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QTR-Linearize-Quad -and- 51-step charts -- not working

QTR-Linearize-Quad -and- 51-step charts -- not working

2015-10-14 by David Lykes Keenan

Is there a known problem with using measurements from a 51-step chart as input (with an associated .quad file) to input to the QTR-Linearize-Quad app?

I'm using the i1PRO and i1Profiler software. I have no problem with 21-step measurement file as input but 51-step input fails with no error message or warnings. It worked once or twice, actually, but fails many more times than not.

I';ve been told that 21, 51, and 100-step charts worked with the app at one time with no problems.

Anyone, anyone??
.
Dave.

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Re: [QuadtoneRIP] QTR-Linearize-Quad -and- 51-step charts -- not working

2015-10-14 by Paul Roark

In general, I think that sometimes the smaller incremental changes of a 51 step test strip interact poorly with the random variations in the paper and the inaccuracies of the rather inexpensive instruments we use to measure the test patches. With a well made profile to start with, a 21-step is usually enough and probably less prone to errors or unwanted artifacts in the final. It's also a way easier target to read and deal with.

I personally like to see a ramp next to the steps. A small glitch that is not seen by a 21-step is often visible as a vertical "line" in the smooth ramp.

I'd guess an averaged read set of something like 3-4 random 21-patterns is the best result for the work (if you use strip readers). See the targets Roy has in the QTR \bin folder.

Paul
www.PaulRoark.com
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On Wed, Oct 14, 2015 at 9:00 AM, David Lykes Keenan ausdlk@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:

Is there a known problem with using measurements from a 51-step chart as input (with an associated .quad file) to input to the QTR-Linearize-Quad app?

I'm using the i1PRO and i1Profiler software. I have no problem with 21-step measurement file as input but 51-step input fails with no error message or warnings. It worked once or twice, actually, but fails many more times than not.

I've been told that 21, 51, and 100-step charts worked with the app at one time with no problems.

Anyone, anyone??
.
Dave.

--
My photography web site
Like my Facebook page
My FAIR WITNESS book released March 2015


Re: QTR-Linearize-Quad -and- 51-step charts -- not working

2015-10-14 by brian_downunda@...

I agree with Paul. I once made a 51x3 image and reference file to average out the variations he speaks of and still use a strip reader. It worked for me, but I think that it resulted in spurious precision. The linearisation plot showed a lot of bumps and wiggles, and this is the sort of thing that can cause the supplementary QTR programs to fail. The 21x4 works for me.


---In QuadtoneRIP@yahoogroups.com, <roark.paul@...> wrote :

In general, I think that sometimes the smaller incremental changes of a 51 step test strip interact poorly with the random variations in the paper and the inaccuracies of the rather inexpensive instruments we use to measure the test patches. With a well made profile to start with, a 21-step is usually enough and probably less prone to errors or unwanted artifacts in the final. It's also a way easier target to read and deal with.


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