B&W paper materials have no real burden in terms of grain and sharpness for a variety of reasons, and therefore silver laydown is in the range of 50 - 150 mg of Silver / sq. ft. Some papers go as high as 300 using the same units. These so-called silver rich papers waste silver because the technology to get high density from low silver is difficult. Color paper runs in the same range.

B&W films need speed, grain and sharpness and these require lots of Silver! So, they use about 150 to 300 mg / ft sq. Color films may use 300 - 900 depending on these factors.

The density formed depends on the following reactions:

4 Ag + 1 coupler = 1 dye (4 equivalent coupler)
2 Aa + 1 coupler = 1 dye (2 equivalent coupler) < these are mainly in use today!

To go one step further though, the dye has an extinction coefficient or in simple terms, how much bang for the buck! How many moles of dye are needed to get to a given density. The lower the "E" (actually it is Epsilon), the more silver and coupler needed to get a given density. These must be calculated for every coupller / developer pair.

So there, something new for today. You see what a little reading can lead to? You can end up making the wrong statement. Sorry. Please do not equate paper coatings with film coatings ever! Same goes for paper vs film emulsions. These are different areas entirely. And, BTW, I worked with Grant on these types of coatings.

PE