A bad lens - Pentax Spotting Scope 500

[luisalegria]

This thing is not supposed to be a camera lens, strictly speaking. Its a spotting scope from the 1980's. I found it among my father-in-laws things some time ago.

Now, it turns out that the spotting scope screwed apart, and the screw was a T-thread - so voila, it becomes a 500mm f/8 reflex lens, all for no money down.



There is a disappointment in here though - it is a pretty poor 500mm, all things considered. Its got lousy contrast, it is near-impossible to focus, its very soft even when focused, it acts more like an f/11 than f/8 for exposure and dimness in the viewfinder, etc. ad infinitum. Any of my 300-400mm lenses do much better.

Since this is the only reflex/mirror lens I've got, I can't say if they are all this bad, or is this is a particularly poor one. The only advantages it does have is that it is very small and light and it can focus down to 3.5 feet, which is pretty good for 500mm, even if the DOF is next to nothing.

Some samples -







A demonstration of the Pentax image stabilization - this was handheld (leaning against a door frame), indoors, at night, under dim tungsten light, 1/6 sec with a 500mm (ISO 3200). Its not sharp, but its a wonder that it can be done at all.

[Rob Leslie]

Spotting scopes etc usually make very poor photo lenses. They are good for pictures of the moon etc.
However I do like the rendering of tones it has captured with your flower shots. Maybe it is your good PP work but I think it may be worth using for similar shots.

[padiej]

Some people are faszinated from mirror-lenses, but I can understand, that a mirror system eats quality.

A big fat "normal" Lens is heavy and must be better, or?

A mirror-lens is a kompromiss.



regards Peter

[Farside]

I wonder if the reject camera lenses were re-badged as Spotting Scopes? For normal eyeball use, the quality doesn't matter as much as for pics, so ...