How does the half-press-shutterbutton on cameras work?

[TheUnnamedNewbie]

For those who have no idea what I'm talking about:
Many highend digital cameras have a default behavior where pressing the shutter button halfway activates the auto-focus and exposure mechanisms, pressing it fully activates the actual shutter and takes a picture. There are usually tactile responses to both of these positions, the shutter button has almost no resistance up to the halfway point, then you feel like you hit a significant increase of resistance (activates auto-focus), then you feel a stop when the button is depressed (activates shutter).

How is this done electromechanically?

[Alex Eisenhut]

AFAIK it's two concentric switches with different actuating forces under the same button.

[Mechatrommer]

Yup just 2 switches, one on top of the other, the rest is mechanical design and manufacturing...

[TimFox]

If you connect the external control switch for those functions, it is often a slide mechanism with a button, connected through a small TRS "stereo headphone" plug.

[Someone]

There are switch parts specifically made for this application, Panasonic "double action" with the first action have a much lighter activation force than the second.

[Ed.Kloonk]

As complicated such a switch design must be, it's not as hard as explaining to a elderly parent with a far too complicated pro-sumer Pentax the subtilty of setting the focus and then squeezing the shutter not just slamming it.

 

 

 

[TimFox]

On any camera, one should squeeze the shutter release so as not to shake the camera.

[magic]

Olympus can be set not to release the shutter in AF modes until focus is acquired

Not 100% sure what happens if you press and release the button before it manages to focus, prolly nothing.

[ledtester]

I was just looking this up a day ago...

In this video at about 0:15 you can see a teardown of a Panasonic remote shutter release:

Arduino Panasonic remote shutter release (DMW-RSL1 disassembly) -- Hirudin
https://youtu.be/DNj48nwUjxk?t=15s

Basically there is a sandwich of three metal strips. Press down halfway and you connect the top and middle strips; press all the way and all three are connected.

For pinout info on different cameras see:

https://www.doc-diy.net/photo/remote_pinout/

Most cameras use a resistor network to distinguish between a half-press and full press.

Update: Look on aliexpress/ebay for cheap clones of these devices.

[magic]

That's how the cheap remotes are made and their tactile feedback is pretty poor.

The buttons on cameras are much nicer, clearly made differently. Besides, if you open a camera, you will see those switches are tiny.

[dkonigs]

As complicated such a switch design must be, it's not as hard as explaining to a elderly parent with a far too complicated pro-sumer Pentax the subtilty of setting the focus and then squeezing the shutter not just slamming it.

And yet this mechanism in cameras is over 30 years old.  We've been having to explain it to people for a very long time.

[Mechatrommer]

Same as trying explaining 1+1=2, you cant stop people from get born to this world. Same reason why camera or oscilloscope sale will never end like forever..

[bson]

And yet this mechanism in cameras is over 30 years old.  We've been having to explain it to people for a very long time.

And it greatly predates autofocus and microcontrollers.  Initially it was used to turn on the light meter circuit and needle...