neutral density film

[P Aphalo]

cawiah at GARNET.BERKELEY.EDU wrote:
: We are looking for neutral density film to reproducably alter light
: intensity in growth chambers. Folks at Edmund scientific don't sell it, but
: claim it exists. Anybody know where to buy it ?

: MC
Adding to Baskin's response, beware of some neutral density films and
acetates: many of them are neutral only in the visible part of the
spectrum but have a different absorptance in the far-red region.
Acetate and polyester films are usually used in theater lamps to create
colour effects on the stage. In the UK Strand is one of the biggest
suppliers.

Shading cloth (e.g. Saran) comes in different grades (33%, 50%, etc.
absortance) as in frequently used in plant nurseries.

Cheesecloth is also effective, as metal, or plastic scrim, or mosquito 
netting, just do not use anything that is not either grey or black.
That is unless you want to change the R:FR ratio.

Regards,

Pedro.

Pedro.Aphalo at metla.fi (metla=Finnish Forest Research Ins