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Re: Light Meters

Wayne wrote:

> I think you could also obtain different readings for the same object
> depending on the angle you view it at through the glass. Also the
> orientation of the object seems to me should matter as well. Wouldn't a
> vertical flat object collect less light than a than a horizontal object if
> there was more light entering the tank at a high angle. I find it hard to
> believe that changing the orientation of something flat would not change
> reading that you get. Changing the orientation of a sphere though
> wouldn't do anything.

Ivo replied:

IMO, all these effects, including the extra low-angle ligth you suggest
(and I agree) should exist with a white reflector hood, are second-order
effects given the precision we can get from such measurements. The main
point in using the cheapo technique is that it costs nothing, and it
apparently can provide me with the data I need in order to design a light
canopy. Of course I would feel more confident if working with a properly
designed underwater meter, but that wouldn't be as fun !

I reply:

I just had a thought that if I bought that cheap light meter that George
recomends maybe I could take measurements with the sensor both flat and
vertical and then add them together. Would that be similar to having a
cosine corrected light meter? If it is I think I will order one. I don't
have even a small portion of your mathematical abilities and for me trying
to do the math is just not any fun at all.

BTW I am now putting together a 6 lamp fixture which has individual
parabolic reflectors for each lamp. I think that the main problem with past
fixtures I have made is that the light in the tank is not evenly
distributed. The top of the tank is much better lit than the bottom of the
tank and this is probably true for a lot of other tanks. For instance, I
don't think that many lawn type plants are particularily light demanding.
They just happen to be placed at the bottom of the tank where there is not a
lot of light. I am hoping that a better reflector design will reduce the
drop in light intensity at the bottom of the tank.

I would also like to point out that while DIY lighting is a lot of fun for
me, I don't think I will ever be able to build a better lighting system than
the ones that you can buy from AH Supply. The more I learn about lighting
the more I come to appreciate what a great system they sell. I just can't
seem to stop myself from trying to improve my setup though. Now maybe if I
can just get a hold of some of those linear HO T5 lamps, I could go with 4
individual reflectors, a 5' tank and ......