Saturday, May 8, 2010
Post 100 - looking at a very thin negative
According to Land in his 1949 MIT lecture, it seems the thinness of the negative is intentional, because the DTR process when used with nucleating metals or sulphides of metals on the receiver sheet produce agglomerating clusters of particles that photonically represent black, and only a very small amount of silver in the negative is needed to do that. The chain of events during development work like an intensification process.
Similar to carbon nanotubes used as wavelength-specific-recievers, the agglomerated silver blob has to be over a micron in size. That's important to us, as we know for instance that a half micron dot next to another dot the same size and distance tends to look yellow and not black to us, as 0.5 microns corresponds to the yellow portion of the visible spectrum. The photonic effects of particle sizes and controlling them are important to improving things like solar photovoltaic operation that you can read about here. A little larger, perhaps around 0.6 microns, we see start to see reds.
Now go back and look at the the Fuji FP-100B negatives that we have tried to reclaim, and we can get the idea that silver clouds of smaller than 1 micron may be present in some areas, and not in other areas. FP-100B is a very fine grained material. Not so with the above negative of the 3000 speed material, where the coarse grain sizes appear to exceed a micron in size, therefore perfectly monochromatic to us.
Posted by Bob Crowley at 4:46 AM