The problems inherent in the wet plate process meant that Brady's studio had to be proficient in pencil retouching, and also in making a copy of the finished work. Many times, defects could be corrected by retouching and copying. Thus, when one looks at a historic photo, the question often arises "which negative was really the original." The photographer would often scratch some identification on the edge of the negative. Pass your mouse over the above image to see some differences, note the second one is much higher in contrast. It bears the scratched in legend " Effect of Explosion of a shell at Fredericksburg" Some history books
also show a highly retouched version of the above photo with clear pencil work.
Many important negatives were in terrible shape due to poor storage, some were lost and broken, some even used as a widow glass after emulsions were scraped off! Scratches and defects were often due to poor handling later, and were not present in the original work.

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