Frame Spacing Changes from Roll to Roll

<p>Hi all,</p>

<p>I recently bought a Phase One 645AF (Mamiya AFD III equivalent) & a HM401 120/220 film back (modified to shoot 15, not 16, frames per roll). </p>

<p>I see variable spacing in between the frames, as you can see here:<br>

<img src="http://rishisanyalphotography.com/ForumPostFiles/photo.net/FrameSpacingIssues.jpg" alt="" width="800/" /></p>

<p><strong>Left</strong>: Fuji Provia 400X | <strong>Center</strong>: Fuji Neopan | <strong>Right</strong>: Kodak TMX 100</p>

<p>I aligned the bottom frames; as you proceed up, you can see the spacing is different, with the largest spacing between frames in the middle strip (Fuji Neopan).</p>

<p>Spacing is even different between 2 rolls of RVP50 (not pictured), so it appears pretty random (not correlated to any one emulsion).</p>

<p>Is this normal? Anyone know why this occurs?</p>

<p>Why does this concern me? Because this back was redesigned/modified by Mamiya to purposefully put more space in between frames so that bent portions of film (film is bent by the rollers it passes over in the 645 system) are placed between exposed frames, not within your exposure (hence the lower # of frames per roll). I would rather have 1 or 2 less exposures/roll than an exposure here & there that's soft at certain regions due to bent film.</p>

<p>Thanks in advance,<br />Rishi </p>

<p>My Zeiss Super Ikonta 532/16 shoots 11 frames, presumably for the same reason. Spacing can be erratic.</p>

<p>I guess I just wonder what the mechanism is... if it's a simple motor advancing a certain # of revolutions, it's weird to me that the spacing changes.</p>

<p>Perhaps it depends on the stiffness of the film? Maybe gears skip with more rigid film? I'm just making stuff up at this point...</p>

<p>-Rishi</p>

<p>The spacing even varies on the same roll of film.</p>

<p>For example, on a roll of RVP50, the spacing varies from:</p>

<p>8/16" to 10/16" of an inch (0.5" to 0.625")</p>

<p>Anyone know how these Mamiya 645 AFD cameras advance frames? On a related note, I can't figure out how this thing decides what the 1st frame is. It wastes all this space at the beginning of my roll & then with the extra spacing I only get 13 shots/roll. If it started earlier in the roll at least I could get 14. No way I could get 15 with this back...</p>

<p>-Rishi</p>

Hello Rishi,<br><br>I'll explain why this errant spacing business is normal, but i'm sure you then will think it unscientific, and not so. ;-)<br><br>First: it is indeed normal. Spacing is considered bad when frames touch or overlap, or gets so wide that the alotted number of frames do no longer fit on the roll. Uneven spacing is quite o.k.<br><br>There are no perforations at fixed, constant intervals on roll film. So the spacing mechanism of (most) roll film cameras can't count perforations, but work on the assumption of the varying circumference of the take up spool (a result of the thickness of the film + paper already wound around the take up spool), i.e. how many rotations of that spool it takes to transport a given length of film.<br>That varies from film type to film type, how tight or loose the film is round the spool, and how you loaded the film to begin with (start mark).<br>And it varies: the more film is on the spool, the larger its circumference, the fewer rotations it takes to transport a given length of film. So any deviation from the assumption will have a knock-on effect, creating a perhaps small error on the first frames that will change to a much larger one on the last.<br>A slightly thicker film + paper combination wil make the circumference (and thus the length of film one rotation of the spool wraps around it) grow faster than a slightly thinner combinaton. So spacing will be wider with the thicker combination, getting progressively so as more film is wound on the spool.<br><br>A film that is loaded loosely also creates wider loops around the spool, and even though the film will be pulled taught and wrapped tighter around the spool, all it can do is wrap around the already formed, too wide loops the first bit of film formed. There's no, or very little, slippage that will pull the entire length of film already round the spool tight.<br>So it's important (because will make a difference) to keep the film tight after removing the sticky tape, not just to prevent fogging.<br><br>The position of the first frame is also the result of a built-in assumption about the number of rotations of the take-up spool it takes to move a length long enough to have the first frame sit comfortably past the beginning of the film. That means that any variation in the position of the film during loading will have an effect on the position of that first frame, and on subsequent spacing. That's why there is that start mark on the backing paper: to allow loading without having to guess.<br>Some cameras sense where the film is attached to the backing paper, and then you will not have to pay much attention to the start mark, just make sure the film is attached securely to the take-up spool. And it will lead to fewer errors. But it too is 'prey' to differences between brands and film types, and even production runs.<br><br>This is also why manufacturers put less frames on a roll than would fit. They can't be sure that spacing will be consistently tight enough to put the number of frames on a roll that in an ideal world would indeed fit.<br><br>The alternative would be a return to the peep hole. No spacing mechanism at all, but visual inspection of the numbers on the paper backing instead.<br><br>Having said all that, it's clear that your back falls in the "the alotted number of frames do no longer fit on the roll" category. So your back is faulty, needs a repair. If you're in luck it is just a matter of readjusting parts to fix such things (it often is). But if not, it could get expensive.

<p>Every medium format camera and back that I ever used (professionally) had uneven spacing (Mamiya C220, Minolta Autocord, Rollei TLR, Mamiya RB67, Bronica ETRS/ETRSi) . This is quite normal.</p>

<p>Q.G.: glad to have you back on Planet Earth ;-)</p>

<p>Seriously, that's a great explanation, & I thank you for it. It makes perfect sense. Exactly what I was looking for!</p>

<p>Guess I'll just have to live with this. The increased spacing is, of course, intentional on this back in order to prevent the film bending problems I brought up in my previous thread (which, after my scans, I certainly hope you believe -- I even tested with a 2nd back I rented... same behavior).</p>

<p>But that brings up 2 questions:</p>

<ol>

<li>Since I'm only getting 13 frames, but the camera allows me to shoot 15, don't I run the danger of a portion of the end of the roll, with the tape/flap, positioning itself on the pressure plate... and then the shutter firing with that tape/flap in place -- possibly damaging the shutter blades with the flap getting caught in between? Easy experiment to do :)</li>

<li>This camera is advertised as having 'automatic first frame' detection. I wonder how it works? Since I have so much wasted space at the beginning of the roll, can I wind the film less (typically the 'Start' is supposed to face up; hard to explain) so that the 1st exposure is earlier in the roll? That might allow me to squeeze in at least 14 frames... but I wonder if the 'auto frame detection' will screw it up. Again, easy experiment to do :)</li>

</ol>

<p>Thanks,<br>

Rishi</p>

<p>I have a Pentax 645, supposedly only able to fit 15 frames on a roll, but you have to push the shutter button for the film to unload, and it takes the 16th frame. I just position the roll so the side points of the start arrow are just visible as the roll is unwinding. Stop there load the insert in and voila 16 nicely spaced frames with about 1/2 inch of film at the end of the last frame. So try it and see what happens.</p>

<p>Thanks Bob.</p>

<p>Yeah I just talked to Mamiya & they said I should just insert the roll into the SPL (take-up spool), and not even bother walking the film... the back has a sensor that apparently senses the thickness of the paper vs. film. Although if that's the case I'd expect the back to wind the film to the same spot whether or not I walk the film... so I'm confused how this'll make a difference.</p>

<p>I was thinking if I rolled the film less then I'd be able use more of the beginning of the film. There's at least 60mm of wasted space at the beginning of the roll, & the 14th frame falls off the end of the film (my frame spacing is actually .5 to .625 inches, or about 12mm to 16mm).</p>

<p>I'm really worried about that tape/flap at the end of the roll getting caught in my shutter & ruining the blades... hasn't ruined anything yet as far as I can tell, but as I understand, shutters are delicate...</p>

<p> </p>

<p>Dang, that's a great explanation Q.G. Congrats.<br>

All I can add is that it's not uncommon on roll film, for the reasons given.</p>

<p>I'd especially reiterate that many roll film cameras are very sensitive to starting the film with it loose on the rolls. Much of the problem can (on some models) be ameliorated by just tensioning the advance while loading and making sure there's no slack in it.</p>

Some cameras use a roller driven by the film to drive the frame counter in turn. If the roller slips (due to dirt, loss of tension, etc.) then frame spacing suffers.

<p>I believe Q.G.'s explanation sums it all up so my question is answered.</p>

<p>I also answered my own question about the fear of the tape/flap ruining the shutter: I measured a good 7.5" of 'leader' at the end of the roll between the last bit of emulsion & the flap... so... probably no danger of the flap ruining the shutter during the 15th exposure.</p>

<p>Also, by loading the film by only inserting the tab into the take-up spool (and not walking the film any further till I can see the 'Start'), it would appear that the 14th frame is on the emulsion (but I won't know that for sure until development).</p>

<p>The 15th exposure is just on the leader, so no way of getting 15 exposures out of this film back on this film. Frankly, I don't care, b/c as far as I can tell the horrendous film flatness issue is solved on this film back with the increased spacing. Though that still requires some rigorous empirical testing that I'll get to in the next few weeks (I hope).</p>

<p>The 16 exposure back for the 645AF system is as good as <strong>trash </strong>(see my previous thread <a href="../medium-format-photography-forum/00YUob">here</a>; scroll to the end for the actual results of the tests). If Mamiya's reading this: <strong>SUPPORT YOUR CUSTOMERS.</strong> I got 'lucky' by complaining enough & finally bubbling up my problem to a manager who then sold me a fixed back that had been lying around for years for ~$400 (it had a newly sealed battery in it that expired in 2007). When in reality Mamiya should support their defective film backs that are defective due to a design flaw, not age/wear & tear.</p>

<p>-Rishi</p>