Digital BW, The Print

Actually, what does one of your curves do at norm PV = 0.5 in order to get
the 50% step = 0.61 density?  Is it shifted at all?   (128 or 50% if your
prefer)


> From: Steve Kale <stevekale@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Fri, 03 Dec 2004 19:07:03 +0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> Paul
> 
> My answer was based on simple maths as you say defined by the parameters of
> a gamma = 2.2 space such as Gray Gamma 2.2 or even SRGB.  If the monitor and
> printer are properly calibrated this mid point should print with a density
> of 0.61 and match the screen.  Whether people, when looking at the scale,
> would agree that 50% at D = 0.61 or a block of pixels with normalised vales
> of 0.5 displayed on a Gray Gamma 2.2 screen are fair descriptions of "middle
> grey" is entirely different question.
> 
> Ansel defined mid grey at 18% reflectance, decided which part of the scene
> he wanted to have 18% reflectance in the final print and then let all the
> other parts fall where they lay. I haven't been through it yet but it is
> interesting to note on Norman Koren's site (again):
> 
> http://www.normankoren.com/zonesystem.html
> 
> "The charts below are derived from an equation intended to make zone 5 on a
> properly calibrated monitor appear as subjective middle gray‹ about 21% of
> the maximum screen brightness level, similar to middle gray on a print (18%
> reflectance referenced to 90% white). I include the equation in a box near
> the end."
> 
> When you pull up a step wedge on screen and run the cursor over it examining
> the luminance levels you might show D = 61 on screen.  But when it comes to
> printing the Epson driver (without benefit of colorsync) performs a tonal
> compression.  If your curve shifts 50% = 0.61 so that it prints fine, I am
> not sure that a displayed and curve adjusted 50% step is still at pixel
> value 0.5.  (But in my proposed methodology where I have access to the
> inside of the RIP I could be assured that norm PV = 0.5 prints at 0.61
> because any and all tonal adjustments are in my single PS curve.)
> 
> Steve