08-03-2014, 08:27 AM
I think a large part of the problem is not just the visible wavelengths from the sun, but also the IR, and to a lesser extent the UV. UV is less of a problem since most glass absorbs a fair amount of it anyway. IR contains a lot of the energy, and you need to ideally remove it before it gets into the lens. There are two basic choices: overall attenuation or selective attenuation.
For overall attenuation, you could try (G)ND filters although it is a bit of an unknown to me how they behave in the IR region, so may not offer much reduction at all. Safer is the use of a dedicated solar filter, BUT these are designed for looking AT the sun and have massive attenuation. For example, the Baader astrosolar film ND 5.0 claims to reduce light transmission by 99.9999%, which is somewhere over 16 stops! They have a slightly weaker ND 3.8 version but it seems hard to find on sale by itself.
For selective reduction of the IR band, the options are even more limited and a lot more expensive. In the astrophotography world, there are UV/IR blocking filters which will only pass visible wavelengths (also called L or luminance filters). To get one big enough to fit in front of a camera lens will be incredibly expensive. To save cost it is normal to get smaller ones to put at the back end. But in a camera, if it were to reflect that unwanted energy it still has to go somewhere and may collect inside the lens still.
For overall attenuation, you could try (G)ND filters although it is a bit of an unknown to me how they behave in the IR region, so may not offer much reduction at all. Safer is the use of a dedicated solar filter, BUT these are designed for looking AT the sun and have massive attenuation. For example, the Baader astrosolar film ND 5.0 claims to reduce light transmission by 99.9999%, which is somewhere over 16 stops! They have a slightly weaker ND 3.8 version but it seems hard to find on sale by itself.
For selective reduction of the IR band, the options are even more limited and a lot more expensive. In the astrophotography world, there are UV/IR blocking filters which will only pass visible wavelengths (also called L or luminance filters). To get one big enough to fit in front of a camera lens will be incredibly expensive. To save cost it is normal to get smaller ones to put at the back end. But in a camera, if it were to reflect that unwanted energy it still has to go somewhere and may collect inside the lens still.
<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.