not.
and i feel that we need a revolutionary discovery to match the film DR
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Why not 16bit?
« on: December 14, 2011, 07:22:45 AM »

tjshot

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Re: Why not 16bit?
« Reply #1 on: December 14, 2011, 08:30:32 AM »
Main constraint is the relatively low speed of actually available 16 bit A/D converters. Of course costs are also an issue.
Given actual sensor densities and consequent data rates, multiple parallel pipelines of A/D C units are necessary for a fast operation (i.e. EOS 1D-X), increasing system costs and complexity; thus 16 bits seems to be  a viable option only for low-speed, low-ISO digital medium format backs (i.e. Phase One IQ180).
As per DXOmark results, dynamic range at low ISO is incredible, but it would not fit the typical use scenario of an actual APS-C or full frame digital camera.
Moreover, effective performance of actual 16bit  A/D Cs seems to be  not much better than top-of-the-line 14bit ones.
As a final consideration, to get the best out of a 16bit depth  converter a relatively large photosite is probably necessary: a condition that may fit digital medium format backs but not actual high density DLSR sensors.
We did discuss this issue in an old thread http://www.canonrumors.com/forum/index.php/topic,1902.0.html, with reference to actual increase in sensor Mpxls.
I still use, and enjoy, a lot of BW and color film, but honestly  dynamic range/SNR combo from actual digital sensors wins hands down, delivering a much cleaner and usable image.
« Last Edit: December 14, 2011, 08:35:28 AM by tjshot »

dilbert

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Re: Why not 16bit?
« Reply #2 on: December 14, 2011, 09:16:12 AM »
Why not 16 bit?

Shouldn't it contribute to a better DR?
There were some cameras that had 16 bit RAW files (so it is possible)

As far as I know, all Canon cameras that generate .CR2 are using 16bits to store the 12 or 14 bits of raw image information. How many bits will be a limitation of the ADC.

Thus far, Canon's cameras seem stuck at around 10 to 11 stops for DR whilst others are achieving 13 or more. I don't think that the number of bits being used to store raw data is the problem that Canon faces in delivering more DR.

Viggo

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Re: Why not 16bit?
« Reply #3 on: December 14, 2011, 10:00:08 AM »
I for one would REALLY like to know the DR of the 1d X. They've never said it was imrpoved before, it has gone unnoticed by most, but this time they list it as a main new feature, which is stupid if it's only 1/3 of a stop. the mk4 is, what 11,9? But with some trickery in Lightroom can go way beyond that. So do we get a 13,5 stops? at least up to iso 800 or 1600? I certainly hope so...
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pharp

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Re: Why not 16bit?
« Reply #4 on: December 14, 2011, 10:04:31 AM »
Maybe the best we can hope for in the near future is an integral software solution - hit the shutter release - camera takes 3 bracketed shots and combines automatically. Should be doable.

torger

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Re: Why not 16bit?
« Reply #5 on: December 14, 2011, 10:22:22 AM »
Medium format backs generally have 16 bit, but they are noisy enough to not need it, 14 bit would be enough. But it is nice to have "16 bit" in the data sheet to differ from the smaller formats, although it has no real meaning in practice.

In the smaller formats speed and file size is also important, so 16 bit will only come when noise levels in the sensor go down further so it starts to provide a real benefit. I don't think we are there yet.

HurtinMinorKey

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Re: Why not 16bit?
« Reply #6 on: December 14, 2011, 12:52:06 PM »
I thought bits were determined by the number of byes of information stored by each pixel. But I'm a hack so...

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Re: Why not 16bit?
« Reply #6 on: December 14, 2011, 12:52:06 PM »

wockawocka

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Re: Why not 16bit?
« Reply #7 on: December 14, 2011, 03:14:04 PM »
I read somewhere that even those cameras with 16bit a/d actually only DXO'd in at around 13-14bits - 1Ds3 territory.

Whilst it's nice to have the best images possible nearly 99.9999% of all photographic images viewed are A4 and smaller (think magazines and ipads).

The human eye can't discern the level detail on an image that size.
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Fish_shooter

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Re: Why not 16bit?
« Reply #8 on: December 14, 2011, 03:35:32 PM »
I for one would REALLY like to know the DR of the 1d X. They've never said it was imrpoved before, it has gone unnoticed by most, but this time they list it as a main new feature, which is stupid if it's only 1/3 of a stop. the mk4 is, what 11,9? But with some trickery in Lightroom can go way beyond that. So do we get a 13,5 stops? at least up to iso 800 or 1600? I certainly hope so...

I too am curious about the 1DX as I am sure are a lot of others. Hopefully we will see some full res high ISO shots soon as well as detailed info with respect to DR, etc.

7enderbender

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Re: Why not 16bit?
« Reply #9 on: December 14, 2011, 04:49:43 PM »
Why not 16 bit?

Shouldn't it contribute to a better DR?
There were some cameras that had 16 bit RAW files (so it is possible)

While the Digital SLR's are replacing the gelatine 35 mm SLR's
wich had astounding Dynamic Range (especially Black & White Film)
they are relatively matching the resolution,
and surpassing the noise/grain (ISO),

The only thing they develope sooo slowly is the DYNAMIC RANGE.
If it continues with this rythm, we are too far away of matching the film

I don't think that there is someone who wouldn't want this,
and i think that at the stage of the digital photography that we are now,
the DR should be the priority of developing instead of resolution and ISO.

Thank you for sharing with me a word weather you agree
with my opinion or not.
and i feel that we need a revolutionary discovery to match the film DR


I'm totally with you. Problem seems to be that it wouldn't really matter since the output (screens or prints) wouldn't match it anyway. If we ever want to see the same kind of depth we saw with film then we need better output technologies first. It's my opinion that cameras have reached a point of diminishing returns as long as nothing new happens on that side of the equation. I have no numbers or detailed technical knowledge to back this up other than looking at my prints from pre-digital printing days and compare it to anything I've gotten back from any lab since the late 90s or so. I compare it to the audio world. We have reached a point where digital audio processing is really really good. So we're back to the point where it really matters a) how good the analog input is (if there is any) and b) how good the analog output device is in the end. You can have the latest greatest guitar amp and microphone or the most nifty digital amp simulation and run all this with a sample rate of 96khz - once it hits your cheap little iPod headphones as poor MP3 files it really makes not much of a difference anymore.

Same will be true with you 16bit files and your L glass and your 48MP 5D Mark VI once your photos come out of that Walmart inkjet (or their more expensive equivalents from a slightly better lab).
« Last Edit: December 14, 2011, 04:52:58 PM by 7enderbender »
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LifeAfter

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Re: Why not 16bit?
« Reply #10 on: December 14, 2011, 05:29:52 PM »
Thanks for sharing the same opinion with me 7enderbender,
just that the output (screens or prints) wouldn't match it anyway, is also right,
but we don't need better DR for the output directly,
we NEED IT for editing the image, getting more details where we need it.

Imagine the miracle we could have from 35mm film
when we developed it and saw some exposures being already completely transparent
and we could still get the hole image with every detail on it,

or when the sky was too bright, we could still
get the clouds by developing (partially) only the sky for 2 or 3 sec.
without losing anything nor having additional grain (Noise?)

We could almost have a High-Dynamic-Range photo from one 35mm film frame
without having to do 3 or more frames with tripod and all the stuff..

Maybe the new generation don't miss this,
but it's just because they did never do it - they don't know it could be possible

Sorry for sounding maybe a bit nostalgic, 
but i really don't care about the dark room, 35mm film and everything else,

All i care is that it could be nice to have the DSLR's as they are,
without losing this Very IMPORTANT thing - DR.
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Flake

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Re: Why not 16bit?
« Reply #11 on: December 16, 2011, 10:54:16 AM »
Let me dispel a myth here, more bits will not make any difference to dynamic range at all.  you still have the same old 0 - 255 in each channel , but the number of steps between the two increases giving better colour and shades.  Dynamic range still remains the difference between clipping and the noise floor.

Nikon cameras allow switching between 14 & 12 bits (contentious statment comming !) to allow them to acheive the same frame rates as comparable Canon cameras, but I don't think anyone can really tell much difference between 12 & 14 bits in real world situations

Jettatore

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Re: Why not 16bit?
« Reply #12 on: December 16, 2011, 11:22:33 AM »
Also worth noting if it hasn't been mentioned, quite a few filters in Photoshop don't work in 16 bit mode (although I wouldn't consider them essential).  Even less tools work in 32 bit.  GIMP doesn't even have 16 bit support at all yet but it's in the pipeline.  I'd say it's not fully necessary to be working in 16 bit or higher, and if you have a specific use for it, you don't need to be in this conversation, lol, and if you don't know what specific use you would have for it, then it probably isn't the most immediate thing that will help you/your photography/etc..  By default, photoshop imports RAW files as 8 bit and I've never seen a specific instance where I thought "wow, I would have been so much better off in 16 bit" when the end result is concerned.
« Last Edit: December 16, 2011, 11:31:33 AM by Jettatore »

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Re: Why not 16bit?
« Reply #12 on: December 16, 2011, 11:22:33 AM »

chriswatters

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Re: Why not 16bit?
« Reply #13 on: December 16, 2011, 01:57:32 PM »
Let me dispel a myth here, more bits will not make any difference to dynamic range at all.  you still have the same old 0 - 255 in each channel , but the number of steps between the two increases giving better colour and shades.  Dynamic range still remains the difference between clipping and the noise floor.
Dynamic range can be limited by the number of bits used to record the data.

If only 8 bits are used to record a value, then the dynamic range is limited to 8 stops. The value 0 denotes a reading that is below the dynamic range. The value 255 denotes a value that is above the dynamic range. Neither of these values are "inside" the dynamic range. The values that fall inside the dynamic range are 1-254. Because values indicate a linear increase in brightness, this range of values allows for the brightest value to be only 254x brighter than the darkest value. Thus the dynamic range of 8-bit data is only 7.989 stops.

Even if the sensor was originally able to record a wider dynamic range, any data from that larger range is discarded along with the bits that recorded it. Some data loss can be avoided by using a non-linear value system. With the gamma correction of 1, Photoshop bends the curve to get 14 stops of dynamic range out of the 8 bit space.

When cameras record data in raw format, they do not record three channels for each pixel. Each pixel only records one channel. When the data is converted from a raw format into a conventional format, the additional channel data is generated based on the color filter array used in the camera. << http://en.wikipedia.org/wiki/Color_filter_array >>

While the number of bits used to record the raw data can limit the dynamic range, it cannot expand it beyond the sensor's capability. If noise from the sensor is randomly assigning the lower bits, there is no point on recording them. Recording 16-bits of data where the last 2 or 4 bits are pure noise is wasteful. RAW files are compressed using loss-less compression. Random data (noise) cannot be compressed using loss-less compression. Adding more bits of noise to the files would increase the file size substantially while doing nothing to improve image quality. Therefore, manufactures balance the number of bits used to record the data against the actual dynamic range of the sensor. You can expect that manufactures will move to 16-bit A/D coversion when their sensors have the dynamic range to use that data.
« Last Edit: December 16, 2011, 03:34:56 PM by chriswatters »

Edwin Herdman

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Re: Why not 16bit?
« Reply #14 on: December 17, 2011, 07:15:44 AM »
When cameras record data in raw format, they do not record three channels for each pixel. Each pixel only records one channel. When the data is converted from a raw format into a conventional format, the additional channel data is generated based on the color filter array used in the camera. << http://en.wikipedia.org/wiki/Color_filter_array >>

If you're going to be this picky, you ought to admit that at this stage they aren't called pixels, but photosites; the source you link contradicts you on this, hewing to the standard convention.  Also, it seems a bit strange that you would only provide a cite for one of the least controversial parts of your statement.

For example:

Quote
Because values indicate a linear increase in brightness, this range of values allows for the brightest value to be only 254x brighter than the darkest value. Thus the dynamic range of 8-bit data is only 7.989 stops.

While thought-provoking and news to me, this also strikes me as misleading (you do not provide a cite here, which would be very helpful).

Even if values DR=0 and DR=255 denote brightness levels below or above the "measured" dynamic range that do not plot along with those other values in a linear fashion, it is simply missing the point to argue that they are not at least usable parts of the dynamic range of an image and therefore record something of the dynamic range of a scene.  Even if full black and full brightness are not "accurate," they provide points of contrast for the final image, and so the usable, not real, DR is barely more than you suggest.  It's a bit like asking the color of black or white, and then arguing from the answer that because they aren't technically colors that they cannot be mixed on a palette.  If there is some photographer who seriously believes that DR=0 and DR=255 are unreliable (or even worse, useless), they have not spent enough time taking actual photographs.

I also question the assumption that DR always scales in a linear fashion.  Silicon is peculiar and, as evidence of this, the DxO data shows that DR (as it is represented in RAW files, at least) falls off in a non-linear fashion when ISO is raised.  In fact, there doesn't appear to be any set relationship at all.

Even if the sensor was originally able to record a wider dynamic range, any data from that larger range is discarded along with the bits that recorded it. Some data loss can be avoided by using a non-linear value system. With the gamma correction of 1, Photoshop bends the curve to get 14 stops of dynamic range out of the 8 bit space.

You act as if Photoshop has done something scurrilous.  No, my friend, the fact that "Photoshop" (in truth, every type of image processing software, including the camera manufacturer's RAW converter, those of third party makers, and that done in-camera) can get "14 stops" means that there are, in fact, 14 stops compressed (in a linear or non-linear matter hardly matters; you run into similar issues in color switching your camera from sRGB to Adobe RGB) into that 8 bit space.  The camera, and the camera's RAW and any third-party RAW converters, have to set or assume a floor, ceiling, and steps (or a "curve," though I suspect that in many cases there is no actual function, but instead something analogous to a look-up table for quick transcribing and interpretation of brightness levels).  Just because the steps are coarser or finder does not mean that the top inside value cannot represent a shade nearly 14 stops, or 9 or 31 or 1000, brighter than the lowest.  The 8-bit value is, in truth, arbitrary.

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Re: Why not 16bit?
« Reply #14 on: December 17, 2011, 07:15:44 AM »