Rafal - a note of caution if I may.

A densitometer is a useful tool, but make sure you don't become overly reliant on it when you test your materials. It should go hand in hand with actual printing tests. It is easy to get caught up in densitometer results, only to find in actual photography you're not getting what you wanted - or what you thought you wanted. I've seen this happen to people when they acquire a densitometer and start systematically determining their films speeds, development times for N, N-, N+ etc all based on theory and generally accepted target ranges (example - find a development time that gives a zone VIII net density of 1.2). Then they start making actual negatives and printing them, and find they are not getting the results they expected or wanted.

Don't misunderstand me - I own a densitometer and I'm glad I have it. But, make sure you combine densitometry testing with "field" testing. Test your densitometry results by applying them to photographs, and make prints. Target density values can be good guidelines, but they are far from absolute. One person's N might be another person's N-1, etc.