I just purchased a nice camera system. Everything LOOKS good, however since i have never used this equipment i have a question about the lens. It has a front ring that is only marked for depth of field. I assume that it somehow allows you focus with this ring instead of the bellows?? However when i tried to turn the ring it refuses to budge and i am afraid to force it. Am i missing something or did i get damaged goods. The shutter speeds and aperture settings seem to be just fine. Please let me know what all of you think as i may return the lens. I am going to shoot a roll of film through it this weekend and if it comes out ok i may keep the lens.
Thanks to all
It is not a focus ring. You can only focus by camera placement and use of the bellows or combination of those two. I honestly don't know what that ring is and haven't found out by looking online. I assume it is a visual scale to determine DOF, but not sure how exactly to use it and honestly haven't sat down to try either. As I see it, I make do without it so.... Maybe someone else out there knows and can help explain its function.
I think you are right it is a DOF indicator but it seems you have to know the distance to the subject to calculate the DOF.
Hey guys just noticed this thread and thought i could help out. If it is the blue ring with a small knobbly bit on it to grab this is the Lens Distance Scale. Usually one side is marked in m the other in feet. The idea is to focus the camera normally (placement and bellows) then using the camera to subject distance scale (on the side of the bellows) find out the distance from camera to subject. Using this number (say 3m for instance) rotate the blue ring (lens Distance Scale) so that the number (in this instance 3m) sits central to the depth of field indicator (the bit where the numbers are small in the middle then get larger but are the same on both sides). Once this is done using the selected Fstop you can now see what your depth of field will be. For instance if you used a 110mm lens at F32 and the distance camera to subject was 3m everything form approximately 2m to 10 m would be in focus (this is read from the depth of field indicator using both F32s and looking straight down at the blue ring which then gives you a range). It is purely for working things out so you can be exact about DOF. It has nothing to do with the light passing through the lens or the way it works. It can be handy, but not very often, unless you want to be extremely anal about things. I admit I have used it before , good for portraits where you can really fine tune things (especially if you have messy backgrounds you don't want or vice versa).
Hope this helps and answers the problem!! Didnt realise how long winded this is!
If you need any other examples give me a shout!!
No one has yet provided the correct answer. On the Mamiya RB KL 65, 90, and 140 Macro this rubberized 'focusing' ring has an important optical function other than depth of field. It fine tunes the lens by shifting internal lens elements back and forth. This provides maximum edge to edge sharpness and minimizes curvilinear distortion.
Oops double post error
Relatively new to site, sorry for double post