RB 6x8 Back on RZ67 ProII

[kauffman v36]

ok, well i accomplished my first goal of finding a place to get the inafmaous "g" adapter that allows rb backs on the rz series. i somehow found a thread on apug from 2007 talking about doing what i am trying to do and it said its impossible to mount a 6x8 back from the rb on the rzproii and it work. my question is why?

the measurement posted in that thread show the rb pro-s having a rear opening of 69x68mm and the rz having one 68x67mm. the 6x8 back is like 74x58 or something along those lines. i dont understand why 74mm works on 69 but it does on the pro-s, so ill accept it. my quesiton is why wouldnt it work the same on the RZ with a g-adapter. it seemed in the other thread that the adapter was the weak link and it was too small, could it not be machined to match the film back or rear camera opening?

is there anything that can be done to outfit an rb 6x8 back to an rz67proii???

[kauffman v36]

also, the opening on the RZ is big enough to fit 72mm x 72mm quaddra images so im about 99.9% sure that the limiting factor in making the 6x8 back work on the RZ67 is the size of the opening on the G-Adapter. if that is the case, and i have pictures of the adapter and why can it not be machined bigger? or even better, leave it how it is, and stack in order from the body of the RZ- G adapter- pro-sd revolving adapter- 6x8 back. im goin crazy trying to find a way for this to work.

[nick mulder]

Just a guess but what if the wide lenses don't cover ? (at infinity at least)

[kauffman v36]

the lenses def. cover. there are people who use rb and rz lenses for 4x5 cameras with little or no light falloff. thanks for the suggestion tho, one more thing to check off the list. once i find the nasty dirty culprit, hes/shes going down. lol

[nick mulder]

the lenses def. cover. there are people who use rb and rz lenses for 4x5 cameras with little or no light falloff. thanks for the suggestion tho, one more thing to check off the list. once i find the nasty dirty culprit, hes/shes going down. lol

Sure the longer focal lengths, stopped down and close focused ...

But the 50mm rectilinear fully open at infinity ? (worst case I guess)

Not to dissuade you though, good luck

[kauffman v36]

maybe, havent thought about that certian situation, thank u for pointing it out nick

[John Koehrer]

Never having seen a G adapter I wonder if there's enough material to remove & still have rigidity enough.
I suspect there is.
Since I have more time than $$$ I'd attack it with files.

[thisismyname09]

It's most likely because the opening on the G adapter is only 6x7. If you managed to file that adapter to the correct size, I guess nothing else would prevent you from using the 6x8 back.

Also, I think it's doubtful that the RZ/RB lenses cover 4x5 at infinity. Some might come close, but 6x7 to 4x5 is a pretty big increase. I don't see why mamiya would design lenses with such large image circles, save the RZ's short barrel 75mm and 180mm for use with the tilt/shift adapter.

[kauffman v36]

yea, i think thats what it it. i will be filiing down, or dremeling down, the opening to bigger. but my question is why doesnt the light baffle have to have an opening 6x8. neither the rz, rb pro-s, or rb pro-sd have a rear opening 70mm or above on either side.

[MattKing]

yea, i think thats what it it. i will be filiing down, or dremeling down, the opening to bigger. but my question is why doesnt the light baffle have to have an opening 6x8. neither the rz, rb pro-s, or rb pro-sd have a rear opening 70mm or above on either side.

The instructions for the 6x8 back say:

Following two steps should be taken before using 6 x 8 roll film holder:

1) Replacement of the light baffle frame on camera body back with a new light baffle frame for 6x8 format (*Mamiya service centre will do this improvement for you)
2) 6x8 revolving adapter should be used.

Matt