Heavily keystoned live video

[casey_cole]

I'm doing an amateur dramatics production of Into the Woods, and at one point, Cinderella needs to sing a duet with her dead mother's ghost. The "ghost" will be an actor filmed live in the wings (so she can sing along with the orchestra) and digitally projected onto a flown hardboard flat.

 

The problem is that the flat is so far down stage that the projector (which needs to go on the downstage-most lighting bar behind the pros)) will need to project at an angle of around 45 degrees.

 

This will keystone the image too much and so I need to keystone-correct the image back to normal. So the projector will correct for about 15 degrees-ish, so the other 30 or so degrees need to be corrected somehow.

 

 

Ideas so far:

# Film at an angle - would this even work? I think it would, but it'll give an up-nose shot of the actor :D

# Put the image as far down the projection as possible so that the projector doesn't need to be so angled - also lower the projector as far as possible.

# Use a back projection section in the flat; could be complicated though as it will be flown in and out during the show.

# Use a real-time computer program to keystone the image heavily - can't find a free-ware one though, any ideas?

 

 

It is not important that the image be as sharp and clear as possible as the character is a ghost, but it would be good to have it recognisable!

 

So, any ideas pleas guys!

 

Thanks, CC

[mi-ul]

The problem is that the flat is so far down stage that the projector (which needs to go on the downstage-most lighting bar behind the pros)) will need to project at an angle of around 45 degrees.

 

This will keystone the image too much and so I need to keystone-correct the image back to normal. So the projector will correct for about 15 degrees-ish, so the other 30 or so degrees need to be corrected somehow.

 

What about projecting onto an angled screen - maybe 10-20 degrees - a 10-20 degree keystoned image (i.e. 45-15-(10 or 20)) may not be so noticable if you can hide the edges of the projected image - e.g. frame the projected area in black and film on a black background and the the frame and image overlap

 

May not work in your theatre / anywhere but may be worth a try

 

Mi-ul

[casey_cole]

You mean angle a little bit of the flat? (or even just kick the bottom out by two feet :D)

 

Could be tricky, and I think it'd be really noticable due to their only being two focal points in the scene.

 

I don't suppose it's possible to get angled prisms to whack in front of the lens is it? Do it low-tech and just put a trapesium shaped sliver of glass in front of the beam? Or would that simply mean I'd have to angle the projector down more and thus lose all advantage.

 

Or even - point the projector at a very steep angle and use a single mirror to to reflect it? Or would it end up just as bad?

 

CC

 

Edit: however, you've got the right idea - it doesn't need to be completely corrected, just by about 30-35 degrees to make the face recognisable.

[cfmjohn]

If you are considering a real time PC program I remember an old n-vidia graphics card I had came with n-View software (nVidea driver toolkit) which could keystone the output image any way you wanted, just by dragging the corners of the image. If you could come across a similar tool with a newer graphics card the PC option might just work. As long as you have a decent capture card in the PC that didn't cause too much of a delay it should work perfectly.

[paulears]

JUst fond somebody with Adobe After effects to just process the file for you. So much easier than trying to double keystone the images.

[peternewman]

The "ghost" will be an actor filmed live in the wings (so she can sing along with the orchestra) and digitally projected onto a flown hardboard flat.

JUst fond somebody with Adobe After effects to just process the file for you. So much easier than trying to double keystone the images.

Not quite that easy Paul. You could probably find a vision mixer with a wipe effect that does that, or a standalone DVE (Digital Video Effects) unit, and just stick that in the signal path. May be cheaper to go for the software route if you can, although there will probably be more delay.

[grizzly]

Does the projector you are using not have any (digital) keystone adjustment available in its on-screen menu?

It might not be able to adjust quite as much as you want, but it could be a start.

[smalljoshua]

So the projector will correct for about 15 degrees-ish, so the other 30 or so degrees need to be corrected somehow.

 

Does the projector you are using not have any (digital) keystone adjustment available in its on-screen menu?

It might not be able to adjust quite as much as you want, but it could be a start.

 

He Already said that.

 

Josh

[bruce]

Have you actually tried it yet? Or is it just a "paper design" at this stage? When you come to build the thing, you may find that relatively small movements in the positions of the projector and/or screen make substantial differences to the image shape. Remember that the keystone angle in this case will be between the projector and the "top" of the image - for a zero-keystone, you'd have the projector level with the top of the screen. So raising the image, or dropping the projector on a longer mount, even if only by a foot or so, or moving the projected image a yard upstage, could make very significant differences to the keystone.

[Pete McCrea]

Is putting a longer throw lens in the projector and then mounting it at the back of the auditorium at the right height not feasible?

 

You could get all heath Robinson and fold the image with a mirror to get the right angle.

[grizzly]

He Already said that.

 

Ah yes, just noticed that. Cheers.

[Tom Baldwin]

Left field idea: don't do it live, instead, sync the orchestra to the video playback by means of a click track.

The video file could then be keystoned offline, using AfterEffects, or for a free solution, mplayer.

 

Relies on the conductor being able to work with a click track - I've no idea how hard that is to do. Surely not that difficult?

[Nick S]

VJ packages will normally let you keystone live. I was doing that in Modul8 a few weeks ago for a show.

[steve h]

If you are considering a real time PC program I remember an old n-vidia graphics card I had came with n-View software (nVidea driver toolkit) which could keystone the output image any way you wanted, just by dragging the corners of the image. If you could come across a similar tool with a newer graphics card the PC option might just work.

 

Thats awesome - im useing a nvidea 7600GT which I bought a year ago so not exactly and old one (not new either though) and its a simple task of right clicking and selecting NVKeystone - never knew I could do that!

 

Steve

[weatherhead]

I think the idea of making the orchestra sync to a click track in a musical just to sort out a technical problem is a little bit like the tail wagging the dog. Conducting or playing in an orchestra to a click track can be hugely difficult, depends on the source material. With Sondheim stuff I imagine it'd be quite a task. If you wanted to go down the "not fully live" route, I think it would be better to film her singing it, keystone offline, and then have her singing it live with the orchestra. The lip sync will be a bit off, but maybe not enough to draw attention to it?

 

I reckon this would be doable with something like gephex, or if you're feeling masochistic, puredata.