Who are we?  Featured Cameras  Articles  Instruction Manuals  Repair Manuals  The Classic Camera Repair Forum  Books  View/Sign Guestbook

Canon SLR focus screen cleaning Log in | Log Out | Topics | Search
Moderators | Register | Edit Profile

Classic Camera Repair » Archives-2006 » Canon SLR focus screen cleaning « Previous Next »

Author Message
Top of pagePrevious messageNext messageBottom of page Link to this message

Jxsoriano
Tinkerer
Username: Jxsoriano

Post Number: 3
Registered: 09-2006

Rating: N/A
Votes: 0 (Vote!)

Posted on Thursday, September 28, 2006 - 11:57 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I need suggestions on the best way to clean a focus screen from a Canon SLR. It has stuck some old pieces from mirror foam.
Top of pagePrevious messageNext messageBottom of page Link to this message

Ethostech
Tinkerer
Username: Ethostech

Post Number: 14
Registered: 07-2006

Rating: N/A
Votes: 0 (Vote!)

Posted on Friday, September 29, 2006 - 07:38 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Respectfully - you need to post more information.
To know the Model of the Canon SLR would be useful.
It is a proposition to remove the focusing screen on some models - but absolutely not on others.
Top of pagePrevious messageNext messageBottom of page Link to this message

Jxsoriano
Tinkerer
Username: Jxsoriano

Post Number: 4
Registered: 09-2006

Rating: N/A
Votes: 0 (Vote!)

Posted on Friday, September 29, 2006 - 12:23 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

It is a Canon FT QL
Thanks.
Top of pagePrevious messageNext messageBottom of page Link to this message

Glenn
Tinkerer
Username: Glenn

Post Number: 62
Registered: 07-2006

Rating: N/A
Votes: 0 (Vote!)

Posted on Friday, September 29, 2006 - 08:06 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

There is plenty of information in the archive on this problem. The basics are as follows: Blow all the loose bits off with an air blower. Then using a cotton bud (Q-Tip) moistened with Ronsonol (Naphtha/Lighter Fluid), gently wipe the exposed surface of the screen along the long side once - ie left to right. Do not reuse the cotton bud and never make more than one pass with moist bud. Repeat, using a new moistened cotton bud for every pass, until the sticky degraded foam is removed.

Do not use a 'scrubbing' action on the screen and do not saturate the cotton bud. If you flood the surface with naphtha it can run onto the upper-side of the screen, This can lead to 'oily' marks being left as the solvent evaporates. On the FT, the only way to clean the upper surface of the screen is to remove the pentaprism.
Top of pagePrevious messageNext messageBottom of page Link to this message

Ethostech
Tinkerer
Username: Ethostech

Post Number: 16
Registered: 07-2006

Rating: N/A
Votes: 0 (Vote!)

Posted on Saturday, September 30, 2006 - 07:30 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Wow! Sorry - I would argue against Glenn's directions - but I don't want to get into a slanging match. I will just say that the fresnel screens are acrylic and any sort of spirit - even pure petroleum spirit or alcohol isn't a good idea. I have been that route and learned the hard way. A cotton-bud moistened with Windex - and applied according to Glenn's directions - is a safer bet.

Glenn's mileage may differ however and I respect his entitlement to a contrary view. It could also be that all fresnels are not equal.
Top of pagePrevious messageNext messageBottom of page Link to this message

Glenn
Tinkerer
Username: Glenn

Post Number: 63
Registered: 07-2006

Rating: N/A
Votes: 0 (Vote!)

Posted on Saturday, September 30, 2006 - 09:58 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Just for the record; I have cleaned literally dozens of CANON screens over the last 30 odd years. All have been cleaned with naphtha - sometimes followed with a washing up liquid/water wash, if out of camera. I have even used the solvent in an ultrasonic bath to clean some very dirty T90 screens.

Assuming 'Windex' is a water based cleaner and the degradation products of the foam being non soluble in water, I'll stick to my very tested method for Canon manufactured products. As I only 'fiddle' with Canon kit, this will be no hardship.
Top of pagePrevious messageNext messageBottom of page Link to this message

Jxsoriano
Tinkerer
Username: Jxsoriano

Post Number: 5
Registered: 09-2006

Rating: N/A
Votes: 0 (Vote!)

Posted on Monday, October 02, 2006 - 06:42 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Can you give me advice on the best way to remove the screen completely to clean it?
Thanks,
Top of pagePrevious messageNext messageBottom of page Link to this message

Glenn
Tinkerer
Username: Glenn

Post Number: 65
Registered: 07-2006

Rating: N/A
Votes: 0 (Vote!)

Posted on Monday, October 02, 2006 - 07:22 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

The top plate is easily removed, just remove wind on lever, shutter speed dial, rewind knob and battery 'door'. Remove the screws in the front plate and remove plate, now remove all top plate retaining screws.

The next bit is the tricky part as you have to remove the eyepiece, pentaprism, meter galvo and then the screen retaining frame. You are likely to come across quite a bit of degraded foam light seal also.The foam will need cleaning off and replacing. The disassembly is quite logical and straight forward - just remove the visible screws, but does need one to take care - especially if you are not to bend the meter needle. Also note the position of any shims under the screen retainer. Check the focus after reassembly using a piece of ground glass/draughting film on the film gate.

Take care also when you remove the prism retainers. I have come across some early FT prisms on which the protective black paint has started to loose adhesion. The paint will fall off with the slightest touch/knock.

Add Your Message Here
Post:
Bold text Italics Underline Create a hyperlink Insert a clipart image

Username: Posting Information:
This is a private posting area. Only registered users and moderators may post messages here.
Password:
Options: Enable HTML code in message
Automatically activate URLs in message
Action:

Topics | Last Day | Last Week | Tree View | Search | User List | Help/Instructions | Program Credits Administration