[argyllcms] Re: Amount of patches
- From: Pascal de Bruijn <pmjdebruijn@xxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 24 Apr 2009 12:44:23 +0200
On Fri, Apr 24, 2009 at 2:19 AM, Graeme Gill <graeme@xxxxxxxxxxxxx> wrote:
> Pascal de Bruijn wrote:
>>
>> So my basic question would be, is there a "logical" "sensible" amount
>> of patches to read for creating a matrix profile?
>
> Generally fewer patches are needed for the more restricted behavior
> model based type profiles, such as gamma/matrix or shaper/matrix.
>
> At its most basic, it comes down to the number of parameters a model has.
> Ideally you need at least as many measurements (numbers) as there are free
> parameters to the model. For gamma/matrix that's something
> like 12 parameters, so a small number of patches may be sufficient.
>
> But in reality, the readings are not noise free (not perfectly
> accurate), and you may want the simple model to represent the
> average of the device behavior over its gamut, so you need to sample
> the devices behavior over its whole range of values to get an average
> and reduce the influence of inaccuracy in each measurement. Past
> a certain point though, the differences will get less and less
> (the point of diminishing returns). This number will depend
> on the profile model chosen and the behavior of the device.
This seem to make sense. I've had decent results with as little as 29
patches. Didn't really try any less.
After looking at some other software, like GretagMacbeth's
ProfileMaker, which uses 99 patches, which takes about 2 minutes to
measure with Argyll and my Huey, so I think I'm going to use that from
now on. It's fast, and using more patches does gain me accuracy.
Thanks for your insights,
Pascal de Bruijn
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