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Author Topic: 16-bit B&W  (Read 5434 times)

Offline TerryB

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16-bit B&W
« on: February 09, 2010, 09:01:38 AM »
Words of wisdom from a Tim Grey free newsletter
http://www.timgrey.com/
suggest working in 16-bit for B&W images.

Is this something we should adopt for our B&W restos?
~~~~~~~~~~~~~~~
Today's Question:

Sorry, but there is still one thing not clear to this knucklehead about 8-bit versus 16-bit for B&W. What if one does most of the editing and retouching on an image while still in color (Adobe RGB) and then uses an adjustment layer to covert to B&W? Is 16-bit per channel still an important matter?

Tim's Answer:

Yes, working in 16-bit per channel mode when creating a black and white image, even if that image is still in the RGB color mode (as would be the case if you were using a Black & White adjustment layer) is still important. The reason is that even though the underlying pixel information consists of three channels (red, green, and blue) to produce color values, the net result when using the Black & White adjustment layer (or any other technique that yields a black and white image) is to have only luminosity information presented, not color information. As a result, what you're effectively getting is a single channel in the final pixel data, not three channels. Thus, the same issue of having only 256 possible shades of gray rather than 65,536 shades of gray would be at play. As such, even if you're working with an image in the RGB color mode, if the end result is a monochrome (such as black and white) image, you should work in the 16-bit per channel mode.

The Winter 2010 issue of Digital Darkroom Quarterly covers the creation of black and white images from a color original in extensive detail. If you're not already a subscriber and are interested in receiving the Winter 2010 issue (and future issues) of Digital Darkroom Quarterly, you can subscribe through my online store here:

http://www.timgrey.com/store/index.php?app=ecom&ns=prodshow&ref=DigitalDarkroomQuarterly
~~~~~~~~~~~~~~~~~~~~~~~~~
Confidence is the feeling you have before you understand the situation.

Offline Mhayes

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Re: 16-bit B&W
« Reply #1 on: February 09, 2010, 03:52:40 PM »
Hi Richard,

I'm not sure I follow all that he is getting out, but I'm certain that if you have a photo that is 8 bits to start out with; you can't upsize to 16 bit, because it didn't start out that way. Yes, you might be able to bring a photo into Raw and maybe on the pull down pick 16 bit, but you can't increase the bit depth of JPG photo that is 8 bit to start with. If you were getting photos straight out of the camera and into Raw; you could go 16 bit.

I also do not agree with his wanting to use only the luminosity and not using the color channels to get a black/white.  I realize that not everyone has CS4, but now there is a black/white adjustment that let you tweaks different channels. You could do this before, but these presets are a good start. A great book for information Is Martin Evenings Adobe Photoshop CS4 for Photographers. On Page 350 of that book he has the title: "The dumb black and white coversion."That includes converted from RGB to Grayscale. He also goes on to say:
Quote
"The same thing is true, if you went to simply desaturated the image or make a Lab mode conversion, copy the Luminosity channel, convert the image back to RGB mode and choose Edit.Paste."

He goes on to show the smart black and white conversions using the Black & White adjustment controls. Even better is to use the Camera Raw black and white conversion, but there again we are talking about true Raw files not jpgs brought into Raw.

And no, this is not something we should adopt for B&W restores. Another thing to consider is if you could have 16 bit file which you cannot on the OPR photos; you are going to really increase the photo's size and it is going to be slower to work and in the end it will have to be changed back to a 8 bit file. Part of the argument for working in 16 bit is to preserve the quality and with our photos it is too late for that.

Hope that helps.

Margie
 
"carpe diem"

Margie Hayes
OPR President
mhayes@operationphotorescue.org

Offline Tori803

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Re: 16-bit B&W
« Reply #2 on: February 10, 2010, 01:31:51 PM »
Even though it's not a viable method for our work, I have to say I sure learn a lot from these discussions!
Tori
"Nothing in the world can take the place of persistence." -Calvin Coolidge

Offline glennab

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Re: 16-bit B&W
« Reply #3 on: February 10, 2010, 03:31:03 PM »
I tried an experiment and scanned in several B&W & color photos at 16 bit.  Some were just snapshots and some were portraits.  It may have been because they were second generation rather than an original photo shot at 16 bits, but I couldn't discern enough difference to deal with the larger file size and the fact that the files couldn't be saved or worked on the way I wanted.  Possibly CS4 addresses a lot of that, but it'll be a while before I can upgrade from CS2, so I'm content - as I think we all should be - with 8-bit images.  Margie's spot on that 16-bit quality isn't going to help us conquer the issues we have with our photos.

GK
What we do for ourselves dies with us. What we do for others and the world remains and is immortal. ~Albert Pine

(Photoshop CS5 /Mac Pro)

Offline paulus

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    • Riverside Photo
Re: 16-bit B&W
« Reply #4 on: February 11, 2010, 07:25:04 PM »
I was taught that your histogram can show the difference as it looks funny with the gaps between the missing lines being the tones that are lost.

I work sometimes with 16 bit it depends on the damage and what I'm doing with it - faded images I will use 16 bit but okay images not - you can be a bit sloppy with your colour corrections as you've more information to work with and lose.

Many plug-ins become unstable or  very slow to work with when at 16 bit and file size racks up very quickly.

OPR wise its a complete non starter - also I personally either use raw or gradient maps for B&W conversions.

My 10p worth
Cheers
Paul

Offline Mhayes

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Re: 16-bit B&W
« Reply #5 on: February 11, 2010, 10:30:47 PM »
Paul,

Ditto on using the gradient maps! That can really make a B&W have a good contrast.

Margie
"carpe diem"

Margie Hayes
OPR President
mhayes@operationphotorescue.org