So the contrast range isn't as great?
Actually, it's greater. Multigrade offers Grades 00 to 5, while graded papers normally offer 1 to 5 at most. But Grade 5 paper still delivers a tiny bit more contrast than VC Grade 5. Some printers keep a box of Grade 5 for this very reason: it keeps for years.
How do the filters work?
The easiest route is a dedicated VC black and white head for your enlarger. Most use dial-in filters that give different contrast grades with constant exposure. This allows you to dial in Grade 13/5 or 33/4 or whatever you want, normally with a minimum grade of 0. Another sort uses a special cold cathode head with two tubes, blue and green, the output of which can be varied independently to create the various grades.
The next choice is a set of filters in half-grade rests, from 00 to 5. These are available in above-the-lens and under-the-lens qualities, again with constant exposure as you change grade. At the extreme ends of the contrast range, a 0 filter may be significantly softer than dialed in, while 5 is normally slightly harder.
These filters are designed to work with tungsten light sources, and may work poorly if at all with cold cathode heads, many of which tend to deliver disproportionately high amounts of blue light.
The third choice is to use a color head. Dialing in yellow gives more contrast; dialing in magenta gives less. For convenience, many photographers use both yellow and magenta, increasing one as they decrease the other, to give constant exposure as they change grades. Again, you can dial in any grade you want. Most color heads cannot duplicate the contrast range of a dedicated VC head, let alone discrete filters: the grade range may only run from 0 to 4 or 41/2.
A fourth choice is to use two filters, 00 and 5, making part of the exposure through one, and part through the other. It doesn't matter whether you use yellow and magenta or the less usual blue and green. This is economical and allows full control across the widest possible contrast range, right out to 00 and 5, but exposure determination on changing grades is tricky and there are no other advantages across the middle range of grades.
What is "split-grade" printing?
This term is used in two ways. One is when you expose different parts of the print through different filtration, to boost or reduce contrast locally. The other is when you use two filters for the same exposure, as described immediately above.
Despite what some people say, this does "not" expose the highlights and the shadows at different contrast grades. Within the limits of the filtration system (in other words, after allowing for deficiencies at the extremes, as noted earlier), it is always possible to choose a single dial-in filter setting that will exactly duplicate the effect of exposing through two filters. It's just that some people find it easier to visualize with two filters.
Are all manufacturers' grades the same?
No. One maker's Grade 2 may be detectably harder or softer than another's. The only thing that is certain is that it will be harder than the same maker's Grade 1 but softer than his Grade 3.
What is ISO(R)?
This is a means of comparing different manufacturers' contrast grades in absolute terms. It is the logarithm of the exposure range required to give a full tonal range, expressed to two significant figures, with the decimal point removed. Typical figures might be Grade 5 = ISO(R) 40 to 45; Grade 4 = ISO(R) 60 to 70; Grade 3 = ISO(R) 80 to 90; Grade 2 = ISO(R) 100 to 110; Grade 1 = ISO(R) 120 to 130; Grade 0 = ISO(R) 140 to 150; Grade 00 = ISO(R) 160 to 180.
Can I influence contrast via developer choice?
Yes. Some print developers can add up to about half a grade of contrast. Others can wipe off as much as a full grade. Such developers will also change overall tonal relationships, and whether you like the effect or not is a matter of personal preference.
How do I choose the right contrast grade?
Make a work print, at your best guess for both paper grade and exposure. Develop it fully, for the manufacturer's recommended time and temperature. "Snatched" prints (pulled before they are fully developed) are no guide at all. They will have poor maximum blacks along with reduced contrast.
If your fully developed print is too contrasty, switch to a softer grade. If it looks flat and dull, switch to a harder grade. Remember that an underexposed (light) print often looks too contrasty, while an overexposed (dark) print often looks too flat and dull, so if changing grade alone doesn't do it, changing exposure may. A good printer may make half a dozen or more prints, gradually refining both contrast and exposure as well as dodging and burning local areas, in order to get the best possible final print.