8mm Forum: Scope lens focusing problem

»	8mm Forum » 8mm Forum » Scope lens focusing problem

UBBFriend: Email this page to someone!

Author

Topic: Scope lens focusing problem

Jean-Marc Toussaint
Film God

Posts: 2392
From: France
Registered: Oct 2004

posted November 02, 2004 06:16 AM

Hi all,

One of my scope lenses (the better one, *sigh*...) has recently become difficult to adjust. The focusing barrel requires some serious grip to rotate (I need to use both hands if I don't want to end up with vertical scope projection!) and sharp focus isn't easy.
Anybody ever encountered this kind of situation? Any suggestion to fix it?

Thanks.

--------------------
The Grindcave Cinema Website

| IP: Logged

Tim Christian
Expert Film Handler

Posts: 219
From: Norfolk, UK
Registered: Jun 2003

posted November 02, 2004 12:08 PM

Two points:

First, the obvious one, is there a separate locking ring on the lens? I was caught out by this once. The focusing ring on one 'scope lens became very stiff - until I realized that half of it was a locking ring [Embarrassed]

Next, if it is not the locking ring, it may be that the lubricant (grease) has dried and hardened. Drop a little white spirit or paraffin into the thread and see what happens. If it is gritty, you may have to take it apart to clean it [Frown]

.

What lens type is it?

--------------------
Tim

| IP: Logged

Jean-Marc Toussaint
Film God

Posts: 2392
From: France
Registered: Oct 2004

posted November 02, 2004 12:26 PM

Hi Tim, thanks for answering.

No, there's no locking ring on the lens. Gave it a good look when it started to get stiff.

White spirit, heh? Sounds a bit dangerous but I'll give it a try tomorrow and see what happens.

The lens is a Chretien/Hypergonar (from the people who invented CinemaScope) and is far more superior to the other lens I have (Kowa 16D).

--------------------
The Grindcave Cinema Website

| IP: Logged

Ugo Grassi
Jedi Master Film Handler

Posts: 506
From: Avellino (Italy)
Registered: Dec 2003

posted November 02, 2004 12:35 PM

Hi Jean Marc,
is the focus worst than in the past? I suppose there is a little bit of grease vapored inside. It's possible the lub. inside is vapored, soiling the lens.
The only way - but very dangerous - is to open the objective.

ps. your signature is very funny! anyway it's the best to sweeten the italian coffe. Do you think it could be dangerous for my health?

--------------------
Bye
Ugo

| IP: Logged

Jean-Marc Toussaint
Film God

Posts: 2392
From: France
Registered: Oct 2004

posted November 02, 2004 01:43 PM

Ugo,
Nope, the lens is crystal clear, there seems to be nothing in there . Focus is just difficult to achieve because the barrel is a bit stiff.

Hope I won't have to open it... [Frown]

--------------------
The Grindcave Cinema Website

| IP: Logged

Jean-Marc Toussaint
Film God

Posts: 2392
From: France
Registered: Oct 2004

posted November 05, 2004 07:07 AM

OK, so far, so good.
The white spirit seems to work. The barrel is easier to turn but we're not there yet. I'll let it rest for another 24 hours.

--------------------
The Grindcave Cinema Website

| IP: Logged

Jean-Marc Toussaint
Film God

Posts: 2392
From: France
Registered: Oct 2004

posted November 07, 2004 04:57 AM

Problem solved! [Big Grin]

The lens is good as new (it makes an interesting "squish" sound now, but I guess it'll pass when the remaining white spirit is fully evaporated).

Thanks Tim and Ugo.

JMT

--------------------
The Grindcave Cinema Website

| IP: Logged

All times are Central

Printer-friendly view of this topic

UBB.classic^TM 6.3.1.2