Originally Posted by dcstep
Depending on the length of the tube, you lose some light, like an f-stop for a 25mm tube on a 35mm camera. With your MF cameras, I don't know the light loss, but you could probably find out in one of the MF forums over at some place like photo.net.
I find my ETs easier to use with my longer lenses. On my 500mm, cutting the minimum focus distance from 12-ft to 8-ft is huge and then I add my TC, which has no impact on MFD, and I've got a bee filling the viewfinder at 8-ft. I use it a lot with my 70-200mm also. I'm shooting at around f/8 when all that stuff is piled on an f/4 lens.
I saw some amazing macros taken with a 65mm macro lens, two ET and flash. The guy specialized in macros and had a complex lighting scheme, but the results were stunning.
I've got both ETs and diopetor lenses and like them both. ETs are a cheap solution on dslr, but perhaps not so much for MF.
the Bronica 18mm extension tube needs 1.7 to 1.8 times the light for an equal exposure on the 80 and 150mm lenses, respectively. :\
sounds like a lot of light loss. but i don't plan on doing any macro - just closer portraits.
so my set as +1, +2 and +4 diopters. the +2 diopter converts the 80mm's .8m minimum distance into a staggering .26m. the depth of field goes out the window, and with the wider frame of the 6x6 format, things get really intimate.