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Comment by lbotos | Hacker News Reader

This is absolutely incredible! I've looked up rangefinders on wikipedia but still don't fully understand. Anybody care to try and clarify?

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I was a bit afraid to submit something with "rangefinder" in the title, so I will take it upon myself to explain it.

"Rangefinder" is commonly used as a short form of "rangefinder camera". Back in the early 1900s you would most likely focus a lens using "zone focusing", which is pretty much a fancy way of saying "guessing the distance to the subject" combined with some understanding of how depth-of-field works in relation to the lens aperture.

There were also external rangefinders [1], devices that measures distance using techniques such as parallax. From a practical standpoint, you get two overlapping images and you adjust the rangefinder until the subject becomes clear [2]. You can then read the distance to the subject from the external rangefinder and transfer it onto your lens and take the shot.

Since this is not particularly, well, fast or convenient someone came up with the idea of combining the two and the rangefinder camera was born. Up until the days of auto-focus, single-lens reflex (SLRs) also used this kind of technique for focusing. However, SLRs and point-and-shoots with auto-focus and zoom lenses now dominate the digital market and most people never see or touch a rangefinder. They are still somewhat popular among street photographers though since they are significantly smaller and also since they are arguably more discreet in appearance.

[1]: http://leicaphotography.org/leica/camera/if/fokos.jpg

[2]: http://reviewed-production.s3.amazonaws.com/attachment/2350f...

> Up until the days of auto-focus, single-lens reflex (SLRs) also used this kind of technique for focusing.

Everything else is perfect, but this is incorrect. SLRs use focusing screens with split prisms and/or microprisms, not rangefinders. http://en.wikipedia.org/wiki/Focusing_screen

You can still mount one of those on some modern DSLRs by simply replacing a piece of glass. http://www.focusingscreen.com/privacy.php

The advantage of focusing through the taking lens is that unlike rangefinders this method works with telephoto lenses. It's very hard to use a rangefinder accurately with anything much more than 135mm (and even that's not easy.) Similarly with macro or close up shots. However, rangefinders have many advantages, the viewing image is never blacked out like a SLR does when you click the shutter, also you can see around the periphery of the area covered by the lens, seeing objects moving into the frame, also the two main advantages are that since there's no mirror the camera can be used at slower shutter speeds without getting moved around by the mirror slapping against its stoppers, and again because there's no mirror needed the back element of the lens can be very close to the focal plane (where the film or sensor is), this means smaller lenses can do the same job as much larger ones on an SLR - they are also sharper because of this, and suffer less distortion.

I use a Leica M6 for many of these reasons, it's a beautiful rangefinder camera. http://en.wikipedia.org/wiki/Leica_M6

small additions. 1. there's also no such thing as zoom lens for rf. 2. i think you can avoid the 'seeing around the periphery' problem somewhat by shooting with both eyes open. 3. i always imagined smaller glass area is always a handicap. the bigger the glass the sharper it ought to be. works even better if there's bigger film to capture the bigger image. i.e. using ever larger format cameras...the larger the sharper... 3.1. larger glass is usually also brighter. i personally always wonder about people who care about sharpness..like unless they always shoot on tripod, how does it work? they get sharp motion blur?

Well, there is the Tri-Elmar :)

Thank you very very much for correcting me, I learned something new today. Also, thank you for the focusing screen link, I may even consider buying one for my Canon DSLR.

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