IMAX 15perf-70mm Tech Specs
>Published - 7th January 2005
>I'm having difficulty in finding concrete tech specs for the IMAX format on the web. Does anyone know (in pixels) how large 15/70 image is?
>I've read on the web 6k x 8k and the film runs at about 4.301 frames/foot but I'm not sure how accurate that is. Also, what Kodak negative and print stock is used?
>From what I remember about the IMAX widescreen format, isn't the image created on a 65mm negative and blown up in the lab to 70mm?
>Does SMPTE have any detailed info?
Santa Monica, CA
>For concrete specs you may want to check out Imax's Website, www.imax.com
>Click on the link at the bottom of the window that says "Corporate Site", that will bring to the area with quite a bit of technical info, PDF's on all there cameras etc. IMAX runs about 334 ft. per minute @ 24 fps so your 4.3 frame/foot is correct. As far as film is concerned, everything Kodak makes can be ordered in 65mm Original Negative and 70mm print stocks with lead time. As far as resolution your 6kx8k is also pretty accurate, David Keighley Productions (DKP 70mm Inc.) in Santa Monica runs a Northlight Scanner for 15/65. It can scan at 8kx6k, 5.5kx4k and 4kx3k. As far as printing goes, CFI in North Hollywood is known as the 70mm lab, you may want to check with them, but the difference in width from the negative to the print has to do with the sound track. The image is in the centre of the film and the soundtrack goes on the upper 2.5mm and lower 2.5mm of the print, making it 70mm.
>I'm still not sure if they contact print or optically print though.
>Hope some of this helps
Los Angeles, CA
class="style9">>I've read on the web 6k x 8k and the film runs at about 4.301 >frames/foot
>65/70mm film has about 64 perfs per foot, same as 35mm.
>So 15 perf frames come at 4.267 per foot.
>Strictly speaking, the perf pitch (like 35mm) is 0.1870 inches, so there are 64.17 perfs in a foot, and therefore 4.278 frames per foot. But you get the idea!
>Imax is film, so it doesn't have pixels. But the frame size is 2.74" x1.913", which is about 2.7 times as big as a 35mm open gate frame. If 35mm is 4k x 3k, then you would need about 10k x 8k to do the same job.
>Hmm...followed up the last post with another, but it does not seem to have gone through...anyway, I failed to mention in the case of IMAX the sound is run off of a 35mm Magnetic Stock Dubber synced to projection or they run off of a Digital System using 3 CD’s - 2 tracks of sound per a CD.
>The optical and magnetic tracks on the 70mm print stocks are only used in 65mm-5perf.
Los Angeles, CA
>Large format projectionists and theatre managers "hang out" at http://www.1570.com
>IMAX also has a password-protected "Affiliates On-Line" user group on their website: http://www.imax.com
>Here is an "unofficial" private site with useful IMAX information:
>And "How Stuff Works" info :
>Kodak still stocks a full line of 65mm and 70mm films, including the latest VISION2 Color Negative Films.
>Many theatres are still equipped to show 70mm 5-perf prints as well. Today, DTS digital sound is available, avoiding the need to magnetically strip 70mm prints :
Eastman Kodak Company
class="style9">>As far as resolution your 6kx8k is also pretty accurate, David Keighley >Productions (DKP 70mm Inc.) in Santa Monica runs a Northlight >Scanner for 15/65. It can scan at 8kx6k, 5.5kx4k and 4kx3k.
>Output everywhere is CRT film recorder only, no laser, so in practical terms, there's not a lot to be gained by outputting more than 4k X 3k - you can feed all the pixels you want in, but the recorder spot size is the limiting factor. That said, 4k from 65mm 15-perf looks a world better than the same number of pixels from a 35mm scan.
Sassoon Film Design
class="style9">>Output everywhere is CRT film recorder only, no laser, so in practical >terms, there's not a lot to be gained by outputting more than 4k X 3k - >you can feed all the pixels you want in, but the recorder spot size is the >limiting factor.
>The Celco's spot size is 6 and 12 microns.
>So for a 70.41mm x 52.63mm IMAX frame, you can record at
11,753 x 8,772 or 5868 x 4386.
>David Keighley has shown you can record live action images from 4096x3062 files with sharpening and get a reasonable and good image. For CGI, wireframe, and text images, a 6K image is superior in quality. For an all CGI frame, even 4K may not be practical though,
so I've found I could get away with a sharpened 3K image.
Pacific Title Imaging
class="style9">>For an all CGI frame, even 4K may not be practical though, so I've >found I could get away with a sharpened 3K image
>DKP is outputting a 5.5K CGI sequence for us right now - I look forward to seeing the result. Another possible limiting factor is they shoot everything out to 5218 for speed.
Sassoon Film Design