dan kessler

Don't see the picture head anywhere. Also unknown internal issues.

The database doesn't appear to include 35mm.

Did anyone else on the forum notice or mention this? He died Jan. 6

Many reasons for the differences. Simon Wyss, who often posts here, is a great one for this kind of discussion. Meanwhile, here's another book for you: Principles of Cinematography, by Leslie J. Wheeler, 1969 Fountain Press Limited

Try yahoo.com ?

Looks exactly like the mushroom cloud from the Atomic Annie test in 1953, the one and only time a nuclear warhead was fired from an M65 cannon. The blast was recorded from approximately 6.5 miles away, with the cannon in the FG in the original footage. Definitely comped here. The explosive yield was around 15 kilotons, similar to the bomb that fell on Nagasaki.

Not only is the whole process astounding, but the tolerances of some of the components that had to be machined are mind-blowing. For example, those solid titanium bars in the coating machines. They're what -- 3 or 4 feet long, machined, ground and polished over their entire length to a tolerance of fifty millionths of an inch. In machinist's parlance, that's half a tenth, or half a ten-thousandth of an inch. Holding that over the entire length along with the smoothness tolerance in some of the world's toughest material will make your head explode. And they've got stacks of those things! I think of the shop and the people who made them and just absolutely cringe. Oh yeah, and then the coating machine is mounted on its own independent foundation that goes down to bedrock below the building. All just so we can shoot film.

I think those bottles are polyethylene, and probably would work well for diffusion, but seems like they'd be less heat tolerant than perspex.

I think perspex, or plexiglas, as it's typically known here, could easily be transformed into a diffuser with ordinary sandpaper. The only issue for your application would be its heat tolerance.

Ground glass used to be pretty cheap from places like those mentioned. I have also made my own, like the example you've shown. The grit wasn't too expensive. In my case, I made a focusing screen for a view camera, so for that you only grind one side. For a diffuser, probably doesn't matter if you grind both sides. Yes, naturally, any light fixtures with built-in reflectors will serve your purpose.

Conventional ground glass is not going to block much heat. There is such a thing as heat-absorbing glass, which was used in slide projectors for this very purpose. Not certain where to buy some, but I used to get all kinds of experimental optic supplies from places like Edmund Scientific and Surplus Shed. Both are still in business, so you might do a search through their online catalogs. The speed difference between your lenses is negligible. Not a problem.

The condenser lens must be of larger diameter than the diagonal of the slide or your light cone will not cover it. Studying the principles a bit, as I suggested, will help you understand how it all works and apply actual measurements to your set-up. Admittedly though, the condenser system does complicate things. You could get away with a simple diffuse light source behind the slide, i.e., just the lamp behind a piece of ground glass. (Your baking paper idea might catch fire). Put a mirror or even just a piece of white cardboard on the other side of the lamp to bounce all that lost light back into the slide. Definitely works and no math needed.

Strongly suggest you do more research on the proper spacing of the condenser lenses, lamp, slide and objective lens. You should get acquainted with the basics of optics and ray tracing, which isn't too difficult, but will help you get better results. In all projectors of this type, it is common to arrange the condenser so that an image of the lamp filament forms at or near the aperture stop of the objective lens. And yes, heat can potentially damage the lens. If you're using low wattage, it's less of a problem, but then you won't be able to project a very large image, either. All in all, it's a good way to learn about optics.

The entire point being that the OP's rejection from film school is by no means the end of the road. He should take heart and press on.

Pretty sure Spielberg was rejected by USC because his gpa was too low