Lens size, magnification and viewangle?

Hi All,

I'm a bit confused . When I'm looking for some additional lenses (both for above water and under). Some manufacturers quote a 16mm wide-angle lens, while others quote 0.5x magnification. How do I compare the two?

Now this is my guess, someone please correct me here....

Ok, most cameras used to be 35mm. A bigger number meant getting closer or magnifying the object (ie telephoto or macro). A smaller number meant getting further away (ie wide angle/fisheye). Now, say you have a 35mm and you get a 16mm wide-angle lens, what is the magnification? Is it simply 16/35=0.457? If so, then I can just apply that to my digital camera and everything is solved

For example, my digital camera has the 35mm equivalent of a 27-110 mm lens. So if I have a 0.45x WA then do I end up with a 12.5-49.5mm lens? So what does this mean? What is my view angle? Is it possible to calculate the viewing angle as well? Again, some people quote a size, while others quote view angle.

Last, how do all these numbers change when you put the camera in water!!!!!

Sorry for all the questions!

Cheers,

Adam L

These web sites give you the relationship between focal length and angle of view. I don't know how the magnification numbers are calculated. Maybe by area?

http://www.rainbowcctv.com/tech/angle.html

http://www.navitar.com/zoom/cctv_op_char.htm

That .5x and .3x nonsense only applies to add-on converter lenses that screw onto the front of the lens you are using on your camera. If you put a .5x converter onto your 28mm lens, you get the equivalent of a 14mm lens.

However, most of the screw on topsides converter lenses are crap.

Underwater screw-on or bayonet mount converter lenses are popular with consumer cameras. They let you change your shooting style underwater, but they degrade the image quality somewhat, and also can sometimes take away your ability to zoom.

HTH

James

Thanks