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class="style7"> Back Projection/Process Shots & High Definition

>Published : 6th April 2008

>Hi CML,

>I have a big project coming up which involves a lot of in car dialogue.

>Thankfully, the production co. have got me on board well in advance and we've had lots of discussions about how we are going to tackle the car stuff. Quantity of material+time+money+UK weather+UK roads=Low loader hell, in my experience.

>So, I have touted the idea of shooting the majority of the car interiors with back projection on a sound stage. I have never done this before and neither has anyone on the production team, but, amazingly, they are willing to spend money to research and test this properly in advance.

>We will almost certainly be shooting the plates on HD, but nothing better than HDCAM or DVCPRO HD. Hopefully, we will also be shooting everything else on HD too, but there is a possibility we will have to settle for SD, probably Digi Beta using the new 970. Lenses will be 35mm primes on the PS Technik.

>There is no option to shoot on Viper or film.

>So, my questions to CML are:

>1. How can I work out what lens I should shoot the plates with to achieve correct perspective when it is projected (we will be shooting 16:9 on 2/3 inch CCD's with 35mm Primes on the PS Technik)
2. Has anyone shot process stuff on HD before and what were your thoughts?
3. Are there any issues with shooting progressive?
4. Any other tips and tricks for process shots in general - especially keeping light off the screens!?!

>Thanks folks and best wishes,

>Jamie Cairney,
London, UK.


>Jamie Cairney wrote:

class="style8">>>There is no option to shoot on Viper or film.

>That's a darn shame.

class="style9">>>1. How can I work out what lens I should shoot the plates with to >>achieve correct perspective when it is projected (we will be shooting >>16:9 on 2/3 inch CCD’s with 35mm Primes on the PS Technik)

>The American Cinematographer Manual contains a section which goes into detail with regard to shooting back projection, especially pay attention to the parts relating to perspective and lens angles, read it first and then ask questions.

class="style9">>>2. Has anyone shot process stuff on HD before and what were your >>thoughts?

>I have done it several times, and it works great. Get the projectors and screens from Ady Gil at American Hi Def in Van Nuys California (818)222-0022 and get a Luther Color correction unit (with panel) from Greg Ciaccio at Technicolor in Burbank at (818)260-3600 for balancing background color from the playback machine to foreground lighting color.

class="style9">>>3. Are there any issues with shooting progressive?

>Progressive works best, I don't recommend projecting interlace.

class="style9">>>4. Any other tips and tricks for process shots in general - especially >>keeping light off the screens!?!

>Yes. Keep the screen in the dark. Do this by walking the screen all the way across, and setting flags with your head right against the screen.

>Dave Stump ASC
DP/VFX Supervisor
back from Amsterdam
on location in Mystic CT


>JDC have an array of very impressive "back projection" and "pre-viz" systems. Have a word with Lester. He should be able to help.

>Joe Dunton & Company Limited
Elstree Film Studios
Shenley Road Borehamwood
Hertfordshire WD6 1JG
tel: +44 208 324 2311
fax: +44 208 324 2336

Ben Bannister
www.jacksonwoodburn.com


>While I haven't shot this type of process shot I can make a few suggestions about shooting projected images. I would recommend an LCD projector. Do not use a CRT projector. LCD projectors are wonderfully inefficient for our purposes. They generally do not flicker because of their slow response times. Gamers are changing this. Hardcore gamers will always use a CRT to test a new game. LCD manufacturers are working to shorten response times in order to compete with CRT's. Some new (higher end) LCD monitors are beginning to flicker when shot. I had one on a set a few weeks ago. I haven't come across this with an LCD projector but make sure you test this with a waveform monitor before you choose your projector. Of course if you have to dial out flicker use flicker free sources but a non-flickering projector is best.

>Color temperature is a big concern. Some projectors (and monitors) can be 8K degrees or above. Dave is recommending you color correct your source on set (if I read his response correctly). That will give you the most flexibility. There are other compromise solutions (like pre or on set filtering) that almost always fall a little short of ideal but can be acceptable for some purposes.

>Make sure your projector puts out sufficient lumens. If you are using an F900 with a Pro35, a projector that puts out about 10,000 lumens will give you sufficient brightness for most working f stops. You can use ND filters to cut the projector's output for specific shots if you need to. This is most relevant if you are going to vary your shooting stop. Your choice will also depend upon how large an image you need to project. Almost all video projectors have built in fans so sound can be an issue - especially if you're using a short throw projector lens.

>Jim Iacona
DP
San Francisco
www.lightbreak.com


>Jim Iacona writes:

class="style9">>>LCD manufacturers are working to shorten response times in order to >>compete with CRT's.

>I'm unclear as to how LCD response time relates to flicker. I always thought the
frequency of the display's backlight (not the pixel response) was the chief determinant of flicker.

>???

>Dan Drasin
Producer/DP
Marin County, CA


class="style9">>>I'm unclear as to how LCD response time relates to flicker.

>The slower the ramp the less the flicker. If the image doesn't fade from the pixels before the next scan, you won't perceive the flicker.

>Jim Iacona
DP
San Francisco


class="style9">>> I'm unclear as to how LCD response time relates to flicker.

>Dan - Here's another way to look at it. Incandescent sources are flicker free at any frame rate because of slow response times.

>Jim Iacona
DP
San Francisco