15mm alignment

[Stephen23]

I have been using the VC 15mm lens on my Bessa L for a while now without a problem, despite the fact that the white dot does not centre in the middle. I have tried it on my new R3M with the adapter and the dot still does not line up. I have just read in another thread that you can solve this problem by "adjusting three screws".
Is this
a.) possible?
and
b.) a D.I.Y. job?

Stephen

 

[kbg32]

Yes. Do a search. Someone had posted pictures of D.I.Y. steps.

 

[peter_n]

Yes Stephen, not difficult to do. Where are you in the West? (County will do. 😉 )

 

[Stephen23]

Thanks Keith
I've just run a couple of searches without results anyone out there now where the thread might be?

Stephen

 

[Stephen23]

Hello Peter
I am in sunny (not) Westport, County Mayo which is currently cold dark and wet which is why they built the pubs...

 

[peter_n]

Westport, wonderful! I love the west, and so do my kids! 🙂

See the two links below, I hope they help with your problem:

http://www.rangefinderforum.com/forums/showthread.php?t=29364

and:

http://www.rangefinderforum.com/forums/showthread.php?t=30918

 

[Stephen23]

Thanks for the links Peter. "If you ever go across the sea to Ireland..."

Stephen

 

[Didier]

Hi Peter

It may happen that the white dot in the middle of the aperture ring engravings does not fit the centre, I have several older LTM lenses with that small problem. It's not an issue unless it's not more than a sixth or an eighth of rotation (-22.5° to 22.5° degrees). The only issue is the inbuilt lenshood of the 15mm Heliar that is not vertical in this case. But that lens has such a large DOF that a 0.125mm (=1/8th of one mm thread) displacement has no effect on focusing. With a 35/1.7 wide open this might be different, but am not shure about.

And I'm not shure whether the 15mm Heliar can be adjusted like the 35mm Ultron shown in the link mentioned above. You may do more bad than good by opening it.

Didier

 

[peter_n]

Thanks for the links Peter. "If you ever go across the sea to Ireland..."

Stephen

I'll be there next year Stephen. Will be attending a wedding in Dublin so I'm really hoping to have enough time to go over to the west. I lived in Dublin for 8 of the happiest years of my life and I miss it terribly still.

 

[derekphan]

How to check if the 15mm focus accurately? I have no idea cause it's not rangefinder coupled. Any expert can help me?

 

[pizzahut88]

I have been using the VC 15mm lens on my Bessa L for a while now without a problem, despite the fact that the white dot does not centre in the middle. I have tried it on my new R3M with the adapter and the dot still does not line up. I have just read in another thread that you can solve this problem by "adjusting three screws".
Is this
a.) possible?
and
b.) a D.I.Y. job?

Stephen

It's possible, and a DIY job, I did personally on my Heliar 15mm.
Think someone already gave you the proper URL to my post.
http://www.rangefinderforum.com/forums/showthread.php?t=30918
Actually, it was frerider who figured it out first.

 

[Stephen23]

Finally found the time to try this out and it works perfectly! Have also adjusted the CV 50/2.5 which hits the middle spot dead on. Thanks for all the help on this one, though can't help wondering why they leave the factory like this??

Stephen

 

[pizzahut88]

hmmm

hmmm

though can't help wondering why they leave the factory like this??

Stephen

I couldn't understnand either. They should fixed it in the first place.
Well, thank god, they left two extra holes for us to do it ourselves.

 

[Abbazz]

The only issue is the inbuilt lenshood of the 15mm Heliar that is not vertical in this case. But that lens has such a large DOF that a 0.125mm (=1/8th of one mm thread) displacement has no effect on focusing.

Didier,

If I'm not mistaken, we are speaking depth of focus here, which is actually shallower for wide angle lenses.

Depth of focus = Aperture x Focal length / 1000

Thus for a 50mm lens at f/4.5, DoFc = 0.225
And for a 15mm at f/4.5, DoFc = 0.0675

You see that a lens displacement of 0.125mm is within the DoFc for a 50mm lens, but not for a 15mm lens used wide open. That is the reason why many people are complaining about the lack of sharpness of their wide angle shots, even though they have no problem when using a tele lens. Usually, this is the indication that their camera has a registration adjustment problem. But they won't admit it, because they are confusing depth of field (which is the degree of out-of-focus permitted on the subject plane and which increases when focal length decreases) and depth of focus (which is the degree of out-of-focus permitted on the film plane and which decreases when focal length decreases).


Cheers,

Abbazz