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Why is CS5 default color mode 8 bit?

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  #11  
Old 07-23-2011, 12:10 PM
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Tony W Tony W is offline
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Re: Why is CS5 default color mode 8 bit?

Interesting reading Murray's and John's comments. Not wanting to take the thread off track but maybe add a little fuel to the discussion with my opinion FWIW and in the process maybe add to my knowledge.

Firstly I suspect that Adobe may have thought that it was not appropriate to add this functionallity to preferences due to the prevalance of 8 bit jpegs (AFAIK until Jpeg2000 all were 8bit). If this is the case could it be due to the fear of potentially making the images worse by converting from 8 to 16bit?

There seems to have been a lot of debate relating to editing 8 bit as 16 bit does it make sense, does it improve, does it have potential to degrade etc etc.

My current view based on experience to date and also coloured by the 'experts' views i.e. those 'experts' whose views I respect. One comment that struck me by a respected Photoshop guru along the lines of 'converting 8 bit files to 16 bits is a voodoo manouvere that will gain no improvement' - I think it may have been Katrin Eisman

When I started using Photoshop I used to convert 8 bits to 16 bits in the belief that I would be gaining something. My revised view is that it may be possible but there are risks associated that need to be understood - I have seen/introduced posterisation into my own images which could be attributable to editing original 8 bit as 16 bit.

So now this is my current thinking. Of course I accept my thinking may be out of date, plain wrong or just a load of c**p and would welcome different views

If an image is available as anything over 8 bit then I will edit in 16 bit. This includes scanning and acquiring from DSLR. In my case I thought my DSLR was 12 bit but it is actually 12 bit compressed which I believe equates to a real bit depth of only 9.5 bits!

There is a problem when converting 8 to 16 bit which may not be seen or we are even aware of. The original 8 bit image has 256 levels when converted to 16 bit it will have 32769 (think PS is actually 15 bit hence losing 32000+ levels). This must mean that there are huge gaps in the histogram. AFAIK PS histogram of a 16 bit image has been converted to an 8 bit view therefore the gaps are probably not apparent. Depending on editing steps taken it is conceivable that the gaps will increase even more due to spreading the 8 bit level information over the new 16 bit levels ?

Robert, thanks for the info. Seems to me that generally Adobe do not remove much, if anything from previous releases. On balance I think probably a good idea to keep customers happy and brand loyal by maintaining legacy features.
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  #12  
Old 07-23-2011, 12:50 PM
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Re: Why is CS5 default color mode 8 bit?

Quote:
Originally Posted by mistermonday View Post
However, there is a significant difference between the practical and theoretical / mathematical. Your example with LAB is actually a perfect example of my argument. If you read the book LAB COLOR: The Canyon Conundrum by Dan Margulis you will find a very detailed explanation of why.
Well the practical and theoretical example in the book should be subject to close scrutiny! Its a pretty awful quality reproduction for one (low linescreen, not very good paper), its far from a high quality reproduction in comparison of say a high line screen print job, let alone a high end ink jet or contone reproduction. So can you convert back and forth dozens of times (the first conversion is really the one that dumps the additional data I’ll point out) and not see anything in terms of this kind of low quality repro? In this case yes. What happens as you continue to edit the image? Or find you need a far higher end quality output device. And the banding usually seen is found in smooth gradients (sky, chrome car bumpers etc). You see anything remotely like this in Dan’s one example? Nope.

The proof here is not all encompassing by a long shot! And in terms of Dan’s belief system about high bit files (which virtually every scanner and pro level camera provides), why dump the data? The famous “prove the need for high bit” Dan debate is one in which the field goals move anytime Dan feels the need as well described here (by a imaging color scientist no less):

http://www.brucelindbloom.com/index....nMargulis.html

Years ago, when I provided Dan a real world image that showed visual on-screen degradation in 8-bits per color that didn’t show in high bit, he then changed the goal posts again and began his new goal to dismiss ProPhoto RGB! IMHO, he’s not too interested in scientific concepts but flat earth concepts.

So the best thing I can say here is, ignore Dan’s examples!

Getting back to the OP, yes, the default is for a new doc to be 8-bits per color. But the dialog is sticky, meaning that once you setup a new doc as you desire, it should stick to the color space and bit depth you ask for. IF the clean, out of the box default where say ProPhoto RGB in 16-bit, people who want to have a clean out of the box sRGB 8-bit would question why.
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  #13  
Old 07-23-2011, 01:57 PM
RobertAsh RobertAsh is offline
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Re: Why is CS5 default color mode 8 bit?

Quote:
Originally Posted by Tony W View Post
...If an image is available as anything over 8 bit then I will edit in 16 bit. This includes scanning and acquiring from DSLR. In my case I thought my DSLR was 12 bit but it is actually 12 bit compressed which I believe equates to a real bit depth of only 9.5 bits!

There is a problem when converting 8 to 16 bit which may not be seen or we are even aware of. The original 8 bit image has 256 levels when converted to 16 bit it will have 32769 (think PS is actually 15 bit hence losing 32000+ levels). This must mean that there are huge gaps in the histogram. AFAIK PS histogram of a 16 bit image has been converted to an 8 bit view therefore the gaps are probably not apparent. Depending on editing steps taken it is conceivable that the gaps will increase even more due to spreading the 8 bit level information over the new 16 bit levels ?

Robert, thanks for the info. Seems to me that generally Adobe do not remove much, if anything from previous releases. On balance I think probably a good idea to keep customers happy and brand loyal by maintaining legacy features.
You're right. Also, part of keeping customers happy in high-end production environments that rely on your product means not introducing unexpected behavior. High end environments have a lot of automation, standardization and reliance on products behaving absolutely consistently. People write scripts, actions, workflows, etc. that make assumptions about the environment they're running in, and anything that changes could conceiveably mess up something for an important customer or group of them. That's one reason it's always important to read release notes.

Regarding compression, it depends on which compression algorithm(s) your camera provides. Nikon has visually lossless compression that allows you to keep full 14-bit image quality, or normal compression that conceiveably could affect image quality. I use lossless in all my Nikons.

Also, there is no way to have 9.5 bits, you have either 9 or 10 because a bit is either there or not, it cannot be halfway there.

Regarding your histogram question, you actually don't have that many gaps in the histogram typically.

One reason is that 8 bits provide you 256 colors per pixel or per dot, not just 256 colors. When pixels, or especially dots, get close enough together they're visually indistinguishable. So 2 dots side-by-side at 256 colors each provides the eye 256*256 = 65,536 different color variants. At 1440 dpi or 2880 dpi with good software interpolation algorithms you get literally millions of possible color combinations even from 8 bits because the print dots are so close together. Nifty!

That's one reason Dan Margulis' point is valid for so many cases, though that's not the reason he gives in his book.

That's also why such beautiful prints can be made from 8-bit files. What matters in the end is not the technical specifics of the exact numbers, what matters is the clever ways people have developed of getting the most out of specs which are so unimpressive at first glance.
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  #14  
Old 07-23-2011, 02:34 PM
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Re: Why is CS5 default color mode 8 bit?

Quote:
Originally Posted by RobertAsh View Post
.......Regarding compression, it depends on which compression algorithm(s) your camera provides. Nikon has visually lossless compression that allows you to keep full 14-bit image quality, or normal compression that conceiveably could affect image quality. I use lossless in all my Nikons....Also, there is no way to have 9.5 bits, you have either 9 or 10 because a bit is either there or not, it cannot be halfway there.
You are right - my bad! For some reason I typed 9.5 bits - probably due to the fact (apart from not thinking!!) that Nikon only offers lossy compression on the 12 bit RAW acquired by the D90. I understand that this equates to a true bit depth of around 9 or 10 bits.

I knew I should have stumped up the additional cash for the D300 when I made the move to digital - I just did not investigate thoroughly enough.

While I would prefer to have the potential benefits of a true 12 or 14 bit capture the D90 is a fine camera for the price and very capable. Too true that beautiful prints have been and are being made from 8 bit captures
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  #15  
Old 07-23-2011, 03:40 PM
RobertAsh RobertAsh is offline
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Re: Why is CS5 default color mode 8 bit?

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Originally Posted by Tony W View Post
I knew I should have stumped up the additional cash for the D300 when I made the move to digital - I just did not investigate thoroughly enough.

While I would prefer to have the potential benefits of a true 12 or 14 bit capture the D90 is a fine camera for the price and very capable. Too true that beautiful prints have been and are being made from 8 bit captures
Well, I can't get too proud A key reason I upgraded from my D200 my wife bought me to the D300 instead of buying a D80 (the D90 wasn't out quite yet) is because my wife was ragging on me. Because she was wondering out loud why on earth I was seriously considering "spending $1000 for a plastic camera" as she put it. I didn't know that she took buying me cameras that seriously It was only later that I found out the other extras the D300 had. Glad I went with it.

I did do a departure recently and bought the D7000 though -- that camera is the bomb! Really remarkable. The image quality and high ISO performance are world-class. With the right post-processing you can make its images look like they were taken with a 4x5-inch camera. From a $1200 camera. My D300 is now my backup camera. And I'm not the only one from a few posts I've read from others who did the same thing.

It's so good that LeicaRumors.com had a video posted awhile back where one of Leica's spokes-photogs compared the Leica M9.......not to the D3x or D3s he had on his bench......but to the D7000 he picked up from right beside those two. And he even conceded that from a technology spec standpoint the D7000 was superior and did a lot more. Then went on to try to tell people why they ought to buy that $8000 camera that did less instead of the $1200 camera that did more. Really amazing.

Yes, you're right about the 8-bit images. That's one thing I really like about Dan Margulis -- the guy understands stuff like diminishing returns from higher bit-count. The guy is a real genius and truly earned his market-leading reputation. I plan to take his 1-week workshop in the next couple of years if at all possible.

Anyone will always have corner cases where their techniques don't work. Anyone. But the large majority of what Margulis is saying is valid, well-explained and just plain works. Certainly for me. And he provides the best explanations I've personally seen for most of the topics he addresses in his book.

Last edited by RobertAsh; 07-23-2011 at 08:07 PM.
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  #16  
Old 03-14-2012, 06:15 AM
adtechniques adtechniques is offline
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Re: Why is CS5 default color mode 8 bit?

sorry but how can change default 16bit? My CS5 always open all my .jpg picture in 8bit? I wanna make default color space working in 16 bit. Can i change?

Last edited by adtechniques; 03-14-2012 at 06:21 AM.
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  #17  
Old 03-14-2012, 09:11 AM
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Re: Why is CS5 default color mode 8 bit?

JPEG doens’t support 16-bit data.
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  #18  
Old 03-14-2012, 10:08 AM
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John Wheeler John Wheeler is offline
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Re: Why is CS5 default color mode 8 bit?

Hi Adtechniques
Andrew already pointed out that JPEGs are already stored as 8 bit. If after knowing this you still want to convert to 16 bit there are a couple ways.

First note at present there is no preferences setting to automatically open/convert images to 16 bit. Previously posted in this thread is the link for feature enhancement suggestions to Adobe.

Also previously in this thread were noted two alternative ways to get to 16 bit
1) Opening through ACR first where you can specify bit depth to open in Photoshop
2) Using Scripts Event Manager
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  #19  
Old 03-14-2012, 09:38 PM
adtechniques adtechniques is offline
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Re: Why is CS5 default color mode 8 bit?

Thks John & Andrew so much.
Rgds,
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