Anyone used a Schneider APO-Digitar lens?

[Messiah Khan]

I've got a 150mm f5.6 Schneider APO-Digitar lens, fitted to a Cambo X2 Pro with a Canon 5D mk2 on the back. Problem is the minimum focusing distance with the full extension (155mm) of the X2 seems to be about 20-25ft which seems huge!

Surely this lens can achieve a shorter focusing distance. I have fitted both spacers that came with the lens and this seemed to help, so I'm wondering if the lens needs to be fitted to a shutter (Lens didn't come with one, and as it is designed for digital backs, does it really need one?) to act as an additional spacer. So I tried one of the Copal-0 shutters of another lens, the back element attaches fine, but the front element has too big a thread for a copal-0 shutter, and it is too small for a copal-1 shutter. Any ideas of what is going on here?

 

[Messiah Khan]

Today I unscrewed the front element and manually held it about 100-150mm infront of the lensboard, and this achieved a minimum focusing distance of about 2ft. So I do indeed need more extension, either between the lens elements or in the bellows. So is the Digitar faulty, or simply not suitable for the X2 (despite it being advertised as such.)?

 

[HoppyUK]

I think it is just a normal long focus lens design, ie not telephoto construction with extra negative elements at the back, which reduce the back focus, effectively making them much smaller. Therefore a 150mm lens will focus on infinity with a back focus equivalent to the focal length, ie 150mm.

You need more extension.