15 or 16 shots (6x4.5)

[Tony-S]

Measure your negatives, the 16 shots on 120 are closer in size to 6x4cm and the 15 shot 120 cameras shoot a slightly different ratio 6x4.5cm, the 15 shot cameras require some sort or mechanical spacing mechanism the 16 shot cameras use either a mechanical advance (Hasselblad) or a red window.

ETRSi images are 42.5mm x 55.1mm, an aspect ratio of 1:1.3 (ish), so not really close to 1:1.5.

 

[darkroommike]

ETRSi images are 42.5mm x 55.1mm, an aspect ratio of 1:1.3 (ish), so not really close to 1:1.5.

Pretty much what I said, since the film is 6mm wide, no back shoots a 6cm wide negative (and yes I'm sure that there are one off backs that shoot right to the edges of the film because, why not!), a 645 is pretty close to 1:1.33333333333333333 and a 6x4 back is closer to 1.5:1 aka 3:2.

 

[OAPOli]

Fuji GS645W (15 shots): 56.5x42mm; Konica Pearl III (16 shots): 58x42mm; Bronica SQ 645 back (15 shots): 56x42mm; Hasselblad 645 (16 shots): 55.5x41.5mm. Measured on a negative and rounded off to nearest 0.5mm (I believe there is some variance due to aperture stop). The widths and aspect ratios are pretty constant. I've never heard of a 6x4 back.

 

[wiltw]

Its interesting that there is no real pattern to it. My Fuji does 16 but older ones do 15. Bronica ETR does 15, but Bronica RF does 16.

Frame's short dimension varies from brand to brand (41.5mm to 43mm), as does the frame spacing.

 

[Tony-S]

Fuji GS645W (15 shots): 56.5x42mm; Konica Pearl III (16 shots): 58x42mm; Bronica SQ 645 back (15 shots): 56x42mm; Hasselblad 645 (16 shots): 55.5x41.5mm. Measured on a negative and rounded off to nearest 0.5mm (I believe there is some variance due to aperture stop). The widths and aspect ratios are pretty constant. I've never heard of a 6x4 back.

Nor I. All the ones I've seen are in the 1:1.29-1.33 range. They are closer to aspect ratios of 6x7 cameras than 1:1.5.

 

[MattKing]

I'm wondering if any cameras that used 127 film used a 6x4 frame?

 

[Donald Qualls]

I'm wondering if any cameras that used 127 film used a 6x4 frame?

As far as I'm aware, all the "full frame" 127 (8-on-roll) use 4x6.5 cm frame. This allowed a half frame that was a little bigger than 35 mm with 16 on a roll (all the half frame 127 cameras I know of were dual red window), about 4x3.1 or 4x3.2 allowing for the additional interframe space).

 

[Model71]

My 645N gives 16 shots but cannot be set for either 15 or 16 unlike the Nii

pentaxuser

My 645N, on the 16th frame, when the shutter is pressed, performs an immediate rewind before the exposure is complete. Consistently, this results in the 16th frame exposing as a very bad (unintelligible) blur.

I don't know if this is a mechanical issue or an electronic issue. My work-around is treat all rolls as 15 exposures.

Does anyone know if this is a common problem?

 

[ant!]

My 645N, on the 16th frame, when the shutter is pressed, performs an immediate rewind before the exposure is complete. Consistently, this results in the 16th frame exposing as a very bad (unintelligible) blur.

I don't know if this is a mechanical issue or an electronic issue. My work-around is treat all rolls as 15 exposures.

Does anyone know if this is a common problem?

Nope, never had a problem like this with my 645n. Once the exposure is done, it winds to the end, not earlier.
The 15 shots on the 645 or 645nII use different frame spacing then the 16 shots on the 645n and 645nII, as far as I understand it. So this seems unrelated to your problem at the last frame.