I'm shooting 35mm color neg because I have no darkroom now, and until my
35mm scanner quit acting rationally I could easily scan color negative.
Now, it seems to like b&w only. On the other hand, I could scan either
paper or film in larger sizes, but the big scanner doesn't calibrate to
the orange color of the negative film. Since I'm working with Antiques
(7 years old!) these issues may not apply to your situation.
It used to be that we always shot color transparency whenever
reproduction was an issue. I really don't think it matters much anymore,
since scanning has become universal. I will be ready to hear what others
have to say about this.
I like negative films better because they are somewhat more flexible and
certainly more forgiving. Transparency films can rapidly run out of
range even in ordinary situations. Since you will be using pinhole and
under extreme low light conditions to boot -- i.e. in cathedrals -- with
the attendent reciprocity anomalies, negative films seem to me to be the
choice. I have used transparency films in similar circumstances, in the
Olympic rain forest. The test sheet I sent out to the lab had come back
with a form stating that I had ruined the film, and that the lab would
not take any responsibility for my stupidity. What I had to do, I would
not recommend to you; I tray developed E6 with a carbonate bath (like
water bath, but much more effective) on the first developer, a sheet at a
time, BY INSPECTION, having first desensitized with pinacryptol. It
worked great, but it took days to get the job done, and tank after tank
of hot water.
To expect that using a negative film will solve the problems you will
encounter would be unrealistic, but it may help.
What I've said here does not particularly address the issues of using the
film as original for alt-process work. Somehow, it seems to me that the
more important issues here are the general ones relating to how you are
going to come home with useable images. It seems to me that if you have
good quality originals, either positive or negative, you should be able
to work with them. If you don't have good quality negatives, Ireland is
an expensive reshoot.
Larry Bullis
Skagit Valley College