can I use a closeup lens with a 300mm lens?

I have a 300mm Fuji lens that I would like to use on my old speed graphic at something other than infinity. I've seen prevous posts reccomending using a nikon T series closeup lens (5T/6t) with a Nikon 300mm. Does adding a diopter somehow "decrease" the focal length? HOw does that work? The nikon catalog is little help. I need a 52mm size diopter and does B&W or Rodenstock or Canon or anyone else may a good quality one in that size or is nikon the only one? Your help would be appreciated.

Yes a "close-up lens" does decrease the effective focal length. Think

about we poor unfortunates who wear glasses, the dioptric correction

that we require performs the same function (changes the focal length

of our optical system so that we can focus on infinity - or closer as

needed). Nikon and Canon both make 2-element lenses (not sure if 52mm

is a "standard" thread size for Canon, but it is for Nikon). Kodak

used to have information in their books on the change in focusing

distances with different dioptric corrections.

Try this link for more info:

http://www.smu.edu/~rmonagha/mf/diopter.html

The Nikon 5T&6T are 62 mm. The 3T&4T are 52mm. I have had reports that they are fine.

If I remember well, a 1,5 diopter lens (3T&5T) will focus at 1:1,5=0,66 m (26") when your lens is placed

at infinity and a 2,9 diopter (4T&6T) will focus at 1:2,9=0,34 m (14").

No need to use the Nikon... look at the B+W filter line also.

Scott

Thanks alot, has anyone used the B&W ones?

The better diopters seem to be two element diopters, like the Nikon.