Real color scientists, who make sure that food dyes look best under TL84 (supermarket fluorescents) while paints for exterior decoration come to life in D65 (daylight) have until now hidden away in research labs or quality control departments.
That is about the change thanks to one small, low-cost instrument developed by California imaging software company Light Source Computer Imaging Inc, prototyped a year ago at Seybold San Francisco.
Colortron is a 32-band digital spectrophotometer selling for under
$1,000 complete with a comprehensive (click here for a full 21" screen
dithered GIF - the only way we can get it to work, sorry, almost 500Kb) Macintosh program suite. The Mac takes over
all the calculations - the reading head, resembling Apple's QuickTake
camera but smaller, just sends data via the ADB keyboard/mouse cable.
Portable devices from companies like Gretag and Minolta were introduced in the early 1990s at prices from $6,000 to $25,000 with no loss of accuracy or precision. A hand-held pulsed xenon (flash) spectrophotometer like the Minolta CM-2002 at around $15,000 can take readings from actual surfaces on location - BMW Rover car paintwork is one example - and store, display and calculate vital functions without needing a computer connection.
Lightsource's Colortron uses similar principles. A diffraction grating
scans the spectrum across a single calibrated CCD sensor in 32 steps (the
grating pivots between each step to place a different exact part of the
spectrum over the CCD sensor) to cover visible light from 380nm to 700nm
in 10nm steps. Instead of flash
illumination, Colortron uses a burst of continuous tungsten light. This
gives it a unique feature, dragged average reading; place it on an
unevenly colored surface like denim, pull it along, and get a reading
which describes the overall look of the color. The software also
auto-averages unlimited numbers of 'spot' readings, useful for
characterising printing inks when the press gives different densities
across the sheet.
Colortron comes with an excellent manual including a primer on basic color science, written with wit and erudition, up-to-date and accurate. That's almost unheard-of in an industry which mostly uses a standard based on subjective visual assessments by seventeen volunteers recorded in 1928.
Does this make it another cumbersome bench tool? Yes, for hundreds of readings in a short time; no, for typical litho printing ink measurement, plastics, fabric dyes, desktop printer calibration and similar jobs involving a few dozen readings at the most.
Its built-in cells recharge overnight from the Mac's keyboard cable (ADB), or in 1-4 hours using a 9V 300mA adaptor. A full charge claims around 350-500 reflected light readings but we found 40-70 more realistic; it's supposed to improve with use. Transmission readings on a lightbox can run into hundreds. Colortron has special control software to prevent it using battery power from a host PowerBook, which will be a common situation when readings in factories or on presses are called for.
In this form as a location kit, the cost is once again going to be around $4,000 - the same as a basic hand-held device - but includes a top of the line color PowerBook with many other uses. Colortron adds to any color desktop Mac system most of the capabilities of a $40,000 benchtop spectrophotometer for only $1,000. College lecturers we have shown it to think its small size and light construction would invite loss or damage, and prefer to keep old bolted-down bench machines while deeply coveting Colortron for personal ownership and use!
For the creative user, the software is far friendlier than scientific or applied packages. Colortron can measure a sample and tell you the closest Pantone ink or CMYK mix to use. It can build new color libraries, usable in PageMaker, XPress or Photoshop. It can 'tween' to produce a shade between two samples, or suggest a set of harmonising colors based on any one. Try some more harmonies... then more...!
It replaces the standard Apple Color Picker with an advanced version which you can install on any machine, and use in most applications. This picker offers selection by CMYK sliders, a vital feature missing from the earlier Apple version, and HSL, or from a palette of saved readings from samples. Colortron also includes the latest version of Apple's ColorSync and will integrate with color management systems using this in future - which means EfiColor, Agfa FotoFlow, Kodak CMS, Daystar ColorMatch, Tektronix TekColor and many more.
Because it reads spectral data, it can predict visual appearance under
different lighting conditions and show this on screen; it can calculate
color difference between two samples (below) using standard equations. It is easy to copy CIELab,
CIELuv, xyY, XYZ, HSB, or RGB readings to spreadsheets, graphing or
word-processing programs. Any three of these values can be displayed and
copied simultaneously.
It has gamut warnings, creates CMYK ink sets by manual entry in Photoshop or other applications, and will calibrate imagesetter films, replacing a densitometer. A monitor calibration utility and reading head is being shipped on return of the registration card, so it also replaces devices of this kind.
We checked out one printer's performance by printing a set of color patches in a regular magazine run. The inks were way down on density compared to Photoshop's standards, and had significantly different colors.
The system can be used for software-resident press calibration, on a variety of levels from Photoshop ink sets to downloadable imagesetter transfer functions. As it normally costs $7,000 to profile a press for EfiColor or similar matching systems, you can be sure Colortron will be verbally trashed from several directions whose newly-discovered revenue sources are threatened.
However, after a month of use and comparison with ICS, Hunter, Philips, Macbeth and Minolta spectrophotometers, we found the accuracy and consistency of the device to be just as high. Its failings do not lie in precision, accuracy or repeatability.
Here are key criticisms of Colortron:
First of all, non-interchangeable sealed-in nicad cells are not ideal. They charge slowly, have limited capacity, suffer from inertia and memory effects, and end up under-performing if the device is not in constant use. If it is, they fade after 1-2,000 recharges. The 2-4 hour 'quick' charging time is too long to break off between readings. When left charging all the time the device never seems to run out of juice, but a big potential use of Colortron is on PowerBook on location.
Colortron needs user-changeable cells so you can charge one set while using another, or direct 9v adaptor power independent of the battery state. If it had this feature, you could hook it up to a Quantum battery on your belt and use it all day.
Secondly, the reading head supplied is flimsy and hard to position correctly, being opaque and obscuring a clear view of the exact 3mm square involved. We would also like to see a kind of pouch or stand, to protect what is a fairly fragile instrument when left standing on your desk.
Finally, the calibration 'tablet' provided is a rip-off - it may be printed to the standards of the Graphic Communications Association, but a laminated bit of paper costing $75.00 to replace once a year smacks of XPress-style exploitation of customer dependence.
A ceramic white reference tile would cost no more and lasts a lifetime. The black calibration procedure - "simply hold the unit under your desk and point it away from yourself" is sound but a little agricultural. How do they know what's under your desk?
One use we tried out was to create a complete color palette of the full swatch of Colorama photo studio seamless background papers! Here is the complete swatch:
You can save a palette like this for use on PM, Xpress, Illustrator etc - you just import the EPS file, and the colors appear. We have saved this EPS in PHOTON's folder. Try clicking here for a Stuffit file or here for the eps. Maybe you'll be able to save this small file and use it! Our copy of Netscape saves the file inside our Mac's System folder even though it appears to do nothing. The graphic may appear just as a small symbol below, or fail to read, but inside this file are all those color values in CMYK.
We obtained our unit in advance of main UK shipping, by ordering last August from Light Source Computer Images Inc, Larkspur, California; it was delivered on January 4th and had to go back by FedEx a month later for repair after developing a fault, a procedure involving customs re-invoicing and considerable hassle from the British authorities, still unresolved in June 1995. The repair was efficient and very rapid, the documented notes on the fault were courteous and comprehensive, and the unit was back in use within five days in perfect order. However, a local region/country distributor and service department is essential given the obstructive UK bureaucratic procedures for an international repair return.
The new UK importer-distributor is Computers Unlimited; the US price we paid was $999 plus shipping, which worked out at £750 pounds after paying duty and non-recoverable VAT. The UK price is now fixed at be £895 + VAT before discounts, so Colortron has a similar actual cost in Europe to its dollar price.
This feature has a joint byline, by the way, because Shirley is guardian of our Colorton and has the know-how to assess its performance. She's doing a Masters Degree in Color Science and works with bench instruments all the time. Her Colortron readings are all bang in the middle of the variation between several (very expensive) bench systems.
