catch in focus

having trouble getting this to work with a reversing ring, which is anodised black, the shutter releases when out of focus. do i need to scrape the coating off the ring to short certain contacts out to get it to work? it works fine with the lens attached (M 28mm f3.5) but this has a chrome mating face. any help much appreciated

answered my own question and just purchased a genuine Pentax one in chrome, this will short out all contacts as the lens mount does.

No, you shouldn't have to do that.

CIF won't work if you have focusing set to the back button only, the camera has to set to focus with half press of the shutter button.

I didn't know that

Stupid moment

Why would you want to short out contacts it's electrical you short out any power circuit it wil cause damage

With a manual lens such as an M series for example that has no contact,s it would short out contacts on the camera body, that in turn would tell the camera that a manual lens is fitted. I think its only 2 pins that have to be shorted and if a reversing ring extension tube or a lens has a painted or anodised mount then the camera will not recognise that a lens is fitted.

By "short out" we mean that bare metal (not a lens connector) touches the cameras connectors. We don't mean sparks, smell of burning, "OMG what have I done" moments

The aperture contacts on a lens/mount are not 'power circuits' they are low voltage data connectors which are read by whether or not they are earthed. This is very common in binary data systems The usual implementation is 5V is 1 & 0V is 0. The cable release on Pentax (& Canon) cameras uses the same system of forcing contacts low to activate.

thanks people, i did have shutter release set to AF as i use CIF quite a bit with macro but it still kept firing even when out of focus. it took a while for my old brain to twig the coating on the ring could be the problem