What's the difference between Kodak Tri-X 400 and Kodak Tri-X 400 Pan?
I can't seem to find the difference anywhere, are they simply the same just re-branded?
There is none, except the labelling. "Pan" is short for "panchromatic" which means that it can record visible light all the way from blue down to red. Amazing, isn't it? These days, it's the films that don't record the whole visible spectrum that get the special labels, like "ortho" (for "othochromatic" -- they don't record orangey yellows or reds, and can be worked with safely under fairly bright red darkroom lighting). There was even a time when ortho film was special new technology -- the earliest films only recorded blue light, which is why mid-nineteenth century landscapes have white skies.
I would expect that Pan X (or Panchromatic X), if it is still available, would still have "pan" in the name, since X isn't a recognizable brand name.
KODAK TRI-X Pan Film has been replaced by KODAK PROFESSIONAL TRI-X 400 Film / 400TX.
The second hit is about Pro Tri-X 400, and that says:
Compared to KODAK TRI-X Pan and KODAK TRI-X Pan Professional Film, the newer TRI-X 400 and 320 Films may have a slightly different retouching “feel”.
At a quick glance, I notice that the timings in development charts are slightly different. So, it is a slightly different film.
320 Tri X has always been designed for flatter, longer exposure curves and is more sensitive to flare; therefore used for studio, interiors and night time city scapes. It is generally not 'pushed' as is 400TX or TX400. Rather than a 'S' curve, with most developers it exhibits a long flat rise after an initial 'bump'. (I suggest you look at the Kodak professional site, look up Tri-X and see the different fim/developer curves yourself.) Actually, this is rather silly asking here, when Kodak maintains a site, real people you can ask development questions to, and descriptions as to which sides of which film sizes you can reliably dye and retouch. 35mm and 120 size 320TX have been discontinued about 2005; suggest exposure of old stock at 160; 4x5 50 sheets still manufactured and very nice.