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get a used one here
This fun accessory is no longer made.
It attaches to the back of any Nikon mount lens that has an aperture ring and makes it into a telescope. The newest G series lenses, which lack an aperture ring, won't work unless you bend the aperture pin with a hammer to keep the aperture open when mounted.
It contains an erecting prism and a 10mm focal length eyepiece.
The power of the telescope is therefore the focal length of your lens divided by 10. A 50mm lens becomes a 5x telescope, a 400mm lens is a 40x telescope, and a 70-210mm zoom is a 7-21 power zoom telescope.
If you are an idiot you can use it to make your 16mm fisheye into a potent 1.6x telescope, and your 8mm fisheye into an 0.8x reducer, and your exotic 10mm OP fisheye into a 1.0x scope. A better way to make a 1x scope is to use a toilet paper tube and no glass!
Mine weighs 7 oz. (200 g).
It has a dioptometric adjustment covering about -5 to +3 diopters.
It allows the full use of up to an f/3.5 lens aperture which provides up to a 2.8mm exit pupil. Faster lenses get no brighter; 2.8mm is the maximum exit pupil.
The Lens Scope Converter works great. The limiting factor is the definition of the lens to which you are attaching it.
The image will be fantastic with ultra-sharp lenses like the 400/2.8 AF-I, and be poorer with lesser lenses.
Mediocre lenses will be on the fuzzy side.
It has enough magnification to allow you to see lens aberrations that you cannot see on film.
This is a fun and useful device, if you can find one. There are discount brands like Bower made today that are not as good, even though they have the same specifications.
I got a deal when I got mine used in 1995 for $80. As of September 2005 one just sold on eBay for $327 here.
I found the 500mm f/8 C reflex lens to be very well suited to this converter because the reflex lens is crappy for photography, but has great central definition.
Make sure to set the lens to its widest aperture, and not the minimum aperture to which most AF lenses are left set with the aperture ring stop. If you don't change the lens aperture you will get a very dark image. This converter has no pin to open the automatic diaphragm of the lens.
Since the exit pupil is limited to 2.8mm you can stop your lens down to f/3.5 to attempt to reduce flare.
Feel free to use teleconverters between the Lens Scope Converter and you lens for more magnification.
Remember that this converter doesn't use the entire image area, just a small area of the center of the lens' image.
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