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Author Topic: My grayscale tester  (Read 1373 times)

Robcat

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My grayscale tester
« on: April 17, 2011, 01:45:32 pm »

As I was working on separating some dark tones on some new images this morning, I pulled up a grayscale tester I made a while back. Not that there aren't a lot our there, but I haven't seen any quite like this and thought some of you might find it interesting and/or useful.

The tester has bars of different gray values withnumbers printed over them. The numbers represent the r, g and b values of that number and go up by 2s. For example, the first bar, "0," has r, g and b values of 0,0,0 (pure black) and has printed over it numbers from 0 to 40; the "2" has rgb of 2,2,2 the "4" rgb of 4,4,4 and so on.

I find this a bit more informative than step scales and gradients as you can see more than one level against another and also know the actual rgb value.

My new, calibrated NEC 3090 monitor shows + and - 2 ok  until the ends of the scale. At the white end it's about +/- 4, and near pure black, 8 is the lowest number I can distinguish on a 0,0,0 bar. When I print (custom profile), one of the more interesting things (at least to me  :)) is the difference lighting makes. In normal gallery light, the lowest number I can see on pure black is 14, however, in bright sunlight, I can see 6. Similar, but smaller, differences exist at other values. Not too surprising, I suppose but a reminder that you have to print for the destination lighting.

Anyway, I've attached a jpg of it for those who might want to play. I don't cover the full grayscale (it was a bit annoying to make, plus I figured the main issues would arise at the ends of the scale).

Rob P
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bill t.

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Re: My grayscale tester
« Reply #1 on: April 17, 2011, 02:23:43 pm »

I like those!  The hardest PP issue (for me) is keeping texture in the dark tones, and what could be a better physical model than wiggly little shapes like numbers!

And 14 is about my minimum threshold for textural detail to reliably emerge out of the murk on a canvas print in gallery lighting, sames as you're getting.  Has something to do with gamma 2.2, methinks.  On my 2690 screen I can just barely see "6" mainly because I know where to look.  "4" is invisible.  Nice idea, rather elegant.  BTW takes a custom print profile for me to get that "14" range on a print, the manufacturer's printer profile signs off in the high 20's.
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Robcat

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Re: My grayscale tester
« Reply #2 on: April 17, 2011, 06:21:42 pm »

Quote
BTW takes a custom print profile for me to get that "14" range on a print, the manufacturer's printer profile signs off in the high 20's.
yeah, isn't that wild? There's a whole lot happening below 20 (and 12 for that matter) and it's the devil to get it on a print. At least we can get right up to paper white.
Rob P
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Ernst Dinkla

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Re: My grayscale tester
« Reply #3 on: April 18, 2011, 02:59:01 am »

Rob,

What is the PPI resolution of the target you use in practice and the width of the character elements in pixels?


met vriendelijke groeten, Ernst


New: Spectral plots of +250 inkjet papers:

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
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Robcat

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Re: My grayscale tester
« Reply #4 on: April 18, 2011, 09:35:13 pm »

What is the PPI resolution of the target you use in practice and the width of the character elements in pixels?
Hi Ernst,
I have the target at 300 PPI, with the file 2550 x 3300. I'm sorry I do not know what the character element pixel size is, as I simply specified a font size (20 point).
Rob P
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Ernst Dinkla

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Re: My grayscale tester
« Reply #5 on: April 19, 2011, 03:11:57 am »

Rob,

Resolution targets to test printer/paper/media preset combinations usually are aimed at the native printer resolution, that could be 300/600 PPI for HPs and Canons and 360/720 PPI for Epsons. That way resampling in the driver (or application in some cases) can be avoided and the print result tells more about the actual resolution / texture possible with that combination of printer/paper/media preset. If you also have the smallest detail (say the serifs of the characters) at a 1 pixel size for each choice of PPI target the total becomes more critical for the test.

I like the idea of the greyscale numbering within the greyscale patches. It extends on some greyscale target additions for bleeding/detail check I have made in the past:
http://www.pigment-print.com/Quad%20QTR/Index.html
When possible maximum tone ranges are discussed in B&W printing, 8-bit, 16 bit, 255 steps, etc, the knowledge is often based on step wedges and nice patches for the densitometer/spectrometer readings, patches that are big enough to avoid bleeding within the area. In practice shadow detail can be as small as 1 pixel within a 720 PPI printed image, not white within black but just a shade lighter than black, enough ink together there to loose that detail.

met vriendelijke groeten, Ernst

Try: http://groups.yahoo.com/group/Wide_Inkjet_Printers/

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artobest

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Re: My grayscale tester
« Reply #6 on: April 20, 2011, 08:32:21 am »

I love it. Beautifully elegant and so informative.
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