There is probably no need to bracket the exposure. The dynamic range of the paper is much less than your camera. I am not sure what might be accomplished with doing the task as a macro vs. a high quality scan.* I have done it both ways and consider both methods to be adequate and roughly equivalent.
As for your intent to crop an individual out and enlarge to 8x10, I would suggest that what you see on the original is what you will get on the enlargement. It may be possible to get a usable 4x6, but probably no larger.
Steve
* It is possible that the scan quality may be to blame for the softness. High dpi is not the same as high fidelity. Most scanners vastly overstate resolution in the published specifications. As a result, using a macro lens may provide better results, but I would not count on it.
Last edited by stevebrot; 10-21-2016 at 11:53 AM.