The XG-M is a 35mm camera. That means it needs "135" format film. The film comes in different lengths ... e.g. 135-24 would mean it's long enough to have 24 exposures. 135-36 means it has enough length for 36 exposures. Generally any 35mm camera can handle up to 36 exposures. I've never heard of a 35mm camera that couldn't. The only reason we had film of different lengths is because if you unwind and process the film before you've taken all the shots then you're just wasting your money. I'd typically carry a few rolls of film of different ISOs or lengths depending on the types of events I'd plan to shoot (btw, ISO was almost always referred to as "ASA" back then, but it's the same thing and even the numbers are the same. 100 ASA is ISO 100.)
Regarding film & filters...
We see in the visible spectrum which is "roughly" from about 400nm up to about 700nm. The UV spectrum starts below 400nm and the IR spectrum starts above 700nm.
The R72 filter is so named because it's cut point is 720nm... it blocks visible light below 720nm but allows IR light above 720nm to pass. That really is the critical detail... you need to make sure that filter is an "IR Pass" filter which blocks normal light. Normally when you find a filter labeled as an IR filter, it's an "IR block" filter which blocks IR and allows visible through (the complete opposite of what he wants for IR photography.)
You can also use a Red #25 filter which is sometimes confusingly named an R25 filter. The "25" in this case is NOT referring to the nanometers like it does in the R72 filter. The proper name is "Red #25". The filter blocks blue & green, but allows red to pass and this causes an enhanced effect. This filter can actually be used with normal visible B&W photography (it's not exclusively for IR photography). Essentially if you use IR film with this filter you're allowing more visible light in and this can help show detail in areas that would be black in shadow with IR film using the R72 filter.
BTW, you can also shoot IR film without using any filter at all.
He should experiment with no filter, Red 25 filter, the R72 filter and compare them. He'll see some contrast enhancement with the Red 25 (as compared to no filter) and a very large contrast enhancement if he uses an R72 filter.
There are lots of film choices with different levels of sensitivity. He'll really need to compare for the "look" he wants.
Go check out this site. They have examples of different films as well as examples using those films with different filters (or even no filter.) Snoop around the links on their Infrared section.
Digitaltruth Photo: Rollei Infrared IR400 film
