Why pentaprisms?

8 Feb

The pentaprism is a feature that until recently was reserved for mid-range cameras and better. Those looking in the second hand market will probably have to contend with the question of how much importance to place on it. Those buying new can avail themselves of an entry level camera that already has a pentaprism, such as Pentax’ K-30 (I actually don’t know of any other). A pentaprism produces a slightly larger, but more importantly, brighter copy of the image that would hit the sensor if a shutter release were made. Why does this matter?

Well, if you’re trying to manually focus, being able to see clearly is important. I’ve also found that I get a much worse case of camera eye after looking through a pentamirror for a while, rather than a pentaprism. On top of all that, in the current market, all models with 100% viewfinder coverage (i.e. you actually see the photo you will get) have pentaprisms. However, a pentaprism is no guarantee of 100% coverage (but the K-30 has both).

I would argue that most people will immediately feel the difference between a pentaprism camera and a pentamirror one, just looking through the viewfinder. If you’ve ever used a pentaprism, all pentamirror cameras will feel claustrophobic, and you’ll tend to obsess over details a lot more, and feel like you’re labouring to get the shot you want. Conversely, if you’ve only used pentamirror cameras before, you’ll either feel the pentamirror to be a breath of fresh air, or you’ll not notice it at all because the things you’ll suddenly see will be so much more interesting. The bottom line is that, yes, it’s a feature you want to have in your SLR camera.


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