Ok, I was testing my noct and found something that might explain why my "hit" ration of in focus pictures is so low. I focus on the door knob across the room (roughly 3 meters) as the test. If I bring the focus from infinity to the knob I get just a bit less than 3 meters. If I bring the focus from 1 meter to the knob I get just a bit over 3 meters! Ok, normally no big deal, but the DoF at f1 with the noct is so small that even this small discrepancy is greater than the DoF.

I remember reading once about the way to focus a rangefinder is to not "hunt" for the focus but to bring it from one extreme and then stop when it is in focus. But what exterme were they talking about infinity or 1 meter? Thanks, Russell

-- Russell Brooks (russell@ebrooks.org), April 15, 2002

Answers

Hello Russel,

when focussing close with lenses wide open, thatīs f2, f 1.4 at 0.7 - 2 m, 3 m would be a bit out of bounds for this, set your r/f and then move your head (with your eye at the camera) to an fro (that is: towards your motif and back a bit). Stop moving where you think focus is perfect and release.

I found, I got more precise results that way. Just try.

Good shooting

-- K. G. Wolf (k.g.wolf@web.de), April 15, 2002.

The advice, which I've seen before, to not hunt for focus is bad, I think. Shoot past the point, in both directions, attempt to figure where the middle is by going over in smaller and smaller increments, and then hit the spot. Regard the last pass as your "not hunting" pass, if you want, but by that time you already know a lot more than just doing it the first time.

Another hint--a overshoot coming from the front going back takes you a lot farther out of focus than the same overshoot with an equivalent angular error on the focus ring if you're coming forward.

And third, check the infinity setting of your rangefinder on a regular basis, and learn how to adjust it yourself.

-- Michael Darnton (mdarnton@hotmail.com), April 15, 2002.

I tried this on both my M3 and M2 with the same results. And they were serviced by Leica in the last 9 months.

The tricks with bobbing your head and with hunting for the focus I understand and have used sometimes. What I am having difficulting figuring out is if my doorknob will be in focus at 3 meters minus a little bit or at 3 meters plus a little bit. Of course I will make a test. But the rangefinder shows that both can be considered in focus depending which direction you start to turn the focus ring from. But there can only be one correct distance! I just want to find a consistant focusing method for my noct... thanks...

-- Russell Brooks (russell@ebrooks.org), April 15, 2002.

If you're asking if the rangefinder delivers different results going in different directions, the answer is no, not on a camera in good condition. If the camera is OK, the problem is your eyes or your method. I'd guess that the correct focus is between that which you get with the two methods you're using.

-- Michael Darnton (mdarnton@hotmail.com), April 15, 2002.

How new is your lens? The Noctilux is a very heavy lens and as the focusing helicoil wears, even slightly, the optical unit sags under the weight. So if you press upwards when you focus the focus will be affected. Check it again very carefully to see if the focus shifts slightly when you let go of the lens. If so, practice using a light touch when focusing. (Thanks to Dick Gilcreast for pointing this out in his article in the LHSA Viewfinder)

-- John Collier (jbcollier@shaw.ca), April 15, 2002.

Another thing to consider is whether there is any "play" in the focusing ring. None of my chrome lenses has any, but all of my black/aluminum lenses have a tiny "dead spot" where the ring turns but doesn't affect focus. It could be enough to show up as a slight difference on the focusing scale while not being a difference in the actual location of the focusing cam.

-- Mike Dixon (mike@mikedixonphotography.com), April 15, 2002.

I read that its best to focus from near to far and stop when the image looks coincided (and not "hunt" back and forth like with an SLR). You may want to try it that way and see if the images are more consistantly in focus.

-- Andrew Schank (aschank@flash.net), April 15, 2002.

I just pulled out my fastest lens, a 50mm 1.5 Zeiss Sonnar (LTM with adapter) and focused it from 1 meter out and from infinity in, on an object about 6 feet away with my M3. I found the exact same spot on the focus scale going from both directions, and repeated the results several times. I wonder if there is some play in your system, either with the lens or in the camera body.

-- Andrew Schank (aschank@flash.net), April 15, 2002.

a) Which extreme? whichever one works - i.e. try actually taking pictures while doing your 'test' and then see which one is sharpest - focusing from infinity or from close-up.

But definitely 'hunting' for focus is to be avoided - if you have to do that you might just as well get an SLR. =8^o

b) Trying to line up the two rf images is like trying to 'see' depth of field. We all know that if the circles of confusion are small enough we will 'see' part of an image as sharp even if it is not PERFECTLY sharp. In the same way the rangefinder depends on our eyesight - we may see the RF images as aligned even if they are not PERFECTLY aligned - and therefore undershoot, or overshoot, the point of perfect focus.

This, Russell, is why you get different results focusing 'in' and focusing 'out' - you are an 'overshooter' by habit and tend to go slightly past the merge point (which I'll bet is actually 3 meters exactly.)

(Thought experiment for everybody - psychologically do you choose 'correct focus' as the place where the images merge - or the point a little further on where you see them start to split apart again? )

-- Andy Piper (apidens@denver.infi.net), April 15, 2002.

I did a quick test with my 90mm summicron last night and got roughly the same results. Hmmm.... The strange thing is both my M2 and the M3 were at Leica last year. And the M3 was there with the noctilux to match the focus. But both bodies were adjusted by the same man and probably the same equipment on his side so it could be that... I dunno. Later this week I will run a test on my friend's .85 body and see if I get the same results. I'll let you guys know with a post here.

-- Russell Brooks (russell@ebrooks.org), April 16, 2002.

Have you checked infinity alignment? I sent my 85/1.5 Canon to someone who gets mentioned here regularly as the king of lens repairs, and he sent it back out of whack (along with a couple of other problems, including all the screws being rattliing loose). I sent it back to him. His response to me (after he tightened the screws) was that it was set appropriately and properly to come to infinity at 200M. With this lens I can tell the difference in focus between one mile and two, and it's visible in photos wide open--200M was ridiculously wrong--so I ended up fixing it myself. Because this lens is the least tolerant of what I have, once in a while I check my two bodies with it, and adjust them to it, letting the less picky lenses take care of themselves. You might need to learn to do that yourself.

-- Michael Darnton (mdarnton@hotmail.com), April 16, 2002.

Incidentally, one of the things I learned from this exercise is that if you align your own RF, don't do it close to a window--the effect of going through glass is enough to throw things off. Either stand back 20 feet or so so the two RF windows aren't looking at the glass from different effective angles and thus seeing slightly differently refracted views, or open the window.

-- Michael Darnton (mdarnton@hotmail.com), April 16, 2002.

Ok, I tested it on my friend's .85 M6 TTL. It really looks like it is the lens instead of the body. The focusing mechanism looks fine but somehow it is off. I will send the lens into Leica now to be repaired. But let this be a heads-up to you guys out there with older fast lenses to confirm the focus...

-- Russell Brooks (russell@ebrooks.org), April 22, 2002.