Just bought 2, very old but fine working, 2000W Strand-quartzcolor castor Fresnels and some things puzzle me.

Is there much difference in lens quality between brands?

1) The beam of a 650W Arri gives much harder shadows than the beam of the Strand. (Both focussed in spot) Is this just the size of the fresnel, 122mm versus 250mm or is the lens in the Arri simply better?

I figured the Strand would give a bigger parallel beam because of the bigger diameter lens, if you like the fresnel type of light this should give even better results. For example Arri made an ST version of their T series with a bigger diameter lens. But is this more of the good per se?

2) The Strand has a matt black inside! (Arri is silver/grey) Would it produce noticeable more light after putting aluminium foil on the inside or might this overheat the lamp?

Any knowledge on these great lights is more than welcome!