Dear Board,
I am fairly certain the photographer(s) are at least partly responsible for the observed color changes. The photos of the two Roman provincials (after the coins were expertly cleaned and possibly lightly smoothed), simply do not reflect their true colors, whether it be due to a (green?) filter, photo editing, or some other process. Further support for this view can be found in Lech's observations.
Mark Fox
Michigan
Yes - getting photos of coins that actually show how they look can be difficult. There are numerous variables, any one of which can mess things up if the photographer does not know what (s)he is doing, or how to compensate for the effect it has:
-- artificial light - different
types of bulbs (LED, fluorescent, etc) and the different lighting they produce (daylight, soft yellow, etc).
-- natural light - direction (
north, south, etc), cloudy, sunny, season, time of day, and perhaps latitude . . .
-- angle of coin in relation to the camera -- ideally they ought to be parallel.
-- angle of light source to coin.
-- background color.
-- camera white balance controls (my camera has daylight, incandescent, fluorescent, cloudy, flash, preset manual, auto.) Automatic is not always the best.
-- the amount of background color showing in the viewfinder compared with the amount of coin showing, can confuse the camera's light meter.
-- the proprietary algorithms of the
software used in the various brands of cameras themselves. Some are better than others for coin photography.
-- playing around with the various color controls in your image processing
software.
To show how different photos of the same coin can be, look at the 2 photos below.
The top one is the dealer's photo.
The bottom one is my photo of the same coin, and it shows quite accurately how the coin looks when I have it in hand.