QTR-Quadtone RIP

Jon's curves assume Gray Gamma 2.2 input files. Roy's curves assume linear input files. Two fundamentally different approaches using the same tool (Quad Tone RIP).

Terry.

> On Feb 8, 2015, at 8:00 AM, brian_downunda@yahoo.com [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
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> I'm coming to this a bit late.  I'm on Windows (7) and so don't yet have the issues with the measure tool that Mac users seem to have.
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> I'm replying because I wanted to take issue with Roy's post.  I think that he and Jon Cone mean different things when they talk about linearising a curve, and especially a piezo K7 curve, where we only have the .quad file.
> 
> When Jon says linear, he means a straight line through the luminosity readings.  I don't believe that this is what Roy means.  Over the years I've seen him talk about perceptually linear.  I'm not sure precisely what that means, but I guess it has something to do with a screen to print match.
> 
> In order to illustrate my concerns, I did as Roy suggested.  Here is a linearisation check of my R1900 using EEM.  The chart is from a spreadsheet that Jon Cone has on his support site to plot linearisation.  Readings are taken using an i1 Phot! o.
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> View image: EEM linearisation 1
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> View image: EEM linearisation 1
> http://postimg.org/image/eqxa2vqut/ Link copy to clipboard http://s10.postimg.org/qssnx103d/EEM_linearisation_1.jpg Direct Link copy to clipboard &n! bsp;
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>  
> 
> So I created an ICC profile from these results and then converted the 21x4 chart from GG2.2 to the ICC and reprinted and remeasured to see just how li! near it was.  This is what I got:
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> View image: EEM linearisation 2
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> View image: EEM linearisation 2   
> http://postimg.org/image/pb77lgvcl/ Link copy to clipboard http://s10.postimg.org/ebm09v4xl/EEM_linearisation_2.jpg Direc t Link copy to clipboard  
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>  
> 
> It has evened things out, but it's not linear in the sense that Jon Cone means it - it is linear in some other (percept ual?) sense.  If you pay Jon his $99 for a custom profile what yo! u'd get is a plot that tracked the straight pink line.  I.e. the L values falling on a straight line.
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> So my question is, is there a way to linearise the .quad file like this?  I.e. Like Jon does?
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> Michael King seems to have a way.  I don't fully understand it.  I have used spreadsheets in the past to tweak quad files, so what I'd really like to know is his methodology.  (I've used them to lower the ink load for papers that were too thin to take what the K7 curve was laying down.)
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> Another way that I've been playing with today is to create a Photoshop curve that is the exact inverse plot of the linearisation data after converting to the ICC in the second image.  I.e. so that it straightens out the grey line so that it lies right on top of the pink.  So you convert to the ICC to remove the wriggles, and then you apply the PS curve to linearise.  It should be possible in theory.  I've had p! artial success - the top 80% is now straight, but the darkest 20% isn't.  I need to check and play further.
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> So I am interested in Michael's appraoch.  Incidentally Michael, I recall your discussion with Jon 6+ years ago.  I took a copy and still read it occasionally.
> 
> B.
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> [If those images don't persist where I uploaded them, then I find somewhere else.p
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> 
> ---In QuadtoneRIP@yahoogroups.com, <roy@...> wrote :
> 
> For those on Mac's instead of trying to re-linearize K7 .quad files which is hard to do,
> go the ICC route.  Just create a custom grayscale ICC built on top of the existing .quad file.
> Then print using this ICC.  It has the same affect as relinearizing the curve plus you get the
> color-management system matching the embedded profile in your image.  This is 
> t he best/ideal way to get screen-to-print matching assuming you are pro! filing your monitor.
> Note that you really have to use Print-Tool on the Mac to get this all to work correctly.
> 
> The MeasureTool issue is still a pain -- I run Parallels on the Mac with WinXP running so
> I run MT on that.
> 
> PCs can do this too but you've got to do your ICC conversions in Photoshop before
> sending to QTRgui for printing.  (most people seem to go the No CM route on PCs I think).
> 
> Roy
> 
> -- 
> Roy Harrington
> roy@...
> www.harrington.com
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>