Thanks for the responses ...

@DHolman - I'll take the printout with me today to study.

@Michelle -

I can't imagine that you would have a problem with this
shooting during daylight hours.

Shooting in the Adirondacks (20 years ago), dense forest
canopy gave even subdued light, extreme macro (Canon
70-210mm, f/4 plus FD50 extension tube) and with bracketing,
I had maximum exposure times in the range 90 to 120 seconds.
And got OK results in the prints.

Some images on the 120 roll I shot for the May challenge had
exposure times in the 2-4 second range -- f/4 lens.

Do you think there will be any color shifts because of the
range of exposure times? On the other end of the scale,
f-stop and resulting shift in DOF might prevent comparisons
among the 4 emulsions that I will be testing.

IOW, for purposes of comparison between emulsions, should I
constrain shutter speed or f-stop?

doubling of exposure time

Good rule of thumb -- no heavy book to carry along.

MGD