Arri 16St to Arri 16Sb, install a bayonet mount

[Mendes Nabil]

Hello all, does someone know if we can convert an Arri 16St to an Arri 16Sb ?

 

These 2 cameras are basically the same, the only difference is that the 16s has 3 Arri standard mount while the 16Sb has 2 Arri Standard and 1 Bayonet mount.

 

So can we remove a Standard mount from the 16s and install a Bayonet mount? If yes, how would that coast? Is that something i can do myself?

 

 

Thank you!

[Tim Carroll]

In the old days ARRI could convert your 16S to a 16S/B by replacing the lens turret. Not the individual socket, but the whole turret. Finding an S/B turret may be a bit difficult these days, and buying a 16S/B camera just to salvage the turret would cost as much as just buying a 16S/B camera, so it may not be too practical.

 

As far as doing it yourself, I wouldn't recommend it unless you have all the ARRI service tools, especially a FFD gauge as you would need to reset that, and then reset the ground glass once you installed the S/B turret.

 

Best,

-Tim

[Peter Welander]

I'm trying to figure out why changing the turret would require adjusting the ground glass. Isn't the ground glass "tied" more to the film plane? Wouldn't doing something to the turret affect both equally? Or am I missing something?

 

Of course there is that long optical path to the ground glass...

 

Thanks.

[Tim Carroll]

It depends on what you want to do. If you just want to slap a different turret on your 16St, yeah, maybe the ground glass and film plane will line up. But they will probably both be out of spec. So let's say your 16S/B turret is a little "longer" than the stock turret (and this is assuming your current 16ST is still at factory spec, which is a huge assumption on cameras of this age and with this many miles on them). And again, by a little longer, we're talking thousandths of a millimeter. If your 16St was exactly at factory spec, then the image you see on the ground glass with the longer 16S/B turret will match the image the film sees at the film plane, but both images will not reach infinity. If your 16S/B turret is a little "shorter" than the stock turret, then the image you see on the ground glass will match the image the film sees at the film plane, but both images will come up short for close focus.

 

This is why, the proper way to set up a turret swap on a 16St is to change the turret, then set the FFD (film plane) to factory spec (again, within 5/1000s of a millimeter, about 1/10th the diameter of a human hair), and then set the ground glass to match the FFD. Then you know that any correctly collimated lens you attach to the 16S/B turret will focus at infinity, close focus to spec, and the image you see in the ground glass will be the same image projected on the motion picture film at the gate.

 

Best,

-Tim