[frank]

[quote name='IanCD' timestamp='1340270894' post='19001']

Hi Frank,

That's - potentially - very interesting..!

Does adding a teleconverter always increase minimum focusing distance? By how much (is it a simple formula)?

I have the 105VR and am finding min. focus distance for 1:1 very close to the front of the lens, particularly with the lens hood fitted. Markus did sort of warn me..!

Could I use a 1.7 TC to increase min. focus distance (reach) more again? And get 1.7:1 magnification?



I guess the downside may be a darker image in the viewfinder with the loss of 1 (1.4TC) or 1.5 (1.7TC) stops on the aperture...

Ian

[/quote]



Hi Ian:



As far as I know, the minimum focus distance is maintained when using a teleconverter. So, if you use a 1.4x teleconverter and focus at the minimum foucus distance, you will get a 1.4:1 magnification because of increase of the focal length. If you only want to get 1:1 magnification, then you do not need to put the subject at the minimumn distance--in this sense the focus distance for 1:1 magnification is extended.



Yes, when using a teleconverter for macro photography the only downside that I can see is the darker image in the view finder.



Frank