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Low Angle Prism

Published : 13th February 2011

Hi everyone,

I have a shoot coming up where some shots require the camera to track with a penny (coin) rolling along the ground and stopping at the foot of the actor. Some shots would be with the penny moving from right to left in frame as we track sideways with it, and one shot might be over the penny in foreground following it as it rolls toward the actor. The penny will be CG with live action background plates. Shooting with a RED camera, Zeiss Standard Speed lenses.

My first thought was to use a Low Angle Prism, but I've never used one  before. I also thought about a periscope lens like a Skater Scope, but the rental cost is a lot more and as per usual I'm already over
budget. I tried to find spots at the location that were below-ground grade level so I could get the lens low enough, and there are one or two positions where this might work, but ultimately I couldn't find
the perfect angles this way. It's kind of a magical moment in the script, so the director and I want it to look like camera angles you don't always see.

Budget issues aside, what do I need to know before employing the prism? Will it be possible to put a 138mm +1 Diopter on the lens or do I have to get a macro lens? How bad are Flare issues? Will I
have vibration problems on the Fisher dolly with skate wheels?

If we go with the prism, I'll probably get to try it a little bit at the camera prep, but I don't want to bother with it if it's not going to work.

Thanks for the advice,

Graham Futerfas
Director of Photography
Los Angeles, CA
www.GFuterfas.com


Every Low Angle Prism shoot that I've ever been on has had unacceptable flare issues, some of which we could not see until dailies. And this after using black photo tape to cover every bit of prism that wasn't in the shot.

I think we gave up using Prism about 10 years ago, after about 4 problematic shoots. Snorkels are so much better. I love doing hand held snorkel shots using one of the light weight Innovision Probes with 90 degree attachment on an SR. We once put a TRex or Revolution on a gals steadicam for a PSA on street litter. Great images.

Mako, Makofoto, 10 > 405 > 101 > 134 > 210 > Home! CA


Mako Koiwai wrote:

> >Every Low Angle Prism shoot that I've ever been on has had unacceptable flare issues

I have to second Mako's opinion. My blood runs cold when I hear talk of using a low angle prism. I can think of only one time when I used one and it wasn't a nightmare. Flare, fitting, filtering... Once good quality snorkel systems came out I've never recommended one again.

Rod Williams
Motion Picture and HD/Digital First Camera Assistant
Petaluma, California
U.S.A.
(707) 778-7524 Home
(415) 309-3407 Cell
facebook.com/rodwms


I mentioned Flare ... but a lot of it was what should more accurately be described as Ghosting. Perhaps if the various surfaces could be treated with modern multi coatings the inherent problems of these low angle prism could be countered. The scary thing is that even though we were aware of the problems and very carefully looked for them and took every precaution they still bit us! Perhaps if you can make sure that there will be NO backlight, light sources and/or bright highlights in the shot, you could venture to give it a try.

If I recall correctly, the only successful use that I've been involved with was the scene (dolly shot) around the swimming pool in the remake of "Breathless." Very flat lighting. darkish overcast sky.

Mako, Makofoto, S. Pasadena, CA


Graham Futerfas writes:

<< I have a shoot coming up where some shots require the camera to track with a penny (coin) >>rolling along the ground ...

For starters I'd try an HDSLR -- and probably a kit lens, which might have a thin-enough barrel to give you nearly zero ground clearance. I'd support the camera from above via its shoe, to avoid increasing
its bottom thickness.

If that's not possible, I'd build a mirror rig like so:

I'd go to a plastics vendor and get a front-surface acrylic mirror, and have it bevelled so that when it's set at 45 degrees to the ground there's no visual gap between the mirror and the ground. Then I'd
build a simple rig to support the camera looking straight down into the mirror. I'd hang the rig upside-down on a fluid or geared head so the whole thing could be panned. Then I'd flip the shot in post.

Devil's in the details, but theoretically I can't see why it shouldn't work.

Dan Drasin
Producer/DP
Marin County, CA



Daniel Drasin wrote:

>> Devil's in the details, but theoretically I can't see why it  shouldn't work.

I have my doubts about a plastic front surface mirror.
--
Steven Gladstone
New York Based Cinematographer
Gladstone films
http://www.gladstonefilms.com
917-886-5858


Steven Gladstone writes:

<< I have my doubts about a plastic front surface mirror.>>

What are they?

Dan Drasin
Producer/DP
Marin County, CA


Daniel Drasin wrote:


> Steven Gladstone writes:
> << I have my doubts about a plastic front surface mirror.>>
> What are they?

Hmmm, flatness, evenness of coating, optical quality pop into mind.

--
Steven Gladstone
New York Based Cinematographer
Gladstone films
http://www.gladstonefilms.com
917-886-5858


If you don't have to move the camera ... just shooting into a piece of front surface mirror laying on the ground is very effective for a super low angle view point. In LA, Otto Nemenz rents something like a 20 X 24 sheet of front surface glass ... as does at least one grip house.

Mako, Makofoto, S. Pasadena, CA


Mako Koiwai wrote:

>>If you don't have to move the camera ... just shooting into a piece  of front surface mirror laying on >>the ground is very effective for a super low angle view point... ....

I have had one bought for every picture I've shot since 2003 and have used them for at least one shotin each film since then. They are not expensive and I usually have the grips carry them for the duration. I try to get an 18x24 and a 24x36 which covers most lens and distance combinations.
Just remember they are very sensitive to scratching and dust shows up easily.

Roberto Schaefer, asc
Detroit, MI


Mako Koiwai writes:

>>If you don't have to move the camera ... just shooting into a piece of front surface mirror laying on >>the ground is very effective for a super low angle view point.

How about renting a 3D mirror rig, installing only the top camera and hanging the rig off an arm from the dolly?

In any case I'd probably try an HDSLR before futzing with mirrors.

Steven Gladstone writes:

>>I have my doubts about a plastic front surface mirror.
>>What are they?

>>Hmmm, flatness, evenness of coating, optical quality pop into mind.

I've used acrylic mirror for various purposes and have found none of the above problems. I get mine from TAP plastics here in the Bay Area. Not sure they have outlets down in LA.

Of course, you don't want to put bending stresses on them. But if you mount them on a support plate that's not an issue. Anyway, you could bottom-bevel a glass mirror, too, if you really wanted the front
surface to go all the way to the ground.

Dan Drasin
Producer/DP
Marin County, CA


If you don't have to move the camera ... just shooting into a piece

> >of front surface mirror laying on the ground is very effective for a super low angle view point

It also works for top views in crowded rooms when you don't have a flip reference and can't climb on a stair,just stick a good mirror big as you need on the ceiling and there you go...

Henrique Leiner
Director de Fotografia
Alameda das Mangueiras s/n lote 09
Barra da Tijuca Ilha da Gigoia 22640-330
Rio de Janeiro Brasil
res 55 21 2494 4315 cel 55 21 9239 6431
nextel 55 21 7830 5054 ID 8*17955


From: Henrique Leiner

>>It also works for top views in crowded rooms when you don't have a flipreference and can't climb >>on a stair, just stick a good mirror big as you need on the ceiling and there you go...

... or in a location where you don't have the space to do a needed OTS shot short of demolition....

Roberto Schaefer, asc
Venice Beach, Ca./ New Orleans, La./ Detroit, Mi.
www.ganzoltd.com