The “5-95%” rule
In a thread on Photography-on-the.net a while ago, someone mentioned reading some advise to set black and white point to 5% and 95% respectively. That’s approximately RGB values (12,12,12) and (242,242,242). Otherwise, shadow and highlight detail would be lost in print.
My first thought was “no way”. After all, white is 255, right? I’d say that’s what printing colormanaged and .icc profiles are for.
I’d accept a bit of a loss, but not thàt much…
So I started to search the web.
One source of the advise was at www.lynda.com: Prepress Essentials by Taz Tally.
He was talking about offset printing. There was also an example about Newsprint. According to that, for a (hypothetical) example where the newspaper press could print a minimum white highlight dot of 20% and a maximum shadow below 80%. The tutorial proceeded to adjust output levels similar to this:
According to the tutorial, you’d be preserving highlight and shadow detail as much as possible for those particular presses.
Yeah, right. What highlights and shadows? They all became midtones…
I’ve taken a black and white image of mine, since that tutorial was also using a b&w image, and adjusted the shadow and highlight values according to that tutorial. The red dots in the middle image represent the picked black and white point.
Negative scan of Popa Chubby in Atak, 1995. Left to right: Original, for “commercial press” and for “newspaper press”:
If I softproof the rightmost image for “Japan Color 2000 Newspaper” (the only “newspaper” profile I could find in PSCS4), it goes to hell in a handbasket…
Frankly, my first thought was the author went nuts.
Then again, this is Lynda.com, right? Maybe I just misunderstood. Or the file was sent straight to the newspaper press? (without color management)
“Desktop Printing Techniques” by Chris Orwig, also on Lynda.com, made one point clearer: The 5 and 95% figures are a starting point, and you should test with your own printer / paper / profile. That makes perfect sense.
He also mentioned “accurate detail” and “relevant white / black detail”, where Taz Tally mentions it, but then sets black and white points that I would let clip: Mr. Orwig is more rational in picking the points he chooses for the color sampler tool. (Not the first highlight appearing, but actually something that you want detail in.)
Okay. Obvious: If you have blown whites, then guess what: They are not meant to show detail. No point in setting a white highlight at (242,242,242) nor a deep black shadow at (12,12,12). But that makes it quite personal: What is “meaningful detail”?
A few “Gotcha’s”
The tutorial then goes on to set the color sampler values to read out as grayscale.
No idea why, and not the best option IMO, since the “gray” readout in the info palette is dependant on the settings in the PS color settings for “Gray”.
And guess what: “Europe general purpose” uses Dot gain 15% where “North America general purpose” uses Dot gain 20% for gray working space. Not a huge difference in this case, but one to know.
Also, why not just use the RGB (or HSB) values? They remain constant whatever color settings. Better yet, use LAB values: They change as the luminance changes: quite a difference between (12,12,12) in sRGB and the same value in AdobeRGB (Give it a try)! So keep in mind your document color space!
The “Gotcha’s” visualised
To demonstrate those issues, here are a few screenshots of 4 color samplers I placed in 4 neutral gray patches of a document (the test print I’ll use later on).
All this also speaks in favour of doing your own tests: Your workflow is probably different from mine, or that of the Lynda.com instructors for that matter. As is your definition of “meaningful detail”.
Let’s stop theorising already!
As easy said as done.
So off to search the web for a test image.
I found this nice test image (and description how to evaluate the print) here
Test print: some thoughts.
I usually use AdobeRGB.
The image is in ProPhotoRGB, which gives the “number” patches a little different meaning: A ProPhotoRGB value of (6,6,6) I can distinguish quite well from pure black. In an AdobeRGB document, I have to look hard. In an sRGB document, it’s quite obvious. Similar, ProPhotoRGB (253,253,253) is less easy to distinguish from pure white to me then the same value in AdobeRGB, while sRGB is easiest. The differences are quite subtle though.
The LAB color pickers came in handy here: I wasn’t going nuts, there is a slight difference.
Now that is cleared up…
Lets get printing
I used the Epson R2880 with Epson Premium Glossy Photo Paper.
Color settings in PSCS2 printing dialog:
Colormanagement off in the printer driver of course.
I used the .icc profile downloaded from the Epson website.
There is one profile provided for that paper. The printer driver however, has a few settings that might influence how much ink is laid down on paper:
Photo – 1440dpi vs. SuperPhoto – 5760dpi and “high speed” on or off.
I decided to use an extra sheer of paper to see what the differences were.
I first printed 5760dpi with High Speed on (since I never turn that off anyway) using Relative colorimetric and Perceptual. Black Point Compensation was turned on.
Relative Colorimetric vs. Perceptual
In this test image, the biggest difference is that Relative Colorimetric was a bit more saturated in red and green, but showed blue a bit more purple. Maybe because of that, purples also look a bit more saturated. Unexpected (to me) was that oranges seemed actually more saturated using Perceptual.
Relative colorimetric (with BPC) has a touch less separation between absolute black and (6,6,6)
The softproof showed all of these differences as well.
So I decided to use Perceptual for the second set of prints: 1440dpi with High Speed on and off.
What were the differences?
Not a heck of a lot. In all “Perceptual” prints (6,6,6) is barely visible. And I do mean barely. Relative colorimetric is a touch darker even: It’s more of a “I think I might see a difference” there. I cannot see (4,4,4) in any of them.
I don’t think I see a visible difference between 1440dpi and 5760 dpi, nor between high speed on or off. Yes, I did use a loupe.
Maybe the absolute black is a tiny bit denser if 5760 or “High Speed off” is used, but frankly, I’m not sure (comparing the two absolute black patches in the top right, holding them right next to each other in good light).
A measuring device would be needed to make sure. This is also the “I think I might want to see a difference” category.
The grayscale image is neutral to my eye. There might be tiny color shifts in the dark patches, but that could be my eyes playing tricks. If you need absolute neutrality you might want to test, but for my uses, the B&W is excellent.
No use in posting (scans of) prints, since you really need to see this for yourself. Take my word on this.
So. What did I learn?
The softproof is surprisingly accurate.
I cannot distinguish anything darker then L=1 (LAB color picker) in print.
I cannot distinguish anything lighter then L=99 (LAB color picker) in print.
That is ProPhotoRGB (6,6,6) and ProPhotoRGB (252,252,252) respectively.
That’s fairly close to what I see on screen on my CRT in the highlights, with a bit loss of detail in the shadows. I might want to compensate for that.
A good way to do that is described in this video by John Paul Caponigro.
If I have an image with very deep and important shadows, I might try a test print. But for my normal (even critical) printing, I can trust the softproof: If I see detail on screen, I’ll see it in print. And I’m not all that concerned about the absolute deepest maximum black. Since I don’t consistently see the difference anyway.
I certainly do not want to limit myself to a brightest highlight of 95% for my inkjet printing. So I’ll take the 95% in the tutorials with a grain of salt. I did find, when examining a random bunch of images I processed using my normal workflow, that most images have meaningful detail at about that value. So the tutorials at Lynda.com are right in a way, but could be more accurate.
I’m still very much in doubt on the “Newspaper Press” image that more or less caused this blogpost however…
If anyone has good info on that, I’m all ears.
Some excellent resources on printing and related stuff:
One Response to “Printing to an Epson R2880. Theory and practice”
July 21st, 2010 at 21:07
Had difficulty printing from my 2880 what i saw on screen. Have an hp lp2475w monitor with spyderpro3 for callibration. Spent many an hour on the net attempting to understand the in/outs of photoshop managing the colours – result was washed out and dull prints no matter what i did or what profile I used next.
Found this site and within an hour of reading and tweaking I had set up the printer to manage the colour and hey presto – I have prints nearly as good as the backlit screen!!! So thank you very much – well appreciated