some photog ?'s for newbie

photo terms for dummies (me).

please define in layman's terms.

aspherical
micro
macro

when people say,

"this lens will work and meter in camera x & y. it will also work in camera z but will not meter."

what do they mean by "meter?"

"L" glass seems to be the best for canon, which is/are the best for nikon?

feel free to add other terms. thank you.

An "aspherical" lens element attempts to diminish distortion across the entire focal length range in a zoom lens.

In terms of Nikon I believe they use the term "Micro" to designate their Macro capable lenses ie "Micro Nikkor"

A macro lens is one that has close focusing capabilities due to special lens construction. I think there is an established standard infocus range for any given focal length. When a given focal length lens will focus closer then that it is said to have macro capability. Normally when you're focusing a lens with macro capability the image will go out of and then back into focus as you go from the general range of the lens to the closeup or "macro" range of the lens.

These are generalizations I know, perhaps Isler can chime in and give us the true technical definitions.

I don't know a lot about Nikon glass or if they have a designation to differentiate their better glass like Canon. I always thought with them it was a matter of the more you paid the better the lens is.

Forgot to mention metering. That's the ability of the camera to correctly determine exposure values. Now a days it usually means the lens is communicating properly with the body. Normally when you're using a lens on any body the aperture stays wide open until you take the shot. At that point the iris in the lens closes down to the f stop specified by you or the cam if in auto and the shot is taken. When you're using a manual lens or a lens that doesn't communicate with the given camera body you have to perform "stop down" metering where you set your exposure with the iris closed down to the fstop you want and either let the shutter float (in TV mode) or set it totally manual. All of your auto and semi auto modes are diabled except for TV. All of the aftermarket lenses like Sigmas/Tamron/tokina etc are reverse engineered to work on Canon bodies as Canon won't divulge their lens software algorithms. Everytime Canon intro's a new body you take the chance that your non Canon lenses will no long "meter" with your new body. Sometimes Sigma et al will update the lens, sometimes you're stuck with what basically becomes a manual lens. Not sure if Nikon forces the same predicament though.

Aspherical lenses are not spherical. Meaning a normal spherical optic is the same curve across the whole lens. The standard for lenses is about 70% of the lens diameter is useful for proper focus. Aspherical lenses change there focal length across the diameter of the lens. This allows the lens to be used to around 85% of the lens diameter. The main aspect of this design allows a lens to have a lower F#. F# is focal length divided by diameter. Lower F# means higher resolution to the camera.

Basically, It allows an optic to be smaller in diameter and still have better light collection than a standard lens of similar size. To a certain degree with modern lens grinding and design techniques, it is a way to cheapen the product while convincing the user it is better and hopefully the manufacturer can convince the buyer it is worth twice the money while saving manufacturing cost. When buying optics, as the diameter of the lens goes up, so does the price. It is cheaper to get more out of the lens than it is to use a larger lens blank at this point.