Mike, the most common densitometers can read either color OR B&W. In the color mode, surprise, one of the readings will use a built-in blue filter. This ought to work for your negs, but you'd probably have to make your own "fudge factors" since it won't have identical response to the paper you're printing on.(posted 9122 days ago)If you make friends at your local 1-hour lab, they probably have a densitometer they'll either let you use or take the readings for you. You are interested in what would be called either the "yellow reading" or the "blue filter reading" (they are the same thing). If they don't know what that means, give them a piece of clear yellow plastic (like a candy wrapper) and ask them to take "Red, green and blue" readings on it. One of the three numbers will be lots higher than the other two; THAT is the setup you want them to use.
Feel free to email me if you need more info!