Nokton 40mm f/1.4 and Back Focusing on the M8

[Doug]

It might be helpful to shoot a series of really dull photos like the one below. I positioned the camera close to a wall with a distinctive feature and some texture, and angled it about 45 degrees from the surface. Then I shot wide open, down one stop, down two stops, down 3 stops, etc. If you closely examine the focus point in each photo you can see whether it's focusing in front of the intended point, or behind the point, and whether the best focus moves as you change apertures ("focus shift").

FWIW, this shot is the Zeiss C-Sonnar 50mm (known for focus shifting) wide open after some fine-tuning by DAG, and going by this photo it appears to be front-focusing by about an inch at this aperture. (click thumbnail to see larger version)

 

[ampguy]

VF / lens focus accuracy

VF / lens focus accuracy

I think it's best to have the VF aligned vertically and horizontally before trying to determine if a lens is front/back focusing.

Since the 50 cron you tried seems to be OK, and the 40 seemed to focus more accurately when you rotated focused with VF rotated 90 deg. I think you might want that checked out.

Here's another test you might want to try: http://nemeng.com/leica/024b.shtml

Wow! Although I've read some threads about misaligned viewfinders on M8s, I would never have thought that people were discussing something that's not noticeable unless you're looking for it. Can you suggest other objects I might try focusing to confirm? This seems like it must be a common propblem and that I'm better off having the dealer warranty take care of it rather than trying to replace it with a completely different M8. Thoughts? Thanks!

 

[ROOOO]

Thanks, I read the page on the FAQ, but it wasn't entirely clear to me. These are probably a dumb questions, but what exactly should I look for when I infinity focus on something in the sky? Just that the edges of the clouds are lined up in the rangefinder patch? And how far do I move laterally when I'm focusing on the black tape on the mirror? I don't understand why the focus would jump from 1m to 2m unless the camera actually was 2m away from the tape.

 

[ampguy]

reflection

reflection

For infinity focus, maybe try a very distant tree, or object on a mountaintop.

For the mirror test, try to move laterally just an inch or two, make sure not to move forward or back after focusing on the tape. The reason the distance is twice is when focusing on the camera, it's the reflection, when on the tape, it's the mirror itself.

Thanks, I read the page on the FAQ, but it wasn't entirely clear to me. These are probably a dumb questions, but what exactly should I look for when I infinity focus on something in the sky? Just that the edges of the clouds are lined up in the rangefinder patch? And how far do I move laterally when I'm focusing on the black tape on the mirror? I don't understand why the focus would jump from 1m to 2m unless the camera actually was 2m away from the tape.

 

[ROOOO]

Ah! So you are no longer focusing on the tape but rather on the reflection. I see! Haha, thanks! I'll try that out. Unfortunately, I don't have anything to try out infinity focus on. It's overcast, so nothing is really visible in the sky. I tried focusing on a tree that's about 500 feet away (by my guess) and focus in the rangefinder is achieved with the focusing ring just a hair short of infinity, which seems right to me, no?

 

[ROOOO]

Okay, so I tried another little test for myself. I set up a piece of 8.5x11" paper with 12-point font printed on it about 0.8 meters away and tried to focus. I could read the text through the rangefinder, but when I aligned the images in the center patch, the text wasn't as clear because, I'm guessing, of a slight vertical misalignment. Now, my question is: Is this something that can be fixed? Or would that be asking for a sort of precision that isn't possible in these devices? Thanks!

 

[ferider]

Vertical alignment is very important to me, since, if done properly, focus "snaps" into place, which is nice when you need to focus fast.

This can be adjusted. But it also depends on your eye position, so see if it changes when you move your eye.

When you do these tests, use the middle of the patch, with a long object (screw driver, pen, a line on paper) that reaches out of the patch. Focus by aligning the object inside and outside of the patch. And do use a tripod.

Roland.

 

[lewis44]

When I first got my M8, I tested my lenses using the chart you did. I found 3 of the 6 were off and 2 back focused and one front focused slightly. All looked fine when I used them on a film camera.

I emailed Don Goldberg and he responded that 90% or more times it's the lens. The M8 sensor is perfectly flat, while film is not, so it may not appear using film, but will show up on the M8/9.
I asked if I should send the camera and he said no need at this point.
I sent the 3 lenses in question and a few weeks later they came back right on.

So to answer your question, it's 90% or more probable it's the lens, especially seeing the 50 looked OK

As for getting Stephen to do anything if you did not buy it from him
"GOOD LUCK"

I inquired once telling him that I had a CV lens and that I removed the mount to send for coding. When I got the mount back, I overtightened one of the screws and it broke. I explained to him that I did not buy the lens from him, but I'm willing to pay the for the screw and shipping and can he help.

He replied that "I should seek out a repair shop, as he doesn't keep things like that in stock and would not order it."

He basically told me to "Piss up a Rope"

He is a repair shop and I actually had him work on a M4 I had some years ago

Don Goldberg sent me a screw "No Charge"

 

[ROOOO]

I took the camera to the local technician, and he also detected the vertical misalignment in the rangefinder. However, he also said that that shouldn't be causing the back focus, in all likelihood.

Anyhow, it looks like I'll be sending it back to the dealer in New York, who will then send it on to New Jersey. They offered to give me a refund, but I would rather just get a camera that I know is correct rather than keep shopping, especially since I would probably be buying via mail order.

I'm going to test out a Summicron 40 tomorrow and see if the back focus is still an issue, or it is was just the Nokton. Either way, should I see if I can include a lens when I have the camera sent in for service? Or should I just send the camera?

Thanks again for all the help you've all provided!

 

[ampguy]

sounds like a good plan

sounds like a good plan

I'd ask your dealer about sending in your lens with the camera.

Would be nice to get the whole system working at one time.

Not sure if Leica NJ would want to try adjusting a CV lens, but let us know ...

I took the camera to the local technician, and he also detected the vertical misalignment in the rangefinder. However, he also said that that shouldn't be causing the back focus, in all likelihood.

Anyhow, it looks like I'll be sending it back to the dealer in New York, who will then send it on to New Jersey. They offered to give me a refund, but I would rather just get a camera that I know is correct rather than keep shopping, especially since I would probably be buying via mail order.

I'm going to test out a Summicron 40 tomorrow and see if the back focus is still an issue, or it is was just the Nokton. Either way, should I see if I can include a lens when I have the camera sent in for service? Or should I just send the camera?

Thanks again for all the help you've all provided!

 

[ROOOO]

I think I'm going to essentially swap the CV 40 for a 40mm Summicron, so we'll see....

 

[ferider]

Remember though (on film):

DOF 40/2 @ 0.8m (Summicron min. focus): 5cm
DOF 40/1.4 @ 0.7m (Nokton min. focus): 2cm

In other words, if the Summicron "works" (due to more than twice the DOF), it doesn't mean the Nokton didn't. Or, @f2 and 0.8m, your Nokton might work just as well.

Roland.

 

[Makten]

I think I'm going to essentially swap the CV 40 for a 40mm Summicron, so we'll see....

My 40/2 front focuses on my M8 unless I stop it down to f/4 or so. :bang:

 

[baycrest]

my 40 f1.4 is spot on, on my M8. My 35 Lux had to go to Leica to add some spaces to focus correctly wide open at 1.4, otherwise I'd have a back focus. As with most 35 Luxes, mine suffers from back focusing from f2 and smaller, however when you hit f8 its hardly noticeable.

Best
Rob

 

[Bébèrt]

I love my VC 40/1.4. Wide open a bit soft of course but still verry good glass for little money.

 

[Bébèrt]

Nice and sharp, bokeh is oké but not like a Summilux.