Talk:Rear projection effect

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[edit] Disagreement

I disagree with what is said, or at least I have my doubts, in the 1931 film "Emil und die Detektive" there is a shot on a train, which looks a lot like rear projection. Juan Schwarz 23:22, 10 December 2006 (UTC)

I did some research and updated the article accordingly. I don't know what the state of the German industry was in the 1931 regarding the ability to easily have adopted the rear projection technology then in its infancy, but according to what I was able to dredge up, the technology goes back to 1930, and thus was certainly possibly used for the Emil film. Hope that puts your mind at ease! Girolamo Savonarola 08:52, 11 December 2006 (UTC)

[edit] Check out compositing

I wrote a new article for the entry compositing, which contains a section on rear projection. The information is accurate and supplied with references. I cannot vouch for much of the info in the history section of the present article, but the sentence

"Finally, the larger film gauges beginning to emerge in the late 1920s demanded more powerful projection lamps, which were subsequently available for making the rear projection screen brighter and thus more properly exposed." Does not make sense. With the possible exception of scattered experiments with larger film sizes, there were no new film gauges introduced in this period.

Also, panchromatic (pan-chromatic = all colors) film was superior to orthochromatic in that its recording of all colors (rather than only the bluish end of the visible spectrum) allowed less stylized makeup, improved contrast gradation, and a generally superior gray-scale rendition of colors (although colors like red and green could be indistinguishable without filtration). But how it made background plates practical is unclear to me.Jim Stinson 22:24, 28 August 2007 (UTC)

Yes, most of the large gauges were introduced - unsuccessfully, mind you - in the 1920's. See list of film formats for the full litany. As for the rear projection and panchromatic film it seems that the article explains it already, though perhaps not as clearly as need be - the panchromatic film's ability to react to more of the spectrum effectively made it more photo-sensitive, and thus enabled the image to more easily be recorded with an image displaying full intensity. Girolamo Savonarola 01:35, 29 August 2007 (UTC)

I don't think so. The questioned passage in the review says,

"Secondly, Eastman Kodak's introduction of panchromatic film stock in 1928 allowed for the camera to expose the projected background more than orthochromatic stocks, making it look less faint than it would have before. Finally, the larger film gauges beginning to emerge in the late 1920s demanded more powerful projection lamps, which were subsequently available for making the rear projection screen brighter and thus more properly exposed."

Film speed (overall sensitivity) and film color rendition (ortho vs. pan) are completely different. Birth of a Nation prints have ample image density to throw on a rear screen.

Projectors did not use lamps, but carbon arc systems; and in any case, the wider film gauges were too experimental and too little-used to motivate the development of brighter projector systems.

Overall, if the original assertions are to remain, they'd better have some convincing documentation.Jim Stinson 20:52, 29 August 2007 (UTC)

Looking at the edit history, it looks like I added most of that info (though I can't really remember this very well right now). I'm pretty sure that most of this was paraphrased directly from another source, but I'm having difficulty finding it right now (curse myself for not adding references at the time!). My usual books can confirm some bits, while I've managed to find some other smattering of info online. I'll work on that sometime tomorrow probably, but for now what I will be able to confirm from what's in question is that Just Imagine was an early usage and projection advances were partially responsible. However, I can't find anything about the ortho/pan issue at the moment, although there is mention of special fine-grain films created specifically for background plate usage. And probably most crucially, I've been able to trace the earliest rear projection work not to 1930 but even further back to 1913 (although it was considered a failure at the time). I'll edit and source these as soon as I can. And I'll continue to look for the ortho/pan question. I was able to dig up some circumstantial mention of the question in a Edouart SMPTE paper, but I don't have access to that paper yet. Girolamo Savonarola 04:49, 30 August 2007 (UTC)

Sounds reasonable. Fine-grain films definitely improved the resolution of the bg plates, and, obviously, projector power did increase -- especially as entrepreneurs like Roxy Raphael and Sid Grauman began building enormous theaters with very long projector throws. (Ironically, Grauman's Chinese in Hollywood now has a shorter throw because they stole the rear seats for a bigger concession stand. Typical!) Re history and early usages, I'm incompetent to comment there. Thanks! Jim Stinson 17:39, 31 August 2007 (UTC)