As with many things we do and discover in life, colorizing black and white images came to me serendipitously, without much forethought or appreciation of the tools and effort required to do something competently. After my retirement from practicing law, I searched for things to do, items to collect, and an enjoyable way to meander through the rest of my life. I knew I liked old images, as shown through my collecting too many century-old lithographic works, eg., cigar box labels, posters and other lithography along the way. As earlier stated, I also knew I appreciated the images that reflected the decades post-Civil War through the 1930's.
So, when I stumbled across a glass negative in an antique store --- the pre-film and pre-digital media for taking photographs invented in 1851--- my interests began to coalesce. But, still, I had no clue about what to do with the glass negatives I was now accumulating. I first had to experience the backbreaking efforts to photograph the glass negatives using my DSLR camera, a tripod with the camera mounted upside down, shooting the negative (placed in a workbench vise) with a light source I mounted looking up through the negative to the camera. Too many hours were spent doing it this way, moving the camera up and down to get closer views and photos of various parts of these mostly 3.25 x 4.25 inch pieces of glass. Why not use a scanner, you ask? Two words: "Too Cheap". I refer you to the little Blurb book I wrote a few years ago to express my wonder and awe over glass negatives and to see how far I have now come. _See, "The Positives of Glass Negatives" at http://store.blurb.com/ebooks/68656-the-positives-of-glass-negatives I now have a wonderful scanner (Epson 10,000 XL) that I use and rationalize buying it for health reasons: to prevent permanently being stuck in a 90 degree angle looking down at the ground for the rest of my life. So, here is the process I now follow to colorize these old images:
Sources for Negatives:
(a) I scour antique malls in any town I pass through for antique glass or film negatives. If they can be found in such places, they are usually tucked away and not readily visible, as they are difficult to display.
(b) Ebay is a "go to" source for these types of negatives, but the good ones are often heavily sought after and often sell for more than I ("Too Cheap") am willing to pay.
(c) For those not interested in owning the original physical embodiment of the image, there are websites, such as the Library of Congress and Shorpy.com that contain a wide variety of wonderful black and white images that can be downloaded. You just need to keep in mind copyright issues and that many internet sources limit the resolution of their images online so that they are of little use if you wish to print your effort in any sizable format.
Preparing and Caring for the Glass Negative:
(a) I clean the non-emulsion side of the glass negative with a spray of distilled water, using a soft cloth to dry it. Conservators will take a soft brush to get dust particles off the emulsion side, but I don't do this step. Why, you ask? Two words: "Too Lazy". Plus, I have found that via Photoshop's Spot Healing Brush and Clone Stamp Tools, I can remove evidence of dust and other blemishes. For a brief history of the glass plate negative and the steps conservators take to preserve them, there are a few resources that provide much better background than I can. See, http://www.webjunction.org/documents/webjunction/The_Preservation_of_Glass_Plate_Negatives.html
Colorizing the Negative:
This is the fun part. I import the negative into programs, such as Adobe Lightroom and Photoshop, as well as various Nik Software tools, such as Silver Efex Pro, Color Efex Pro and Viveza. Then, I use the "infinite monkey theorem" to colorize the image. See, http://en.wikipedia.org/wiki/Infinite_monkey_theorem
I bet you thought I would impart important tips on how to colorize antique black and white negatives, right? Well, since I follow the infinite monkey theorem, I just bang away, with little planning involved and not much memory as to how I got to the end result. The more simple negatives (ones without detailed compositions) take me from one to a couple of hours to get them in a shape I am ready to print or move on. But, negatives with more complex subject matters can take 15 to 20 or more hours of trial and error. So, experiment, experiment, erase, then experiment some more, use the "step back" command a ton, then push on. Soon, you will see your technique improve and the time shorten for obtaining your goals. Then, step back to admire your craft and experience a sense of true satisfaction.