Very important question!

[kubakaznowski]

Please explain one thing to me...

FILM REGISTER ISSUE.

1. as far as I was told: here ad in other well informed places
film registration for LTM cameras is 28.8mm.

2. Moreover my Voigtlander Bessa - L , IS LTM camera, right?

3. Do I get it right that a lens will work properly:
having same thread / different thread using adaptor
when THE LAST LENS part will fit in between those
28.8mm, yes?

So if I buy german lens like porst 28mm M42, use an adaptor
the last part of the lens must fit 28.8 mm to keep infinite focus.
Yes?

Please explain with patience and precisly as my first language is Polish

Jacob.

[Bryce]

Jacob-
The film registration distance is the distance between the film plane and the surface on the front of the body where the lens attaches. It does not include threads, bayonet lugs, etc.
To use a M42 lens on a M39 body, the adapter would have to hold the back surface of the lens assembly forward of the front surface of the body by the difference between the two systems registration distances. Since M39 lenses use a distance of 28.8mm and the M42 system uses 45.5mm, the adapter would have to be 16.7mm thick, not including threaded portions, for the lens to focus correctly.
Hope this helps.

[kubakaznowski]

THANK YOU, so due to my english understanding possibilities a PERFECT adapter
has the SPACE between the end of one thread to the beginning of second
exactly 16.7mm.
16.7 is not the lenght of whole adapter just the distance between the end of one thread to the beginning of second . Correct?

[jaapv]

No- between the front and back flange of the adapter. Forget about threads and lugs etc. It just makes your body 16.7 mm thicker.

[kubakaznowski]

Ok. but if that lenght will be, let's say 11,5 like in my adaptor, will I have
infinite focus: I don't need minimum, that's why I ask.

If the distance will go shorter then 16.7mm, how will it affect the focus?
WHAT IS THE rule, if you have longer what it does and if it is shorter what it does.

Thank you and sorry for being annoying.

Jacob

[kubakaznowski]

so the distance (length) of my adaptor from edge to edge is exactly:

[jaapv]

You simply cannot focus as close-up, maybe not closer than 5 meters. On the other end , the shorter register allows you to focus beyond infinity, which is of course meaningless.

[jaapv]

Oh- and you will have to find out which marking on the distance scale correponds to infinity. If you want to visualise what happens, open the back of the camera, stick a piece of semi-tranparant paper where the film goes, open the shutter and you will have improvised a focussing screen.

[kubakaznowski]

So with no worry I'll buy 20 mm lens from east germany factories of golden
1980's.
That's what I need a wide angle for landscapes.

Thank you Jaap!
Golden Boy you are.

[kubakaznowski]

So infinity may happen to be "before" infinity?

What then would infinity be?

[jaapv]

The simplest thing to do is to get the correct adapter! Good luck.

[rxmd]

What then would infinity be?

It's possible, if very inconvenient, to actually calculate that from the length of your adapter. But I would really suggest getting an adapter with the proper lens. You can have this made for you at any machine shop for low cost, it's really not a complicated item.

The Flektogon 20 is a great lens, by the way. I wish I had one. Are you after the f/4 or the MC f/2.8 version?

Philipp

[kubakaznowski]

the f/4 one...

[kubakaznowski]

By the way the length of my adapter is 12,5 mm

[jaapv]

I see you mention getting Porst lenses. I wouldn't if I were you. Porst is often rebadged stuff that has been bought el cheapo elsewhere. Quality is uncertain at best. A CZ Jena Flektogon is, as mentioned above, a whole different story.

[ffttklackdedeng]

Originally Posted by kubakaznowski

By the way the length of my adapter is 12,5 mm

If your adapter is 12.5 and you need 16.7 it means that you will have to move the lens away from the body (by focusing from infinity in the direction of the closest distance - that way the lens moves away from the body) by 4.2mm to have it (with your adapter on LTM body) focused on infinity.

A 35mm lens you will have to focus to approx 0.5m to move it 4mm away; a 50mm lens to about 1m. Looks like you would have to focus a 20mm lens to about 30cm to get it 4mm away (i.e. at inifinity).

Robert

[kubakaznowski]

I am astonished. Clever man you are. Thx

[cruz]

cze wlasnie kupilem taka przejsciowke na eb*y i czekam kiedy typ mi ja przysle, ale gadalem tez dzisiaj z typem na gieldzie ktory robi w metalu powiedzial ze kosztowaloby to 50 pln

[kubakaznowski]

Originally Posted by cruz

cze wlasnie kupilem taka przejsciowke na eb*y i czekam kiedy typ mi ja przysle, ale gadalem tez dzisiaj z typem na gieldzie ktory robi w metalu powiedzial ze kosztowaloby to 50 pln

This is mainly an english speaking forum, and so I suppose other
members would appreciate writing so anyone would understand,
my polish mate.
Please join polish forum or switch to english.

[cruz]

Ups sorry, just got emotional to see someone from my country who came up with almost the same idea, at the same time. Hope no one here feels offended by using foreign language