AcademyExtras.com
28
Jan

There is a quick and easy way to check your viewing lights using an iOne Pro and iOne Share . This is not a detailed scientific document. It is intended as a simple answer to a common question, “Are your lights correct for color viewing?”

Review:
When we perceive color it is due to three basic components:

  1. Light: the light under which we view an object or the type of light used to illuminate an object. In the graphic arts industry, consistent and controlled light should always be used to illuminate proofs and press sheets.
  2. Object: the surface of an object such as a proof or press sheet that we are viewing. It could be the surface of anything such as a car or the walls of a room.
  3. Observer: you, your eyes, or me and how I uniquely perceive color. One person may see color differently than another.

There is a term used in communicating color: Metameric or sometimes you hear the word Metamerism. When viewing a proof that was printed with Inkjet ink and a press sheet with a different kind of ink, they have their unique spectral differences, yet when viewed under certain light, such as what is referred to as D50 Lighting, and a given observer such as you or me, those two objects, the proof and the press sheet, can be perceived as the same color. When two items with different spectral values communicate the same end color, they are referred to as Metamers or they are Metameric. That is good but it also must be consistent.

The Graphic Arts Industry standard for viewing lights in the United States is D50. That is a fairly specific version of Daylight or 5000 Kelvin. In most cases, those lights are Florescent bulbs. So called, Daylight bulbs can be purchased, even from local hardware stores, but they are not necessarily consistent with Industry Standard D50 lights.

How do you know if you have correct lighting?
One good way is to purchase lights from a graphic arts supply company that get their lights from a reputable light manufacturer who make lights specifically for the graphic arts industry. Request D50 lights, not just Daylight or 5000 Kelvin lights.

Most viewing booths are illuminated with florescent bulbs. (Florescent bulbs produce a “Band Spectrum” i.e. spikes at certain points along the visual spectrum). This is not a blanket statement but in most cases, you will find press consoles and viewing booths to be illuminated with florescent bulbs. If you find your viewing station has Tungsten bulbs, you may want to investigate your specific lamp and bulb type or, if it is not specific to your needs you may want to replace the lamp with something that is known to be correct.

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Quick and Easy Tests
Historically, the quick and easy way to check viewing conditions has been to use a small sticker that is intended to show bands of a darker color if the lights are not D50. I have experienced some problems with that method and have run into problems where the sticker led me to believe the lights were OK, when in fact the stickers did not reflect the actual or accurate output of the lamps.

There is another more sophisticated method that I prefer and have found it to be quite dependable for general viewing in the graphic arts industry.

I like to use an Xrite iOne Pro spectrophotometer in conjunction with Xrite/Gretag iOne Share, an application designed to measure ambient lighting. You can review the tutorials and the instruction under the help menu for the use of iOne Share or you can follow this outline for how to use the system.

The application iOne Share can be found on the iOne Application CD.
Install the application on your laptop computer and connect the iOne device to your computer.
Launch iOne Share.

Review the display as shown below how the application looks when first launched.

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Select the E as shown.
In the Tools list select Light.
Select the icon for the small Light Bulb.
Notice in the upper-right corner the device pointing up with Yellow and no color in the dots.

There should be a Light Measuring Head Packaged with the iOne Pro. It is comprised of two parts, a round cap with a small white/translucent spot in the center (used for light measurements) and a black cover used for calibration.

device

Carefully screw the light measurement head onto the iOne measurement aperture.
Place the black cover on the light measurement head.
Press OK.
That will begin the Calibration procedure. Follow the prompt instructions for OK.

Remove the black cover > Point the device in the direction of the light you want to measure and press the measure button.

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After measuring the light you will see the spectral output on the graph in Red compared to the Default D50 which is in Black. The Default is a theoretical D50 output.

Your measurement of a new viewing light very probably will not align perfectly with the theoretical D50 even if you have a high-end viewing booth with new factory D50 bulbs. It should be close in spectral shape and it should have a high CRI.

You can select the new sample in the Work window and rename it in the space above.

Suggestion:
You can measure new D50 lights that are known to be from a high-end manufacture for the Graphic Arts Indus-try and save that measurement as an actual D50 Reference. Once you have that measurement as a reference you can compare other light measurements to your reference that you know is good.

Using a Custom Reference
Launch iOne Share Go to File > Open – Select and open the saved custom measurement file. You will see the custom measurement in the Work window.
Measure your new light – the light you want to test or compare to a reference.
Both the Custom Reference and the New Sample will show in the Work window.

Click-Drag the custom reference to the left-hand bulb. That graph will turn red.
Click-Drag the new sample to the right-hand bulb, the graph for that sample will turn red and the custom sample will turn black to allow you to see the comparison.

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To save a measurement as a Reference.
After measuring a light source that is known to be good, go to File > Save As.
That measurement file can be opened in the future and used as a good Reference.

Category : :Apogee Color / :Apogee Prepress / Proofing / QMS / Tips & Tricks