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Need advice on front projection for feature film


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#1 Martin Oller

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Posted 07 December 2017 - 04:43 AM

In a few years time, I'm about to realize my dream and produce a fantasy feature length film that I've been working on for the past 15 years. And I've come to be interested in using front projection for most of the sceneries, because:

 

1. Done right it looks amazing, and

 

2. The movie will be shot on very old anamorphic lenses with lots of distortion, thus making in-camera effects preferable over chroma, and

3. Considering the length of the movie, although it will be expensive to buy gigantic scotchlite backgrounds and projectors, it can make it possible to shoot most of the film in the same place, and create immersive sets for the actors that will be far cheaper than actually building full sized fantasy themed sets or shooting outdoors, and look better than greenscreen due to the unique visual style/lens distortion.

 

My idea at this point, is to create a set similar to what they did in "Oblivion" (2013). According to this article they used a total of 21 projectors and a 270 degree coverage, which is way out of budget for this project. I'm thinking 1 or 2 projectors and a flat mobile background on wheels that can be moved as needed.

maxresdefault.jpg

When I read about front projection, they always talk about shooting through a one-way mirror. I'm assuming that shooting like this is the only way to do it on smaller sets, where the distance between the talent/background is too short and you don't want to cast a shadow? I've watched some videos about front projection on youtube and I stil don't quite get the point of the mirror, other than the obvious (that the projector isn't in the way, and the above mentioned).

Or is there some other technical point that I'm missing here?

Front_projection_effect.jpg

 

Looking at the BTS picture from Oblivion, you can see the crew walking around on set being lit and everything. Are the bright spots beneath the platform the projectors themselves? It looks like they are angled straight up onto a mirror, and then cast onto the screens. I guess similar lighting could be made with a smaller, flat screen, using a camera with good light sensitivity and carefully add fill light primarily from above? (because light from the sides would reflect and destroy the projection, would it not?)

Also, any idea where I can buy these kind of massive scotchlite backgrounds? I just find clothes on Google...

 

Appriciate any advice on this, or other sources of information about modern uses of front projection in films. Thanks!


Edited by Martin Oller, 07 December 2017 - 04:46 AM.

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#2 Phil Soheili

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Posted 07 December 2017 - 06:09 AM

another point in using the mirror is that your projected footage is at 90° perfectly.
You don't want to (at least most of the times) see perspective distortion in the background images.

If you have a tilt/shift lens or other means to control the perspective on your projector AND if you can manage not to have your actors and buildings cast shadows on the backdrop you might give it a try. Test it.

But from my experience of some decades (!) ago:
I don't think the image above is actually front-pro. To me it looks like a painting.
Front-pro was projected on a 400% (or better) reflective silvery foil.
The image could actually be seen ONLY in the camera's viewfinder because the
ambient light during prep. would kill the image. Ambient light is high in the pic. as

you can tell by the shadow in the unequally lit seamless background (in the curve)

Maybe things have changed...
;)

 

Good luck!


Edited by Phil Soheili, 07 December 2017 - 06:24 AM.

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#3 Phil Soheili

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Posted 07 December 2017 - 06:31 AM

Ah, ok!
I just saw the bts.
It's projected but not in "front-pro" process as in your "diagram".

Maybe they call this process front-projection too, I thought it refers to the mirror system only.

Cheers.


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#4 David Mullen ASC

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Posted 07 December 2017 - 12:53 PM

There are two types of front projection -- what "Oblivion" did was just the opposite of rear-projection, they projected the images onto a white screen like in a movie theater.  In this case, the projector has to be hitting the screen from an angle to be in a position to be off-camera, and the screen has to be large enough and far back enough so that the angle of projection isn't too far off to one side, the projector being behind the set and actors hidden somewhere.

 

The more advanced form of front-projection first used on "2001" involves a screen made up of 3M Scotchlite and a projector lined up with the optical axis of the camera lens so that the projected image travels straight out from the lens and any foreground actor blocks their own shadow on the screen, and what gets reflected back is very bright.

 

Besides the off-angle of the projection in the case of "Oblivion", the other issue is the light levels -- those scenes for "Oblivion" were shot around an T/1.4 on Master Primes on a Sony F65 camera, I assume rated above 800 ASA.

 

The brightness of both approaches depends on the lumens output of the projector but the 3M Scotchlite approach will give you more output back to the camera (which was useful in the days of slow film stock.) One of the problems with this approach though is that it is hard to move the camera around, it's nearly always a lock-off because of the alignment of the mirror to the projector, unless built all as one unit as in the Zoptic process used for the flying scenes in "Superman: The Movie".


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#5 Simon Wyss

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Posted 07 December 2017 - 01:24 PM

I strongly advise you read the corresponding pages of

 

Motion Picture Camera Techniques by David W. Samuelson.

 

I have a copy of the second edition with me.

ISBN 0-240-51247-2. Check libraries or bookstores.


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#6 Tim Smyth

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Posted 28 December 2017 - 11:35 PM

I, like Simon, think you may want to read up on the subject.  It will not be as easy as doing green screen, and may end up being way more expensive, as you will also need a bigger studio. 

 

You may want to do is talk to effects guys, you may be interested in hiring for the project, and they can probably let you know the best ways of doing things.

 

I love old time effects,  but some of them are just hard to recreate, of find the need to do so, in today's computer age.


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#7 Webster C

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Posted 04 June 2018 - 03:58 PM

One thing I learned recently (courtesy VFX cameraman Jim Aupperle) is that in classic front projection (with a beam splitter) your projector must have a lens with f-stop control. You need that to be able to adjust the depth of field on the projector to minimize the "halo" that can happen around your subject.

 

I'm sure that's covered in the Samuelson book. I don't have my copy with me to check.


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#8 Doug Palmer

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Posted 05 June 2018 - 04:27 AM

One thing I learned recently (courtesy VFX cameraman Jim Aupperle) is that in classic front projection (with a beam splitter) your projector must have a lens with f-stop control. You need that to be able to adjust the depth of field on the projector to minimize the "halo" that can happen around your subject.

 

I'm sure that's covered in the Samuelson book. I don't have my copy with me to check.

Presumably though you could just add black washers onto the front of the lens till you get the best result ?


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#9 Gregg MacPherson

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Posted 06 June 2018 - 01:09 AM

Martin, I did a project which had front projection years ago. 3M reflective screen and half silvered mirror. The screen was only about 4m wide or so, but we had joins in it to get that. You didn't see the joins, but it wasn't a bright clean sci fi look like oblivion.

 

You could just use NDs to adjust the projector f stop perhaps.


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#10 Mark Dunn

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Posted 06 June 2018 - 04:35 AM

 

 

You could just use NDs to adjust the projector f stop perhaps.

No. It's not the output that needs to be adjusted, it's the diameter of the beam of light.


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#11 Gregg MacPherson

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Posted 06 June 2018 - 05:30 AM

Not sure what you mean there Mark.  The effective aperture of the projector lens?  I thought that for a given exposure the output will need to be controlled if the projector f stop is changed. 


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#12 Mark Dunn

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Posted 06 June 2018 - 06:19 AM

Not sure what you mean there Mark.  The effective aperture of the projector lens?  I thought that for a given exposure the output will need to be controlled if the projector f stop is changed. 

I believe you have to change the actual lens aperture to control the halo problem.


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#13 Doug Palmer

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Posted 07 June 2018 - 04:01 AM

I believe you have to change the actual lens aperture to control the halo problem.

Yes surely. I've never done 3M front projection :unsure: , but doing optical effects with normal projection the halo problem is less when using smaller stops on the projector's lens.


Edited by Doug Palmer, 07 June 2018 - 04:05 AM.

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