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Author Topic: DSLR v Medium Format  (Read 18548 times)
Jonathan Wienke
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« on: August 15, 2005, 02:04:38 AM »
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Bit depth has no direct relation to color gamut. If you're having color issues with a DSLR it's far more likely a color management problem than an intrinsic limitation of the camera. Most DSLRs can record colors outside Adobe RGB, well outside what's printable in most cases.
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DavidB
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« Reply #1 on: August 24, 2005, 11:08:44 PM »
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The size of the gamut is not an issue with the number of bits, but more bits allow you to record finer changes in value within the gamut. Hopefully the device has good enough noise characteristics that the extra bits aren't all used up by noise...

By the way, when Photoshop says it's dealing with 16-bit data it's actually only using 15 bits, but that's still a step up from 4096 steps (12-bit) to 32768 steps (15-bit).  In fact because of the maths being used by Photoshop it's not exactly 32768, but close enough for this comparison.
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photo0551
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« Reply #2 on: August 15, 2005, 01:39:20 AM »
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The DSLRs all come with 12 bit data.  The film scans and the medium format backs (rented not bought) come in 16 bit flavors with an apparent major step up in color gamut.  Does this mean anything to anyone or am I being driven crazy?
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Ray
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« Reply #3 on: August 15, 2005, 03:01:40 AM »
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I understand that bit depth is more about noise and dynamic range. 48 bit film scans generally have less noise than 24 bit scans. However, the dynamic range of a sensor has physical limitations depending on the strength of internal noise sources as well as the size of the photosites and the maximum electronic charge they can hold. 16 bit A/D converters and 16 bit signal processing are just trying to make the best of what's there. They can't create something from nothing.
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haidergill
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« Reply #4 on: July 19, 2007, 04:26:01 AM »
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12 bits (per channel) colour = 69 billion colours
16 bits (per channel) colour = 28 trillion colours

A gamut is a collection of shades nothing more. A ggamut could contain a gazillion colours but 12 bit file could only contain 69 billion of those shades simultaneously. Where as the 16 bit can contain 28 trillion colours. So yes 16 bits per channel photo should look better

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The DSLRs all come with 12 bit data.  The film scans and the medium format backs (rented not bought) come in 16 bit flavors with an apparent major step up in color gamut.  Does this mean anything to anyone or am I being driven crazy?
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digitaldog
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« Reply #5 on: July 19, 2007, 07:58:35 AM »
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I understand that bit depth is more about noise and dynamic range. 48 bit film scans generally have less noise than 24 bit scans.

I don't think so. First, a lot of this is theoretical math. 12 bits 69 billion colors, 16-bit 28 gizillion. Use either capture device and shoot a gray card and how many colors are you getting?

As for noise, I don't see how more levels equate to less or more noise OR dynamic range. You're just splitting the possible numeric values captured into finer numbers. How would that equate to less noise or more range? These would appear to be totally different specs based on a lot of factors.

In my mind, high bit (more than 8-bit) is about editing overhead. I want to send the best 8-bits to an output device. If I start with 256 values and edit the image, the net results are less than 256 values. If the same data starts with 64000 values, I can edit and end up with more than enough levels to send the best 256 to the device. Doesn't mean that provides better appearing images, less noise etc, it just means I start with finer steps of numeric values.
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Andrew Rodney
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haidergill
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« Reply #6 on: July 19, 2007, 08:37:50 AM »
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Andy you may well be right as 16 billion cols is large no., it's not exactly like viewing a photo in like say 16 cols. I'm not sure how many colours the average human can see?
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Graeme Nattress
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« Reply #7 on: July 19, 2007, 08:46:28 AM »
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Gamut is not really the number of different colours a system can see, but more how different the different colours are. 12bit / 16bit governs dynamic range / noise floor and number of different tones. Gamut is defined by the colour filters on the sensor, image processing etc.

And when a camera claims 16bit, you've got to go and look at the dynamic range and noise floor, as some of those bits couldbe just pure noise, or even blank.

Graeme
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Rob C
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« Reply #8 on: July 19, 2007, 02:05:05 PM »
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Opening no old debates here - promise - but how simple it was in the days of film! You had more or less grain, or your film had dyes and practically no grain. Now some of us have headaches instead of confidence.

Yes, that´s progress, folks, modern style!

Ciao - Rob C
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marcmccalmont
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« Reply #9 on: July 23, 2007, 04:55:29 PM »
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Just because an analog to digital converter is a 16 bit device there is no guaranty that the least significant bits aren’t lost in noise and distortion. In audio 24 bit a/d converters you’re lucky if the 14 most significant bits are valid data. I'm curious what the usable bits are in both 12 bit DSLRs and 16 bit digital backs? I’m sure less than the a/d converters bit depth as they don’t have DAC ovens, controlled impedance circuitry etc.
Marc
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Marc McCalmont
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« Reply #10 on: August 05, 2007, 01:17:46 AM »
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How bit depth was explained to me.....

Think of bit depth as a ladder....as you increase bit depth...you dont extend the size of the ladder...just how many rungs are between each end.

Roman
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Lester
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« Reply #11 on: August 08, 2007, 02:23:43 PM »
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All you people worry about bits, do you really see it? in a print? Everyone talking about DSLR at 12 bit. Look again the Canon 1D Mk III is 14 bit. It might be the first Canon at 14 bit but it won't be the last. So, are you willing to paid over $20,000 grand for a MF to get the 16 bit.

I shot the Horseshoe bend at Page, Az. Both with a 1Ds MkII and Phase One P45, looking at both images, there is little difference in the images. Yes the P45 does show more, but at what price? 1Ds MkII at $8000 or the P45 at $33500, that is just the camera body and MF back.
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marcmccalmont
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« Reply #12 on: August 08, 2007, 05:14:13 PM »
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All you people worry about bits, do you really see it? in a print? Everyone talking about DSLR at 12 bit. Look again the Canon 1D Mk III is 14 bit. It might be the first Canon at 14 bit but it won't be the last. So, are you willing to paid over $20,000 grand for a MF to get the 16 bit.

I shot the Horseshoe bend at Page, Az. Both with a 1Ds MkII and Phase One P45, looking at both images, there is little difference in the images. Yes the P45 does show more, but at what price? 1Ds MkII at $8000 or the P45 at $33500, that is just the camera body and MF back.
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Would you post both images as a comparison? (I know it is hard on the web to compare) I'd be curious, not concerned about bits but real world dynamic range. Initial reports of the Mamiya zd back show it to be a noticeable improvement over the 5D in this regard.
Marc
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Marc McCalmont
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« Reply #13 on: August 09, 2007, 09:16:02 PM »
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I guess everyone is waiting for me, thanks to Marc, I will try to post the pics. The 4:3 is the P45 shot with the Mamiya 35mm at f8, the 3:2 was shot with the Canon 1Ds MkII with the 24-70 zoom at 24mm and f8, both was output with C1. They are full frame and nothing was done to the images, except to make them jpegs. The color and contrast does not match, because nothing was done to them. They are taken about 1 minute apart.
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Forsh
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« Reply #14 on: August 11, 2007, 08:03:39 AM »
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The DSLRs all come with 12 bit data.  The film scans and the medium format backs (rented not bought) come in 16 bit flavors with an apparent major step up in color gamut.  Does this mean anything to anyone or am I being driven crazy?
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I thought the Fuji and new canon are true 14-bit not 12-bit? Did you check the [a href=\"http://www.okinawahdr.com/okinawajapan/]okinawa news in english[/url]?
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Futenma Shrine My HDR Photography from Okinawa Japan.  | okinawa japan Other from Okinawa Japan. So what do you do? You don't want create a scene as they can call upon their members beating you down with their home made reflectors in nanoseconds, and creating an international incident over a pix of the rare Zebra butterfly is probably not a great idea.
John Sheehy
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« Reply #15 on: August 11, 2007, 08:28:45 AM »
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The DSLRs all come with 12 bit data.  The film scans and the medium format backs (rented not bought) come in 16 bit flavors with an apparent major step up in color gamut.  Does this mean anything to anyone or am I being driven crazy?
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You can't readily tell why the MF backs are better though.  It can be for other reasons besides bit depth.  Just because a manufacturer uses high bit depth, doesn't mean that it is actually used in any truly beneficial way by the camera, although it may force a converter to use a higher precision; it may simply "pad" the least significant bits with noise instead of zeros.
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John Sheehy
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« Reply #16 on: August 11, 2007, 08:35:52 AM »
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12 bits (per channel) colour = 69 billion colours
16 bits (per channel) colour = 28 trillion colours

A gamut is a collection of shades nothing more. A ggamut could contain a gazillion colours but 12 bit file could only contain 69 billion of those shades simultaneously. Where as the 16 bit can contain 28 trillion colours. So yes 16 bits per channel photo should look better
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In reality, noise is humongous compared to digitized RAW levels in the highlights, and significant in the shadow areas as well.  Bit depth is not a limit in most digital cameras; most have more bits than can be efficiently utilized.  Extra bits in the RAW files guarantee higher conversion precision at best, in most cases, but that can be done by just fabricating the LSBs.
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Graeme Nattress
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« Reply #17 on: August 11, 2007, 03:50:55 PM »
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With a Stouffer 13 1/3 stop test wedge, I could clearly see more steps (about 2 stops worth) on a Canon 1D MK III than a Canon 20D.

Graeme
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Ray
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« Reply #18 on: August 11, 2007, 08:26:20 PM »
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I don't think so. First, a lot of this is theoretical math. 12 bits 69 billion colors, 16-bit 28 gizillion. Use either capture device and shoot a gray card and how many colors are you getting?

As for noise, I don't see how more levels equate to less or more noise OR dynamic range. You're just splitting the possible numeric values captured into finer numbers. How would that equate to less noise or more range? These would appear to be totally different specs based on a lot of factors.

In my mind, high bit (more than 8-bit) is about editing overhead. I want to send the best 8-bits to an output device. If I start with 256 values and edit the image, the net results are less than 256 values. If the same data starts with 64000 values, I can edit and end up with more than enough levels to send the best 256 to the device. Doesn't mean that provides better appearing images, less noise etc, it just means I start with finer steps of numeric values.
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Andrew,
I'd forgotten I had expressed an opinion on this matter (2 years ago!!).

It's not clear to me precisely under what circumstances 16 bit will be noticeably advantageous compared with 8 bit. However, if we start from your premise that 16 bit is all about editing headroom, then let's ask the questions, 'When are images never edited? Have I ever seen a completley unedited image? What does it look like?'

There's such a thing as in-camera processing, even of RAW images and certainly of jpegs. That's editing, isn't it?

When I scan my slides, I make all sorts of adjustments to the preview of the slide before I hit the 'scan' button. That's editing isn't it?

When I shoot a high contrast scene with my Canon DSLR, there will be a very limited number of levels available to describe the deepest shadows in 8 bit mode, more in 12 bit and even more in 16 bit. If I'm trying to get the maximum DR and the least shadow noise through all sorts of in-camera processing (which would appear to be a trade secret since I've never seen such processes explained in detail), then it would be reasonable to suppose that 16 bits per channel are better than 8 or 12 bits, wouldn't you say?
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John Sheehy
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« Reply #19 on: August 11, 2007, 09:08:48 PM »
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With a Stouffer 13 1/3 stop test wedge, I could clearly see more steps (about 2 stops worth) on a Canon 1D MK III than a Canon 20D.
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But why?  You'd see them on a mk2, also, because the read noise is the same, relative to max signal, at ISO 100.  The pixel read noise is lower in the mk3 than the 20D at all ISOs, plus it has more pixels, so if you achieve the same FOV, you will have even less subject read noise.

I've quantized ISO 100 RAWs from the mk3 to 12 bits, and they are indistinguishable from the full 14 bits after RGB interpolation, even zooming deep into the shadows, as long as the 12 bit version is promoted back to 14 bits with zeros in the 2 LSBs.

So, more bits might help for indirect reasons, and not necessarily because of what they contain.  In my experience, working bit depth in conversion is generally more important than the significant bit depth of the RAW data.  That's because there is so much noise, and the noise gets softened in conversion, and the greatest dangers of posterization occur in the rendered product.
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