Print them Ken - and have a careful look at tonal gradations - the stepping effects which cause posterisation are very difficult to discern on a screen, but are usually very clear on prints...Originally Posted by Ken Lee
Print them Ken - and have a careful look at tonal gradations - the stepping effects which cause posterisation are very difficult to discern on a screen, but are usually very clear on prints...
Last edited by Don Hutton; 8-Dec-2009 at 20:13.
Will do. It will have to wait until tomorrow AM, but I'll let you know what I see.
Can't wait to hear the results... all of my color prints have been 8 bit, as my lab's lambda printer is limited to 8 bit sRGB.
There is the thing, is it not? The histograms don't lie, but your eyes might!Its the all the fault of histograms you know...
Somebody might want to go back and look at some of my previous messages. I work all the time with 8 bit files that are converted to 16 bit for correction because I have to. My Eversmart Pro makes the analog to digital conversion in 14 bit but will only save the files in 8 bit. So I have learned to know how much I can push the corrections before I get posterization.
Now clearly I am able to do a fair amount of correction on the 8bit > 16 bit files before an artifact like posterization takes place and is visible on the print. But you can see it happen little by little in the histogram, and at some point, the posterization breaks through visually on the image. It is not a question of "if" you will get the posterization, but "when".
BTW, I scan mostly 5X7" B&W negatives with the Eversmart, and typically scan at 2540 spi RGB, which gives a file size of about 650 mb in 8 bit. I convert this to 16 bit RGB and then apply corrections. I can do a lot of corrections on the file, but if it is pushed far enough I will eventually get posterization. I fluid mount most of my scans and noise from grain is very low.
What I have learned from this thread is that I can probably get just as good a scan in Grayscale, which at 2540 spi 8 bit would reduce file size to 215mb, or 430mb converted to 16 bit for processing.
Sandy King
For discussion and information about carbon transfer please visit the carbon group at groups.io
[url]https://groups.io/g/carbon
in PS people refer to curves but in trad printing changing the curve means adjusting contrast. All traditional printers know (at least they should) that if you increase contrast you lose detail and the transitions from one tone to another become more abrupt. Increasing the curve slope in PS does exactly the same. It is a destructive process (although undoable) but has finer control. You don't need a histogram to tell you that or at least you shouldn't.
Before I printed digitally, I printed photochemically (RA4 and B&W). Comparing "wet" RA4 to Lambda, I find that the digital process gives you more plasticity in the tonal range, at the expense of a very small amount of sharpness.
In other words, a photochemical RA4 print will be marginally sharper, but the tonal range is much harder to control. Your adjustments in the darkroom will either be global (subtract 1 point on yellow) or local and non-repeatable (dodge bottom left corner).
Overall, I am more than happy to trade that tiny bit of sharpness for the flexibility of the "Curves" tool. That is just my perspective. 16x20 is the smallest I print.
As for histograms, I think I have proven definitively that they have no direct relationship to image quality. You can have an "empty" histogram (nothing between 0 and 255) and still wind up with a gorgeous print. What matters is the SNR of the file you send to the printer.
Post #50
Am I missing something here? Scan in 8 bit, post process in 16 bit? May as well scan in 16 bit and avoid the discussion altogether. I've never had any problems with posterization with 16 bit scans....I have with 8 bit.....regardless of the resolution of the drum or Imacon Scan. Memory is cheap, hard drives are cheap.....scan to the best of your equipments ability and then all discussions like this become pointless.
Oh, and as I've seen posterization in B&W images from 4000ppi drum scans of 4x5 in 8 bit after adjustments, I know beyond the shadow of a doubt that it's better to scan in 16 bit to start.
Oh, and by the way.....scanners don't scan in "DPI"....they sample the film. So, more accurately, you have PPI or SPI. A scanner can't "dot" an image.....but it can sample it. Printers use dots. Sorry, a pet peeve of mine!
I agree with this.
I have a 8 bit Lambda printer, I use to scan in 8 bit and do my work all in 8bit.
I must be getting old but around 1000 prints ago we decided to scan in 16 bit, and then at the very last stage change into 8bit for printing.
I seem to recall the reason was because at high magnification on glossy prints we were getting some issues with images that had lots of curve adjustment , colour shifts, or over sharpening .** even though we did not see these issues on screen**
I also have a 16 bit ink jet printer, a all 16bit workflow from scan to print,vs a all 8bit workflow scan to print, magnified to 30x40 with little adjustment on glossy stock**Harmon FB inkjet** will ***not show any difference***.
I am not willing to bet the farm that the artifacting we use to see was from 8bit scanning , I am willing to print out bensyverson files. As his observations are interesting .
From practical application we have shifted to 16bit scan for critical prints , maybe the switch was not needed, It would save us a lot of time , but for now this is how we scan.
Most scanner operators I have spoken with have recommended a flat file to keep as much shadow and highlight detail.
Some clients prefer a very ***strong **** look to their prints,, this requires a fairly significant curve adjustment, if done in RGB without a perfect nuetralization a whole can of whoopass will occur.
Our eyes are funny devices and if left for hours on monitors will create magic and eventually everything looks good. Until the next day when all the artifacting shows its head on the print and you say to yourself wtf was I thinking.
I think if your imagery is very ***soft**** without a lot of adjustment then one would never see a difference on monitor or print.
A lambda printer does not care what tag or colour gamut is applied to it.
We print 8bit adobe 1998, srgb , both work.
Posting Permissions
Reply With Quote
Bookmarks