Projecting A 35mm Slide

Friends,

I've been playing with projecting a 35mm slide for use as a BG in a shot. my Dedo 100 with proj lens almost pulls it off-but its not bright - or large.

I'm trying a carousel today (loud). I may disconnect fan and place slide in a glass projection plate to protect from heat.

Any suggestions for a lighting unit I can rent/buy to project a slide bright and quiet?

Thanks,

Caleb Crosby, s.o.c.
DP/Cameraman
www.calebcrosby.com

Caleb Crosby wrote :

>Any suggestions for a lighting unit I can rent/buy to project a slide bright >and quiet?

Greetings Caleb,

Did exactly that about two years ago on a TV series. The slides we were projecting were of the 120 format or 6X6 all in a glass protected anti Newton frame. The projector made by Leitz was hired from a local professional photographic rental place. Because of sound best boy dismantled the fan.

The unit never really stayed on very long. Never had a problem, the projector nor the slides. If in doubt have some extra copies of the slide.

Regards

Emmanuel from Munich

Hi,

>I may disconnect fan

NO!!!

You'll cook the lamphouse, the dichroic coatings will fall off the lamp and reflector, making the light go yellow-brown. You risk starring any composite lenses in the projector and melting the electrics, cracking the ceramic lamp mounting block. You can end up burning the paint off the outside of the unit, if it isn't already.

Terminally bad idea.

I know this, because I've had fans fail on projectors we use for putting the logo and audience notices on-screen at the cinema where I sometimes work.

Phil Rhodes
Uses slide projectors a lot
London

>I'm trying a carousel today (loud). I may disconnect fan and place slide >in a glass projection plate to protect from heat...

I don't think the glass mount will save the slide. The light is so concentrated coming through the 35mm slide that it will probably warp in a couple of minutes.

We used a Carousel in a front projection rig years ago by building a sound blimp around it with a 6' chimney to direct the fan noise up toward the top of the stage.

This worked very well, but I don't know where you could get such a thing nowadays.

I don't recommend turning off the fan.

Wade K. Ramsey, DP
Dept. of Cinema & Video Production
Bob Jones University
Greenville, SC 29614

I did this a few years ago and the trick is to find the longest projection lens you can. A professional projector like the Kodak Ektagraphic units will give you the best light output with a choice of optics.

The four factors that you've no doubt discovered already are :

image size, image brightness, screen reflectivity and projector lumens output.

I think we were able to get 5'x7' images with our setup if memory serves. Shot on Beta with a 600. We had a zoom lens for our unit and we moved it as far from the talent as we could, zoomed the lens to a good compromise of brightness and size, wrapped it in sound blankets leaving only a hole in top for air circulation and then put up a sound blanket baffle between talent and projector.

Remember, for brightness it doesn't matter how far from the screen the projector is, it's all about the screen image size. A 5x7 image projected from 10' is as bright as a 5x7 image projected from 30'. Slides were chosen for their inherent brightness as well as content.

We weren't able to completely eliminate the projector fan noise but we did bring it down to the sound mixer's satisfaction. If you can shoot in a large , soft walled room all the better. If you have the resources, have a projection wall built with a piece of glass for the projector to, ah, project through.

Randy Miller, DP in LA

Scan the slide. Capture as a .bmp. Run thru a laptop to video projector.

Kirby Hamilton
www.kirbyhamilton.com

Randy Miller wrote:

>...Remember, for brightness it doesn't matter how far from the screen >the projector is, it's all about the screen image size.

Theoretically, yes. However, the longer lenses are usually slower than the standard lens.

Wade K. Ramsey, DP
Dept. of Cinema & Video Production
Bob Jones University
Greenville, SC 29614

Randy Miller wrote:

> A 5x7 image projected from 10' is as bright as a 5x7 image projected >from 30'.

I'm sorry, I'm just an editor, but were the law of physics revoked for this particular shoot or is there a special projector out there the rest of us don't know about??

Dave Marks
Editor,
Pennsylvania

Randy Miller wrote:

>...Remember, for brightness it doesn't matter how far from the screen >the projector is< >theoretically yes

Please explain why illumination falling off at the square of the distance doesn't make an apparent difference--or does it not fall off because of the narrower angle?

Larry Gibbs
Producer/DP
Tennessee

WR>

>Theoretically, yes. However, the longer lenses are usually slower than >the standard lens.

Thanks, Wade for keeping me honest. Obviously there are going to be compromises, you'll have to look for the trap doors as you prep. I suppose the longer zoom lenses might even exhibit some ramping and portholing, too.

The one thing I didn't try was a wide projector lens with the projector behind the talent, out of frame. More difficult, perhaps to get a square image that way but depends on your needs. Might be easier to isolate the sound with it back there.

Randy Miller

David Marks wrote:

>I'm sorry, I'm just an editor, but were the law of physics revoked for this >particular shoot or is there a special projector out there the rest of us >don't know about??

No, it's image size, not throw, that determines brightness -- excepting factors like lens speed and atmospheric haze.

There are always caveats to any rule like this, but it holds pretty well.

Jeff "16 ft. lamberts or else!" Kreines

David Marks wrote :

> but were the law of physics revoked for this particular shoot or is there >a special projector.....

David,

In a word, of course not. Not sure what your understanding of how image size affects brightness is, but there is no relationship between projector to screen proximity and image brightness. Image size dictates brightness rather than how close the projector is to the screen. As Wade points out, the variable here will be the speed of the lens. An F2.8 50mm lens will be brighter than a F4 100mm lens given the same image size.

As you cover more screen real estate when the image (bigger image) the light is spread out over more area and the image brightness diminishes.

Randy "not trying to project bad information" Miller, DP in LA

Thanks for the thoughts.

Anyone ever try projecting a slide with a focusable spotlight? (Quiet)

My Dedo 100 with proj lens is fair.
I might try a Leko.
Callinj the AV house to see if they have any ideas.

Just got some velvia and broke out my Nikon F2...

It's gonna be a good day!

Caleb Crosby
DP
Maine

Randy wrote:

>...The one thing I didn't try was a wide projector lens with the projector >behind the talent, out of frame.

Also, it will be more difficult to keep the screen illumination even, depending on what wide lens (and projector) you use. You would probably have definite falloff on the corners.

Wade K. Ramsey, DP
Dept. of Cinema & Video Production
Bob Jones University
Greenville, SC 29614

>Anyone ever try projecting a slide with a focusable spotlight? (Quiet)

You would need a metal slide, as the ellipsoidal reflector focuses all the heat as well as the lumens on one plane--this is the slot where metal gobo's slide in. A regular Kodachrome slide might last 3-4 seconds....if you're thinking about putting the slide where the gel goes, or anyplace downstream, the photometrics of the lamp and lenses preclude your slide image reaching focus.

Chris Taylor
DGA/IA 600 (and former theatrical lighting designer)
Santa Monica

Would a xenon slide projector be available for rental in your area?

I haven't used them but they are supposed to be much brighter than regular projectors.

Here are some references from a quick web search :

http://catalogs.infocommiq.com/AVCAT/images/documents/pdfs/Omni-550Xenon.pdf

http://www.navitar.com/av/xenon_gen.htm

Bruce Douglas, DP
Sao Paulo, Brazil

Did some research today and found the Finelight by Angstrum- 4K and about the same price.

Looks nice tho...

Rosco makes something called Imagepro (sorry the links I saved not on this computer) which fits on a Source 4. 250 USD.

It has a fan built in (supposed to be low DB) and projects 4" transparency that can be home PC printed. sounds like a good fix.

Will try to test an LCD projector tomorrow.

It is the digital age - but slides ARE more fun

Caleb Crosby, s.o.c.
DP/Cameraman
www.calebcrosby.com

Although I have never tried it, I do know the new large Dedos (650t & 400D) with the new focal lens can project 35mm slides. But it seems a step backwards as the new lens system in not a zoom, but fixed 100mm & 185 mm. I have the photometrics but it does not list the beam angle (it does give square projection sizes at given throw & fc). If you would like the info, please email me.

P.S. I have used the Large Dedos (both Tungsten & HMI) and love them! But I must say the new lens system is a bit much! VERY LARGE (screws the centre of gravity) and complicated. That much glass and aluminium and no zoom?? Although building it makes you feel a bit like a sniper from a Bond film!!!

Joshua Breckeen
Gaffer
London, United Kingdom

>were the law of physics revoked for this particular shoot

No, but you have to use the right laws the right way.

The inverse square law of light (twice the distance, a quarter the brightness) applies to light radiating from a point source (as used when shooting). It also applies to a projector with a particular lens, and the light radiating outwards in a cone. However, changing the lens changes the angle of the cone and the relationship is therefore altered.

So the principle to follow is just one of the ratio of enlargement. A certain intensity of light on a 24mmx36mm slide will be reduced by the ratio of the area of the slide to the area of the projected image. The lens doesn't come into the equation. If the image is 2.4m x 3.6 m (100 times each way) the intensity will be 1/(100x100). Still an inverse square law btw. Obviously that makes for a pretty bright slide, hence the need for cooling fans etc.

Note also that the condenser optics of the projector normally focus ALL of the light through the middle of the lens, so the speed of the lens (in the terms that apply to cameras) isn't a factor. (Provided the condensers match the chosen image lens).

Dominic Case
Atlab Australia

>You would need a metal slide,

But if an ellipsoidal ( or any focusable light) will resolve a gobo at the focal plane- why not a slide?

So far I've tested good focus with Dedo/proj lens and with Mole junior w/focus snoot. The regular plastic 35 slide gets warm but has lasted for at least 30 mins so far.

Heat is a problem - but so far focus is friendly.

Caleb Crosby, s.o.c.
Director/Cameraman
www.calebcrosby.com

WARNING WILL ROBINSON, DANGER, DANGER

On a lot of slide projectors, the fan doesn't just cool the slide - it cools the lamp. Those lamps need forced air cooling and may well fail in an exciting manner if left uncooled.

Consider building a little box out of particle board lined with foam with a baffle facing away from set and a hole for the lens - you could kill a lot of the sound that way

>I'm sorry, I'm just an editor, but were the law of physics revoked for this >particular shoot or is

Given the same projection lens aperture and a room that is not too full of smog, this is right - think of the image as light energy - the flux density - the amount of energy per square foot of screen will be the same if the projected image size is the same.

That is to say, if you project a 4'x6' image with a short focal length lens from close up and the same sized image with a long lens of the same f stop further away they should be the same brightness...and if it is for rear projection, there will be less hot spotting as well since the rays will be more nearly parallel.

Mark Weingartner
LA based (repaired slide projectors for the school district in high school) talk about being the ultimate Audio visual nerd...at least I got paid

Dominic Case writes :

>normally focus ALL of the light through the middle of the lens, so the >speed of the lens (in the terms that apply to cameras) isn't a factor.

Dominic,

Can you explain this further? Once the light leaves the condenser and passes through the slide how is it different from the opposite instance of taking a photograph?

I checked my trusty Carousel Projector and the lens does indeed have an F number on it: 2.8. I thought the condenser's function was to create an even field of light, bigger than the slide so that the bulb was not a point source behind the slide, but became a flat "disc" of light with parallel rays that are essentially the same intensity across the surface of the slide.

Randy Miller

>Can you explain this further?

Difficult without diagrams.

But forget the image, and think of the condensers focussing all the light onto, and through the lens. Ideally, something approaching a point source (well, the size of the filament) will image in the middle of the lens. Provided the lens has a big enough entry and exit aperture to admit the entire cone of light, making it bigger won't get any more light in.

The reason for this arrangement is to maximise the amount of light getting through the lens and onto the screen. A bigger diameter (and therefore f/stop) condenser lens will gather more light.

Now put the film (or in this case, the slide) in that cone of light at just the right place so that it is entirely illuminated. Too close to the lens, and the cone is too small, you'll get vignetting. Too close to the lamp, and the cone is too big, you waste light.

The focal length of the lens has now been determined (as you've just defined the slide-to-lens distance).

For a different throw or different sized screen, you need a different focal length lens, and therefore you really need a different condenser focal length for ideal light efficiency. In practice, you don't always end up with the imaging lens at exactly the point of focus of the condenser lenses, in which case the actual aperture of the imaging lens becomes more significant.

It's the same principle in an optical printer or back-lit rostrum camera such as an Oxberry.

In the reverse case where you are taking a picture with a camera, there is no condenser system to gather the light. You have to settle for what the taking lens can gather.

If you're still here, you'll agree - its easier with pictures and ray diagrams.

Hope that's some help though.

Dominic Case
Atlab Australia

You can always make a large 8x10 inch transparency, and use an overhead projector. Usually able to put out much more light than a 35mm slide. 35mm xenon arc projectors are also available -- much more light with less heat.

Glass mounted slides do stay flat, but the glass traps heat and moisture
(sometimes seen as moving "amoeba" like shadows on the screen).

Large format photo and inkjet materials are also available for photographic backgrounds :

http://www.kodak.com/global/plugins/acrobat/en/professional/products/

papers/enduraAppsGuide.pdf?id=0.1.16.14.28.14&lc=en

http://www.kodak.com/global/en/professional/hub/labDig/

media.jhtml?id=0.1.16.14.28&lc=en

http://www.kodak.com/global/en/professional/products/papers/

enduraTransClear/main.jhtml?id=0.1.16.14.28.22&lc=en

John Pytlak
EI Customer Technical Services
Eastman Kodak Company
Rochester, New York 14650-1922 USA

Dominic Case wrote:

>...But forget the image, and think of the condensers focussing all the >light onto, and through the lens.

The usual problem is that with ordinary projectors you are changing lenses but not changing the condenser optics. So, although the condensed hotspot is calculated to fill the lens aperture, when you change focal lengths radically it no longer does. Using a faster lens of the same focal length as the one that came with the projector won't increase the illumination; using a slower one, or a especially a longer one that is slower, will decrease the screen illumination.

Wade Ramsey

>Please explain why illumination falling off at the square of the distance >doesn't make an apparent difference--or does it not fall off because of >the narrower angle?

Hi, Larry!

The inverse square law applies strictly to light rays radiating from point sources. As the distance from the source is doubled the area covered is quadrupled and the illumination at any point on that surface drops to one-fourth.

With a projector the light is controlled by the optical system which projects (theoretically) all of the output into a defined area. It doesn't radiate out in all directions, it is focused. The focal length of the projection lens determines how large a screen area will be covered at any given throw. Longer lenses will take (theoretically) all the light and concentrate it into a smaller screen area, shorter lenses will spread it over a larger area. It is the total area covered that counts, because (theoretically) all the light is being focused into just the area the lens focal length provides.

Thus, it isn't the throw, it's the area the light is concentrated into that counts. So long as the projector's condensing optics are correct for the focal length projection lens in use, for a given screen size, you'll get the same illumination at whatever throw it takes to fill that screen with that lens.

Wade K. Ramsey, DP

>Scan the slide. Capture as a .bmp. Run thru a laptop to video projector.

>I'm totally bewildered to find any benefit in this idea.

The original problem was screen brightness versus projector noise. All this does is degrade the image without necessarily improving either of the problem factors.

But -ah! it's the digital solution! There you go!

Seems to me that the best ideas to come out of this (interesting) thread have been a longer lens and blimping the projector. (A useful set of ideas that could well date back to -say- 1927, except then it was moving the camera away and blimping it.) Oh, and taking time out to learn about projector optics and the inverse square law.

>Using a faster lens . . . won't increase the illumination;

Well clarified, Wade, thanks. That's the crux of the problem here of course - you can make it worse but not better.

Dominic Case
Atlab Australia

>...I might try a Leko.

Better work quickly!!!

It's way too hot in there for a regular slide. Maybe something on glass like the Rosco products. But a regular slide would only last a few seconds in a Leko.

FWIW, I saw a beautiful large format transparency projected at an art gallery. At the time, I made a few calls and found that there *are* very bright, large format projectors available. Try calling some staging companies.

David Perrault, csc

>FWIW, I saw a beautiful large format transparency projected at an art >gallery.

Pani and Pigi projectors are large format slide projectors (a refinement of theatrical scenic projectors) Call Art at 4th Phase in NY - they have offices all over the world

Mark Weingartner
Usual disclaimers apply
LA based

Wanted to share some projection findings with anyone interested.

After seeing my Dedo was sharp but dim with a 35mm color slide I thought of a better suited light but found the affordable contraptions were all too loud and the better options way too pricey.

Next I shot a roll of Velvia and side by side tested a $2000 InFocus brand "DLP" projector (it was licensed by TI but too what extent it was a spinning mirror I can't say, it did have a nice tonal range and greyscale compared to, well compared to what I expected. I took it home for the wk end and had a small film festival. I can report a white sheet works almost as well as a Daylite screen.)

I had the developer scan the transparencies to disc at 300 dpi. I later re-scanned them myself at 600 which made an improvement. I connected a laptop via an SGA (?) connector.

In the other corner, with the white shorts... was an old Kodak Carousel projector with a zoom Ektar lens.

The set up was a front projection screen placed behind the talent keyed with a 2k zip light and a small fresnel backlight. I flagged the key off the screen with a flag. the projectors were beside the camera and about 10 feet away. the image was keystoned but out of my taking frame.

The DLP was brighter by 1 stop on my spot meter. also it can produce a much larger image closer to the screen- a big advantage for my needs. but this is where the digital advantage ended.

After seeing the film transparency on the Kodak. Well, being an old film lover I got diverted from the test and started stopping people walking thru the studio and inviting them to have a look. everyone was surprised the old "flea market" thing looked so much better than digital.

It was universal, the test ended before it began. in a way it was too bad because the DLP was quiet and I liked the idea of having a library of images available on disc- emailable in the field etc...Digital is just so damned easy. but in this case - it couldn't produce the picture I was after. The DLP was blocky, contrasty, false and well. I just don't have enough words too describe the lack of wow it produced.

So now I'm soundproofing an 18" square box that will fit into a low roller light stand yoke for "quick" set up/adjust. Got small Radioshack fans, nautical hull fittings, bilge hose, DC power supplies -and coming soon-inch thick glass (or acrylic) for a lens port. The Crosby LiteBox.

I'm swimming against the stream back to the 1930's, but at least I'm doing it for a good reason - sometimes the old ways are the best. To misquote a 'deadeye maker' in Nova Scotia I interviewed last summer.

Best part is the reversal stills shooting : Velvia, Kodachrome, Scala. That's some nice technology.

So thatâ€™s my report - many many thx for the insights from the valued Knights of the Table here. It was a great help in getting this started, a large thank you to Sir Geoff in London as always.

Life is good. and the light just keeps coming!

Caleb 'catching it as fast as I can' Crosby
reverse engineer/ DP
Maine USA

Hi,

A while ago, I produced a lot of advertising stills on slides for a local theatre. We looked at digital projection and found the same as Mr. Crosby. Eventually I wound up producing 2K stills in Photoshop which were shot out to slides on a CRT-based recorder, and they looked fantastic - contrast and sharpness completely destroyed the digital, colour saturation in particular was gorgeous - particularly in pink and red, it was like projecting a light field with a dichroic filter.

And this leads me on to the question. What on earth kind of dyes do they use to create the colours in something like slide film and motion picture prints? These dyes get clobbered with an enormous amount of light, way higher than any display print would ever have to put up with, and they don't seem to fade - at least, they do, but only over about six months of eight hours a day. What gives?

Phil Rhodes
Video camera/edit
London

Dye-forming coupler technology for color films and papers has evolved considerably in the last few decades :

http://www.kodak.com/country/US/en/motion/about/chrono4.shtml

http://www.kodak.com/US/en/corp/researchDevelopment/

technologyFeatures/enduraTech.shtml

http://www.kodak.com/US/en/corp/researchDevelopment/

productFeatures/enduraProd.shtml

John Pytlak
EI Customer Technical Services
Research Labs, Building 69
Eastman Kodak Company
Rochester, New York 14650-1922 USA
Telephone: +1 585 477 5325
website : http://www.kodak.com/go/motion