Canon AV-1 50mm disaster!

[philc]

So, long time since I've been on here. Up until a few weeks ago I hadn't touched my camera for a good few years. Work got in the way, COVID happened etc.

Anyway, went on holiday last week for the first time in 5 years, so took my Canon AV-1 with just my 50mm lens (travelling light), went through two rolls of Ilford XP2 super. Got back and took my rolls to get developed yesterday, and in the interim I was having a little clean of my lenses and just generally sorting stuff out.

In cleaning the 50mm, I was fiddling with it and noticed that the aperture was stuck wide open... d**n!

I was on holiday in sunny Cape Verde, mostly taking landscape photos or shots with the subjects a fair distance away, with a large f stop (or so I thought). I'm trying to figure out if the photos will be completely ruined or if they will still be ok despite the camera thinking the lens was on a low f stop and compensating with the appropriate shutter speed?

Now I need to try and find my precision screwdrivers and start taking the lens apart to see if I can fix the issue, hopefully it's nothing major.

However, I am now on the hunt for a rangefinder to have a little play with something different

 

[Ian C]

With an full-aperture-viewing SLR lens with the diaphragm stuck open, the problem is almost always due to the oil component of the helicoid grease that has seeped out and fouled the aperture blades. Oil-contaminated aperture blades are most often due to heat damage to the helicoid grease. That might have happened one or more years ago. It takes time for the oil to seep out onto the aperture blades and immobilize them.

Once coated with oil, the “sticktion” (drag between adjacent blades) is too great for the relatively-modest tension of the closing spring to overcome. Over time, the oil will oxidize to a gummy, or even a varnish-like consistency. The aperture assembly needs to be degreased with a compatible solvent, such as mineral spirits or naphtha and dried.

The problem will reoccur unless the old damaged grease is removed from the focusing helicoids and replaced with the CORRECT very-light-bodied grease. It’s a fussy job. The helicals must be disassembled, cleaned, relubricated, and reassembled in the same orientation in which they were assembled. Most helical-focusing lenses have 6 threads (6 starting positions). Only one of these is correct. For most of us, that’s not a DIY job. It requires particular tools. The small screws holding the lens together are not Phillips cross-slot screws. On a Canon or Canon-compatible lens, they are JIS (Japan Institute of Standards) cross-slot screws, which use a different geometry than the Phillips standard.

There are several cross-slot screw socket designs shown in the following link:

https://en.wikipedia.org/wiki/List_of_screw_drives


Here is a list of greases from Japan Hobby Tool. #30 is usually about right for manual-focus SLR lenses.

https://japanhobbytool.com/products/hg

 

[MarkVII88]

What you are describing is perfectly normal for Canon FD lenses, when dismounted from the camera body. There is an aperture tab on the back of the lens that the camera engages to stop down the lens prior to taking an exposure. The lens is normally wide open, to allow for brighter viewfinder when focusing and composing your shots. When dismounted from the camera body, the lens will remain wide open unless you move the aperture tab, then the lens will stop down to whatever aperture is set on the aperture ring. I do not think your lens needs to be disassembled or serviced. Chances are your images will come back looking just fine.

 

[Ian C]

I hope Mark has the answer. If you mount the lens and it closes down correctly when set to an opening smaller than wide open when the shutter is fired, then it's fine. I'd assumed that the diaphragm was stuck.

 

[philc]

Cheers guys,

Mark, I used a tool to depress the lug which would be depressed if the lens were fitted to the camera and then used the L-shaped 'pin' to simulate the shutter being activated and the aperture was exceedingly slow to respond if at all. I hope you are right and that the pictures do turn out fine though!

Ian, thank you for the guidance, having done some reading online etc, I think that is probably it and it may be best to send the lens away for someone to do it properly rather then me mess it up more! I anticipate this being like asking how long a piece of string is, but do you know roughly how much this may cost? If it is more economical to buy another lens then I can do that and use this one as a practice for if I need to service lenses in the future.

Thank you!

 

[Ian C]

You should contact a reputable camera repair service for an estimate. Cleaning an oily diaphragm, removing the old helicoid grease, relubricating the helicals and reassembling, and making sure that the infinity focus matches the focusing ring is a standard service.

I’ve done my own in the past. One shop that has had good feedback here is Zack’s Camera Repair. Its advertisement runs on APUG/Photrio. Here is a link to the business. There are others as well. Hopefully, others will comment on shops from which they have had satisfactory service for problems such as yours.

https://zackscamerarepair.com/