Mike Wilde's comments are pretty much my sentiments.
Originally Posted by Mike Wilde
In The Good Old Days, before digital took over the market, I made thousands of internegatives, and by thousands I mean that literally. Most of those were colour, but many were B&W. Most of those were made on the late lamented Super-XX Pan Film, and when that was gone, we switched to T-Max 100. But I have made inegs in the past on Ektapan (also gone) as well as on Plus-X, both the 4x5 pro version as well as the 35mm version. I have a PXP ineg from a very contrasty Kodachrome slide of my parents, made about 1974, and there is excellent shadow and highlight detail. The key is in giving the correct exposure, as well as the correct development for the type of original AND the subject.
The two films which I found gave the best results were Vericolor Internegative Film for colour originals, and Professional Copy Film for B&W originals, although it could be used carefully with colour originals under certain circumstances, as it had only orthochromatic senstivity. Yes, we did get B&W positives from time to time, plus colour transparancies for which large volumes of B&W prints were required, which meant an ineg for a large print run. Both of these materials were similar in that the exposure partially determined the contrast of the image.
Both films had (and this is a bit over-simpliflied) a compound curve, with the top part upswept. This was to provide proper separation in the highlights, which in any positive original, be it B&W or colour, have not only less density, but also less contrast. Overexposure of these films led to excessive contrast, and in the case of Pro Copy, it could not be properly adjusted by reducing development time. The key with both of these films was to have absolutely the correct exposure, and for Pro Copy, the correct development time. For Vericolor Internegatives, you had to have an absolutely mega-in control C-41 process. Errors introduced in the exposure and/or development stages could lead to the technician (me!) leaving the manager's office "chastised." Tests were always the order of the day. Our "standard" development times for our B&W films were a starting point, as development was altered to suit the subject matter AND the material onto which it was to be printed.
It was sometimes necessary to use colour filters to alter the tonal balance in the final B&W print. I remember one job, in which the original was an 8x10 colour transparancy of an aircraft in flight. I made an 8x10 ineg on Super-XX, exposed through, AFAIR, a Wratten 29 filter. The clouds in the final prints "popped out" of the sky, and a logo on the tail of the aircraft, which was red-on-white, stood out in all of its corporate glory!
I tended to avoid thin-emulsion films, such as Panatomic-X, when it was still available, as I found that Plus-X did an excellent job, when a 35mm negative was required. I found the best use for Tech Pan was when an original was so badly faded as to be almost invisible. I copied a 100-year old print on Tech Pan, so badly faded that there was almost nothing there, and developed it for maximum contrast in Dektol, AFAIR. I was amazed at just how much detail was still there, and the customer just loved it!
Get a copy of the Kodak book, if it is still available. It is full of excellent information, and should provide you with a point of departure, even if many of the materials specified (in the 1986 edition I have, at any rate) are no longer available.