Focusing the M10 and Eye Correction

[jaapv]

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How to focus the M10

The M cameras work the same way as any rangefinder camera, the central patch in the viewfinder is your focussing tool.
It is important to look through the viewfinder in the optical axis. Looking into the camera skewed will result in inaccurate focus.

The first thing to do is to ascertain that you can see the rangefinder patch properly. A correct match between the rangefinder and your eye is even more important than it is using an SLR.
Leica sells corrective diopter lenses. Determining which one you need - if any- can be done by going to your optician and holding his try-out lenses between your eye and the viewfinder. The one that allows you to see the rangefinder patch and framelines sharply is the correct one. Order the nearest value from Leica. In a pinch, you can use over-the-counter reading glasses for this test. If your eyes need special corrections, you can use your spectacles, provided you can see clearly at 2 metres distance ( the virtual distance of the rangefinder patch).

For special cases, there are viewfinder magnifiers (not for the M10 (yet)). They can help, especially with longer and fast lenses and they can give confidence, but they can also be not very useful; they cannot correct errors in the focussing mechanism or the eye. In fact, they may magnify issues. Leica offers a 1.25x one and a 1.4x. These need diopter correction like the camera, but often of a different value than the camera viewfinder.
Basically, for an experienced user, magnifiers are not needed and will only lower contrast and brightness, but many users do like and use them.

Once the viewfinder is corrected optimally, there are three methods of focussing, in ascending order of difficulty aka training.

1. The broken line method. Look for a vertical line in the image and bring it together in the rangefinder patch to be continuous.

2. The coincidence method. Look for a pattern in the image and bring it together to coincide. This may lead to errors with repeating patterns.

3. The contrast method. Once you have focus by method 1. or 2. a small adjustment will cause the rangefinder patch to "jump" into optimum contrast. At that point you have the most precise focussing adjustment.

Side remarks:

If you try focussing on a subject emitting polarized light like a reflection it may happen that the polarizing effect of the prism system in the rangefinder will blot out the contrast in the rangefinder patch, making focussing difficult. In that case rotate the camera 90 degrees to focus.

Note that when one focusses and recomposes the camera will turn. For geometrical reasons one must bend slightly backwards to keep the focussing distance constant.

[dbeids]

No one, until now, has answered my question about the rangefinders virtual distance. I arrived at my diopter for the M10 by trial and error, and the 2 meter virtual distance makes total sense…confirming my choice. Thank you. 

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[Jeff S]

On 12/4/2021 at 5:31 PM, dbeids said:

No one, until now, has answered my question about the rangefinders virtual distance. I arrived at my diopter for the M10 by trial and error, and the 2 meter virtual distance makes total sense…confirming my choice. Thank you. 

Glad you figured it out.  But this FAQ is 3 years old and the topic has been covered ad nauseam in many other threads, typically whenever someone discusses focusing difficulty, eyeglass issues, diopters, etc. 

 

I suggest you read through the entire FAQ (including the original FAQ thread), which has lots of other helpful information and tips. For instance, while the focus patch is set at a 2m virtual distance across M models, the frame lines are optimized for framing at different subject distances depending on the camera: 2m for the M10 and M240; 1m for M9, .7m for the original M8; 2m for the M8.2 (or upgraded M8), etc. Trial and error can often lead to better learning, but sometimes it just helps to understand the technical underpinnings.

Jeff

Edited December 10, 2021 by Jeff S

[dbeids]

Thank you. Already read through. Much appreciated.