My DMC-G1 with manual focus lenses

[Jonas]

http://cgi.ebay.com.hk/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWNX:IT&item=130292061386

Thank you.

I have a thread of Navitron 75mm F1.3 as below:
http://forum.getdpi.com/forum/showthread.php?t=6941

(...) But as long as you use it as a portrait or close up lens, it is quite usable. Closet focus distance is 1m, extension tube may prefer.

Hi pentacon6,
Yes, I remembered there was something about that lens and the mount. I found your thread with the four lenses.
Well, I would be interested if somebody was able to make it work for any shooting distance. As I haven't seen the lens in real life I don't know if that is possible at all. It sounds as it may be undoable.

thanks,

--
Jonas

 

[pentacon6]

To Jonas,
You are welcome. From the observation, the modification should be
quite precision. I think the diameter of the rear lens should be trimmed
down for 1mm and the about 1mm shorter to prevent it hit the shutter
plane. The standard of C mount lenses are not in consistent standard.

 

[Jonas]

I guess the trimming can be done by somebody with the proper tools. For mechanics I'm a kitchen table guy and so I'm not prepared to do it myself.
It seems as it could be worthwhile provided the rear lens element will stay untouched and if it possible to measure the distances making sure nothing will touch the shutter. I wouldn't mind paying for the work if the modification could be ordered.

thanks again, /Jonas

 

[Y.B.Hudson III]

Post a pic of the rear element of the Navitar 75 in the infinity position... there might be a easy fix...I have modified other Navitars with similar problems.


hudson

 

[pentacon6]

Post a pic of the rear element of the Navitar 75 in the infinity position... there might be a easy fix...I have modified other Navitars with similar problems.


hudson

The one at right top is Navitron. You may find out the rear parts of the element is extra longer than other lenses. That' why I suggest a trim down of diameter and the extra long part.

 

[Y.B.Hudson III]

Try this. With the focus ring on infinity, Remove the rear element retainer ring. For test purposes the rear element can then be retained in place with surgical tape. If the removal of the rear element retainer ring provides the required clearance, the rear element can then be cemented in place.


The focus helicoil and c-mount can be removed to provide easier access to the lens...

 

[pentacon6]

Hope this help. However, the lens seems has no trace of screw on the lens body.
I really have no idea how is the c-mount removable.

May you give me hints, Hudson?

 

[Y.B.Hudson III]

Pentacon6... I will write up the procedure with pics and post it later this evening. (California time )

 

[butterdada]

Infinity of my D.O. Industries Navitron TV 75mm F1.3 is ok
No need for modification~

 

[butterdada]

Canon FD 135mm F2 wide-open

 

[Jonas]

Infinity of my D.O. Industries Navitron TV 75mm F1.3 is ok
No need fot modification~

Hmm. Now I really would like to get one and try it. What adapter (seller) are you using with the lens?

/Jonas

 

[butterdada]

Hmm. Now I really would like to get one and try it. What adapter (seller) are you using with the lens?

/Jonas

New generartion (3rd) C to M4/3 adaptor made by Hawk factory, Taiwan


Lomo OKC2-100-2 100mm F2.8 wide-open
modified by Hawk Factory

 

[butterdada]

Minolta G-Rokkor 28mm F3.5 (L39 mount)
I used adaptor made by RJ camera (from China).

 

[Jonas]

New generartion (3rd) C to M4/3 adaptor made by Hawk factory, Taiwan

OK. Cheers, /Jonas

 

[butterdada]

OK. Cheers, /Jonas

Do you have Hawk's email?

Here.
[email protected]
He is a nice guy.


Elgeet Rochester 1 inch F1.9 wide-open

 

[butterdada]

Canon FD 135mm F2 wide-open
This FD to M4/3 adaptor is made in China (RJ camera).

 

[pentacon6]

Infinity of my D.O. Industries Navitron TV 75mm F1.3 is ok
No need for modification~

Hi, butterdada. I was confused, I really tried hard to reach the very end of the infinity.
How comes the rear element just touch the square part in front of the sensor?

I am using jinronfinance's adapter, is it the main problem? I still doubt about it.

But there is already a press mark on the square part.
May be the screw thread not exactly in the center. Really headache......

 

[Y.B.Hudson III]

... it's the lens design that's the problem, not the adapter. ask butterdada if his copy of the Navitron 75mm 1.3 can focus to infinity at f/1.3 (which I doubt)...the picture he posted is stopped down.

 

[pentacon6]

... it's the lens design that's the problem, not the adapter. ask butterdada if his copy of the Navitron 75mm 1.3 can focus to infinity at f/1.3 (which I doubt)...the picture he posted is stopped down.

Yes, that's what I doubt . F5.6 start to get sharp, F8 seems no problem.
I have compared the image between out and in focus at F1.3 that the
image present quite different. F1.3 produces soft image but not out focus blur.
You may see this picture. I turn the lens to infinity and you can see rear element.
The metal ring seems quite thin and need extreme care. I think 0.5mm trimming may be enough to make the thing totally different.

 

[Y.B.Hudson III]

You have to remove the metal ring and then it is possible to glue the rear Lens element in place...as it is retained on the sides by the lens barrel and there is a spacer insert to seat the element square.