True or False:

A negative with an optimal tonal (density) range for contact-printing will also be optimal for enlarging.

false (at least in my experience)

Depends on the medium. Azo, for contact printing, takes a neg with a higher density range than negs to be printed on enlarging paper, either by contact or by projection (and then depending on the light source, you might want a more or less contrasty neg for enlarging), and then negs for some alt processes like platinum or albumen need contrastier negs than Azo.

David,

Firstly - HI! Long time no see :)

I'm testing my exposure/developing methods (of tx400) for ideal densities/tonal range on a given paper. Setting Azo & other complication aside, what I'd like to know is if I can simply contact print my test negative on the paper or if I'd have to enlarge each and every test negative, looking for the desired effect/result? (considering the aim is to obtain enlargement-worthy negs)

Dumbing this down for myself -

If the neg looks great contact-printed on ilford MG Fiber, does that also mean it will look comparable (tonality) when enlarged?

You should be able to get it close enough on the proof sheet to decide what you want to print and to get the print in the ballpark. In general, you need a more contrast for bigger enlargements, and the enlarging light source can make a difference (more contrast needed for diffuse light than for hard light).

So I can safely base my speed/processing decisions on results from contact printed negatives, considering the light source for subsequent enlargement?

Heh.. it'd be nice to somehow state this in empirical terms. Qualitative elements leave me with so much uncertainty.

- purely as an aside, why is it that contrast will drop with increased enlargement?

You just get more light scatter with larger enlargements, so bigger prints often need to be printed at a little higher contrast than smaller prints.

If you have a good contact sheet, with some experience, you should be able to make one good print, and then use the contact sheet to determine your approximate exposure time and contrast grade for subsequent prints based on the exposure and contrast of the first print and by looking at the contact sheet. Meaning, you shouldn't have to make a test strip for every print, but you still might want to tweak every print based on your first attempt. How much you tweak depends on what your goals are.

If the only variable you are changing when going from the contact print to the enlargement is the fact of enlargement, a contact print will be a very good approximate guide to the final result you'll get when you do enlarge. That said, because you are not enlarging at all, the contact print will exhibit the greatest sharpness and overall contrast, because you are getting NO light scattering at all, and you do not have any optical glass creating effects between the negative and the paper. If you are talking about a contact print as a final result vs. an enlargement as a final result, they are two different animals and not really comparable.