Images

Digital DV Formats Comparison of tape formats http://www.cinematography.net/default.htm Good tech info site Film Stocks Camera models

A lens with focal length approx two times the diagonal of the frame on the neg (or chip) corresponds to what the eye would normally see, with minimal distortion. For 35mm movie film this is an angle of view of 50mm, for 16mm film it is 25mm. For mini DV (quarter inch chip) its around 6mm.

The physical size of the image receptor (film gate or video chip) also has a bearing on the depth of field achievable (for a given aperture), the larger the area, the shallower the depth of field that can be achieved (generally giving a more pleasing image).

In a film camera all parts of this image are exposed simultaneously (usually) at 24 frames per second.
Most video cameras, for historical reasons (to do with TV picture transmission) scan at 50 (PAL) or 60 (NTSC) fps and interleave every two images to give a 25 or 30 fps image. However the scanning is not instantanoeous and the two images that produce each frame are 1/50th second apart, so motion effects are visible (usually a combing effect on moving edges).
With the advent of DV generation cameras, faster electronics have enabled "frame mode" video, where the image is scanned once.. again not instantaneous, so motion tends to "bend" streight edges. The faster the chip is scanned the less obvious this is, but the trade off is exposure time and lack of " film-like" motion blur. Larger chip size mitigates this to some extent, as larger chip size means more light/less noise etc.. This is most obvious in the new generation of stills/video cameras (2007..) that have excellent low light capability (because of large sensor size) but "jelly roll" pans because of the time taken to scan the sensor.

IMAX 65mm neg moving through the gate horizontally
image size 71.09mm x 52.63mm

65mm neg moving through the gate vertically
image size approx 50mm x 27mm (aspect ratio a natural 1.85:1)

35mm stills camera (standard gauge) neg moves through the gate horizontally (not a movie size!)
image size 32mm x 24mm (40mm diagonal) (aspect ratio a natural 4x3)

35mm stills camera half-frame (standard gauge) neg moves through the gate vertically, similar to movie film.
image size 24mm x 18mm (30 mm diagonal) ????? (aspect ratio a natural 4x3)

DX stills camera (eg nikon digital camera, D40, D50,D70 etc)
image size 24mm x 16mm (28.85 mm diagonal, so this is 4x2.67 rather than 4x3, or 16x10.67 rather than 16x9)

Four Thirds stills/video cameras (eg Panasonic Lumix DMC-GH1, Olympus E-P1)
18 x 13.5 mm Four Thirds & micro four thirds system use the same sensor size (3x4)

35mm movie (standard gauge) neg moves through the gate vertically
image size 24mm x 18mm (4:3, open gate, usually quoted: 27.26mm diagonal)
22 x 9.5 ( 2:1 mask, technoscope)
21 x 11 ( 1.85:1 mask )

Super16 image size approx 12mm x 7.2mm. (14.55mm diagonal) (aspect ratio 1:1.67 = 15x9 (crop the top and bottom a little to get 16x9)

(aside: with Kodak Vision 2 100T (7212 introduced in 2005) filmstock it is possible to exceed the resolution of uncompressed 1080p HD D-5 video video with Super 16.)

16mm movie (standard gauge) neg moves through the gate vertically
image size approx 9mm x 6.5mm. (aspect ratio 3x4) pretty well now an obsolete format.

2/3" video, eg top end Hi-Def, digibeta etc (11 mm diagonal) see focal length comparrisons

Video 1/3" CCD chip: (eg PD150 etc, (5.5 mm diagonal))
Video 1/4" CCD chip: (a tad under 5mm x 3.5mm)

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70mm

super 16

not quite to scale!!

 

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Focal length v image comparison Hi-Def / 35mm / super 16mm
how to use this: a 5mm hi-def lens will give the same image (or angle of view) as 6.6mm super 16mm film lens:

Lens	2/3" HD-EC 11mm diag	35mm Academy (27.26mm diag)	Super 16 (14.55mm diag)
Fjs5	5mm	12.4mm	6.6mm
Fjs9	9mm	22.3mm	11.9mm
Fjs14	14mm	34.7mm	18.5mm
Fjs24	24mm	59.5mm	31.7mm
Fjs35	35mm	86.7mm	46.3mm
Fjs55	55mm	136.3mm	72.8mm
Hj8x 4.78 KLL-SC	5.5 - 44mm	13.6 - 109mm	7.3 - 58.2mm
Hj11x 5.58 KLL-SC	4.7 - 52mm	11.6 - 128mm	6.2 - 68.8mm
Hj21x 7.58 KLL-SC	7.5 - 157mm	18.6 - 391.6mm	9.9 - 209mm

 

35mm stills lenses on 1/3" chip cameras (XL1, XL2 etc)
Without any additional glass or "depth of field" adaptors like the PS techik, the "equivalent" focal length is 7.2x the rated focal length. ie a 50mm stills lens on the video camera gives the same angle of view as a 360mm lens on a 35mm stills camera!!. Telephotos are rendered virtually unusable, and wide lenses impossible to achive...
(based on the ratio of the image height behind the lens, or the diagonal in mm, 5.5mm:40mm ).

An anamorphic adaptor, to convert a 3x4 image to 16x9, increases the width of the image by 1/3rd, for the same camera lens, whilst keeping the height the same.
(Not to be confused with a streight wide angle adaptor, which are marked with a conversion factor, usually 0.7 or 0.4).)

So it in effect reduces the focal length horizontally of the camera's lens by 1/4 (just multiply by 0.75).

lens focal length	effective focal length with anamorphic adaptor
5.5mm	4.125mm
9mm	6.75mm
12mm	9mm
100mm	75mm

note the slight skew induced by the anamorphic adaptor (camera position for the two pictures is identical), because, in this case the adapter was deliberately rotated to make the window sides appear vertical..... (ed: interesting... so you can use an anamorphic adapter to give the illusion you have moved the camera, every camera crew should have one.... :)

 

Focal length v image comparison miniDV
miniDV 5.5mm lens give the same object size on the screen as 12mm lens (16mm Movie) as 25mm lens (35mm Movie) as 40mm lens (35mm Still camera)

Links:

IMAX
format history pages

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