ghetto auto collimator explanified better

Thought I'd elaborate on this ghetto auto collimator thing from the other day, but then I could just repost some old material on it here. Hope this works, and I hope you get a laugh out of it all.

Here goes...

Ghettocollimator? I was sitting here, with a couple of cameras, dreaming of my autocollimator, when I got this crazy Macgyver idea. I figured, a collimator just shines an infinitely far away image into a camera, and if the camera is correctly focused to infinity, the picture would look good on the film. The secret is that the film image would then be visible if you could look in there with another camera focused to infinity. With a half silvered mirror, you can have the camera and the light source on the same axis. Sounds weird, but it works. Well, I didn't have any of that crap, but there were a few slide projectors, and a magically appearing half silvered mirror floating about. Here is the completed contraption. I must say, it works very well! This nonsense is obviously unnecessarily complicated as the mirror is in front of the viewer lens, thus making two optical sysyems necessary, (one for the projector, and another one for viewing) but hey. I only had a half hour to spare, and wanted to know exactly how well calibrated several cameras were. To reduce flare, A piece of black foam core with a hole punched in it keeps the light going only where it makes an image on the film. It hepled out quite a bit. Should be pretty obvious from here. the projected image (on left) passes through the mirror, and goes into the bessa in question (on right.) Since the lens on the projector is set to make an image at infinity, the bessa lens, set to infinity, should bring the image into sharp focus on the film. The viewing camera (on the bottom) uses the half silvered mirror to look into the camera and see the film. Since that lens is also focused to infinity, you can see right in there and know exactly how good your camera really is. Turns out, this old Voigtlander Bessa 6x9 is really sharp! ... and horribly out of line. Since you are viewing an actual image on a real live piece of film, this takes into account all sorts of things like film flatness. you can even wind the film live to make sure it all stays lined up. The longer the viewing lens, the greater the magnification obviously. with a 400mm on the viewing camera, you can on ly see the a very small part of the original slide for extreme pickiness! It's really fun to watch the image distort as you bend around the camera rails, and turn sharp when the lens says something other than infinity. You can reset focus dials with perfect precision, recollimate lenses, see all sorts of stuff, and find out the real effect, or lack thereof, that features and filters have on the final image. Turns out that of all cameras tested, this Bessa 6x9 is the only one that really needs mechanical help. I had no idea the lens was so sharp. Perhaps it might be worth a little work. Here is looking into the viewfinder of the "viewing" camera, which is some sort of screwmount Vivitar thing that was laying about. That is the actual image projected on the film inside the Bessa, as looked at right in there through the bessa's lens. The magnification is rather high, so you are looking closely at a tiny piece of the image in the middle of the film. Simply rotating the camera, you can view the corners of the image to see how the camera performs at different apertures. Yea, it's stupid, but it just takes too long to build a real autocollimator. Perhaps that will be the topic when there is a full hour or two for this insanity.

Nutty. I was really bored though. Hey.