Tag: light meter

Canon AV1

I now have a Canon AV1 with a shutter problem. Can I fix it? I’ll have a good go…

What the listing stated:

This camera is in very good overall condition. Some light signs of use but this is generally minor. The light meter is responsive when you press the shutter button down. However, the shutter will not fire. Spares or repairs only.

EBay

I’ve just paid £8:98GBP for this camera, and I believe this is a great price for a piece of camera history. The AV was introduced due to there being a demand for aperture priority at the time, whereas its Sibling, the AE1 was purely shutter priority. Later cameras would come to incorporate both systems. This one has a known problem with a stuck mirror – it won’t fire and I think I can easily sort this problem. Well I hope I can.

The Canon AV1 I have just purchased

Here’s a little information about this camera:

The Canon AV-1 is a 35 mm single-lens reflex camera with an FD lens mount, introduced by Canon Inc. in 1979.

The AV-1 is very similar to the 1976 AE-1 but provides aperture priority autoexposure rather than the AE-1’s shutter speed priority AE. The camera is not capable of fully manual exposure. Canon’s international distributors, particularly in the United States, had clamored for such a camera because competing brands offered mostly aperture-priority cameras and some preferred it. The AV in the name referred to the type of autoexposure; Av (Aperture Value) is a common abbreviation for aperture priority.

When this camera appeared, a new range of FD lenses was introduced, with instant mounting/unmounting of the lens. This is called the New FD mount and does away with the older type of mounting ring which was fitted on to the rear of the lens and was awkward to use and needed two hands, to a newer, easier system whereby the user lined up the red dot on the lens, with the red dot on the camera and simply turned the whole lens clockwise until it clicked into place.

All the other AE-1 accessories fit the AV-1.

Wikipedia

I’ve decided to collect all of the Canon “A”Series of cameras, and this adds to my current collection that consists of an A1 and an AE1. There were I believe, six cameras in this range and this current camera will be my fourth. Here’s a list of the “A” range of cameras below. I have highlighted with an asterisk all that I currently have at the date of this blog post being published:

Assessment:

The original listing description does not match the issues that I have found. It originally stated that the light meter is responsive, it isn’t. It also stated that the shutter does not fire, it does when a battery is installed. The battery level indicator in the viewfinder does work when the check button on the camera is depressed. However when you focus the camera and half depress the exposure button to get a meter reading, the needle in the viewfinder doesn’t respond, this is the only real issue I can see, I guess the seller must have been looking at another camera as he wrote the listing for this camera.

Battery level reading in the viewfinder

All settings appear to be working as they should, the “B”setting allows me to scroll through the “f” stop settings to see the aperture leaves working as they should. All “f” stop settings appear to work on the auto setting.

Camera appears tidy but grubby

It’s a smart little camera, this a tidy example of this version with no dents, dinks and just some very fine scrapes on the base as you’d expect from a camera fast approaching 46 years old (1979-2025). It’s a bit dirty and needs a good clean inside and out, the light seals are in a good state and not requiring replacement or repair just yet, however the mirror bumper has deteriorated and this will need replacement.

Mirror bumper needs replacement

The shutter curtain is in a good and untouched condition.

I’m going to research issues with the exposure indication, and I will incorporate my findings within the repair section.

Repair:

I thought, perhaps the camera is suffering from lack of use? It certainly is probably some considerable time since this camera was last used. Firstly I’ll try exercising all the controls that affect the exposure reading, including the mode dial, film speed dial, aperture ring, etc. I’ll work them backwards and forwards a few times to see if this helps to clean the variable resistor tracks inside from any surface contamination. When the FD lens is attached you must be mindful that the “A” setting on the lens is not used and that the f stop settings are used in a manual manner, lens auto is not a function on this camera.

Auto shutter on camera
Do not use the “A” setting on the lens. It doesn’t work

To be honest, this did seem to work sort of. The needle has moved off the bottom a bit. The ASA setting was on 100, so I put it up to 1600 as it is quite a dark day and the sensitivity of the light sensor would be reflected better at this setting. It moved a bit but I wasn’t totally convinced that this indication in the viewfinder reflected the true light situation.

I set a higher ASA for testing

There’s also a small, silver push-button just inside the lens mount at about the 4-5 o’clock position. If you press this in and release it a few times for the same reason, as exercising the dials as I did above, it is just like exercising a body part and keeping it supple. Leave items like this, designed for high usage redundant for a while and they soon seize up. it has also been known to assist with getting the needle indication working after a long lay off.

That silver button, highlighted

(A little bit of trivia here – this button is normally used for the lens to inform the body of the lens’s maximum aperture. This information isn’t needed on the AV-1, but Canon included it anyway for some reason, and it does affect the exposure.)

And combining these actions, moving the settings dial and the button inside the lens mount seems to have revitalised the light meter and I’m now quite confident that it is working as intended. It was just lazy due to low use and needed a bit of non invasive intervention to get it working again. And non invasive intervention is always a good thing. So with the setting back to 200ASA I was able to show the meter working in this very short and basic video below.

A brief video showing the meter needle moving

I’m confident that the metering issue is now sorted so let’s get that new mirror damper installed.

A lot of dirt came off of the area where the replacement damper had to go, it had completely deteriorated and took quite a bit of cleaning.

New damper in place
Dirt that came off, and replacement damper ready to go into place

Now in place it has silenced the mirror movement somewhat, and will provide some longevity as it moves into the twilight of its years. It will be good for many more rolls of film yet. Whilst in the lens area I have cleaned the mirror and prism, and given the area a good blow through and put the lens back in place to seal it all up. It is now clean internally. I have a couple of body caps on order that will assist with storage when the lens is removed.

Just a final clean with some cockpit cleaner, and this camera has come up lovely, I’ve tested it on a Power winder “A” as well and it sounds just so good and “retro”. It’s perfect.

Result:

Well. I now have another lovely example of one of the Canon “A” range of cameras to add to my collection. This brings my current total to four out of the six available, two of which are still currently under repair. For less than £10:00GBP it is so easy to own a piece of photographic history. I have been lucky here that the work that had to be done was non intrusive, and to be quite honest was just basic everyday maintenance. The only real work of sorts was installing some mirror damper felt, of which I have plenty of stock. Cleaning was quite intensive but the overall result is amazing.

Front views after cleaning
Looking amazing compared to what arrived

I will eventually run a roll of film through for a final quality check, however I have such a backlog it will take me a while. When I do however run that test roll I will post a link here:

Really pleased with this repair, and the fact that another lovely old camera has been saved from the scrap heap and been given a new lease of life.

Thanks as always for passing by. It is as always, very much appreciated.

Sangamo Weston Master V light meter

What the listing stated:

Sangamo Weston Master V  Exposure Light Meter includes Invercone & Cases The exposure meter is not working The invercone will also fit the Weston IV

EBay

Weston V light meter and Invercone

I have brought a little item from my past history here, going way back to the days when you had to work out the light levels in photography for yourself. The exact date of this unit is unknown, however it was manufactured between 1963 and 1972. That’s two years prior to my birth and up to the age of when i was 7 years old. And I was using them when I went into photographic work approximately ten years later. These units were made to last and did their job well, hence their longevity. I’ve paid the total cost of £8:40GBP and that includes postage. I’m surprised to be honest as not only is it the light meter, but also an Invercone (I’ll explain later) and two cases. An absolute bargain in my eyes as the Invercone itself, in a case can sell for more than I’ve paid for the entire package today. Oh, and it doesn’t work and to be totally honest I don’t think I will be able to get it working ever again, as the suspected component fault is one of those little things that are only dealt with by specialist craftsmen. Add to that the problem of locating a replacement piece, as they are nigh on impossible to obtain, or in layman’s terms, as rare as hens teeth.

But I have read about people reviving these parts and I’m going to give that a try. If I’m unsuccessful it will be a nice piece to get mounted into one of those box frames as a historic photographic memento.

What is this part you’re referring to?

A light meters main purpose is to react to available light and direct the photographer toward making a decision regarding the settings for his camera. Things like ASA, shutter speed and f stop settings.

Therefore it needs something to sense the light. It’s not a solar panel, these were not invented back then, but it was a similar system and it was called a selenium light sensitive cell. When exposed to light, the cell generates a small electric current that deflects the needle of an ammeter coil within a strong magnetic field. The whole system is basically a Selenium cell, a resistor and the ammeter coil. The lightmeter is entirely dependent on the light sensitivity of the selenium cell for accuracy. Over many years the selenium cell ages and degrades to the point that it just stops working. It dies. Its main cause for demise is usually moisture getting into the workings and causing degradation at the contact points on the Selenium cell.

There are a number of posts/sites I have visited that claim you can revitalise these items, however I am sceptical at this. There seems to be only one person in the uk that seems to totally replace these items and that is a guy called Ian Partridge, who I believe charges around £90GBP for a repair and his site can be found Here. A fully working serviced unit can sell for up to £189:00GBP.

I’m not doing that. No way. I’m going to see if I can even get it slightly working, I’m never going to use it seriously again but I’d at least like to see the needle moving without causing any damage to its original design.

Is that the only potential issue?

No of course not. There is one other potential reason why it is not working and that is related to the ammeter coil, the axis on which the needle moves, sometimes it can become stuck, if this is the issue then happy days, the fix would be a lot easier. However this is me, and things are never that easy for me 😂

There is also a fine tuning screw on the rear that someone may have been a little bit too enthusiastic with, in the past.

And of course. The pointer lock on the side of the unit could have been simply left on. Now wouldn’t that be nice and easy?

So what’s this Invercone thing you’re going on about at the beginning?

It’s that weird shaped piece of plastic with a bit of metal on it, in the pictures above.. it assists greatly in incidental lighting conditions where there is a back lit scenario.

The inverted cone shape is designed so that as the meter is angled to the light source, the readings remain accurate which they would not do if it were a dome. And because backlight effects the exposure, a small part of the invercone sticks-out beyond the top of the meter case to pick any such light up.

westonmeter.org.uk

A little history lesson…

Sangamo Weston was a company that made light meters, among much other electrical equipment. It is particularly known for the Weston Master series of selenium meters.

The Weston Master V was produced in the UK from 1963 to 1972. It was Model S461 in the UK and Model 748 in the US

Weston was founded by chemist Edward Weston—no relation to the famous photographer—who held many patents for electrical inventions, from permanent magnets through cellulose manufacturing, dynamos, arc and filament lights and the magnetic-drag speedometer to electrical measurement instruments (and even US 895218 – a fruit box!). Weston’s son, Edward Faraday Weston, applied for a U.S. patent on the first Weston exposure meter, granted as No.2016469 in October 1935. This was a cylindrical case with an electrical meter at one end, and an iris at the other; an adjustable scale around the meter opened and closed the iris, and showed the exposure. 

Sangamo was originally “Sangamo Electric Co.”, in Springfield, Illinois. It set up a British subsidiary in 1921. Sangamo acquired the Weston Electrical Instrument Co. in 1936.

Since Weston was one of the first makers of light meters, before film speeds were standardised, Weston had its own film speed scales.

At some point, Weston products were distributed by Ilford in the UK. The company was bought out by Schlumberger in 1976, but still exists, making electrical timers.

The EuroMaster light meter, very close to a Weston design, was later made by a company called Megatron.

Camera-wiki.org

Assessment:

For those who have made it this far, well done and thank you. Let’s have a look at what has arrived and assess the overall condition. It’s taken some time to arrive what with there being two recent bank holidays closely placed in proximity to each other in the calendar. Translated that means the UK comes to a halt during this period, whilst everyone gorges on poorly cooked barbecued food in bad weather whilst drinking too much alcohol.

And some of us are just working. Most annoying.

Anyway enough of the whining, here’s the assessment:

The meter has arrived and is in an excellent cosmetic condition, it came in a small leather case with a lengthy string neck strap. It’s all original and is still marked up with the original owners details on a small label. The Invercone is just what it is, a piece of shaped nylon/plastic and not much to rave on about. It is as it is, in good condition and also in a small leather case.

Original case
Excellent cosmetic condition

The calculator panel on the front is undamaged and in full working order, the light baffle on the rear is also operating as it should and the info panel under the viewing glass changes as the baffle is operated. The pointer lock is operating as is the fine tuning screw on the rear.

Baffle closed
Baffle open

There is a very slight movement when exposed to intense sunlight with the baffle open or closed however it is only very slight. It struggles to move past the zero indicator on the scale, hence as described it is safe to say that it is not operating as it should. We will have to look inside to see if there are any obvious issues, however I strongly suspect it is related to the Selenium cell. I would like to see if we can get this operating, I’m not overly worried about its accuracy as I’d just like to see it move through its entire range. It would be good to see if it is at all possible to revive a “dead” light meter. We can only learn from dismantling and investigating such items.

Repair:

I’ve left the unit in sunlight for a few days, as this has been known in some rare cases to just kick start it back into life. That doesn’t seem to have worked in this case so let’s have a look inside.

Remove securing thumb screw
Remove two nuts
Case lid lifts off
Carefully remove fascia plates
Remove sliding needle lift mechanism and expose selenium cell
Cell, armature ring and ammeter coil removed
Cell connecting ring cleaned
Cell contact ring, cleaned and renewed

The whole unit came apart quite easily to expose the selenium cell deep in its workings. Using a multimeter on the cell, indicated life in the item as values changed as the cell was moved from the dark into the light and vice versa so I am confident there is some life still present in this cell, but is it sufficient to power the meter? I have then used the lowest Ohms setting available and put the negative lead on the magnetic case (Ground) of the ammeter coil and the positive lead on the wire connected to it and there is no movement at all. This indicates to me that the ammeter coil is at fault and unresponsive to any voltage, I believe this is the problem and at this point the repair is not possible. I have cleaned the cell connecting ring to the point that it is now shining and free of any age related contamination. The contact ring on the cell itself I have revitalised with a metallic silver pen. I have checked continuity and that is also good and acceptable. One thing I did not see in this model was the use of a resistor that is used in most selenium cell light meters between the cell and the ammeter coil, maybe there was never one used within this range of meters, I’ll have to check that out. I have checked this out via numerous sources and it appears the Weston light meters never had a resistor placed in line at any point, so that has cleared that question up. This unit is dead due to a faulty ammeter coil.

Result:

The unit is cosmetically very good and I believe the actual selenium cell is functioning but at an exceptionally low level. The tests on the meter ammeter coil have come back negative indicating that there is no life in this part of the meter. I suspect the fine wires on the coil are possibly damaged. The only way I can get a working unit would probably be to obtain another faulty unit to transplant parts, I may well do that in a later post.

I hate not getting the fix done, however this unit is in excess of 50 years old and to be honest the odds were stacked against me from the start. I did state that I may actually mount this item in a frame as a photographic art piece, that may still happen but I’d love to prove the original cell is still functional if I can. Maybe I just might buy a donor unit to test my theory on.

I’ve learned a lot from this post on the repair and dismantling of these units so that is a big positive. Knowledge is always king as they say.

It will not go to landfill. It will be reused in some form, you may even yet see a follow up post regarding it.

Thanks for passing by, it is always very much appreciated.