Rangefinder question for a not-expert

Started Aug 23, 2013 | Discussions
docvale
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Rangefinder question for a not-expert
Aug 23, 2013

Hi Folks,

I have some questions about the rangefinder mechanism (that I've never used, so far). How does it work exactly? Is it that different from an optical viewfinder? When you're adjusting the aperture on your lens, is there any change on the rangefinder?

Thanks in advance

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JDLaing
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Re: Rangefinder question for a not-expert
In reply to docvale, Aug 23, 2013

Adjusting aperture has no effect on a rangefinder viewfinder.

The Rangefinder Viewfinder only works to focus the lens and show the result with a "patch" that lines up when the lens is focused.

You are not looking thru the lens as with a SLR camera.

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MichaelToyeImages
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I wrote this in a recent DPS article
In reply to docvale, Aug 23, 2013

"If you’re unfamiliar with Rangefinders, the name is simply a reference to the distance oriented method by which you focus the lens. You are presented, within the viewfinder, 2 overlapping versions of the scene and as you turn the lens to find focus, the overlapping images merge together into one, at which point you are focused!"

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docvale
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Re: Rangefinder question for a not-expert
In reply to docvale, Aug 23, 2013

Thanks Michael and JD.

I knew about the split image focusing system, but I didn't know about the insensitivity to the aperture control (despite it might sound obvious, since you don't see through the lens... but since you can see how you're focusing...).

So, I guess it takes very high skills to shoot with a rangefinder!

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JDLaing
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Re: Rangefinder question for a not-expert
In reply to docvale, Aug 23, 2013

docvale wrote:

Thanks Michael and JD.

I knew about the split image focusing system, but I didn't know about the insensitivity to the aperture control (despite it might sound obvious, since you don't see through the lens... but since you can see how you're focusing...).

So, I guess it takes very high skills to shoot with a rangefinder!

The focusing is done through a coupling cam driven by the lens mount. The rangefinder mechanism is calibrated to the focal length of the lens. When you mount the lens it tells the mechanism which one is on.

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tony field
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Re: Rangefinder question for a not-expert
In reply to docvale, Aug 23, 2013

docvale wrote:

So, I guess it takes very high skills to shoot with a rangefinder!

The rangefinder does not take any special skill - it just gives a different view for the eye.  Some people like it, some don't.

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Godfrey
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Re: Rangefinder question for a not-expert
In reply to docvale, Aug 23, 2013

docvale wrote:

Thanks Michael and JD.

I knew about the split image focusing system, but I didn't know about the insensitivity to the aperture control (despite it might sound obvious, since you don't see through the lens... but since you can see how you're focusing...).

So, I guess it takes very high skills to shoot with a rangefinder!

With a coupled rangefinder, you have a fixed mirror and a rotating mirror that's connected to the lens' focusing mount. When you turn the lens, it moves the rotating mirror to line up a pair of images in the viewfinder. When the images line up, the lens is in focus.

The aperture setting is not relevant to the focusing operation since you're not looking through the lens. It still influences the focus zone that the lens captures, of course.

Is it easier or harder to focus a rangefinder than an SLR or TTL electronic camera? With any TTL imaging system, you have to learn how to judge the point of correct focus as the focus plane moves when you turn the focusing ring. With an RF system, you have to line up the image in the doubled view patch. In most cases, I'd say it's easier to get the focus roughly correct with the SLR, but critical focus is much harder. Whereas with the RF camera, it's easy to nail critical focus every time if you have a well calibrated system and can see the doubled image line up.

It take lots of skills to be a photographer ...  

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bosjohn
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Re: Rangefinder question for a not-expert
In reply to docvale, Aug 23, 2013

docvale wrote:

Hi Folks,

I have some questions about the rangefinder mechanism (that I've never used, so far). How does it work exactly? Is it that different from an optical viewfinder? When you're adjusting the aperture on your lens, is there any change on the rangefinder?

Thanks in advance

your range finder is an optical device which will measure distances from your camera position to your subject. When well designed and well made they can be sufficiently accurate for photographic purposes.

you can find many discriptions of how the range finder works on line but essentially it uses prisms and mirrors to allow two separate windows to see the subject at the same time and it uses triangulation to measure the distance. the distance apart the two windows are and the magnification of the eye piece will determin how accurate the device will be,

in the leica the rangefinder can be used in two ways or a combination there of ,When you look through the eye peice on the me camera your using the view finder, on this camera and many others the range finder uses the view finder for one of its windows. In the center of the view finder you will see a rectangle patch that is lighter then its surroundings. This is the range finder patch. if you turn the  focusing lever on your  lens and observe the patch you will see two images of the same scene which will move closer together or further apart. when the two images are alighn so you only see one your in focus. this we call coincidence rangefinding. both the top and bottom edge of your range finder patech are carefully machended so  the line between is quite sharp you can use the top or bottom then in what we call split image method. that is a vreical straight line lines up from inside to outside the range finder patch.  This method will achieve slightly more accurace but it requires some straitht or almost straight lines in your view.

range finder focus is the same accuracy for any lens on the camera and in the case of the Leica there is no connection  to the aperature setting.  Because the accuracy of the same regardless of the lens on the camera it means that the wider angle the lens is the easier it get the focus right, the longer the lenses the more the range finder will be taxed to find good focue becase the depth of fields will be narrower and narrower.  and a fast and long lens push it to the limit/

the main reason Leits and now Leica doesnt offer very long lenses for range finder focusing is do to the above.

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bosjohn aka John Shick bosjohn@yahoo.com

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docvale
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Re: Rangefinder question for a not-expert
In reply to docvale, Aug 24, 2013

Thanks to all you guys!

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John Siward
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It was designed to be quick!
In reply to docvale, Aug 24, 2013

docvale wrote:

Thanks Michael and JD.

I knew about the split image focusing system, but I didn't know about the insensitivity to the aperture control (despite it might sound obvious, since you don't see through the lens... but since you can see how you're focusing...).

So, I guess it takes very high skills to shoot with a rangefinder!

When it was first introduced, the coupled rangefinder was the fastest way to accurately focus, designed for photojournalists and similar who needed to shoot quickly and in low light.  Ironically, these days people often like using a rangefinder camera for the opposite reason - because with an auto-focus DSLR it is all to easy to take 20 photos before you've even though about what you are shooting!

There's nothing particularly hard about taking an in-focus shot using a rangefinder, but experienced rangefinder photographers can focus and shoot very quickly, which does take a fair degree of skill and a lot of practise...

J.

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Z (is real)
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Re: Rangefinder question for a not-expert
In reply to docvale, Aug 25, 2013

docvale wrote:

So, I guess it takes very high skills to shoot with a rangefinder!

It is very difficult to judge depth-of-field with most DSLR optical viewfinders. Especially with fast lenses. (Generally focus screens on DSLRs show no difference in their projected image below a certain aperture, often f/2.8 or so.) You can easily see this by playing with depth of field preview with a fast lens mounted.

If anything it is  easier to place the focus plane using a rangefinder, though there are issues due to having to use focus-and-recompose because the rangefinder patch is only in the center of the viewfinder. One learns to judge the depth-of-field for a given focal length and aperture intuitively.

Cameras which support displaying the image of the sensor on an LCD or via an electronic viewfinder allow much better judgement of final depth-of-field. They can also allow precise positioning of the plane of focus when zoomed in.

The rangefinder on a Leica M-series camera is an optical prism based triangulation device. So yes, like a traditional optical rangefinder uses in other disciplines. (Often replaced by laser based devices now.)

-Z-

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