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Film cameras capture 25 frames per second, and usually use a 180 degree shutter, which means they only expose the film for 50% of the frame duration.
In other words although the film camera is shooting at 25 frames a second, it only exposes the film for 1/50th of a second. If you run film (or 25 frame per second progressive video) at 1/25th second shutter the motion blur is very noticable and things look very smeary.
Standard def interlaced video cameras capture 50 images per second, using interlacing, and each of these 50th second images is only sent at half the vertical resolution of the video frame, as a field. This is why video is sometimes described as having 25 interlaced FRAMES, and 50 interlaced FIELDS. This means that there are twice as many images per second, and usually each field is exposed for 1/50th of a second. This means that much more motion is captured, and twice as many images are sent, and you get smoother, less jerky motion.
Because producers and directors think film has a higher budget look than video, it is now common to process interlaced standard def video to look like film, or to shoot progressive standard def or HD video at 25 frames per second. (Only a relatively small number of standard def camcorders can shoot progressive 25fps and no standard def studio cameras do AFAIK)
This means that most SD stuff shot on video but with a film look requirement is shot 50 fields interlaced and given a post-production film effect (rather than being shot 25fps progressive native video). Most decent HD cameras allow you to shoot natively at 25fps progressive, so there is no post-production procesing required.
The early way of doing the SD film-effect was to drop every other field, and repeat the other. This meant you got 25 different images per second with a 1/50th second shutter, but at half the vertical resolution. It looked like it had film motion, but it was very jagged, soft and unpleasant. (This is a dead easy process to do though - most gallery DVEs and edit suites can do it). Then people started filtering this so it looked soft, but not as jagged. Then people experimented with mixing the two fields together a bit (75% from one, 25% from the other), which retained most of the film motion but improved resolution a bit reducing the softness and jaggedness, but introducing some more motion blur. It was still pants. (I think this is what Casualty tried the first time)
However the best way of doing this is to do things properly, and do a full motion tracking system where you track the direction vectors of images moving in the frame and interpolate entirely new 25fps frames from the information both 50 field per second images, to give much higher vertical resolution. This is how the SD Doctor Who stuff and other high end film-effects are done, using standards converters like Alchemist, and pretty good results can also be obtained using something quite a bit cheaper like an ARC from S&W.
However it is important that camera operators shoot for the film effect, as because the number of images per second is halved, motion (such as panning) that looks fine 50 field interlaced, can break up when converted to 25 frame progressive.
Many cheap film-effects are done in Avid or FCP though - and unless a very good plug-in is used, the results can be pants.
Top Gear have a nice dynamic, they film-effect their location films, but keep the studio and track stuff interlaced. I suspect this is what Watchdog wanted to emulate, but they may not have been able to explain it to their post guys clearly enough? (Or the post guys may have edited in a way that made this tricky?)
noggin
Founding member
Can anyone point me to an explanation of the technicalities of the filmic effect as I am trying to describe it in some detail on a related post elesewhere? It's a denegration of the video content I know but how is it done?
Film cameras capture 25 frames per second, and usually use a 180 degree shutter, which means they only expose the film for 50% of the frame duration.
In other words although the film camera is shooting at 25 frames a second, it only exposes the film for 1/50th of a second. If you run film (or 25 frame per second progressive video) at 1/25th second shutter the motion blur is very noticable and things look very smeary.
Standard def interlaced video cameras capture 50 images per second, using interlacing, and each of these 50th second images is only sent at half the vertical resolution of the video frame, as a field. This is why video is sometimes described as having 25 interlaced FRAMES, and 50 interlaced FIELDS. This means that there are twice as many images per second, and usually each field is exposed for 1/50th of a second. This means that much more motion is captured, and twice as many images are sent, and you get smoother, less jerky motion.
Because producers and directors think film has a higher budget look than video, it is now common to process interlaced standard def video to look like film, or to shoot progressive standard def or HD video at 25 frames per second. (Only a relatively small number of standard def camcorders can shoot progressive 25fps and no standard def studio cameras do AFAIK)
This means that most SD stuff shot on video but with a film look requirement is shot 50 fields interlaced and given a post-production film effect (rather than being shot 25fps progressive native video). Most decent HD cameras allow you to shoot natively at 25fps progressive, so there is no post-production procesing required.
The early way of doing the SD film-effect was to drop every other field, and repeat the other. This meant you got 25 different images per second with a 1/50th second shutter, but at half the vertical resolution. It looked like it had film motion, but it was very jagged, soft and unpleasant. (This is a dead easy process to do though - most gallery DVEs and edit suites can do it). Then people started filtering this so it looked soft, but not as jagged. Then people experimented with mixing the two fields together a bit (75% from one, 25% from the other), which retained most of the film motion but improved resolution a bit reducing the softness and jaggedness, but introducing some more motion blur. It was still pants. (I think this is what Casualty tried the first time)
However the best way of doing this is to do things properly, and do a full motion tracking system where you track the direction vectors of images moving in the frame and interpolate entirely new 25fps frames from the information both 50 field per second images, to give much higher vertical resolution. This is how the SD Doctor Who stuff and other high end film-effects are done, using standards converters like Alchemist, and pretty good results can also be obtained using something quite a bit cheaper like an ARC from S&W.
However it is important that camera operators shoot for the film effect, as because the number of images per second is halved, motion (such as panning) that looks fine 50 field interlaced, can break up when converted to 25 frame progressive.
Many cheap film-effects are done in Avid or FCP though - and unless a very good plug-in is used, the results can be pants.
Top Gear have a nice dynamic, they film-effect their location films, but keep the studio and track stuff interlaced. I suspect this is what Watchdog wanted to emulate, but they may not have been able to explain it to their post guys clearly enough? (Or the post guys may have edited in a way that made this tricky?)