Size Matters

Questions, comments and suggestions regarding Phase One P+ series and P series digital camera backs.

Size Matters

Postby damienlovegrove » Fri Nov 12, 2004 5:44 pm

When processing P25 portrait images for printing to 20\"x16\" and larger, I am finding a degree of posterisation in skintone highlights. The images are all shot at 100 ISO and processed to 8 bit tiffs before selective tonal adjustments are made. I'm sure using a 16 bit workflow will help sort the problem although I will probably have to get a G5 to handle the processing.

The point is, eaking out the best quality working solution is somewhat a trial and error process for me at the moment. I am convinced of the potential and want to share my findings. I will for instance be using my Pshop 'film grain' action to add the fine detail missing through lack of noise to produce an analogue look. Unlike adding 'noise' the action I use doesn't speckle the highlights or shadows. Are any of you also shooting skintones and making big prints? What techniques do you use and can we post actions, profiles and workflows to share?

Damien.
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Postby Hugh11 » Thu Dec 08, 2005 8:39 pm

Damien,
About 8 months ago I switched to 16 bit processing and yes I add noise to all images 16x20 and larger. The quality of skin tones using 16 bit are dramatic. Of course i had to go to a G5 to keep from staring at the progess bars on the G4. The noise I add is done with an action: 1. Dup layer 2. Noise 25% uniform 3. 20% opacity on the layer 4. flatten image. The action takes about one or two seconds on a 100mb file. The results look like film, and disguise the slick look one gets when adding a gaussian blur to skin. The noise looks like fine and natural skin pores!

My old mac was a dual 1 gig hz w/ 1.5 mb ram. The G5 is dual 2.5 with 3.5 gigs of ram. On most things is is about 4-10X the speed of the G4. The new quad ought to be about 60% faster than my current computer. enjoy your posts...
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I compared

Postby Jrgen1 » Fri Dec 09, 2005 3:57 pm

Compairing 16bit vs 8bit from my P20 did not show any difference when printed on a Epson4000 with custom profiles on both back and printer...
Maybe I am missing something ???
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Postby Hugh11 » Fri Dec 09, 2005 5:31 pm

Jorgen,
I have no definitive reasons that 16 bit is better than 8, other than my own antidotal experiences. I do know that when I changed to 16 bit, the overall quality of prints leaving our studio improved, and our lab called one day to comment on our prints, and how good they looked. (they had no idea about 16 bit, as I convert all shots to 8bit before sending them to the lab)

If you do most of your adjusting in C1, it might be that adjusting a raw file shot in 16 bit would be lossless if no adjustments are made in photoshop in 8 bit. These are good questions for the more knowledgeable people out there.

I adjust most of my images in photoshop. Final color, curves, levels etc.

One thing you might try (assuming you don't know this). Open a newly developed 8 bit file (C1 file) in photoshop. Adjust the levels or curves, and then look at the histogram before and after. You will see in the before histogram that it is solid, and that in the after it will have gaps. This is called \"combing\" and is missing image data that is lost. In 16 bit, there is no loss. Missing data means a loss of even gradations in the image. This is my understanding, and if I have it all backwards, I'm sure someone out there will let me know.

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Size Matters

Postby Guy G » Wed Dec 21, 2005 4:44 pm

Jorgen,

I am not a technical expert but to sum up what I know editing your file as much as possible in 16 bit mode, whether Raw or Tiff in PS will do the least amount of damage to the data. Raw being the best and 16 bit Tiff being second best. 16 bit files are always converted into 8 bit for printing for as far as I have ever learned there are no printers of any kind that print in 16 bit. So whether you send to your printer an 8 bit or 16 bit file will make no difference in print quality, unless your printer makes further adjustments before going to print.

Guy

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16 bit

Postby David5 » Wed Dec 21, 2005 5:18 pm

There is a printer driver for epson printers called \"Image Print\" which sends the 16 bit data to the printer, I have not used it yet but intend to. I have seen great results from it.
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Sorry guys

Postby Jrgen1 » Wed Dec 21, 2005 10:21 pm

I tested again and there is still no difference between the files.
And Yes I know about the combing effect in histogram, but I can not see any difference when printed on a paper. (I printed a 16x20 inch @ 300dpi)

Quality of light (CRI value) make big difference in color rendition, at least that is what I have experienced. I have thrown all my old strobes away and use Profoto D4 which gives a CRI value of 100/100 compared to a Profoto Compact 600 (3 years old) which have only 95/100. Big difference in colors...
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Postby damienlovegrove » Wed Dec 21, 2005 11:49 pm

One year on with my P25 and I'm really clued up with the 16bit - 8bit issue. The thing is, I tend to lift the contrast and tonal position of the skintones in most of my images, this streach causes 8 bit images to block out in the red chanel. I get contours unless I process to 16 bit and do all my tonal adjustments before droping down to 8 bit. If I'm doing black and white I convert as a 16 bit image then drop to 8 bit before I get going on cloning or patch tool repairs. The final image quality I'm getting is truly fantastic now I know what I'm doing. If you do your tonal adjustments in C1 then there is no need to use 16bit. I really pull my images about in Pshop hence the need for 16 bit.
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