Inaccuracy on my RF

[Herman Zhang]

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On my M240, when focusing to 0.7 meters(with RF), the focal plane is actually slightly behind 0.7m by a few centimetres. Is this normal? I'm using a 35mm lens. However, when I try infinity, 2m and 3m, it was accurate and was in perfect focus. On 1m it was slightly off, but barely noticeable. 

[dpitt]

6 hours ago, Herman Zhang said:

On my M240, when focusing to 0.7 meters(with RF), the focal plane is actually slightly behind 0.7m by a few centimetres. Is this normal? I'm using a 35mm lens. However, when I try infinity, 2m and 3m, it was accurate and was in perfect focus. On 1m it was slightly off, but barely noticeable. 

If you have only one lens it is hard to tell, but it sounds normal for most lenses. They are calibrated at infinity mostly against a standard body. But some models suffer from focus shift more than others. Which 35mm do you have?

It would be great if you have an other 35mm or even other lens to compare with on your M240.

 

[Herman Zhang]

8 hours ago, dpitt said:

If you have only one lens it is hard to tell, but it sounds normal for most lenses. They are calibrated at infinity mostly against a standard body. But some models suffer from focus shift more than others. Which 35mm do you have?

It would be great if you have an other 35mm or even other lens to compare with on your M240.

 

A chinese APO 35 f2 asph.

I also tried my 50 and it was slightly off at 1m(which is the closest focusing distance)

[dpitt]

It looks there is nothing wrong with your M240 and with your 50mm. I do not know this chinese 35mm of yours, but it sounds like that could be fine too.

Even the best Leica lenses can have these issues. e.g. the Summilux 35 pre-ASPH is known for these issues.
With some designs it is simply impossible to match focus perfectly on all distances and with all apertures. If you send it in to fix minor issues, chances are that the lens will be corrected in these area's but will be off in zones where it is accurate now.

Try to use the lens as is. Test how much you have to adjust on certain distances and you should be fine. Maybe use LV or EVF more than the RF in situations where the lens does not focus accurately.

YMMV

 

Edited January 27, 2024 by dpitt

[pop]

22 hours ago, Herman Zhang said:

On my M240, when focusing to 0.7 meters(with RF), the focal plane is actually slightly behind 0.7m by a few centimetres. Is this normal? I'm using a 35mm lens. However, when I try infinity, 2m and 3m, it was accurate and was in perfect focus. On 1m it was slightly off, but barely noticeable. 

The rangefinder should be accurate from infinity down to the closest focusing distance, 0.7m. If the lens does not focus properly within this range, either the camera or the lens or both are off. If the deviation is important enough, the usual procedure would be to send in both the camera and the lens to Leica. This would, of course, not work with a lens that's not from Leica, as they wouldn't touch it.

Much depends on how you determine the exact position of the focus point. How can you tell that your camera (or lens) is off at ~1m and below?