Rolleiflex & film sensing - how does it work?

Søren · Mar 11, 2017

This might be a bit of an unusual topic, but I really need to know.

I'm constantly amazed that although being a fully mechanical camera the Rolleiflex (2.8F in my case) is able to sense the start of the film. This means that one does not have to wind on and get the '<- start ->' arrows on the backing paper in specific position (which I have to do on my Hasselblad for instance). My question is: Is there anyone who knows how this really works? Sure, there is this little roller where one has to feed the film under when loading and from the point where the film starts it is backing paper plus film which means an increase in thickness. But can it really be that the camera just 'notices' the additional thickness? After all, film isn't that thick, and for a mechanical layman like me it seems quite miraculous that such a reliable mechanism is possible on that parameter.

BrianShaw · Mar 11, 2017

You described how it really works. And, yes, it can. Remember, though, that there is tape at the beginning if the film do the thickness is a bit more than just paper and film.

Leigh B · Mar 11, 2017

Mechanical assemblies are able to measure very small dimensions if designed to do so.

And such measurements can be made very accurately, again if designed to do so.

I have instruments that can measure thousandths of an inch, and fractions thereof.

- Leigh

Dan Daniel · Mar 11, 2017

Using levers, you can take very small changes and translate them to larger changes. I won't explain everything going on here. But at the top center, you'll see a dog-legged part with a hook at the top end that is resting on the end of a flat bar-shaped piece. That's the trigger. A couple of parts below, mostly hidden by the light shield, transfer motion from the lower roller to this trigger part. See how the hook is half-way down the end of the flat bar? This is adjustable, the amount of offset of the hook, hence the sensitivity of the Automat mechanism. When the film goes from plain paper to tape/film, the lever motion will cause the hook to move down (to the right in photo) and release. Then, put simply, the wind mechanism is engaged and the whole game starts. The 'clunk' you hear and feel is this action.

Well, more could be said, but it would take too long. Basically it uses levers to magnify small differences and a trigger mechanism to release spring forces to engage the full counter mechanism.

etn · Mar 11, 2017

How does it work? well, it doesn't (only half-joking here)
I have a 2.8E and a 2.8FX. Recently I took my 2.8E on a weekend with two friends, shot 6 rolls during the trip, and the camera wrongly detected the start of 2 rolls out of the 6. It started halfway through the film, which means I lost half of the frames (including some portraits of my friends I wanted to print and offer them). The camera is now at the tech for a full overhaul. I hope this will solve the problem. I have somewhat of a dilemma here, as I like the looks of the pictures taken with my 2.8E best, but I find the simpler loading mechanism of the FX much more reliable... (it is also 40 years younger).

One question I don't have an answer is, how does the feeler mechanism reacts to films of different thickness. Does anyone know?

shutterfinger · Mar 11, 2017

Backing paper is .004 inch thick (.1mm). Kodak T Max and Portra films and Ilford films are .0045 inch thick in 120 format, Fuji list their color films as .0035 inch thick in 120 format. Arista EDU Ultra B%W is .004 inch thick in 120 format.
Modern films are about .001 inch thinner than they were in the 1950's. A .0075 to .0085 sandwich is plenty thick enough to make a mechanical triggering system for and the rest is gear ratios and cams.

etn · Mar 12, 2017

Thank you.

ic-racer · Mar 12, 2017

When T-max 120 came out in the 1980s, the TLR repair folks at the time were offering to 'recalibrate' the rollers if there were issues with the thicker film. My 2.8 F seemed to work fine sensing the film, but would not hold the T-max 120 from the 1980s flat in the cold weather.

mitrajoon · Mar 12, 2017

That was a great description by Dan. I found out the hard way (wasted rolls) that the mechanism gets out of alignment and needs adjustment now and then. In my case the start of the roll wasn't detected. I got very good at rewinding rolls from the camera back onto another spindle.

Off topic:
Etn, what difference do you detect in images from your 2.8F versus 2.8FX?

Feel free to PM me rather than post here.

etn · Mar 12, 2017

mitrajoon said:
That was a great description by Dan. I found out the hard way (wasted rolls) that the mechanism gets out of alignment and needs adjustment now and then. In my case the start of the roll wasn't detected. I got very good at rewinding rolls from the camera back onto another spindle.

Off topic:
Etn, what difference do you detect in images from your 2.8F versus 2.8FX?

Feel free to PM me rather than post here.

It's very subtle, if not (most probably) completely imagined. The lenses are virtually the same (both planars), only difference is in coatings.
The older Planar seems to flare a bit more and have "smoother" contrast, if that's a good description. It gives a sort of more vintage look. I therefore tend to use the E for B&W (mostly TriX) and the FX for color slides (Velvia).
But again it's probably only in my head. And we are really splitting hairs here, both are truly excellent.

Did I answer your question? we can indeed continue to discuss this in mp so as
not to further hijack this tread. But I think it might be interesting info to others members.

john_s · Mar 13, 2017

etn said:
How does it work? well, it doesn't (only half-joking here)
.......

One question I don't have an answer is, how does the feeler mechanism reacts to films of different thickness. Does anyone know?

I use a Rolleiflexx SL66 which has the same film thickness feeler system and it had to be adjusted after several rolls were wasted. I much prefer the "line up the marker" system in the later model SL66SE: simple and it always works. I assume that varying thicknesses of films+backing led to the change.

Leigh B · Mar 13, 2017

etn said:
...how does the feeler mechanism reacts to films of different thickness.

It doesn't care.

Any thickness greater than the set value will trigger the mechanism.

All it looks for is a dimension larger than the thickness of the backing paper.

- Leigh

mitrajoon · Mar 13, 2017

etn said:
It's very subtle, if not (most probably) completely imagined. The lenses are virtually the same (both planars), only difference is in coatings.
The older Planar seems to flare a bit more and have "smoother" contrast, if that's a good description. It gives a sort of more vintage look. I therefore tend to use the E for B&W (mostly TriX) and the FX for color slides (Velvia).
But again it's probably only in my head. And we are really splitting hairs here, both are truly excellent.

Did I answer your question? we can indeed continue to discuss this in mp so as
not to further hijack this tread. But I think it might be interesting info to others members.

Thxs. Answered just fine. I've been toying with getting the FX simply because they are newer. I've got a 2.8F and 3.5F I'd have to sell to help pay for the FX and I'm not sure I want to do that.

etn · Mar 13, 2017

mitrajoon said:
Thxs. Answered just fine. I've been toying with getting the FX simply because they are newer. I've got a 2.8F and 3.5F I'd have to sell to help pay for the FX and I'm not sure I want to do that.

Do it, if you can find one at reasonable price. I have been toying with the idea of replacing my 2.8E by a second FX myself. The FX is my first Rollei (bought new in 2006)
and the last camera I will ever sell. You can reuse your 2.8F accessories with the FX, by the way.

Note that in the recent years Franke & Heidecke made a newer version of the FX called FX-N. It has the great advantage of focusing closer than all other Rolleiflexes.
It also loses the Bay III bayonet, you get a Bay IV instead, for which accessories might be more expensive and more difficult to find.
For trademark licensing reasons the lens is not called Planar anymore, but in my understanding it is virtually the same lens.
The FX-N does not look near as cool as the original FX, in my opinion, but the close focus capability can be a plus. It also costs an arm and a leg,
and there is virtually no used market for it. Used "first version" FX pop up from time to time.
See: Dead Link Removed

Feel free to pm me if you want more info or just discuss Rolleiflex!

BAC1967 · Mar 13, 2017

Thanks for that great description Dan. The Baby Rolleiflex has a different mechanism for sensing the start of the film. There's a sharp metal catch that is triggered by the leading edge of the film. I found from winding my own film if you tape the film to the backing paper all the way to the edge the catch wont grab the edge of the film. I prefer lining up the marks on the backing paper like I do on my Automat 3.5.

dpurdy · Mar 14, 2017

One question I don't have an answer is, how does the feeler mechanism reacts to films of different thickness. Does anyone know?[/QUOTE]
When I dedicated myself to Fuji Acros my 2.8F started messing up a lot, not being able to detect the thin tape that fuji uses on the film.
Personal preference... I would rather line up the arrow than trust the feeler roller.

Dan Daniel · Mar 14, 2017

The feeler mechanism doesn't react to 'different' thicknesses. It reacts to a thickness of 'X and greater than X.'

I have a repair manual from 1973 (National Camera, not official Rollei) that recommends changing standard procedure and adjusting for the tape thickness, not for the film thickness, because of the problems with thinner film stock. When set properly the mechanism will handle any film without problems.

Harry Stevens · Mar 14, 2017

dpurdy said:
One question I don't have an answer is, how does the feeler mechanism reacts to films of different thickness. Does anyone know?

[/QUOTE]When I dedicated myself to Fuji Acros my 2.8F started messing up a lot, not being able to detect the thin tape that fuji uses on the film.
Personal preference... I would rather line up the arrow than trust the feeler roller.[/QUOTE]

I agree, I was told that Fuji can cause problems for the feeler mechanism so I have never tried Fuji in my flex, it as took everything else though and worked fine so it may work with Fuji. I like the extra flex roller but only for the percieved film tension it gives but I prefer the arrow system and the film wind knob on my Rolleicord Va.

etn · Mar 14, 2017

Yes, Acros is said to cause problems to Hasselblad backs too due to the thinner base.

Leigh B · Mar 14, 2017

Dan Daniel said:
I have a repair manual from 1973 (National Camera, not official Rollei) that recommends changing standard procedure and adjusting for the tape thickness, not for the film thickness, because of the problems with thinner film stock. When set properly the mechanism will handle any film without problems.

There are three dimensions that contribute to tripping the sensor mechanism:
1) the thickness of the backing paper,
2) the thickness of the film itself, and
3) the thickness of the tape that holds those two together.

Of those three the tape is the thickest.

If you adjust the sensor so it just trips with paper+film, it will definitely trip going over the tape.

- Leigh

Vaughn · Mar 16, 2017

I have two Rolleiflexes, a Rolliecord and an Autocord that all have issues with film transport, stopping at each frame, etc. Frustrating...but at least one of the Rolleiflexes senses the film and advances the film correctly and winds the shutter -- it just does not automatically stop winding the film after each shot. But it is kinda neat. The mis-function gives me control over the spacing between the negatives; I can get the frames to touch edges (eliminate the space between) or give more space between to isolate a negative....opens possibilities for printing multiple negative images in platinum/palladium.

Ferdi · Mar 30, 2018

There was (still is?) an official German (DIN) standard for the thickness of backing_paper+film+tape. Originally all film manufacturers complied to this standard. After Rollei had abandoned its feeler mechanism a number of films are marketed that no longer comply. Therefore the need for recalibration of the feeler, depending on the films that are used.

E. von Hoegh · Mar 30, 2018

Søren said:
This might be a bit of an unusual topic, but I really need to know.

I'm constantly amazed that although being a fully mechanical camera the Rolleiflex (2.8F in my case) is able to sense the start of the film. This means that one does not have to wind on and get the '<- start ->' arrows on the backing paper in specific position (which I have to do on my Hasselblad for instance). My question is: Is there anyone who knows how this really works? Sure, there is this little roller where one has to feed the film under when loading and from the point where the film starts it is backing paper plus film which means an increase in thickness. But can it really be that the camera just 'notices' the additional thickness? After all, film isn't that thick, and for a mechanical layman like me it seems quite miraculous that such a reliable mechanism is possible on that parameter.

Not at all miraculous, quite far from it. A moderately good mechanical wristwatch will make the Rollei's film sensor (introduced on the "Automat", late 1930s) look crude in comparison. Fine mechanisms were once commonplace, now are apparently unknown. Very sad.

Rolleiflex & film sensing - how does it work?

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