hi there,

i had post a question on apperture and tele-convertors and i got satisfactory answer. this is just an extension of that. i wonder what happens to the minimum apperture while using a T/C, say 2x T/C, with any lens of say minimum f/32 apperture. does the apperture goes further down. ofcourse, this low apperture is seldom used by most of the photographers, especially due to diffraction effects. but i just wonder what happens to the mimum apperture.

-- sajeev (chack74@yahoo.co.in), February 11, 2002

Answers

With a 2X TC an f/32 min. aperture becomes an f/64.

-- Jim Strutz (j.strutz@gci.net), February 11, 2002.

it means that the apperture must change in steps of double the stops that a camera is capable of doing without the 2x T/C. i mean after 5.6 the next apperture value should be 8.0 and not 6.7. only then one can go upto 64 if the min apperture for the lens is 32.

does it affects the Depth of Field. i mean the DOF one gets with say 200mm @ f/32 and 400 mm @ f/64. will they change.

-- sajeev (chack74@yahoo.co.in), February 12, 2002.

If you used a 1.4x TC with your lens set at f/5.6, your real/effective aperture would be f/8. If you used a 2x TC with your lens set at f/5.6, your real/effective aperture would be f/11.

200mm @ f/32 has the same DOF as 400mm @ f/64. So in that sense it stays the same.

-- Jim Strutz (j.strutz@gci.net), February 12, 2002.

The camera will still adjust aperture in half-stop steps (if that's what it did without the TC). Only the minimum and maximum aperture ratios (f-stops) will change. The effective aperture diameter doesn't change.

-- Geoff Doane (geoff_doane@cbc.ca), February 13, 2002.