How Can I Get More Bellows?

[miket-nyc]

With a converted lens, you need more bellows than the nominal focal length. The only convertible lens I have converts to 475mm in one configuration, but the flange focal length is 545mm.

Mine is apparently a DX. (I say "apparently" because I bought it on eBay and decided it was a DX by comparing features, but "DX" does not appear on the camera). It has 300 mm of extension, but that's not enough to reach infinity for the converted lens. I'll do a few tests to see how much more extension I need.

A top-hat lensboard would be fine for a lens that always needs one, because you'd mount it on that board and leave it there. But a 150 Symmar doesn't need one for normal use -- only if I convert it by removing the front element, which would not be often.

Mike Taglieri

[Doremus Scudder]

Mine is apparently a DX. ... It has 300 mm of extension, but that's not enough to reach infinity for the converted lens. I'll do a few tests to see how much more extension I need.

A top-hat lensboard would be fine for a lens that always needs one, because you'd mount it on that board and leave it there. But a 150 Symmar doesn't need one for normal use -- only if I convert it by removing the front element, which would not be often.

Mike Taglieri

If a top-hat board won't do it for you, then you'll be better off just getting another lens. It will certainly be cheaper and less bulky than the other options to increase bellows extension. Plus, the image quality of the converted lens won't be nearly as good as a dedicated lens in the longer focal length. I'd suggest the Fujinon A 240mm f/9; I love mine.

Best,

Doremus

[Bob Salomon]

Mine is apparently a DX. (I say "apparently" because I bought it on eBay and decided it was a DX by comparing features, but "DX" does not appear on the camera). It has 300 mm of extension, but that's not enough to reach infinity for the converted lens. I'll do a few tests to see how much more extension I need.

A top-hat lensboard would be fine for a lens that always needs one, because you'd mount it on that board and leave it there. But a 150 Symmar doesn't need one for normal use -- only if I convert it by removing the front element, which would not be often.

Mike Taglieri

That’s the beauty of the Wista extended board set. It has 25mm of extension plus 2 additional screw in extensions and more are available as optional accessories. The 0, 1 and 3 boards screw into the front of the tubes. You use the 150 on the basic board. When you want to use it extended you just unscrew the 0 board from the front, add whatever tubes you need for the conversion and screw the board back into the front.
But since a converted lens is not a quality performer in the first place a dedicated longer lens would be your best choice.

[Neal Chaves]

On the convertible Symmar, there appears to be little difference in using just the front element alone or the rear. The easiest solution to reducing bellows extension is to use a good quality mild plus lens (close up filter). I have B+W 0.50 filters in 67mm and 77mm. I use them on my 250mm Fujinon W and 450mm Nikkor M. This is not a radical approach. Once when I worked for the Navy they had a big Nikon zoom lens in a case the photographers claimed was defective and wouldn't focus. I was tasked to fix it or send it for repair. It had a matched Nikon plus lens in place. Without it, close focus was more than 30 feet, but with it in place infinity focus could not be attained.