Studio strobe projector

Cropline · Sep 2, 2018

Back in my early to mid '90's college days, I recall the school having a unit that could be connected to a studio strobe. The unit would accept 35mm slides and the slide image would appear as a background when black material was used and the strobe was fired. Does anyone know if these units are still made, where I might find one, even used. Any help appreciated.

Mr Bill · Sep 2, 2018

I don't know if they still make em, but you're probably thinking of "the scene machine," from "Virtual Backgrounds" or, I think the older name was "EPS" (Environmental Projection Systems).

There's probably a lot of them sitting around in back rooms somewhere, or for sale online. Something you should know, though, is that they're basically useless without the special background. It's a special material, called a high-gain retroreflecter, with a gain factor on the order of five hundred or a thousand times (meaning that it is seen, by the camera, as being that much more reflective than white paper). So if you try to buy a system, make sure it comes with a clean, undamaged screen. Fwiw, the backgrounds themselves cost roughly a couple thousand US dollars back in the day. You won't be able to buy a "proper" new screen elsewhere, to the best of my knowledge.

These were pretty incredible systems back in the day; I think the advent of digital imaging, with dirt-cheap chroma-key backgrounds mostly displaced them. Best of luck.

Ps, the black screen you recall was something that EPS stretched out an inch or so in front of the retroreflector. It helped to get darker blacks in the projected image in bright ambient light.

AgX · Sep 3, 2018

I know it as front-projector. But also background projector was used.
The problem is that both terms also are applicable on standard slide projection. In this case though it is about making a composite image out of real-life subject and slide-projected background.

The idea:
-) the reflection from the screen is much stronger than that from the subject
-) spill light from subject lighting onto the screen will not be reflected into the camera.

Thus one gains a perfect composite between subject and projected background. As long the projection is along the optical axis, what is achieved by semi-reflective mirror.

http://www.blende-und-zeit.sirutor-und-compur.de/download.php?type=image_full&id=1406030830

http://www.wochenschau.ch/tromboni/frontpro/frontpro.jpg

Should be available used or made by oneself.

btaylor · Sep 3, 2018

I remember 3M made a front projection system for special effects for movies. I visited a studio made for this years ago. Alignment was critical for projector and camera involving a special mirror in front of the camera. Finally the screen, as mentioned above, had to be perfect (and in this case they were huge, with sets built in front of them). Chroma key killed it.

Mainecoonmaniac · Sep 4, 2018

Why not use a regular slide projector? Use a gel to make your strobe balance out the color temp of the projector. There are tons of slide projectors that are cheap and even FREE.

AgX · Sep 4, 2018

Even if the background lighting is string enough to compete with a strobe lighting of the subject (high gain background reflectior), then still it is continuous lighting with the chance of unsharp edges around a moving subject. At least these are things to consider.

I already hinted at making such set-up one self, but even with a plain projector and the other components at hand it is a bit fiddly.

Mr Bill · Sep 4, 2018

Mainecoonmaniac said:
Why not use a regular slide projector? Use a gel to make your strobe balance out the color temp of the projector. There are tons of slide projectors that are cheap and even FREE.

Just having a slide projector is only ten or twenty percent of the whole deal, and you'd be forever handicapped with its limitations. You'd still need the special background, a proper beam-splitter with a good light trap, and a way to rigidly mount components with full alignment adjustability.

There's more to it than AgX mentions. In addition to the camera and projector being on the same optical axis, the relative (optical) distances, measured from lens "entrance pupil" to background screen must be nearly the same. For example, if the projector lens is too close, then the shadow left behind a portrait subject's head grows large enough to be seen by the camera, as a hard "shadow outline." Or if the projector lens is too distant, similar shadow outlines will appear on the inner parts of "openings" in the subject - for example, if a person has hands on hips, with their elbows out, then the arms will have inward shadow lines.

If one finds a used "Scene Machine" (with a background screen) for a decent price, it's probably not worth messing with diy solutions. Once you align the system (with a specific camera/lens) it stays aligned, even if the camera is removed. You can freely move the system around, while shooting, on a studio camera stand or heavy-duty tripod. Scene Machines have both a modeling lamp (allowing one to see the complete scene, for composing, though the camera eyepiece) and electronic flash with multiple power levels, as well as a zoom lens to adjust scene size. Whatever you shoot is complete, no further manipulation is necessary.

Cropline · Sep 4, 2018

My college had some nice equipment, but this item was rather simplistic. It was basically a black light tight box that could hold a 35mm slide. It could connect to the 7" reflector and we used a traditional black muslin background. I know there were some pretty sophisticated systems made, but style wasn't one of them. Anyone else ever see or use a basic model?

Mr Bill · Sep 4, 2018

Well I guess I was completely off on this one.

Regarding the simple box that attaches to the front of a light head, I'm sure I've seen them; we probably tried them out in our R&D lab in the office. Such a thing won't be able to efficiently get the light into the projection lens, so probably a large diameter simple lens, likely a Fresnel version. So a fairly low quality image, but ok for general patterns.

Did it look like this attachment (no longer available) from B&H?
https://www.bhphotovideo.com/c/prod...tems_SPBIP_Image_Projector_SP100_147_920.html

Or here's something similar from Denny Manufacturing - https://www.dennymfg.com/pattern-projector/ProductDetail/4916

M Carter · Sep 5, 2018

Anyone interested in this stuff should look into one of the "Making of 2001" books or online articles. Pretty fascinating, Kubrik had sort of a godzilla-level system made with an arc light and cooling system, projecting 8x10 transparencies ("Dawn of Man" scene). The background material was some sort of 35m reflective stuff with an adhesive back. It wasn't available in big enough sheets, so they cut it in random shapes and covered a huge cyc wall with the stuff.

Cropline · Sep 5, 2018

Mr Bill said:
Well I guess I was completely off on this one.

Regarding the simple box that attaches to the front of a light head, I'm sure I've seen them; we probably tried them out in our R&D lab in the office. Such a thing won't be able to efficiently get the light into the projection lens, so probably a large diameter simple lens, likely a Fresnel version. So a fairly low quality image, but ok for general patterns.

Did it look like this attachment (no longer available) from B&H?
https://www.bhphotovideo.com/c/prod...tems_SPBIP_Image_Projector_SP100_147_920.html

Or here's something similar from Denny Manufacturing - https://www.dennymfg.com/pattern-projector/ProductDetail/4916

I vaguely recall it looking like the B&H model. BTW, I think you hit the nail on the head with the Denny unit. I simply hadn't called for pricing on it but your post lists the price. I will have to see what they say about mounted slide usage.

Arklatexian · Sep 6, 2018

M Carter said:
Anyone interested in this stuff should look into one of the "Making of 2001" books or online articles. Pretty fascinating, Kubrik had sort of a godzilla-level system made with an arc light and cooling system, projecting 8x10 transparencies ("Dawn of Man" scene). The background material was some sort of 35m reflective stuff with an adhesive back. It wasn't available in big enough sheets, so they cut it in random shapes and covered a huge cyc wall with the stuff.

This is what we once called a "rear-screen projection system" and as you pointed out above, they were used by Hollywood for many years. I am sure there are modern day systems that do the same thing. I see something similar on TV frequently. The subject is very sharp but the environment that the subject is supposed to be standing in, behind the subject, has a "soft" look to it. Watch for it sometime. The process is used often........Regards!

AgX · Sep 6, 2018

There is no technical reason for a soft look of such background.

Do not overlook that also a rear projection in its classic meaning was applied. Its disasdvantage is that it needs more studio space than a in-line front projection, and that there is a great chance for a hot spot.

btaylor · Sep 6, 2018

Actually, I believe it was the front projection system that was used. Rear projection used a projector and huge, flat translucent material to project upon for a background.
Now they often make a gigantic transparency for backgrounds. It makes the illumination much more compact.

Mr Bill · Sep 6, 2018

M Carter said:
The background material was some sort of 35m reflective stuff with an adhesive back. It wasn't available in big enough sheets, so they cut it in random shapes and covered a huge cyc wall with the stuff.

Yes, 3M made material with the highest factor, at least back in the day. It's essentially similar to the high-visibility reflective tape people use when working near auto traffic at night, except much more directional with the appropriately higher factor. I think the widest they coated was about 3 feet, so anything larger had to be "assembled." The US company EPS mounted it on "rollable" plastic sheets for portable background use; they also had a method of getting a pretty clean slightly overlapping seam which would not be noticeable in normal photography. But if someone didn't have their seaming techniques near perfect, then disrupting the pattern, like in camouflage, is probably the best way to go. Fwiw I'm a little doubtful that one can buy this material in anything over 1" or 2" wide tape today, but just guessing.

Fwiw, in fairly recent times some systems have been marketed for use as a green-screen for video. They used an array of green LEDs in a ring around the lens, along with a flexible retro-reflective background. The bg base was a flexible material, like muslin fabric, with, I am told, the bead materials "glued" on. In some tests vs a high-gain screen (like EPS) it was, as I recall, about 10x less efficient, but worked well for the LED green (or blue) screen video application. You could just drape it over furniture and get a good chroma key dropout.

wiltw · Sep 7, 2018

Consider the Norman Tri-Lite, or the Profoto Pro Focus. Not a general add-on to a strobe source, though

Studio strobe projector

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