[xxyyzz97]

I don't think optical dot gain is something new or no one bring it out in this forum before. There should be many members know about what caused the dot gain.
Attached a pdf, which was posted (by me) in March in one the thread, that was summary of the dot gain explanation published in one of the magazine in late '90.
Franky to said that the ppt content is nothing special. Nowadays density is using more in process control instead of as a printing standard.

[xxyyzz97]

作者: Bloodsaler

我们当年学网点扩大的时候就已经讲过网点扩大包含光学扩大和物理扩大了，这个不是什么新观点了。
我好奇的是爱色丽的测试设备测量的网点扩大时基于密度的，但是好像这个网点扩大分成光学扩大和物理扩大来看这个测试扩大值又太小了~像这类测试设备又是如何平衡这两者之间的关系呢？

Density is a measure of the percentage of reflected light. In printing processes, this usually means the percentage of light that is reflected from the substrate and the ink.
Density = log10 1/Reflectance factor
The Murray-Davies formula for calculating dot gain (the most common method used in densitometers) includes a factor for optical dot gain.
In the 1930s, Murray - the first measurement of dot gain, who related the three quantities—dot area (A), density of the tint (Dt), and solid density (Ds)—in the following equation, known as the Murray-Davies Equation: A = (1-10-Dt) / (1-10-Ds)