An OD5/99.999% solar filter used for visual observing (e.g. the Baader solar film) is like a ~16 stop filter, and an OD3.8 filter is about ~12.5 stops.
Furthermore, if you look at the transmittance charts for most photographic ND filters you'll see that they typically allow a very high amount of UV and IR light to pass through. The OD5 solar filters block virtually all UV and IR light.
It's not a problem photographically since digital cameras have a UV/IR filter over the sensor, but unfortunately it's the kind of light that burns your eyeballs (without you knowing it)...
|