Home  1: Introduction and research  2: Basic parts and materials 
3: Initial test box  4: Framework mockup  5: Designing lens and aperture mount 
6: Designing camera back and film holder  7: Design tweaks  8: Film holder construction 
9: Camera back construction  10: Camera aperture failure  11: Camera aperture success 
12: Camera back framework  13: Camera shutter  14: Ground glass 
15: Camera front framework  16: Bellow test 

CHAPTER 6: DESIGNING CAMERA BACK AND FILM HOLDER

Phew, now this project have come to the point where I realize what Iīm actually trying to do. I have done numerous small modifications to the front element for the camera as well as designed the back and film holder. The biggest addition to the front peice are an additional slot for the shutter behind the aperture. I figured there is no reason to make the shutter more complicated than neccessary and go with the same basic mechanics as for the aperture, the blades will look somewhat different though, then I will add a manual shutter trigger and control that one completely by hand. As I had that idea laid out in my mind I realized I had another problem with the shutter, how will I be able to by hand control exposure times below one second? I probably wonīt be able to do that with any accuracy at all, so what can I do about this? Itīs really simple, After some thinking I realized that all I need to do is adding a neutral density filter in front of the lens, a filter that gives me about 4 stops less light should ensure I get exposure times above one second at daylight. I made some measuring with my D200 and at ISO100 and an aperture at F10 I got exposure times around half a second, and thatīs still a long time when shooting in daylight which can vary alot. Anyway I have been thinking for some time to buy a Cokin filter system for my D200 which uses flat filtes that are attached to a holder on the lens, I can very easily create another small pocket in front of the lens on this camera to allow these types fo filters to be inserted.

On the second image you can see the back side of the camera. The box that the film is in will be removed and replaced with the ground glass when setting the focus and composing the image. That whole module will slide in and out of the main frame in the same manner as all the other components (see the last image on this page). The knob on top of the box will be used to advance the film inside, and the small axle sticking out on the back will get a small dial attached to it showing how many images that have been taken on the current roll of film.

Another thing I have solved are how to mount the front and back camera element to the lego frame I intend to build. I have done some experimeting with glueing some sheets of the black cardborad together with simple carpenters glue and it seems to become very strong. Iīm thinking of adding a physical locking mechanism as well to these peices so the camera elements wont be able to slide off the mount, even if they will get pretty tight anyway.

Camera seen from the front.

Camera seen from the back.

Below you can see the film holder and the mechanics involved for advancing the film. To load film the bottom peice of this contraption will be removed to allow insertion of the rolls. The film will go from the inside of the right roll, around the guide to the front and film plane, then around the second guide roll and onto the inside of the recieving roll on the left. Above the recieving roll is a mechanism that only allow that one to be turned in one direction with the knob on the top of the module. The feeder roll will drive a small gear through a "worm gear" that in the end turns a small dial on the back of the camera which will show the number of the image in the camera. The film type I intend to use allow six (6x6 cm) images to be taken on one roll. One thing I will add to this construction are a frame on the front that will help keeping the film flat on the image plane, as it is now the film will easily bulge outwards and will not be kept in place properly. Gotta remember to move my ground glass back that extra millimeter then as well, otherwise my focus will be different on the film :)

Back of film holder.

Front of film holder.

In order to test the movement of the image number dial on the back of the camera I made this little contraption. I was unsure if the dial would turn more than 360 degrees when moving from the first to the last image on the film, but it turned out I was all right and I expect the dial to turn about 300 degrees from image one to six. Since there is no way to see what position the film has once itīs in the camera itīs important that this dial works and is set up properly. Since the film is marked on the back with numbers and direction for mounting it in "real" cameras I will use the films "start" mark and align that with a start mark on the dial, then I insert the film into the camera and advance it until the dial is on image one, then I should be ready to rock.

Film test roller.

Below are a picture showing the various parts of this camera. A few things will be added such as a shutter and a filter slot in the front.

1: Film holder (Goes into the film case). 2: Film cover (Goes into the film case in front of the film). 3: Film holder lock (Slides into the film case and locks the film holder in place). 4: Lens. 5: Aperture. 6: Ground glass (replaces the film case in the back for focusing and image composing). 7: Film case. 8: Camera back rack. 9: Bellow. 10: Camera front rack. 11: Back mount (will be fixed to camera shift/support structure). 12: Front mount.

Camera parts.

Continue to chapter 7: Design tweaks

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