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Film to video aspect ratio and HD Cropping
Understanding film and HD video aspect ratios
Will my film to video transfer be full HD video?
Many Home Movie Depot customers desire a 16:9 film to video transfer to HD with no pillar boxing (black bars added to the side). Although this is technically possible, it would result in cropping out a significant portion of the top and bottom of the film. The problem is we are starting with 8mm film or 16mm film which is fairly square (4:3) and trying to fit it into a rectangle (16:9). The best way to transfer 8mm film and 16mm film to HD video is to fit the entire frame of film from top to bottom. Once the edge of the film frame reaches the edge of the video frame there will naturally be dead space on the sides, again putting a square into a rectangle.
Continue reading to understand more of the math and specification requirements for film to HD video and how Home Movie Depot optimizes for the film to video conversion.
Aspect ratio technical definitions
Small gauge film aspect ratios
Small gauge film formats have an intended aspect ratio of 4:3.
| Film format | Scanned image width | Scanned image height | Aspect ratio |
|---|---|---|---|
| 8mm film | 0.173" | 0.130" | 4:3 |
| Super 8mm | 0.211" | 0.158" | 4:3 |
| 6mm film | 0.368" | 0.276" | 4:3 |
These are taken from SMPTE Recommend Practice 27.3-1989 (Specifications for Safe Action and Safe Title Areas Test Pattern for Television Systems) and SMPTE RP 56-2002 (.Safe Action and Safe Title Areas for 8-mm Release Prints). The latter document describes a safe title area at 80% width and height, and a safe action area at 90% width and height.
Home Movie Depot full frame film to video
Many customers of Home Movie Depot prefer a larger scan area than described by the standards. Transferring film to video beyond the "safe" areas significantly increases the resolution of the film and therefore the quality of the film to video transfer.
The maximum scan areas are as follows:
| Film format | Maximum width | Maximum height | Aspect ratio |
|---|---|---|---|
| 8mm film | 0.315" | 0.150" | 2.10:1 |
| Super 8mm | 0.315" | 0.167" | 1.88:1 |
| 6mm film | 0.629" | 0.300" | 2.10:1 |
These scan areas are the full width of the film and the frame-to-frame height.
Standard Definition TV aspect ratio
Standard definition television has an aspect ratio of 4:3. At a DVD resolution of 720x480, this implies a pixel aspect ratio of 0.888:1 (the pixel is taller than it is wide). A wide-screen (anamorphic) DVD has the same resolution, but the pixel aspect ratio is changed to 1.18:1 to make the wide-screen picture.
High Definition TV aspect ratio
High definition television has an aspect ratio of 16:9. Resolutions are 1280x720 or 1920x1080. Both of these resolutions use 1:1 (square) pixels.
MPEG-2 Format aspect ratio
The MPEG-2 format includes, in the sequence header, a four-bit field called "aspect_ratio_information". The following aspect ratios are enumerated:
| aspect_ratio_information value | Aspect Ratio |
|---|---|
| 0 | Forbidden |
| 1 | 1:1 Pixel Aspect Ratio |
| 2 | 4:3 Display Aspect Ratio |
| 3 | 16:9 Display Aspect Ratio |
| 4 | 2.21:1 Display Aspect Ratio |
| 5...15 | Reserved |
For high-definition resolutions, values 1 and 3 are equivalent because high-definition resolutions use both square pixels and a 16:9 display aspect ratio.
Pillarboxing and matting film to video transfer
Pillarboxing in film to HD video
To fit a 4:3 source within a 16:9 frame, the image width is 960 pixels (for 720 line HD) or 1440 pixels (for 1080 line HD). The theoretical matte on the left and right of the screen is 160 pixels per side (720 lines) or 240 pixels per side (1080 lines).
Matting video in film to HD video
To enable maximum flexibility for HD capture, we perform the following procedures:
- Add a matte border on the left and right of the frame ("pillarbox")
- Centers the frame in case the borders are unequal
