How does Shutter Priority AE work?

[runswithsizzers]

On my Konica Autoreflex T4, if I select the shutter speed, the camera will stop down to the aperture indicated by the camera's meter. How does the meter reading get translated to the mechanical process of stopping down to the correct aperture? Does the meter battery power some kind of electro-mechanical device?

This is not a repair question - my Konica seems to be working normally. I am just wondering how it works. It seems to me that the meter batteries are rather small and low powered to do much mechanical work like moving the aperture blades against the resistance of the diaphragm return spring.

 

[AgX]

A variety of approaches can be applied.

The likely very first was kind of pure mechanical. A serrated wedge made part of a lever controlling the aperture. The lever was activated at releasing. Over that wedge swung perpendicularly a needle controlled by and part of the exposure meter. At releasing the wedge was pressed against that needle. Dependent on how far that needle had swung the wedge got arrested at a different serration and by this the angle of that lever was different.

 

[MattKing]

What AgX says.
Speaking more generally, the force that stops down the aperture is supplied by springs which stop down the lens at the time the shutter release is pressed. The amount that the lens is stopped down is determined by the meter, which causes a lever to stop the stop-down procedure at the right place.

 

[Pieter12]

Most slr lenses have a mechanism that allows you to compose and focus with the lens wide open, then it closes down the diaphragm to the chosen stop when the shutter release button is pressed. A shutter-priority camera will usually use that same mechanism to automatically close the diaphragm to the proper stop as dictated by the shutter speed selected and the meter reading.

 

[cmacd123]

the leaver stoped by the meter needle is called a "Trapped Needle system" and was very common. many cameras the meter needle was totaly inside and did not show, or only appered as a "too low light" indicator. other methods used some sort of electronics to to control the mechanism that stops down the lens.

 

[BobD]

See this:
http://www.konicafiles.com/6-technical-questions/-konica-s-shutter-priority-exposure-system/

 

[Sirius Glass]

See this:
http://www.konicafiles.com/6-technical-questions/-konica-s-shutter-priority-exposure-system/

I probably should have taken the time in all these years to think about how aperture priority worked, but I did not. Thank you.

 

[runswithsizzers]

Thanks to all who replied - and especially thanks to @BobD for the link in post #6 which explains it very well.

 

[AgX]

The very first program AE camera, the Agfa Optima from 1959

Here there is no movable serrated wedge, but instead a static, serrated curve and a straight, sliding ridge, which controls that lever.

schematic

Here you will find photos of the exposure meter assembly from above. A invertedU shaped brass spring swings around a serrated curve

http://knippsen.blogspot.com/2017/04/agfa-optima.html

 

[Chan Tran]

I probably should have taken the time in all these years to think about how aperture priority worked, but I did not. Thank you.

Aperture priority involves less mechanical and purely electronics. It's the easier of the two and thus I think that is why it is more popular.

 

[Alan Edward Klein]

Aperture priority involves less mechanical and purely electronics. It's the easier of the two and thus I think that is why it is more popular.

The aperture still has to stop down to the selected setting after the shutter is released. It stays fully open until then so you can see better through the viewfinder when the aperture is fully open.

Selection of which priority for me is based on what I'm shooting. Since I normally shoot landscape, DOF is very important. I keep it very deep. So I leave it in aperture priority. I let the shutter speed go to wherever since I'm on a tripod and really don;t care about that. If I was shooting sports, then I'd put it in shutter priority since I want to catch the fast action.

There's another issue with aperture priority that has to be considered for some. If you're shooting an older camera, shutters are in full stops only. If you set the camera for aperture priority, you will get an in-between setting for the shutter speed which isn't settable. This doesn't happen with shutter priority. When that's set, you can always move the aperture to a setting that's between the stops.

 

[Sirius Glass]

Aperture priority involves less mechanical and purely electronics. It's the easier of the two and thus I think that is why it is more popular.

I disagree. Most people choose the shutter speed to make sure that the stop the action. Set it once for the day. Setting the aperture may need to be done for each subject. Most people think of the shutter speed first.

 

[runswithsizzers]

Another question about how this camera works:
The aperture ring on my Konica Hexanon AR 50mm f/1.7 lens has click stops for full F-stops, only. I can manually position the aperture ring in-between the click stops to set the aperture at half-stops. But what happens in AE (auto exposure)? That is, if the camera's meter indicates a setting half-way between f/5.6 and f/8.0, will the AE system stop down the aperture to f/6.7 for the exposure - or will it round up or down to one of the full stop values like f/5.6 or f/8.0?

In the <link> provided in post #6, the author says:

"...the light meter’s needle is coupled, by means of a notched connector plate, to a stop-ring located behind the camera’s bayonet mount so that when the shutter release button is depressed halfway, the aperture indicator needle in the viewfinder and the connector plate are immobilized in a position determined by the amount of light read by the meter at a given ISO setting. Pressing the shutter release button further turns the stop ring as far as the notched connector plate will allow it to go. The stop ring has a protrusion against which the lens’ aperture actuating cam rests and the position of that protrusion determines the aperture used."
​

If I understand correctly, that seems to be saying mechanisms inside the camera are determining how far the diaphragm is stopped down, so click stops in the lens may not be involved?

For those who are interested in discussing the relative merits of shutter priority vs. aperture priority exposure automation - which would best be done by starting a new thread - the author of that link presents some history and talking points.

 

[Chan Tran]

The aperture still has to stop down to the selected setting after the shutter is released. It stays fully open until then so you can see better through the viewfinder when the aperture is fully open.

Selection of which priority for me is based on what I'm shooting. Since I normally shoot landscape, DOF is very important. I keep it very deep. So I leave it in aperture priority. I let the shutter speed go to wherever since I'm on a tripod and really don;t care about that. If I was shooting sports, then I'd put it in shutter priority since I want to catch the fast action.

There's another issue with aperture priority that has to be considered for some. If you're shooting an older camera, shutters are in full stops only. If you set the camera for aperture priority, you will get an in-between setting for the shutter speed which isn't settable. This doesn't happen with shutter priority. When that's set, you can always move the aperture to a setting that's between the stops.

The aperture stop down that has to be done on purely mechanical and manual only camera. To make it aperture priority all you need to add is electronics you don't need to add the mechanical. To make it shutter priority you don't simply make the lens stop down you have to make it stop down a varying degree based on the light. Stopping down in manual or aperture priority the mechanism simply stop down all the way. It's the aperture ring that limit how much it will stop down. In shutter priority the aperture ring must be in A which allows to lens to stop down all the way and the camera must control this.

 

[Chan Tran]

I disagree. Most people choose the shutter speed to make sure that the stop the action. Set it once for the day. Setting the aperture may need to be done for each subject. Most people think of the shutter speed first.

But shutter priority isn't as popular as aperture priority that is because aperture priority is easier to make.

 

[Sirius Glass]

But shutter priority isn't as popular as aperture priority that is because aperture priority is easier to make.

OK for those who toss logic out the window. Having sold cameras for years, it just ain't so.

 

[AgX]

Another question about how this camera works:
The aperture ring on my Konica Hexanon AR 50mm f/1.7 lens has click stops for full F-stops, only. I can manually position the aperture ring in-between the click stops to set the aperture at half-stops. But what happens in AE (auto exposure)? That is, if the camera's meter indicates a setting half-way between f/5.6 and f/8.0, will the AE system stop down the aperture to f/6.7 for the exposure - or will it round up or down to one of the full stop values like f/5.6 or f/8.0?

In the <link> provided in post #6, the author says:

"...the light meter’s needle is coupled, by means of a notched connector plate, to a stop-ring located behind the camera’s bayonet mount so that when the shutter release button is depressed halfway, the aperture indicator needle in the viewfinder and the connector plate are immobilized in a position determined by the amount of light read by the meter at a given ISO setting. Pressing the shutter release button further turns the stop ring as far as the notched connector plate will allow it to go. The stop ring has a protrusion against which the lens’ aperture actuating cam rests and the position of that protrusion determines the aperture used."
​

If I understand correctly, that seems to be saying mechanisms inside the camera are determining how far the diaphragm is stopped down, so click stops in the lens may not be involved?

For those who are interested in discussing the relative merits of shutter priority vs. aperture priority exposure automation - which would best be done by starting a new thread - the author of that link presents some history and talking points.

A generic answer already has been given in post 11.

To go a bit more into detail, but to remain generic, in my explanations the resolution of aperture control depends on the coarseness of those serrations

Concerning your model, try to a find a respective repair manual, this would show you how in your case the mechanism works.

 

[MattKing]

Most people choose the shutter speed to make sure that the stop the action.

Sirius' point reflects the prevailing wisdom during the 1970s and early 1980s, when so many people shot relatively slow slide film.
That was one of the reasons that the Canon AE-1 was as successful as it was - unlike most competitors, it offered shutter priority automation.
In more recent years I would say that many more people who understand the difference tend toward aperture priority automatic systems because, providing that the shutter speed is sufficient, the aperture choice is one that has greater effect on the appearance of the photograph.
Most modern cameras that offer automation offer both and, from what I've observed, younger people are more likely to choose aperture priority. Younger people who seek to teach photography also tend to recommend it.
In the 1970s with manual metering I would choose the shutter speed first. Nearly a half century later I tend to do it the other way.
Old dogs you know ....

 

[Alan Edward Klein]

When i shdot digital on a trip I pr it on P programmed mode. The camera is smart than me and quicker.

 

[Chan Tran]

OK for those who toss logic out the window. Having sold cameras for years, it just ain't so.

As you said it's more logical to choose the shutter speed first and I do not argue with that but isn't it true that there are more cameras with aperture priority than those with shutter priority. I said it's because it's easier to make.

 

[Sirius Glass]

Sirius' point reflects the prevailing wisdom during the 1970s and early 1980s, when so many people shot relatively slow slide film.
That was one of the reasons that the Canon AE-1 was as successful as it was - unlike most competitors, it offered shutter priority automation.
In more recent years I would say that many more people who understand the difference tend toward aperture priority automatic systems because, providing that the shutter speed is sufficient, the aperture choice is one that has greater effect on the appearance of the photograph.
Most modern cameras that offer automation offer both and, from what I've observed, younger people are more likely to choose aperture priority. Younger people who seek to teach photography also tend to recommend it.
In the 1970s with manual metering I would choose the shutter speed first. Nearly a half century later I tend to do it the other way.
Old dogs you know ....

I am an old dog?!? Do I smell like one?

 

[MattKing]

I am an old dog?!? Do I smell like one?

Only when wet.

 

[Sirius Glass]

Only when wet.

 

[reddesert]

Another question about how this camera works:
The aperture ring on my Konica Hexanon AR 50mm f/1.7 lens has click stops for full F-stops, only. I can manually position the aperture ring in-between the click stops to set the aperture at half-stops. But what happens in AE (auto exposure)? That is, if the camera's meter indicates a setting half-way between f/5.6 and f/8.0, will the AE system stop down the aperture to f/6.7 for the exposure - or will it round up or down to one of the full stop values like f/5.6 or f/8.0?

In the <link> provided in post #6, the author says:

"...the light meter’s needle is coupled, by means of a notched connector plate, to a stop-ring located behind the camera’s bayonet mount so that when the shutter release button is depressed halfway, the aperture indicator needle in the viewfinder and the connector plate are immobilized in a position determined by the amount of light read by the meter at a given ISO setting. Pressing the shutter release button further turns the stop ring as far as the notched connector plate will allow it to go. The stop ring has a protrusion against which the lens’ aperture actuating cam rests and the position of that protrusion determines the aperture used."
​

If I understand correctly, that seems to be saying mechanisms inside the camera are determining how far the diaphragm is stopped down, so click stops in the lens may not be involved?

For those who are interested in discussing the relative merits of shutter priority vs. aperture priority exposure automation - which would best be done by starting a new thread - the author of that link presents some history and talking points.

I don't think you mentioned this, but am pretty sure the aperture ring on a Konica lens needs to be in the "EE" position for shutter priority auto to work. This effectively takes the mechanical aperture setting out of the picture; it frees the camera to stop down the lens as far as it needs to. Most cameras with a shutter priority mode and a lens aperture ring require turning to a minimum setting to use S mode (including Nikons, Canons, Canonets, etc). The click stops on the aperture ring are just a little ball bearing that falls into detents as you turn the ring, not a mechanical limitation on the aperture.

The debate between shutter and aperture priority is one of the oldest in the book and the fact that people are still litigating it on the Internet is tedious but a reflection of not being able to get outside this week.

 

[Sirius Glass]

Sirius' point reflects the prevailing wisdom during the 1970s and early 1980s, when so many people shot relatively slow slide film.
That was one of the reasons that the Canon AE-1 was as successful as it was - unlike most competitors, it offered shutter priority automation.
In more recent years I would say that many more people who understand the difference tend toward aperture priority automatic systems because, providing that the shutter speed is sufficient, the aperture choice is one that has greater effect on the appearance of the photograph.
Most modern cameras that offer automation offer both and, from what I've observed, younger people are more likely to choose aperture priority. Younger people who seek to teach photography also tend to recommend it.
In the 1970s with manual metering I would choose the shutter speed first. Nearly a half century later I tend to do it the other way.
Old dogs you know ....

Early on people preferred Programmed, Shutter Preferred, Aperture Preferred. As people became more knowledgeable the demand for Aperture Preferred when way up.