Difference between a lens and a filter


Status
Not open for further replies.

Ian

Senior Member
Feb 20, 2002
2,548
0
0
56
Perth Australia
#2
A lens is a device that exhibits magnification due to the refraction of light. This magnification can be positive (image gets larger) or negative (image gets smaller) depending on the design of the lens.

Many lenses are made up of a series of elements of differing refractive values, for example the Cooke Triplet, doublet and so on.

A filter is a device that selectively removes or adds to the original 'signal'. For example, a UV filter rejects most wavelengths of Ultra Violet light and stops them from reaching the film. A cross screen uses fine wire etching to 'add' diffaction spikes to a bright light source.
 

Ian

Senior Member
Feb 20, 2002
2,548
0
0
56
Perth Australia
#4
Originally posted by BlueAngel
then i dont get it .......how does a close-up filter works then ?
It's a lens that magnifies the image scale before it reaches the camera lens.
 

#5
Originally posted by Ian


It's a lens that magnifies the image scale before it reaches the camera lens.
I think he's confused cause a "Close-up Filter" is actually a "Lens" which goes infront of the main lens.... heh.

Then there are those wide/tele adaptors for digital cameras which goes in front of the main lenses as well.... which adds to the confusion.

Regards
CK
 

M

Midnight

Guest
#6
Originally posted by BlueAngel
then i dont get it .......how does a close-up filter works then ?
Although "close-up filter" is the common parlance for these things, as Ian and CK have pointed out, it is actually a lens, and indeed official sales catalogs and such will normally list these items as "close-up lenses".

To address the source of confusion CK mentioned, I prefer to describe close-up lenses, teleconverter lenses and the like as "auxiliary lenses", so it's a "close-up auxiliary lens" and a "teleconverter auxiliary lens" (though admittedly it's a bit of a mouthful ;) )
 

Status
Not open for further replies.
Top Bottom