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roof prism vs porro prism

Started by bobk, 09/06/2002 05:56AM
Posted 09/06/2002 05:56AM Opening Post
Hi All,
Does anyone have any thoughts/recommendations on roof prism vs porro prism binoculars?

I am embarking on my new amateur astronomy career and thought since I can't decide what type of telescope to buy, I might as well learn the sky with binoculars first and maybe a couple of star parties and a little experience will reveal the telescope answer.

I currently have Nikon 8x32 Superior Es (which I love) but want a little more aperature. I was considering the Pentax DCF WP 10x50s which are a roof prism design and didn't know whether one type of design was inherently better than another type.

Any thoughts/feedback would be appreciated.

Thanks,
Bob
Posted 09/06/2002 07:43AM #1
Hi Bob.

Porro-prism binoculars don't have an inherent advantage in image fidelity, but it is "easier" & less costly to arrive at comparable image fidelity via porro prisms (versus roof prisms). An excellent 8x42 porro-prism binocular will very likely cost *significantly* less than an excellent 8x42 roof-prism binocular.

A roof-prism design gains very little beyond *potential* bulk savings, over comparable porro-prism designs. I stress the word "potential," because larger-aperture roof-prism binoculars can be just as bulky (if not more bulky) than comparable porro units -- particularly at or above 50mm aperture. As aperture shrinks, yes, the roof-prism design's advantage (bulk/weight) becomes more and more obvious.

If I were considering non-waterproof binoculars with larger aperture (say, 50mm), then I would eliminate roof-prism choices altogether.

If I required a waterproof design, I'd *still* go for a porro unit, so long as its weight/bulk and price remained reasonable (compared to comparable roof units).

The DCF 10x50 is indeed a nice binocular. However, the PCF WP (waterproof) 10x50 can be found for about half the cost of the DCF. The PCF WPs are fairly new, and I have no experience with them. If their optical qualities are shared with the standard PCF line, I'd expect them to yield equal or better image fidelity than the DCF. Of course, other factors are important: weight, bulk, field of view, fit/ergonomics. -Just an example, since you mentioned the DCF.

My own bias: for stargazing, I stick with porros.

Best wishes.
-Dan