Why Mamiya RB67 220 back works fine with 120 rolls?

[marck mcgill]

Talking of 220 vs 120, when I bought my first RB67 it came with a 220

back. I decided to take some shots just with a 120 roll just to try

the camera, figuring that the frames would be misaligned and that the

counter wouldn't work fine, knowing that I would need to buy a 120

back sooner or later...<br><br>

 

Well, I'm still using that 220 back, and excepting the fact that it

doesn't release the lever at the 12th frame, I can't notice any other

problem (like: reduced number of frames, bad focusing, etc.) nor I

ever felt the need to switch to a 120 back for real.<br><br>

 

Then are there any <b><u>PRACTICAL</u></b> differences at all between

the 120 and 220 backs, excepting the counter?

[enrico_pocopagni1]

Hello Marck,

 

film path is wider on 120 back to accomodate the paper extra thickness. I've read somewhere that Mamiya discourages the employ of 120 film in 220 backs for the extra effort made by film advancing gear, and by the slightly wrong position of the film plane.

 

Greetings

[marck mcgill]

Thanks Enrico, I see your point... Still, for consumer use, I would say that it make no sense spending a lot of cash to purchase a 120 unit. Nor the winding gear seems very stressed to me. What do you think?

[derek_stanton2]

Maybe the difference you'd notice would come into play with very shallow DOF, or

close-focus/macro use? I would think, just like film flatness issues, stopping down

would help. I wouldn't risk it for professional use, but if you've got 'non-critical,'

personal work, why not, until you do encounter a problem?

[derek_stanton2]

From another thread:

 

"220 film hasn't protective paper like 120 has, so it's thinner (film only) than 120

(film+paper). Thus it's discouraged using 120 film in a 220 back because increased

thickness can damage film advancing gears, and the placement of film plane can be

wrong." -Enrico Pocopagni apr 08, 2004; 02:16 a.m.

 

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=007vMg

[greg_jones1]

Come now, just what is "non-critical" work if you are bothering to use a Mamiya RB67? Non-critical, to me, means I use 35mm!

 

Seriously, given the caveats and exceptions noted here (about possible focal plane placement, stress on winding gear)if it works for you then there probably are no real issues with using 120 in the 220 back.

[andreas_carl]

I am using 120 film in a Hasselblad 220 back (A24) and it works just fine - in fact since the advance lever does not lock at frame 12, I usually am able to get a 13th frame on the 120 film! The film advance does not feel any more stiff with 120 than 220 film.

[paul ron]

All this about paper backing and DOF...etc is a load of bull. THere is no difference in anything except the length of the roll... THAT'S IT! THe spring loaded preasure plate keeps the film flat on the film plane regardless of thickness. The physical thickness of he film is the same as 120, it's the same film just a longer roll.

 

The ONLY difference is the stop frame wheel in the frame counter mechanism of the back. No difference in frame size, no difference in film thickness, no difference in distance to film plane, no difference in DOF regardless of paper backing or not.

[enrico_pocopagni1]

http://www.macuserforums.com/webx?14@41.d0JDasUAifP.15@.1dce01e1/0

 

I found this thread on Mamiya User Forum some time ago. I too sometimes ran 120 film in 220 back with no (visible) problem, but after I read this I had some fear overstressing 220 back and I didn't this way any longer. Maybe it is an excess of care but I'm not a professional, so frames number is not very important.

 

Greetings.