Well then, one alternative would be to carry a "white card" along with you, and use it in the general manner of a gray card. Gray cards typically reflect about 18% of the light, whereas a white card will reflect about 90%. So a nominal 5x more light to hopefully bump your meters needle into a usable range. The adjustment factor, in f-stops, would be roughly a bit over 2 stops; say 2 to 2.5 stops. (Since the actual scene is darker than the meter "thinks" it is, your adjustment has gotta INCREASE exposure to the film.)
Here's a way to demonstrate the difference... first, use your "magnifying glass" to focus light from the sun and, as I'm fond of saying, try to "burn ants" or make dry leaves start to smoke. Ok, it works, right? Next, try the same thing using light reflected from your "scene" (to be photographed). No success, huh? I bet you already knew it wasn't gonna work either.
Yup, white reflects more, but I don't know how much that would help in a dark scene the same way.
I understand the demonstration and
that it would happen that way, still there's the question of why that I haven't wrapped my head around. Is it because one is taking the bright object of the sun and shrinking that light down to the size of a pin, certain to make a large effect? But focusing a bunch of light at night is probably collecting a whole lot of not-much-light in the scene onto a point producing... not much light still. The effect is only drastic with a large input, is that right?
agreed but it should be simpler to do this electronically by just increasing the gain. An optical solution seems old-fashioned, even though it gives a bettersignal/noise ratio.
If you know an easy mod I can do to increase the sensitivity of my CdS meters (or just adjust it up or down either way), let me know! That is my ultimate goal, I just was thinking optically because it seemed non destructive, and maybe possible by an amateur like me, and kinda a fun idea.
Is it just providing proportionally more voltage? If I jam a 3V cell into the slot for the 1.3V cell on most older meters..... it wouldn't fit, but if I
did do that, will I read a bit over a stop faster?
Or, for the non-powered selenium cell, is there a tiny tiny amp I can put between the cell and the meter??
That (the condenser lens idea) is basically what a pair of binoculars does. A 10x 40mm pair of binoculars takes the light entering the 40mm aperture and produces a 4mm exit pupil, which is a good match to your eye's pupil. If you take them (or any pair of binoculars really) out at night and look up, you'll see way more stars than with the naked eye. However, if you point them at a night scene down the block, it won't be magically brighter. The improvement comes by the higher resolution the binoculars afford on stars or other small astronomical objects, which are unresolved objects to the eye. For a surface brightness, such as the night scene down the block, the binoculars just magnify it, but don't make it brighter. This is the point
@bernard_L was making.
You can try, but my guess is that for a roughly uniform scene brightness, it isn't going to help much, and will be somewhat tedious to calibrate how it responds to a scene of non-uniform brightness. It's sort of like metering through an SLR. Sticking a larger telephoto lens onto the SLR doesn't make the meter cell more sensitive to a lower LV, but it makes the meter cell subtend a smaller angle. The way to make a more sensitive meter would be to have more detector area: multiple meter cells.
Wait, but doesn't it actually do so, a larger telephoto lens capturing more light? I mean, after all, they get wider/bigger the larger the aperture is.
If you can have multiple detector areas having a larger effect, why can't it be condensed onto one using a lens? x.x
