What kind of switchinng devices they use in the command dials of modern camera?

[Chan Tran]

On most modern cameras (film or digital) they have one or more of the dial which is really a counting dial to set various things (aperture, shutter speed etc...). I know these are quadrature encoders but I wonder what kind of switching devices they use in these? In industrial application the switching devices are usually optical. Just a transparent disc with a lot olf lines on it and optical sensors to read the lines. I don't know how they do it with camera dial. I like to know so that I can figure out how to fix them in case they malfunction.

 

[xkaes]

Whatever they are -- there may be different styles -- they certainly do malfunction a lot.

 

[koraks]

I don't know how they do it with camera dial.

AFAIK simple electrical contacts consisting of two metal parts that momentarily connect, one of them being in a fixed position and the other being a springy kind that's momentarily pressed against the static one.

Whatever they are -- there may be different styles -- they certainly do malfunction a lot.

I've personally come across two 'malfunctions' on modern camera's in this area:
1: A Canon EOS 5 (non-D) where the 'click stops' on the command dial failed. This appears to be a common defect, with the command dial still being operational apart from not neatly clicking into a position.
2: A Nikon D800e I recently had on loan with a command dial that turned with much difficulty after the camera had been dropped. The dial worked OK apart from the friction.
No other defects in 25 years of using several cameras with such dials. I've not held a camera myself that didn't work due to a malfunctioning command dial. IMO they're pretty darn dependable things.

 

[monopix]

Never had a problem with them. All the ones I've seen are electrical contacts. Never seen an optical one. Doubt they exist in cameras. Some cameras have potentiometers, particularly for ISO input but I've also seen them used for shutter speeds. More common in cameras with simple metering systems. Pots can get dirty and cause problems. But seems a pointless question. How can you figure how to fix something if you don't know how it works and you won't know that for sure until you get a problem and open the camera to find out.

 

[4season]

Given their greater power demands, I'd be surprised if optical encoders saw much use in cameras.

 

[Chan Tran]

Never had a problem with them. All the ones I've seen are electrical contacts. Never seen an optical one. Doubt they exist in cameras. Some cameras have potentiometers, particularly for ISO input but I've also seen them used for shutter speeds. More common in cameras with simple metering systems. Pots can get dirty and cause problems. But seems a pointless question. How can you figure how to fix something if you don't know how it works and you won't know that for sure until you get a problem and open the camera to find out.

The ones that use potentiometer are older ones and they are not counting dial. Those with pot can be set when the camera is off. The counting dial can't be set the same way. You have to turn the camera on then when turning the dial it generate pulses to increase or decrease the value stored in camera memory. It's the counting dial that I am talking about. I never took apart one from the camera but I took apart a lot of them from industrial machinery and all are optical.

 

[wiltw]

The ones that use potentiometer are older ones and they are not counting dial. Those with pot can be set when the camera is off. The counting dial can't be set the same way. You have to turn the camera on then when turning the dial it generate pulses to increase or decrease the value stored in camera memory. It's the counting dial that I am talking about. I never took apart one from the camera but I took apart a lot of them from industrial machinery and all are optical.

OTOH, what would explain the intermittency of the control dial that controls aperture (while in Av mode; it controls shutter speed while it Tv mode) on my Canon 7DII, which got flakier and flakier over time, if it were an optical device?!
(At the same time, it does not seem to be a contact-connect device, as working the dial rapidly back/forth does not seem to improve/alter its making electrical contact.)

 

[koraks]

it does not seem to be a contact-connect device

It definitely is. Just a plain, bog-standard rotary encoder.
The intermittency problem is likely due to fouling or corrosion.

 

[Chan Tran]

OTOH, what would explain the intermittency of the control dial that controls aperture (while in Av mode; it controls shutter speed while it Tv mode) on my Canon 7DII, which got flakier and flakier over time, if it were an optical device?!
(At the same time, it does not seem to be a contact-connect device, as working the dial rapidly back/forth does not seem to improve/alter its making electrical contact.)

The disk with the lines on it or the sensor is dirty. The lines can also be faded.

 

[xkaes]

I've personally come across two 'malfunctions' on modern camera's in this area:

I'll add to the list.

I've seen this on two different cameras. A dial will turn correctly, but will only adjust in one direction -- UP OR DOWN -- but not both. For example, in MANUAL mode, the shutter speed will be a 1/60, and the dial will turn one way and increase the speed, and turn the other way without any change.

Other dials have just had erratic displays, such as a +/- dial reporting different numbers, no matter which way the dial is turned -- +1.5 then -0.7 then -1.0.