What's this on my Sinar F1?

[Merijn]

Hey guys, I just bought my first large format camera and I have a question. On the camera back there's these two horizontal metal push buttons centered above and below the ground glass (not the big levers for opening the back to slide the film holder in). My best guess is that they're for switching the camera back from landscape to vertical but since they take a fair amount of force I haven't tried to use them yet for fear of breaking something.

What are they? And in the second picture you can see a small circular opening on top of these push buttons, should something slot in there when the back is properly inserted?

Image 1: http://i.imgur.com/mJ1yQuz.jpg

Image 2: http://i.imgur.com/8LdvH17.jpg

Your input is appreciated.

[Peter De Smidt]

Those are part of the back mechanism that holds the back firmly in place. Pressing in allows one to remove the ground glass frame, which is needed to mount some accessories, such as some roll film holders, digital backs.... At least that's what I remember. I can check later today.

[Rick Rosen]

They release/remove the ground glass spring back when you use the "Graflock" system for some roll film backs or other accessories.

[Luis-F-S]

Suggest you read the manual, available on line.

[AtlantaTerry]

Hey guys, I just bought my first large format camera and I have a question. On the camera back there's these two horizontal metal push buttons centered above and below the ground glass (not the big levers for opening the back to slide the film holder in). My best guess is that they're for switching the camera back from landscape to vertical but since they take a fair amount of force I haven't tried to use them yet for fear of breaking something.

What are they? And in the second picture you can see a small circular opening on top of these push buttons, should something slot in there when the back is properly inserted?

Image 1: http://i.imgur.com/mJ1yQuz.jpg

Image 2: http://i.imgur.com/8LdvH17.jpg

Your input is appreciated.

Yes, pressing those two bars in will allow the ground glass back to be removed in order to use Graflok accessories.

Almost all "modern" 4x5" cameras feature the ability to use Graflok accessories.

[RSalles]

With the camera mounted vertically, press both bars and slide the glass mounting frame upwards. Inside, these bars have a hook shape and it's attached to a metal pin, pressed against the front standard frame by strong springs.