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03-29-2010, 03:17 PM   #1
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pentaprism vs pentamirror

I am new to photography.

But which is better?

03-29-2010, 05:29 PM   #2
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Pentaprisms are generally considered to be better.
03-29-2010, 08:42 PM   #3
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Pentaprism viewfinders typically have a larger and/or brighter image than pentamirrors. My camera has a pentaprism and is rated at 0.95x magnification, and a nearly identical model with the pentamirror has 0.85x magnification. The mirror design can't transmit light as efficiently so the designers often reduce magnification to maintain similar brightness. I've used the nearly identical model and if I did not know to look for a difference, I probably would not see it.

The prism adds weight too. Here is the prism from a Pentax SF1 film camera, bigger because the film format is larger:

04-15-2010, 09:39 AM   #4
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Pentaprism in general. In some cases the difference is more obvious, like with the Olympus E-510, which I used for a while. The viewfinder was dark and small, relatively speaking, and wasn't pleasant to use. You'll not find the same kind of performance on all pentamirrors however, as some of them are very high quality. If you have the choice, go w/ pentaprism, and aim for 100% view.

04-15-2010, 12:09 PM   #5
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what difference does it make in a k-x?
04-15-2010, 12:28 PM   #6
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QuoteOriginally posted by techmulla Quote
what difference does it make in a k-x?
It would cost more to produce which may be the biggest single factor.
04-15-2010, 01:51 PM   #7
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QuoteOriginally posted by techmulla Quote
what difference does it make in a k-x?
Well, it's not like you get a choice between the two in a K-x - all K-x's have the pentamirror. Compared to a *different* Pentax camera with a pentaprism, the viewfinder is *slightly* smaller and *slightly* dimmer. A $40 O-ME53 magnifier solves the former problem very nicely. Like Dave, I can see the difference in size & brightness if I really look for it, and in theory it might make manual focus slightly easier with a pentaprism camera. In practice, as someone who has owned both, I'd say I don't enough of a difference to really worry. If you plan on mostly using manual lenses, and you have enough experience to know that the small difference would really matter to you, then take that into consideration. Otherwise, if you're just asking because you saw the words in a review and have no idea how relevant it is to you, I'd say it's 99% irrelevant.
04-15-2010, 03:53 PM   #8
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I have never noticed the difference between a pentaprism and a pentamirror style assembly, they both look exactly the same to me, but maybe I'm just not sure what I'm supposed to be looking for. I don't notice any more darkness in either one of them, and manual focusing seems just the same too. Those are the only real things that I've heard are improved by it.

04-15-2010, 05:04 PM   #9
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You'd have to compare them directly side by side to notice - lookng through one then immediately switching to look through another, with the same focal length lens mounted to each. If you do this, you'll see the Pentax pentamirror cameras definitely have a smaller viewfinder than the pentaprism ones. But Pentax pentamirror cameras have larger viewfinders than some of the competitors'.
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