In the printing technology, the color density measurement technology is widely used in the color inspection in the proofing and printing process, the color evaluation of the printed samples, and also in the evaluation of standard inks and color correction equipment in multi-color printing. The term color is used to describe the color saturation of the machine in printing. It depends on the pigment concentration in the ink and the ink layer thickness of the ink. The color density of the solid color patch can be measured with the complementary color filter, but the ink layer The thickness cannot be read directly through the measurement of the filter. All the World are waiting to welcome the Panda, even they never see them face in face, but from TV, from Movie like Kunfu Panda series, all the kids even all adult have a dreams to see the panda and kept them as pets, but we know it is impossible, but you can have a panda plush toys, though it different still, without the body temperature, cant feel their breath and smell, but Still you can get the funny from a panda fluffy toys with price from usd1.00 to usd20.00, the size can from 8cm to 100cm (Real Panda size), I think it trully worthable to have a panda toys when you without time or chance to meet panda face to face, of courses, even you meet with them, kept in memory only by plush, it is best memory we can have...stop waiting, and call us now..panda plush is waiting you in DAC Plush Panda,Plush Animal Panda,Plush Panda Bag,Plush Panda Pillow NINGBO DAC ARTS & CRAFTS COMPANY , http://www.dacpets.com
In printing technology, when viewed from above, the color density is defined as the decimal logarithm of the inverse reflectance or the negative logarithmic value of the reflectance, ie
However, this is just a general expression. In practical applications, it is necessary to measure the density in different spectral ranges according to different purposes. Therefore, the color density can be divided into narrow-band spectral color density, broadband filter color density, and visual density.
D (λ) = lg1 / β (λ) = ï¼ lgβ (λ)
Spectral reflectance β (λ) is the reflectance for monochromatic light with a wavelength of λ, which is equal to the measured sample's spectral radiant intensity Leλ and the ideal matt white material's spectral radiant intensity (Lbλ) under certain conditions proportion.
β (λ) = Leλ / (Leλ) W
Narrow-band measurements increase sensitivity to small changes in density, and they are less like human visual responses than those measured with broadband filters. Narrow band density measurement is mainly used to measure dot gain, overprint, ink layer thickness and ink strength.
The broadband filter color density is the most commonly used density measurement method in the printing industry. It uses standard broadband color filters for measurement. The color density measured by each filter is given by:
DF ï¼ ï¼lg∫LKβ (λ) · S (λ) · S (λ) r · Ï„ (λ) · dλ / ∫LKS (λ) · S (λ) r · Ï„ (λ) · dλ
In the formula: K and L——effective wavelength range, generally 380 ～ 780um;
β (λ) —— The spectral reflectance of the object;
S (λ)-the relative energy distribution of the light source;
S (λ) r——The relative spectral sensitivity of the sensor;
τ (λ) —— The spectral transmittance of the filter.
The measured value of the broadband filter color density does not depend on the absolute value of the optical radiation distribution, but depends on the relative spectral radiation distribution, that is, it is always related to the relative spectral sensitivity of the sensor used for color density measurement and the filter with the spectral transmittance .
Broadband measurement is mainly used to evaluate hue, grayscale, transparency and color correction.
DV ï¼ ï¼lg∫LKβ (λ) · S (λ) · V (λ) · dλ / ∫LKS (λ) · V (λ) · dλ
The visual filter should be used to measure the visual density. The spectral transmittance τ (λ) of the filter and the relative spectral sensitivity S (λ) of the sensor must be combined to simulate the spectral sensitivity V (λ) of the human eye. formula:
τ (λ) ≈V (λ) / S (λ)
The above formula is called Luther condition.
Types of printed color density measurements
1. Spectral narrowband color density
Spectral narrow-band color density is the spectral color density D (λ) measured with a narrow-band filter in the wavelength range of Δλ. D (λ) is the decimal logarithm of the reciprocal of the spectral reflectance, or the negative decimal logarithm of the spectral reflectance . 2. Broadband filter color density
3. Visual density
The visual density DV mainly refers to the density measured on the non-color sample. The definition formula of the visual density is: