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Author Topic: 8 bit vs. 16 bit for Black & White Scanning  (Read 30612 times)
danacasto
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« on: November 04, 2007, 07:01:01 PM »
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From what I have been able to read up on regarding the value of 16 bit color depth versus 8 bit regarding scanning of film negatives is mostly geared toward the value [of 16 bit] in regards to color negatives. I have yet to find any real conclusive information regarding whether or not black and white film should be scanned for optimum results in 8 or 16 bit. Does anyone have any experience with scanning black and white in 8 or 16 bit? Is there a perceptible difference in b&w? Anyone know of any resources that talk about the pros & cons directly related to 8 vs. 16?
Thanks,
danacasto
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Rob C
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« Reply #1 on: November 05, 2007, 09:54:01 AM »
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From what I have been able to read up on regarding the value of 16 bit color depth versus 8 bit regarding scanning of film negatives is mostly geared toward the value [of 16 bit] in regards to color negatives. I have yet to find any real conclusive information regarding whether or not black and white film should be scanned for optimum results in 8 or 16 bit. Does anyone have any experience with scanning black and white in 8 or 16 bit? Is there a perceptible difference in b&w? Anyone know of any resources that talk about the pros & cons directly related to 8 vs. 16?
Thanks,
danacasto
[a href=\"index.php?act=findpost&pid=150600\"][{POST_SNAPBACK}][/a]

This will probably highlight my deep ignorance of such metaphysical matters, but why would anyone choose to use anything other than the highest degree of quality available to them?

Rob C
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sanking
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« Reply #2 on: November 05, 2007, 10:27:10 AM »
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You should definitely scan grayscale in 16 bit. In fact, it is probably even more important with grayscale than color since there are only 256 values, as opposed to 3X256 in color. If your scanner  or software does not allow 16 bit scans I would suggest that you scan in 8 bit RGB. Immediately convert to 16 bit RGB and then to 16 bit grayscale before making any changes to the file.

If you are new to scanning you might want to consider a copy of Real World Scanning and Halftones, by Blatner, Chavez, Fleishman  and Roth. It covers this issue and provides a very good introduction to most of the issues of scanning.

Sandy King
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mbutler
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« Reply #3 on: November 06, 2007, 03:50:00 PM »
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It probably depends on the scanner. A 16-bit scan on a drum scanner would be overkill--westcoastimaging.com has some good information on this.

Best,

Mike
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danacasto
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« Reply #4 on: November 06, 2007, 03:54:02 PM »
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It probably depends on the scanner. A 16-bit scan on a drum scanner would be overkill--westcoastimaging.com has some good information on this.

Best,

Mike
[a href=\"index.php?act=findpost&pid=150973\"][{POST_SNAPBACK}][/a]

It's a Nikon Super Coolscan 9000 ED. I will check out the website and other suggested resources. Thanks for the info!
Dana
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Chris_Brown
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« Reply #5 on: November 06, 2007, 05:32:13 PM »
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From what I have been able to read up on regarding the value of 16 bit color depth versus 8 bit regarding scanning of film negatives is mostly geared toward the value [of 16 bit] in regards to color negatives. I have yet to find any real conclusive information regarding whether or not black and white film should be scanned for optimum results in 8 or 16 bit. Does anyone have any experience with scanning black and white in 8 or 16 bit? Is there a perceptible difference in b&w? Anyone know of any resources that talk about the pros & cons directly related to 8 vs. 16?
[{POST_SNAPBACK}][/a]
If you plan on applying major corrections in Photoshop (curves, masks, filters, etc.) then I'd definitely scan in 16-bit mode.

If you think you can nail the scan and won't make any changes in PS, then save time and scan in 8-bit mode.

[a href=\"http://tech.groups.yahoo.com/group/colortheory/]This forum on Color Theory[/url] has plenty of info on 8-bit vs. 16-bit. It can be a contentious group, but the info harvested is excellent.
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digitaldog
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« Reply #6 on: November 06, 2007, 05:37:29 PM »
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If you plan on applying major corrections in Photoshop (curves, masks, filters, etc.) then I'd definitely scan in 16-bit mode.

Absolutely!

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This forum on Color Theory[/url] has plenty of info on 8-bit vs. 16-bit. It can be a contentious group, but the info harvested is excellent.
[{POST_SNAPBACK}][/a]

Most of the stuff posted there in regard to high bit by the moderators is flat earth theory, and ironically color theory at its worst.

Yup, Adobe put all that high bit editing capability into Photoshop and Lightroom for no reason: Not!

The arguments are best summed up here:
[a href=\"http://www.brucelindbloom.com/index.html?DanMargulis.html]http://www.brucelindbloom.com/index.html?DanMargulis.html[/url]

And further:

http://staging.digitalphotopro.com/tech/th...h-decision.html
« Last Edit: November 07, 2007, 08:34:23 AM by digitaldog » Logged

Andrew Rodney
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Kirk Gittings
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« Reply #7 on: November 06, 2007, 05:39:01 PM »
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If you plan on applying major corrections in Photoshop (curves, masks, filters, etc.) then I'd definitely scan in 16-bit mode.

If you think you can nail the scan and won't make any changes in PS, then save time and scan in 8-bit mode.

This forum on Color Theory has plenty of info on 8-bit vs. 16-bit. It can be a contentious group, but the info harvested is excellent.
[a href=\"index.php?act=findpost&pid=150992\"][{POST_SNAPBACK}][/a]

I agree. Even if you nail the scan, if you are going to "work" the file much you are better off in 16 bit as your transitions will be better and there will be less enhancement of noise in the shadows and transitions. This is less important with drum scans that have very low noise, but still a good idea.
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Thanks,
Kirk

Kirk Gittings
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Chris_Brown
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« Reply #8 on: November 07, 2007, 09:28:44 AM »
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Most of the stuff posted there in regard to high bit by the moderators is flat earth theory, and ironically color theory at its worst.

Yup, Adobe put all that high bit editing capability into Photoshop and Lightroom for no reason: Not!

The arguments are best summed up here:
http://www.brucelindbloom.com/index.html?DanMargulis.html

And further:

http://staging.digitalphotopro.com/tech/th...h-decision.html
[a href=\"index.php?act=findpost&pid=150994\"][{POST_SNAPBACK}][/a]
What? Linking to your own article? Mercy!

The biggest difference in the Color Theory group and the links you provided is that the Color Theory is a forum, where one can post questions and theorems. It does help to have feedback (even if you have to take a few darts).

I remember the 8- vs. 16-bit debacle. It was weird, and caused a schism in the group. However, the "debate" caused my studio to test, test, test. I tend not to take web info for granted.

What did I learn from that debate? In high resolution inkjet prints, the most obvious problem was the breakdown of smooth gradients in the reflections in sheetmetal (cars). Even after a single, strong curve had been applied, banding was easily visible. In heavily detailed stuff (i.e., bushes and plants in a landscape) it was impossible to detect problems caused by one applied curve.
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digitaldog
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« Reply #9 on: November 07, 2007, 10:15:02 AM »
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What? Linking to your own article? Mercy!

IF you have a technical issue with the piece, I'm all ears.

This isn't by the way the only article on the subject. Would you care for other links?

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The biggest difference in the Color Theory group and the links you provided is that the Color Theory is a forum, where one can post questions and theorems. It does help to have feedback (even if you have to take a few darts).

Unless the group of moderators decides they will not post this (its heavily moderated) or Dan decides the subject is no longer about promoting his classes and books, then the topics are often closed. I have plenty of examples of this over the years if you need proof of this.

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I remember the 8- vs. 16-bit debacle. It was weird, and caused a schism in the group. However, the "debate" caused my studio to test, test, test. I tend not to take web info for granted.

You did good by testing (something that many on that list refuse to do, rather they would prefer to take the list's host word for it) and to not necessarily take the web info granted.

Quote
What did I learn from that debate? In high resolution inkjet prints, the most obvious problem was the breakdown of smooth gradients in the reflections in sheetmetal (cars). Even after a single, strong curve had been applied, banding was easily visible. In heavily detailed stuff (i.e., bushes and plants in a landscape) it was impossible to detect problems caused by one applied curve.
[a href=\"index.php?act=findpost&pid=151091\"][{POST_SNAPBACK}][/a]

I have no arguments with that take (its similar to mine). So what about posting to the list your findings and let's see how long it takes for that to get moderated or dismissed.

My only point about all this is the link to this list (Color Theory) is useful if you want to find a place to argue with fundamentalist flat earth, non intelligent design moderators and hosts who's actual agenda isn't to discuss either color theory or imaging facts (the high bit math is undeniable).

The reason I posted the link to Lindbloom, who IS a color scientist is to point out the silliness of both this particular Yahoo list and host and his lame arguments with respect to high bit editing. Don't even get me started on his views about wide gamut spaces or Raw processing. That's even more prehistoric in mindset.
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Andrew Rodney
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Scott_Eaton
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« Reply #10 on: November 13, 2007, 08:38:39 PM »
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Missing the point.

Andrew is going to *love* hearing from me, but we're missing some logical points here at the expense of arguing about quasi_applied post processing that's not dealing with the aquisition stage. Given a properly profiled scan from a device of known good caliber only a fool would argue that there's no advantage to the better data assigned via 16 -vs- 8 bits. If I'm paying somebody $50 for a drum scan of a 6x7 chrome, he'd *better* deliver something that has more than 8-bits per channel.

Color me wrong (sorry for the bad pun), but how many desktop scanners out there scan in a *legitimate* 16-bit greyscale (intensity) levels? 'Greyscale' to many desktop scanners really means:

(1) scan in color - sloppily
(2) convert to monochrome -via- a process worse than you can accomplish in Photoshop.
(3) invent those extra bits to fit into Photoshop's 16-bit preferred image space.

Essentially it's not much different than using a dSLR with the absurd 'monochrome' feature and then converting to a 16-bit working space when there wasn't 16-bits of data per channel to begin with.

So a more important question would be the difference between 8-bit and 16-bit *if* you aren't scanning native 16-bits per channel. Obviously if you have a device that can aquire 16-bits of greyscale (or color) native, then sticking to 16/48-bit file at least for initial editing is obvious and there is no arguement to the contrary. Andrew is dead right on this.

However, 48-bit desktop scanners aren't the norm, many that are 48-bit capable essentially hack it from cheaper A/D components, and while a 16-bit greyscale file can certainly take more editing than an 8-bit one, is this really a question dealing with processing and not really dependant on the scanner? Epson flatbed scanners now seem to be able to handle 48-bit scans. Many Nikon scanners however are only able to scan at less than 48-bits. So, please convince me that the Epson makes a better scan simply because of the larger bit depth that is only psuedo-native in the first place.

Also, a film scanner *is* a digital camera, and all analogies apply. However, if my dSLR can't map 48-bits, and my film scanner can't map 48-bits, why is it more important for the film scanner to produce 16/48 file even if it can't do so native?

Also, I've been scanning junk film on good scanners and had to 'wing' my own profiles for too many years to NOT emphasize that quality of aquisition during scanning trumps all other considerations. Proper mapping of the density range of film via a good profile will yield a more workable scan at 8-bits per channel than a 16-bit per channel scan from a badly nurfed black point. If we go back to the dSLR analogy, a RAW capture gives you more data to work with, but only a bit more wiggle room on the exposure ends (over/under). If you can't expose properly in the first place, RAW isn't going to save your skin for long.

My advice on this has not changed in over a decade and it doesn't now. Get a good film profile, and/or learn to set white/black points properly. *Then* scan at the maximum data level of the scanner, 24, 36, 48-bits, with a *color* film profile to a 16-bit space in Photoshop. Convert the resulting file to monochrome in PS and *then* apply your tonal curve. Unless Andrew can convince me otherwise, I don't see the benefit to scanning at 8 vs 16 bit greyscale when you should be scanning with *all* the color bits and capturing all the data the scanner is capable of.
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TylerB
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« Reply #11 on: November 17, 2007, 11:48:28 AM »
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actually it's even more important in B&W, since it's only one channel. In color, the other two channels can sometimes mask tonal/level loss and banding in one.
A 16 bit single channel image is smaller then the equivalent size 8 bit color image in terms of file size anyway, hardly difficult to deal with and not worth the risk.
I get a lot of 8 bit B&W files here to print, very often problematic.
Tyler
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