It is here necessary to say, that hardly any two persons see alike the same degree of color, so as to be enabled to judge correctly the exact tint, i.e.what one might describe as light rose red, might appear to another as bright or cherry red; consequently, the only rule for the student in Daguerreotype, is to study what appears to him to be the particular tint or shade required to aid him to produce the desired result.

Practise has proved that but a slight variation in the chemical coating, of the Daguerreotype plate will very materially affect the final result.
The operator will proportion the coating of iodine and bromine or accelerators according to the strength and composition of the latter.
Experience proves that the common impressions, iodized to a rather light yellow gold tint, and brought by the bromine to a very light, rose color, have their whites very intense, and their deep shades very black.

It is also known that if you employ a thicker coating of iodine and apply upon it a proportionate tint of bromine, so as to obtain a deep rose tint, delineations will be less marked, and the image have a softer tone.

This effect has been obvious to everyone who has practised the art.

Thus I may observe that the light coatings produce strong contrast of light and shade, and that this contrast grows gradually less, until in the very heavy coating it almost wholly disappears.