Hello again,
First of all, many thanks for all your contributions.
Phew, what can I say - I am learning a lot!
If by "correct" you mean "not a misread", then repeating the set of measurements in a different order, and then checking the delta E's between the data sets is one way of doing this.
Yes, this was exactly my primary aim.
Patchtool is also a good product and can easily create (and provide metrics on the result) a set of patches across a printer's gamut with a desired stepping in L*, a* and b*. Quite handy to test round tripping with.
Could you explain the term 'round tripping' to me in this context?
Sure, reference vs. measured is one metric but what you really want in most cases is to compare the measured color with the predicted color from the profile or the round trip as discussed below, using a technique defined by Bruce Fraser, the idea outlined in a PDF I produced awhile ago.
Many thanks for providing the link. I've not had time yet to really study the document, I will need a bit more time to try and digest it.
... then test your profile by printing a target of known values to see whether it is allowing you to print accurately enough for your needs.
By 'known values', do you mean print it one of the recognised printer test files? Or is there a file available you can recommend. Maybe there isn't, because if I understood Andrew's document correctly, the first steps are all about creating the 'known values'.
Well, I have now completed the profile. And with a bit of fun with dE calculations and euclidean distances, I am pretty sure, that the profile does not contain any measurement errors.
So far so good. Next, I've printed a test image - I'm sure you're all familiar with it. It's the one with the boat, the fish, the coloured fabric and Bill Atkinson's balls.
There are issues. The colour is pretty good, apart from Cyan. There is quite heavy banding with all colours, there seems to an abrupt switch from 'dark' to 'light'. That's maybe not surprising since my printer doesn't have any Light Black inks.
Btw, my printer is an Epson SC-P 400 and the paper I am profiling is an Innova 315gms Soft Textured Bright White Cotton paper.
I have attached a picture of these balls. Now I know that it's rare to get a perfect print of these balls, since it's so taxing. And looking at the pictures included with the test file, I am pretty happy with the result.
But my question is:
Looking at the attached picture, where do you see the opportunity to optimise the profile? As I said, I'm well aware that my printer may have certain limitations I won't be able to overcome. I struggle to interpret the resulting print a little - how good or bad is what I am seeing?
Secondly, what would be the suggested workflow to improve or optimise an existing profile? I read about linearisation for b&w profiles, but what would you do for a colour profile? Is there a way to improve my existing profile?
Kind regards
Andy