CANONET G-III QL 17 AND HYPERFOCAL FOCUSING

[vincenzo_maielli]

It's possible to use the hyperfocal focusing with the Canon Canonet G-III QL17?

Ciao.

[winfried_buechsenschuetz1]

Of course, the optics of Canon follow the same rules like all the others. Only problem is that the QL17 has no DOF indicator. I made my own by printing a piece of self-adhesive film with indicators for DOF at f/8 and f/16. But where to put the marks? I used the DOF indicator of another 40mm lens as a template.

[vincenzo_maielli]

Thanks, Winfried.

Ciao.

[miles_s.]

Vincenzo,

 

I hate to disagree with Winfried. I too added a DoF scale to my canonet. However, with no way to ensure it was precise and well fastened I gave up on it.

 

I now keep the lens at infinity for all hyperfocal work. The rational behind this is well explained in Harold M. Merklinger's book _The INs and OUTs of FOCUS_.

[frank_scheitrowsky1]

The problem of copying another lens' DOF scale is that the focusing throw of the lens may be different. This could be measured.

[sexgun]

Would it be possible to place or tape a piece of ground glass, or a focusing screen from another camera, right at the film plane, and check different focus points with the camera back open? Maybe by looking at it with a loupe or other means of magnifying the image?

[miles_s.]

"Would it be possible to ... check different focus points with the camera back open?" Yes, I highly recommend doing this for all RF cameras that one uses. There is no need to do this for the purposes of establishing a DoF scale.

 

There the throw/helical pitch of a camera is encoded in the lens' distance scale. So while copying a set of DoF marks from another camera is not advisable do to differing throws the pitch is readily available.

[winfried_buechsenschuetz1]

The difference in turning angle of the lens is no big problem when drawing your own DOF scale. Of course I did not copy one directly - each lens has its own focussing thread pitch and own "throw" for focussing.

 

I checked the DOF marks for f/8 and f/16 when the lens was set to 5m, and placed the marks close to the distance markings indicated by the DOF indicator of the 40mm "reference" lens.