InstrumentSpotlight eXact

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We are starting our series of instrument reviews with the instrument we have most recently added to our Maxwell Client and Curve4 supported instruments. It also has the singular faculty of prompting your spell checkers to redline. This is the eXact by X-Rite (small e, capital X).

The eXact by X-Rite


This is a superior measuring device that measures spectral wavelengths and returns density readings, L*a*b readings, or outputs the spectral measurements through software. What you get with a top-notch instrument like this is very accurate, very consistent readings. There are different “models” of the eXact available, from a basic unit that only supplies density, to the full-featured model that includes scanning and bluetooth wireless connectivity. These range in price from around $4300 to over $8000. It has what’s been called a “clamshell” form factor - the spot to be measured is aligned in the aiming reticle in the bottom plate, and then the top, main section of the instrument, is pressed or folded down to meet the bottom plate and take the measurement.


Contents

History

X-Rite has a long history of making quality spectrophotometers and spectrodensitometers. The company had a series of acquisitions where they absorbed Monaco, GretagMacbeth and Pantone, along with the instruments those companies produced. Eventually X-Rite had a slew of spectros with overlapping features and different model names. (504, 508, 518, 520, 528, 530, 552, 938, 939, 960, 962, 964… I’m sure I’m missing some…) In 2012 X-Rite came out with the eXact which was designed to replace all of those earlier models.

This kind of instrument has traditionally been used alongside a press to get solid ink densities, and perhaps Lab readings. The more basic versions of the eXact certainly continue to provide those functions well, but the addition of the scanning capability has the potential to make this one of the most accurate profiling instruments you can buy.

Charts

When used to take spot measurements, the eXact obviously does not require any specific chart arrangements. You aim and measure any individual color you want on any normal, printed sheet.

For an additional price, a scanning feature can be added to the eXact. The instrument is fastened into a rolling cradle, and it can be rolled across a sheet, scanning an entire row of colored patches at a time. The original intent seems to be for scanning a long row of color bars, and the software X-Rite provides for extracting measurement data when scanning (DataMeasure) is suited for that purpose.

Now, in addition, this scanning feature makes it possible to scan entire targets. Anything from 2-3 row control strips to multipage profiling targets can be scanned, although the DataMeasure software would be pretty cumbersome for this purpose. More on that below.

We have added support for the eXact to the measurement modules in the Maxwell Client and Curve4. In either of these apps, scanning with an eXact is as easy to set up as any other handheld instrument. We can even make use of target definition reference files that were made for other instruments. So you can use your scanning eXact to measure an i1Pro chart, or an iSis chart - or even a chart made for a Barbieri instrument.


Measurement Modes

Depending on the model, the eXact can scan in M0, M1 & M2 modes, or all four M-modes: M0, M1, M2, and M3. Visit colorwiki.com for more information on these measurement modes.

When in strip scanning mode, an interesting extra step is that the instrument wants a separate measurement of the white point at the beginning of a measurement session for M0, M2 and M3 measurements.

At CHROMiX, we have been beating the drum for years for hardware makers to include the ability to make polarized measurements. The polarizer aids in making wet ink vs. dry ink comparisons. When making printer profiles, we have found that polarized measurements can draw out more detail in the shadows of matte papers and fabrics. So it is nice to see that M3 is included in this feature set.

In our research with the eXact and comparable instruments, it is possible to get inconsistent readings with M3 measurements depending on the orientation of the instrument on some materials. So we recommend that the user position the instrument on the substrate the same way every time.

Speed

Making a series of single measurements is not something that requires a lot of speed. That is good, because the action of pointing and then pressing the unit down to take the measurement is not as fast as some other devices that make single measurements a breeze.

In our testing, we were able to scan in strip mode a 300 patch P2P target in about 1 minute, using the measurement module in Curve4. This is scan time alone, which does not include calibration time, or time to launch software, place reference files, etc. This is in the ballpark of other row-scanning handhelds such as the i1Pro. However, the action of scanning is slightly more cumbersome than instruments that are originally designed for the purpose. There is no “ruler” to guide the instrument in its track across the page. (If your purpose is to scan long color bars, then this is a benefit.) On the cradle, a half inch of black line acts as a pointer with which to guide its path down a row. There are rollers on the bottom of the cradle, and that helps guide the unit in a straight line across the page. The unit is larger and heavier than other handhelds.

Still, if you are an intrepid learner of new things, you can catch on to the unique way in which this unit scans.

If scanning is going to be a big part of your use for the eXact, the fundamental accuracy of the instrument cannot compensate for poor scanning technique that might capture other colors outside the row down which you are leading the instrument. You must also be sure to use realistically-sized patches based on the aperture of your instrument. Don’t use a 6 mm-apertured instrument to measure 7 mm patches, for example.


Additional spectral bands as measured by an iSis. (Illustration courtesy of Maxwell)
Notice the missing spectral bands at the extremities as measured by an eXact. (Illustration courtesy of Maxwell)


Accuracy

If you hail from the market segment that trusts the i1Pro to be the pinnacle of accuracy, you might wonder what the eXact does that an i1Pro does not do. Aside from M3 measurements, some sophisticated on-board calculations, Bluetooth capability and on-screen results - the real answer is accuracy. The specs for this instrument show that repeatability of measurement on a white tile is 0.05 deltaEab, and the maximum difference between different instruments is 0.45 deltaEab. These are such small differences that they don’t even come close to being detectable by the human eye. The eXact can take advantage of X-Rite’s NetProfiler software which helps readings from this instrument align with those from other instruments.

Aperture

The eXact can be purchased with aperture sizes of 1.5 mm, 2 mm, 4 mm, and 6 mm. These are fixed aperture sizes and cannot be changed. A larger aperture size will tend to give a more complete sampling of the printed color than a narrower sampler area, so it’s recommended to use a larger size if possible. - especially when measuring printing with larger dots.

Wireless

Most models of the eXact can can be ordered with Bluetooth capability. So within the limited range of Bluetooth, you can take your eXact to many places a tethered spectro can’t go. Here, I am thinking of more than just going out on the floor and getting spot Lab measurements off the back of the display. With some CHROMiX software, you can be measuring proof pass/fail strips on a printer within Bluetooth range, and get the pass/fail result or other metric results on the eXact’s own display immediately after measuring.

Software

X-Rite offers some free, basic software for using the eXact to measure and save the results. DataCatcher works with spot measurements only and allows the writing of data to a text file or a spreadsheet program like Excel. DataMeasure allows the scanning of a strip or a series of strips. It does not use a predefined reference file, so the page parameters for each chart arrangement need to be defined manually in the software. For example, the eXact requires the physical length of the strip (or the patch width) to be entered in order to scan. This is different from other handhelds. Also, it exports data into a .csv format for use in Excel. This works fine for most press-side uses. If you are measuring a profiling target (which is a little outside of its intended use), further manipulations need to happen in order to get the data into the CGATS text form that profiling packages want to see.

Operation of the eXact in spot or scanning mode is much, much easier using Maxwell Client or Curve4 - especially if you already have charts and reference files that you use with other instruments. You need to be a Maxwell customer in order to use the Maxwell Client software for the long term. It can measure RGB or CMYK targets. Curve4 is limited to CMYK targets only. The Maxwell Client will also display the resulting metrics on the eXact’s touchscreen display at the end of the measurement, in addition to displaying them in the Maxwell Client and uploading the data to Maxwell online.


How many nanometers?

The eXact follows the precedent of earlier models by limiting its spectral sampling to 400nm to 700nm. Other instruments (even those currently sold by X-Rite) have a wider spectral sampling of from 380 - 730 nm. It’s good to be aware of this in case you go looking for spectral bands and are puzzled when you can’t find them. Here is an illustration of the spectral signature of a white patch measured with an eXact. Compare that with a similar measurement from an iSis. Whether or not this is a problem is up for debate in the industry. The presence of the lower bands can aid in detecting optical brighteners in paper. At the same time, the eXact seems to do a very good job of taking consistent, accurate readings even without the “extra” bands.


Wrap up

If you get a model with all the bells and whistles, you can have a very highly accurate spectrophotometer that can take spot measurements or scan entire targets - in all four scanning modes - and do this all wirelessly. When checking pass / fail status of control bars on a sheet that is still on a press, you can do this remotely, wirelessly and receive the status of your measurement right on the screen of the eXact. It is a bit pricey if you are just thinking of measuring profiling targets. However, those familiar with press-side spectrodensitometers, won’t be shocked by the price, and should be very happy with the performance of an eXact.

See the eXact in action in this YouTube video.


Comparable instruments:
X-Rite i1Pro
Techkon Spectrodens
Konica Minolta FD-5, FD-7


Thanks for reading,


Patrick Herold
CHROMiX

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