Topic: advancing/mod problem

[formica]

i recently picked up this little point and shoot cam called the arcan mf-10t(it's the yellow cam with the turtle in the polaroid shot below). i tore it apart and flipped the lens and moved the lens in front of the barrel(it wouldn't fit properly in it's regular place flipped). i just got the test roll back and the effect of the lens i'm liking(i'll post a few shots below), but i'm having some advancing problems. the first part of the roll  has some very serious ovelap, this then disappears only to reaappear(but to a lesser degree) towards the end of the roll.  now the overlap isn't without its charms, but i'd like to know what's causing it. any ideas?

speaking of this camera, when i got it, i posted about it on my regular blog(not my photoblog - post is here) and how i planned to mod it, and if that failed to turn it into a pinhole camera. well, someone left this comment on that post:

The mathematics of pinhole imaging is complex. The hole diameter is dependant on both the focal length and the wavelength of the light. With a standard distance of 50mm from the lens cap to the sensor plane the optimum hole size is about .0.312 mm. This gives an f number of approx 185. It is possible to reduce the exposure time by replacing the pinhole with a Photon, or Pinhole Sieve. The former consists of a pinhole surrounded by concentric rings of decreasing width; the latter is similar but rather than concentric rings, consists of groups of concentric pinholes.. I am currently developing lenses based on these which should be available in the near future at a cost of $8-10 each, or $15-20 for a set of 3 (Pinhole, Pinhole Sieve, and Photon Sieve). Initial production will be for Canon EOS and Nikon cameras, but subject to demand, I will produce other lines as and when necessary. The body cap lens is only appropriate for film based SLR?s, having a 47 to 50mm focal length, depending on manufacturer. Most Digital SLR?s have a 24mm sensor, apart from the top of the range Canon which is 36mm. The smaller size means that to achieve the same results and perspective as a film camera the focal length needs to be reduced to approximately 33mm, a problem that I am currently working on a solution. Olympus has even smaller sensors and it would be impossible to produce a lens with the correct focal length for them. It is also possible to change the parameters of the lens to focus different wavelengths of light, e.g. daylight, infra red, ultra violet etc. This requires only a minor adjustment in the production process.

that's the whole comment.  it just seems so odd. it's almost like spam, but there is no url and only i can see the email address. anyway, just had to share that oddity with you all.

                      william

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[Francois]

Overlaps on 35mm can be quite hard to fix. From experience, they are generally related to a defective part inside the camera.
The only way to know for sure is to open it up and look inside. These cheap cameras usually have small screws inside the film chamber. Don't forget to look near the take-up spool as there is often one or two screws hidden there.

As for the pinhole mod, you can hold the shutter open with a piece of tape. For the pinhole size, I swear by the Pinhole Designer (www.pinhole.cz)

[formica]

thanks for the response francois. you know when i finished putting the camera back together i did have an extra screw. but i couldn't find any place that it may have belonged.  i think i'll have to tear apart the camera again and look around.  i've made a few pinhole cameras so that's not something i'm terribly worried about, but i'd rather put the camera to use as other than a pinhole.

                 william

[Francois]

That's usually my way of looking at things.
If it can be used as-is, do so. If it can't be fixed, turn it into a pinhole

[moominsean]

the advance thing may be as simple as the film not laying flat against the sprockets. i've had a couple 35mm do this. i think that was a lomo problem, too. guess you could just layer some tape on the backside to help press the film down.

[Francois]

Actually the film not being flat against the sprockets (and jumping) shouldn't cause overlap but increased spacing.

The way these work is quite simple. The sprocket turns a set of gears that end up at a stop gear (a bit like in a clock). The stop gear has a little lever which locks the film advance when a certain number of rotations of the sprocket has been completed. This is basically the way they calculate the length of film that has been advanced. When the film jumps the sprocket, you should logically get incredibly large spacing in between frames.

What is most probably broken is the stop lever inside the camera. Depending on how it is made (I've seen quite a few designs), it is most probably that the lever springs back to the stop position before advance is completed. When you look at the part, it looks pretty insignificant (read cheap).

On some cameras, the sprockets and take-up spool are linked. In my view of things, this is the model which is most likely to break. On these models, the take-up spool turns at the same time as the sprockets when you wind with the back open.

The other models (action-sampler look alike are in that section), the sprockets are independent. These have more chances of having wide spacing.

Hope it helps.

[formica]

thanks for the input you guys! the second roll had almost no overlap, but did have a spacing problem. a spacing problem is something i can live with. i just finished the third roll(should have it back tomorrow) so i'll be curious if it has any overlap or if that problem has gone away. most of the first roll can be seen here if anyone is curious.

               william

[Francois]

Hopefully, it was only a part that was sticking...

[formica]

well, i got the third roll back and the overlapping seems to be back(but inconsistently so). i'm nearly done with roll number 4 so we'll see how that fares. but at this point i may just have to accept what i get as i can't seem to fix whatever the problem is.

                               william

[Francois]

Sad to hear it still causes problems...

I know I have a camera (a Yashica) which I totally gave up on because of that...
The cost of repairing it would have gone way over the camera's value...
And opening it proves to be nearly impossible...

That's part of life... getting 15 frames per 24exp. roll is not fun...

[formica]

well, i'd be more concerned if it was a yashica, but this is a cheapo plastic point and shoot so it's not such an issue.  it sounds like your advancing problem is worse. i'm still getting something like 25-30 shots  out  of a roll of 36 so it's not a real serious problem. i just got back roll 4 and it looks fine. i mean still a minor advancing problem, but no overlap or anything.

          william