GETTING IT ON FILM #3 - FRAMING CONSIDERATIONS

Aug 97 - Gord Harris


Many filmmakers moving from 35mm cinematography into Imax filmmaking have had some difficulties breaking old habits and adapting their compositional "eye" to the new demands of our larger, wider angleformat. Life gets even more complicated when one considers that most movies are released to both Imax Dome and conventional flat screen Imax theatres. To ease this path we have added a number of "framing lines" in the viewfinders of Imax cameras in an attempt to provide some useful reference points. This article will explain what these mean and how to use them intelligently.

In the beginning days of Imax, before the debut of Omnimax, life was very simple. The only lines that appeared in the camera viewfinder where a few pencil lines sketched on by hand by Bill Shaw, Dave Douglas or myself to indicate the centre of the film format frame, and a guideline horizon placement. The frame centreline cross is useful primarily as a reference focus mark when doing critical focusing in high magnification mode, and also for lining up shots in a repeatable fashion - simply telling you where smack dab centre of frame appears.

The dashed "recommended Imax horizon" deserves more explanation. Because of the steeply tiered seating deck in an Imax theatre and the very high screens, it is a common error for neophyte filmmakers to induce some stiff necks in the audience by framing subjects too high - up in the top third of the frame. While this is perfectly acceptable in 16, 35mm and TV, if overdone it can become quite uncomfortable and annoying to Imax viewers. The most ergonomically comfortable viewing angle for humans is actually looking slightly down - about 15% from the horizontal - not looking up at the top of the screen. I guess this evolved from millions of years of watching ahead where we walk (or else looking at all that good food on our tables!).

If an Imax camera with the standard 40mm lens is placed on a normal sized tripod out in a field and aimed horizontally, this "recommended horizon line" will indeed approximately match the real-world horizon (unless you are in the Himalayas or something). The resulting film shot, when projected in an Imax theatre would also have the horizon appearing in a comfortable, natural position for the average viewers in mid theatre. So generally, it is a good idea to keep the centre of interest down somewhere near this line - not in the middle or top of frame. Obviously this guideline can and should be violated at times, but a sure sign of compositional failure is if your film looks best to everyone from the back row of the Imax or Imax Dome theatre. The best Imax framing produces compositions that look weird and too small when previewed on your video tap or from way back in an 35mm screening room, with too much sky or headroom. This takes some getting used too, and some explaining from the DOP or director to a sponsor or producer without much Imax viewing experience! The best training is simply viewing some of your film rushes in actual Imax theatres.

When Omnimax (Imax Dome) debuted a few more lines appeared in our camera viewfinders. The more-or-less egg shaped lines represent the cutoff angle when your film is projected with a fisheye lens. Anything outside this region simply will not appear in a dome theatre on the screen, sobe wary of putting important information out in the corners of frame. If you film your shot specifically for the dome with the 30mm fisheye lens, you won't capture much out here anyways. The curved "Recommended Imax Dome Horizon" is even lower in the frame than the Imax horizon, because of the larger vertical viewing angle in a dome. For example, something composed at the very top of frame in a dome theatre will literally only be visible to your viewers if they look straight up ninety degrees (or even up and backwards for viewers in the front of the theatre)! Hence a good placement for titles is typically between these two horizon lines.

As the Imax theatre network developed, accommodations were occasionally made to put projectors into buildings where the full height or width of full format Imax could not be projected. Architectural and client demands have occasionally necessitated compromises in how much area of the film will actually be cut off in projection. The dashed lines called "Minimum Imax screen cutoff" is the Imax equivalent of a "TV Safe Action Area" - because TV sets differ in the amount of over or under scan - this minimum rectangle defines the area that you can absolutely count on appearing on every Imax screen in the world. Be careful not to frame so tightly that your centre of interest is above or below these lines! Many a filmmaker or computer animator has been distressed to learn their carefully planned and composed shot is simply cutoff top and bottom in some theatres...

Finally - there is a corresponding Min Omni line at the bottom, which corresponds to changes in seating deck and projector tilt, and a circle for the Imax Dome optical centre or lens axis. Note this is considerably lower than the Imax frame centre, and is a useful "centre of interest" for fisheye shots of things like space shuttles as any straight lines radiating from this centre will remain straight, rather than banana shaped. For shots taken with longer rectilinear lenses, it is helpful to avoid placing strong verticals near the edges of frame, as these will have an unpleasant curvilinear distortion when projected in Imax Dome. A variety of placements and compositions alternately favouring the strengths of Imax and Imax Dome can be an effective strategy for producing films that will play well in both formats.

Obviously rules and even "guidelines" are meant to be broken, but the true filmmaker/artist attempts to learn the rules first to know when to break them. I hope this article aids a bit in understanding why some films "play better" technically than others in the theatre network, by understanding how wide angle Imax cinematography differs from conventional 35 and TV.

(Reprinted from The IMAX Experience August 1997 Volume 1 Issue 4 with permission from IMAX Corporation)

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Copyright © 2003, Gord Harris, go-R&D Consulting. IMAX®, IMAX® Dome, IMAX® 3D, IMAX® 3DDome, IMAX®
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