Do you see square or do you see rectangular....
Do you see square or do you see rectangular....
The square format is quite hyped because you don't have to worry about the orientation of the camera.
However, it's the laziest format if that's your reason for using it. If you are ultimately going to produce your work in a rectangular format, then you are wasting film in a huge way. Fashion and event photographers created the rush to square format because they could snap off rolls of shots fast, and crop later. But the markets where most of them sold their work were rectangular markets, resulting in a lot of unused film area cropped and tossed.
Therefore, that is the first question you need to boil down an answer to in the MF decision.
If you feel that you are going to print or display your work as a final rectangle, then you will save big dollars on film by choosing:
1) the 645 format for 15 exposures on 120 or 30 exposures on 220. A real advantage to 6X4.5 will be a whole range of cameras that are not unlike the OM experience you have. SLR's, great rangefinders, and these will be cameras that dance easily between hand-held and sitting atop a tripod. Consider that 6X4.5 is 2.7 times the negative size of 35mm.
2) 6X7 or 6X9, will offer the more usable rectangle with 6X7 being a standard closest to standardized rectangular print. 6X7 will be 4X the size of 35mm. The cameras will be heavier, but again you will have an excellent range of SLR, and rangefinder cameras to choose from. Mirrors will be bigger and thus having the ability to Lockup the mirror will be a consideration. Locking up the mirror is not very usable for hand held, so consider that. With that in mind, the rangefinder style is a plus.
6X9 does start to renew the concern about wasted film as many processors are not equipped to print the 2:3 format large.
My two most strenuous objections to a twin lens camera are:
A) The square format, which for my shooting style wastes film.
B) Horrible studio camera because of the parallax issue. I did try one with the Paramender attachment, but that was just one more chore on correcting for the two inch difference between the viewing lens and the taking lens. That difference seems to occur more, and need compensation, in tight studio shooting.
My favorites for MF are Fuji 645 rangefinders, and Bronica ETRSi SLR 645's. For larger, I favor and use Fuji 690 rangefinders. I used a lot of Mamiya 645 and RB (6X7) and found those very nice, until I decided to move from focal plane shutters (Mamiya), to shutters in lenses (both Bronica in all formats and Fuji in all formats).
Over the years 645 has been the most productive format for me in terms of justifying film and per image processing expenses. It costs me $5.00 to process a roll of 120, no matter how many images are on the roll. Therefore 645 gives me twice the images for the same processing price as 6X9.
When I crop a 645 or a 6X9 that I composed for the format, I lose very little of the taken image. 6X6 had me always tossing an unjustifiable amount of the capture to get my rectangle.
So again.... answer, in your own mind, the square vs rectangle question.
Square is certainly a choice that seems to work for some.
