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>All the Nikon F3 screens with split-image have the same bright in the >ground-glass part.
Well, actually, there are two versions of F3 screens (the ones with the
small red dot at the edge of the frame are a tad brighter than those
without), or three, if you count the F4 screens which will fit the F3,
and which are a tad brighter yet.
>The type G screen is brighter than every screen with split-image.
The G screens are clear, with Fresnel lens, and a microprism center.
Since there is no ground-glass, focus is impractical except with
the (for me, poor) microprism, and DOF cannot be checked. Also, I do
not find these screens appreciably brighter than the ground-glass screens.
>But, wich is the difference between G No. 1, 2, 3 and 4 types ?.
The G1-G4 types fit different lenses, but not in a clear short-to-long
order (there are many overlaps and exceptions).
>Wich is the best G screen for a f/3.8 to f/5.6 zoom lens (28-200mm) ?.
Probably none - my choice would be the B or E, since I hate "focusing
aids".
>Could I have problems with this type G screen with a f/2 or f/1.4 >lenses ?.
Not if you select the one that matches (probably the G2).
>The depth-field check is not good with type G screen ?.
Correct.
>Is a good choice use the type C screen with a f/1.4 lens ?. What
>about with the f/5.6 lens ?.
The C is matte with a clear center with cross-hair, intended for
paralax focusing very dark images from telescopes, microscopes, etc.
I would not recommend this screen for general use. (I have one to sell...;-)
>Is the type B screen brighter than a K type ?. What about the B screen >with f/1.4 & f/5.6 lens ?.
The B, E, K, etc. of a given series all have the same ground-glass screen surface, which works well for a wide range of lens speeds and focal-lengths. The B and E work well for me for lenses from 8mm to
700mm, and from f1.2 to f11. Most of the other screens I would consider
special-use screens.
Hope This Helps