Focus checking

[filmboy]

I recently bought an M8 off Ebay (yes, I know, I know...) and then added a Summilux 50mm and Zeiss 28mm to it. The focus was clearly off a little bit, as when focusing on a cutting mat with a grid printed on it from about one meter away, the focal plane of the image was quite far back from the point on which I had focussed. So I read the threads on the forum about adjusting the back focus and had a bit of a fiddle once I had located a 2mm allen key.

I was wondering if anybody has an example of perfect focus at 100% magnification, like a test image, against which I could compare my results. Although I now get "acceptable" focusing results, I'm not sure if I have adjusted the camera into "perfect" focal alignment or not - a slight amount of anti-aliasing around sharp lines of buildings at infinity might be a result of the M8's JPEGing process, for all I know, or might be a slight amount of focal alignment error. (I'm checking through the playback function on the camera - perhaps it's a better idea to use C1?) I might be able to get it better (find some kind of "sweet spot") with further experimentation, but would prefer to avoid unnecessary messing about with the camera's interior mechanics if there's no benefit. Possibly, this idealised "perfect" focal alignment isn't achievable on the M8 due to issues discussed elsewhere, but I would be interested to see other people's level of "acceptable" focus.

Advice or test images would be much appreciated!

[Shootist]

First off you have to check the camera and lens that is focuses correctly at infinity.
At night turn the lens to infinity and point the camera at a star. The image in the viewfinder should be exactly aligned. If it isn't then it could be the camera or the lens.
If you do this with 2-3 or 4 lenses and the majority of the lenses DO focus correctly at infinity, and the images you get from it are sharp, then more then likely the lens that does not align the viewfinder images is probably off and will need adjustment.
If none of the lenses align the VF images @ infinity then it more then likely the camera that needs adjustment, although the lenses could also be off slightly.

Once you have a lens that is good @ infinity then you need to do some close focus tests with that lens. If with that same lens you get acceptable close focusing results then the camera is probably good, although some fine tuning could make it better.
If the close focusing is off with that same lens then the camera needs to have the whole RF/VF adjusted.

In recent months people experiencing focusing problem have been told by Leica to send the body and all lenses in for adjustment. I'm think this is to make sure that all the lenses are within tolerances and they adjust the camera to those same tolerances.