Received in the post this morning, -one freshly picked Camera lens.
Bittersweet, this. Because I`ve been told by a gentleman on Youtube who has built one of these units that the lens I`ve bought will not let enough light into the device for an effective unit.
Silly me… should have remembered my photography… the lens is a beautiful piece of engineering, its in pristine condition but unfortunately has an F stop range of F22 to F4.
F1.8 is the least the lens should be, in order to work. -The smaller the ratio, the more of the light entering the lens front will leave the back of the lens and enter the tube.
Generally , the smaller the ratio, the higher the price. F1.2 lenses are expensive, F1.4 are average, and F1.8 are more common.
Also , zoom lenses and lenses over 50mm get progressively higher ratios, -you will be lucky to find a 500mm lens under F8.
The lens I purchased (at the admittedly low price of £5.00) is an F4.
Edit:- Have just read the data sheet sent by the tubes suppliers and I quote “Any lens from a 35mm SLR will work with these tubes,…..A Zoom lens is an ideal candidate for use with an image intensifier”.(There are VERY few zoom lenses that deliver better than F4 – the ones that do are VERY expensive).
When I think about it, it SHOULD work,- the tube will have a specific light input threshold. -Anything over a certain limit will produce a white screen (well, green) so as long as the lens meets that threshold AND if the actual supplier says a zoom will work, then I`ll take their word for it. I think I`m going to have to “suck it and see” – I`ll fit a pentax K mount and if the lens does not perform, then I can just fit another one easily.