Did you know? D65 light source, does it refer to the morning sun? Or the afternoon sun?

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Date：2021-01-04

Laboratory color, is there a difference between morning and afternoon sunlight?

【Printing and Dyeing Learning and Exchange】It is learned that the international standard light source box is divided into two types: domestic light source box and imported light source color comparison box. The imported light source box is expensive, with high accuracy of calibration, mainly for large enterprises and enterprises with strict color requirements. The domestic standard color comparison box is cheap in price and suitable for most small enterprises. Because,For printing and dyeing plants, choosing the source of light is a very important thing!Let's look at the following analysis:

Standard light source lamp box use parameters

The standard light source color box is usually a combination of multiple light sources,helping users to simulate sunlight with D65, D50, and simulating the lighting of the store display hall with TL84, CWF, U30,as well as home lighting F, INCA, horizontal sunlight HORIZON, ultraviolet lamp UV, etc., each light source corresponds to different parameters.

Source name	Color temperature (K)	Tone	RGB	Please note
A	2856			Incandescent lamp/tungsten
B	4874			Midday sun shines directly
C	6774			Average/North Sky Daylight
D50	5003			Light on the horizon
D55	5503			Morning/afternoon sunshine
D65	6504			Midday Sunlight: Television, sRGB Color Space
D75	7504			Daylight in the northern sky
E	5454			Equal energy
F1	6430			Sunlight fluorescence
F2	4230			Cool white fluorescence
F3	3450			White fluorescence
F4	2940			Warm white fluorescence
F5	6350			Sunlight fluorescence
F6	4150			Lite white fluorescence
F7	6500			D65 Simulator, Daylight Simulator
F8	5000			D50 Simulator, Forest City F40 Design 50
F9	4150			Cool white luxury glow
F10	5000			Philips TL85, Ultralume 50
Season	4000			Philips TL84, Ultralume 40
F12	3000			Philips TL83, Ultralume 30

A light source:Color temperature of 2845K, equivalent to the light radiated by an incandescent lamp at 2800K.

B light source:The related color temperature is 4800K, which is equivalent to the sunlight at noon.

C light source:The related color temperature is 6700K, which is equivalent to the natural light of the day, it has more blue components.

D65 light source:the related color temperature is 6500K, which is equivalent to the average illumination of the day, in recent years, it is often used as the standard light source for color television.

E light source:Also known as the equal energy white light, i.e., P(l )= constant, it is a hypothetical light source that does not actually exist. It is used purely to simplify the calculations in colorimetry, and its correlated color temperature is 550K.

F seriesLuminous bodies represent a variety of types of fluorescent illumination.

Different color temperatures result in different light colors.

Different light sources have different color temperatures, resulting in different light colors and different feelings:

Color temperature	Luminous color	Feeling
<3000K	Warm (with red white)	Solid, warm
3000－5000K	Middle (white)	Satisfactory
>5000K	Cool type (white with blue)	Cold

Some people think that the preference for color temperature is individual, which is related to the scenery we see in our daily life, for example, people near the equator, the average color temperature of the scenery they see every day is 11000K (8000K (dusk) ~ 17000K (noon)), so they prefer high color temperature (looking more realistic), on the contrary, people in higher latitudes (average color temperature is about 6000K) prefer low color temperature (5600K or 6500K), that is to say, if you use a high color temperature TV to show the scenery of the Arctic, it will look blue; on the contrary, if you use a low color temperature TV to watch the subtropical scenery, you will feel a bit red.

Colors are usually observed under daylight, so in the industrial production of fine color matching work,the lighting source must have a spectrum power distribution close to the real sunlight, that is, the CIE specified D65 standard light source,D65 standard light source box is also a color matching box with a large market demand.

However, during the color matching process, there is a very special phenomenon:The samples and test samples will appear to be the same color under *** light source, but under another light source, they will show a color difference, which is known as the phenomenon of the same color but different spectra.

If you are producing a large number of color products in your own light environment and fail to eliminate the problem of the same color and different spectra, when customers have objections in a thousand different light environments,complaints and even returns may occur, and trouble and loss are inevitable.

Therefore, when you need to test the metameric effect with "A" light source before determining the color or issuing the production order, to ensure peace of mind.

Use the color comparison light box to observe the angle

The textile printing and dyeing industry, the use of color matching is ***more is the color matching light box, the method of use is improper, resulting in users to appear in the color matching color light deviation,How to make different observers observe the color light consistent under the light box?

So we need to use the color light box correctly according to the standard, which can be started from 9 aspects.

Observation angle

The following items are all the facilities that must be equipped with standard color comparison light boxes, and the viewing angle will also directly affect the evaluation results. According to international standards, there are only two viewing angles that can be used, they are:

Zero degree light source, 45 degree observation (0 °-45 °) i.e. the light source is incident on the sample at zero degree (vertical) and the observer observes the sample from 45 degree.

Light source, 45 °斜台

45 degree light source, zero degree observation (0 °-45 °), in this arrangement a specific 45 degree斜台 (45 angle table) must be used to direct the light source at 45 degrees onto the sample, and the observer views the sample from zero degrees (vertical).

45° light source detection sample placement position

No matter which of the above observation methods is used, it must be noted that the test sample is placed as much as possible in the middle of the light box to reduce the influence of external light sources.

Also, ***it is important not to overlap the items when comparing the colors of two or more items***, ***i.e.***, place them side by side in the same box for comparison.

Light box maintenance

A perfect maintenance plan is needed to ensure that the light box remains in standard condition for a long time: 1. Be careful when using it and do not stain the inner wall of the light box; 2. If there are stains or paint peeling, personnel should be sent to correct or replace the inner wall panels immediately, and it is necessary to regularly check the use or brightness of the tubes, etc.

Requirements for environmental factors during the execution of the color

All extraneous light that has the opportunity to fall on the inspection sample must be avoided as much as possible, and if there is a window in the line of sight, it should also be covered with a gray curtain to screen it, so the use of a color light box in a dark room is *** ideal. One more point that is often overlooked is that the color light box must never be placed with other miscellaneous items.

Have the function of testing the color-matching effect.

The so-called colorimetry effect is to show that under a certain light source, the color of the sample is the same as the requirement, but under another light source, the color difference can not be accepted. Under the D65 light source, the color is no different from the standard, but under the A light source, the color of the sample can not be accepted. Therefore, all equipment for color matching must be equipped with two or more light sources to test the colorimetry effect.

Requirements for changing the light source

Based on the daily life experience, in our eyes, it is like having a register, when the color changes in an extremely short time, we can clearly feel it. Therefore, when observing the same color with different spectra, if we want to change the light source, it must be completed in an instant, and it is absolutely not allowed to be like the ordinary lighting tubes we use, which will shine after flashing, because this will stimulate the eyes and affect the evaluation results.

Record the time the standard tubes have been used

All standard color matching light sources are also produced by tubes or lamps, and the manufacturers will also list the quality of their products within acceptable tolerances for a period of time. Therefore, an accurate time recorder is indispensable. These tubes are usually replaced if used for more than 2000 hours or one year.

Ultraviolet light source

Due to the widespread use of fluorescent and brightening dyes in the current industrial world, and the fact that the only reliable method to detect such effects is to use a non-ultraviolet light source, it is imperative not to favor any particular area.

The position of the tubes

Although there is no specific requirement for the arrangement position of the tubes, the position of the distribution must be such that there is a uniform light source within the color-proof box, and it is absolutely not allowed to be biased towards a certain area.

Other matters: The placement of the test samples. Regardless of which color inspection method is used, it is necessary to ensure that the test samples are placed as close as possible to the center of the color comparison box to minimize the influence of other light sources in the room. Additionally, it is **ABSOLUTELY** important to avoid overlapping items when comparing the colors of two or more objects, instead, they should be placed side by side in the color comparison box for comparison. After inspecting the samples with the color comparison box, it is necessary to press the ON/OFF key, and if not in use for a long time, the power switch of the color comparison box should be turned off.

Maintenance and repair of color light boxes

1. No miscellaneous items are allowed to be placed inside the color light box to avoid damaging the inner wall's neutral gray, which could lead to color matching errors.

2. Do not start the tube too frequently, otherwise it will affect the life of the tube.

3. The distribution of various light sources within the body must be installed according to the "Light Tube Distribution Map" to obtain a uniform and sufficient light source.

4. Do not place heat-retaining materials on the top of the light box to allow the heat generated by the electronic ballast to be dissipated in time, extending its life.

5. Check whether the power supply is live or check whether the fuse below the power supply socket of the body is damaged, if the start button does not respond when the power supply is connected.

6. If the tube flickers, please check whether the tube is properly installed or check whether the electronic ballast is stable.

Light box maintenance

The color box needs maintenance, especially the imported color box, which can cost 50,000 or 100,000. Only with proper daily maintenance can the color box remain in standard condition for a long time. For example, when using the color box daily, be careful not to stain the inner wall of the color box. If there are any stains or paint peeling, *** should send personnel to correct or replace the inner wall panel in time. Check the usage time or brightness of the tubes inside the color box from time to time.