The darkening lenses used for welding are in the -10 to -12 area, and some also have a gold film shield on them, like the visors used on space helments.
I would like to catch the transit too.
Here's a tech question; When you use a telephoto lens vs a wider angle, does the telephoto image of the sun on the sensor have higher energy levels or lower? I would guess the tele image would be lower energy per square m m because it is spread over a larger area on the sensor than the tiny dot produced by the wide angle lens. Think about how most of us have experience with burning ants with a lens when we were kids. The smaller the dot of light, the hotter it is.
The darkening lenses used for welding are in the -10 to -12 area, and some also have a gold film shield on them, like the visors used on space helments.
I would like to catch the transit too.
Here's a tech question; When you use a telephoto lens vs a wider angle, does the telephoto image of the sun on the sensor have higher energy levels or lower? I would guess the tele image would be lower energy per square m m because it is spread over a larger area on the sensor than the tiny dot produced by the wide angle lens. Think about how most of us have experience with burning ants with a lens when we were kids. The smaller the dot of light, the hotter it is.
Yes, the energy density is lower with a telephoto... the total energy may be higher, though because the telephoto collects more light (larger objective lens).
Re the question about manual aperture rings on the Nikkor D and Ai lenses.
The aperture is wide open until you either press the DOF preview button, or trip the shutter. The aperture closes down when you move the ring when the lens is off the camera, but there is a lever inside the camera that mates with one on the back of the lens, holding it wide open until you shoot. If you take the lens off, set the aperture at f22, you can work the lever with your finger and see how it works.
There are some Nikkor lenses made with manual only aperture control, like the early PC Nikkors, which had the aperture ring at the front of the lens, but not coupled to the camera linkage. I have one of the 35mm ones, and you set an adjustable ring to the aperture you want to use, compose with the aperture wide open if you want, then turn the aperture ring until it hits the stop set with the "setting" ring then shoot.
Some of the non Nikon lenses used with adapters will allow manual only aperture control as well, so that viewing is done at "stopped down" aperture.
Earlier Canon FD lenses worked the opposite. They stay wide open until you mount them on the camera.
ETA, This may be a good opportunity to use the "live view" feature if you have it available, so that you can see what's going on without looking directly at the sun through the lens. A mirror would make it a little easier with cameras that do not have swivel LCD's. I use the mirror trick for astro photography when shooting upward.
I`m looking forward to the venus transit.
To watch or photograph just slap some of this baader solar film over the end of lens or binoculars/telescope.
This is safe unlike nd filters,film etc.
