Frédéric wrote:
I would like to know if there are some free hardware profiler projects (for CRT/LCD)?
In France there is something to calibrate video-projectors; it is not designed to generate ICC profiles, but I was wondering if it could be supported by Argyllcms ? Or do you know other projects like this one which could be supported ?
Link to the french project:
http://www.homecinema-fr.com/colorimetre
It looks like an interesting project. The key is the sensor, which seems both an accessible (via Farnell), and convenient colorimetric sensor (as long as you fit the Hoya CM500 filter to it! - though these seem harder to obtain than the sensor itself.).
Of course I'd be a bit surprised if it meets the Luther condition (is equivalent to a CIE observer), but it is possible to compensate for this to some degree if the spectral characteristics of the display are roughly known.
They mention the software is GPL, but then it also says "The associated sources and other files will be issued later.", so it's unclear whether the PIC micro source is under GPL or not.
Ignoring the above project for the moment, the biggest hassles in creating a display colorimeter based on such a device are:
Programming a single chip micro to do the sensor to USB interface. Most of these micros are still at the 8 bit assembler level, and it's often relatively expensive to do a one off setup for programming them the development kits are typically one to a few hundred dollars).
Creating and producing suitable PCBs (Printed Circuit Boards) (Hmm. I think I have a copy of Protel somewhere, and it wouldn't take too much effort to remember how to use it.)
Creating suitable mechanical arrangements to house the sensor. It would need to be something easy to do, yet would have to provide the necessary functionality. A mass producable approach would involve getting injection moulding setup (an relatively expensive step.)
Calibrating the sensor is expensive to do properly. It would be simple enough to calibrate it against some other commercial display colorimeters, but to make it a first class device, means that you need a good, laboratory standard instrument to measure it against (and all the other associated standards). Any reputable commercial display measuring instrument will have been individually calibrated against some better standard (rather than relying on the manufacturing tolerance of the sensor.)
An attempt to manufacture such a thing and sell it, would quickly run into some regulatory red tape. The main ones would be RFI regulations, and safety regulations (e.g. UL). These are not insurmountable, but would require a business to take responsibility for the product, and getting such approvals costs money. Selling a kit may avoid some of these issues.
None of the above is insurmountable given suitable enthusiasm, and there are plenty of cost vs. quality trade-offs that can be made, depending on ones goals.
Perhaps adapting the French colorimetre project might be simplest, if critical parts were available in kit form (ie. the PCB) ?
I didn't really see any reference to kit availability on the French web pages, but perhaps I missed it.
Graeme Gill.
