Taking the pulse of your colours

This is a new, comprehensive colour management tool from one of the major players in the field (some would hold the major player in the field!). X-Rite have been slow to join the "lower end" party but seem to have benefited from their late start with a product which has none of the wrinkles exhibited by its competitors.

Colour

The Concept

This is a profiling kit, which enables the user to profile their entire workflow from camera and scanner through their monitor and out to their output device.The greatest improvement you are likely to see is in your inkjet output and within that, your monochrome neutrality. In round figures you can expect to improve your colour error by a factor of between 100% and 500% using a bespoke profile.The size of this improvement depends largely on where you start. Whilst the Epson large format printers such as the 4000, 7600 and 9600 are "D2" machines with a manufacturing tolerance of 2 delta E, if you ply them with fine art papers from a variety of sources you will need more control than you can achieve without a profile. For desktop printers (of all makes) you can expect larger variations and it is a matter of luck where your machine falls in the overall population statistics. However, in our experience, even the most wildly behaved machine will be brought to heel with a bespoke profile!

The profiling process works in the same manner for all devices. You measure a set of colours, compare them to a standard set and then build a profile, which pulls the colours into the right spot. The measurement may be made with a spectrophotometer or a colorimeter. The former is best for print profiling, the latter is best for screen calibration; some systems use only one, a bit of a compromise. Pulse uses both. For a printer profile, you print a target (usually between 1 and 5 sheets of A4) let it dry and then measure it. The number of colour patches you measure affects the precision of the profile - more patches are usually better. In order to measure typically 729 patches the spectro must pass over the patches in the correct order, dwelling over each for sufficient time for measurements to be made at about 10 wavelengths. Traditionally this has been done with sophisticated x-y tables or roller-driven transport systems. One of the major cost savers with Pulse is that transport has been taken over by the operator's hands - which comes free of charge! In order to assist, a cradle has been designed which constrains the spectro to run along a line of patches and (cleverly) measures the speed of movement so that the natural slowing of the arm at the end of the travel does not fool the system. No doubt the advances in electronic and the speed of data transfer of USB 2 have allowed this method to be employed. The system is even clever enough to enable you to traverse in either direction and to go back and fill in missed lines of patches.

In Use

The software is a dream to use; it could not be simpler. Just in case you have not seen it done, there is even a video clip explaining how to push the spectro up and down. The profile building is entirely wizard driven; you simply do as you are told, when you are told! You start by making a single A4 sheet of 343 patches or, for more precision, 2 A4 sheets of 729 patches. You then allow the prints to dry.Dye inks need to be left over night, pigment inks (e.g. Epson Ultrachrome) are instant dry, but we usually give them 10 minutes or so to be sure.

The prints are stood on a couple of sheets of the same stock if they are thin, so that the colour of the bench does not interfere with the readings. Art papers are thick enough not to need this precaution. The plastic cradle is positioned over the ID strip and measured first. Then, each row is measured by clicking the spectro button, waiting for the beep then running it smoothly along the strip. A reassuring beep tells you the row has been captured and the on-screen display is also changed to show it has been measured.You then move down a strip and repeat the process until you get to the end. You are then prompted to make and name your profile, which is automatically placed in the correct location. It really is that simple!

The spectro takes its power from a powered USB 2 port, which also charges the on-board battery. There is sufficient battery capacity and memory to make 10 profiles with the spectro untethered. This makes it easier to handle and also allows for shop floor measurements to be made. Then, when you return to the host computer you simply transfer your data and build you profiles in the usual way.

Performance

We tested Pulse against the very much more expensive X-Rite DTP41 and Monaco Profiler and against Monaco EZcolor, using our colour audit process as the arbiter of quality and accuracy. Be alert to the fact that most profiling software reports a colour average error after profile making. This is a measure of the compromises that the mathematics has had to make to fit the patches into their positions and a value of 0.5 to 0.9 is normal. This is not the same value as that which you obtain by running the profile out into a real print where the values are more typically 4 to 8 on the same Lab Delta E scale. It is this latter measurement we concentrated on for that is where the rubber hits the road! We built profiles from the same printer using the same paper stock and then ran the audit prints through our calibrated DTP 41 spectro.

The results from Pulse were impressive. Consecutive profile builds produced print errors within a couple of hundredths of a point of each other and the difference between the Pulse and DTP 41 was no more than a few tenths of a point. We chose to test on a new paper from Konica, which has the highest loading of brighteners we have measured, a severe test indeed for the uv rejection filtering of the Pulse system. Results from EZcolor were inferior to Pulse and the price difference is well worth paying if the output is for professional use. The issue we have with EZcolor is that you employ your scanner as a colour measuring device.This leaves you at the mercy of scanner metamerism, which pigment inkjet prints are particularly susceptible to.

Examining and Adjusting profiles

The Monaco software with the Pulse enables the user to examine their profiles and gamuts in detail and compare one with another. Profiles may also be adjusted to give you an extra little precision (or preference - remember the print that looks best is the best!).This is one area where the Pulse software is cut down from the high-end siblings from Monaco, you have slightly less capable adjustment facilities. However with the ability to adjust for red, green, blue, lightness or saturation curves, the professional user is unlikely to find themselves short of control. Only pre-press professionals on high value work would have the time to tweak more than this and even then only if they were experts.

Below The X-Rite DTP41 in operation checking out the prints made using a profile from Pulse. x rite

Input profiling

Profile

Input profiles are made for cameras and scanners. The concept is the same as that for printer profiles, you compare a scan or camera image against a known, standard target and the profile forces your image to be like the standard.There are a number of standard targets, the best known of which are the Macbeth 24 Swatch Color Checker and the IT8 (reflective). The Pulse is supplied with an IT8 target, for our own scanner work we prefer the more accurate IT8 version available from Nova Darkrooms which is created and measured to a higher standard. For camera work we use the 24 Swatch Color Checker. Pulse is able to work with the Colour Checker, the Color Checker DC and the Color Checker SG - the last two are more complex and more expensive. Although the IT8 reflective target may be used to profile cameras we do not like its reflective properties for use in the studio. The simpler, 24 Swatch Color Checker has acquired a reputation for producing more accurate profiles than its more expensive cousins!

The composite image shown illustrates the improvement obtained by making a profile specifically for a camera set up (and remember the lighting and camera setting have to stay constant!). The adjustment of the whole gamut produces greater overall accuracy. The monochrome tone scale was 7 Lab points too blue-cyan before application of the profile and within 1 point of neutral afterwards.The tone level was 14% too dark before profiling exactly correct afterwards. The speed at which you can profile a camera makes it feasible to profile studio product shots every time. For wedding work our preference would remain with using RAW files and correcting a Macbeth shot occasionally.

For the scanner profiling we used the Nova Darkroom IT8 target. With a scanner target you are either supplied a data file on disc or you can visit (for example) the Kodak web site and pull the relevant one down. This is where the Wolf Faust (i.e. Nova) targets have the edge because they are controlled to a closer tolerance than that demanded by the ISO standard. The process is simple to use. You scan the target with all colour adjustments turned off and then save a TIFF file with no profile tagged. When prompted by the Pulse wizard, you navigate to this TIFF file and also to the data file, which you have precopied into the Preferences folder of Pulse. Assuming your target is the right way up Pulse finds the marker points and positions itself automatically to take the measurements. You then build the profile and assign it in Photoshop to correct all future scans. Both transparency and reflective targets may be scanned although only a reflective target is provided in the kit. If you are new to colour management you need to know that it is not possible to calibrate for negatives, so don't even think about it!

Conclusion Part 1

We like Pulse a lot! It is well thought out, easy to use and accurate. If you are at Focus make sure you go and see it at either the Colour Confidence stand or the Bodoni Systems stand. We will report on the monitor calibrator next issue.

Key Points · Patch sizes are small, giving less wastage and faster profiling · Intelligent strip identification and speed adjustment · High repeatability · High accuracy · Remote, un-tethered use · Comprehensive camera, scanner, monitor, printer and RIP abilities · Good Profile Adjustment tools · Good gamut display · Absolute simplicity of use In Part 2 we look at the monitor calibration device and software.

Macbeth chart

Scanner Profiler

Profile adjustment

Photo Quote: Simply look with perceptive eyes at the world about you, and trust to your own reactions and convictions. Ask yourself: "Does this subject move me to feel, think and dream? Can I visualize a print - my own personal statement of what I feel and want to convey - from the subject before me? - Ansel Adams