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MiniDV frame rate/color loss?


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#1 Dory Breaux DP

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Posted 11 March 2007 - 01:03 AM

When transfering film to MiniDV, is the frame rate and or color of the origional film compromised at all?
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#2 David Auner aac

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Posted 11 March 2007 - 09:55 AM

When transfering film to MiniDV, is the frame rate and or color of the origional film compromised at all?


Hi Dory,

your question is a very broad one. So here is a broad answer: yes. The color of film is hard to match by even the best of video formats, and DV isn't among these by a long margin. When you film was shot in 25 fps and you do a scan to PAL DV your framerate would still be 25 fps. Else its a problem to be solved by some king of pulldown. If you could be a little more specific, I'm sure some experts here could help you out with details...

Cheers, Dave
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#3 Robert Houllahan

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Posted 11 March 2007 - 11:17 PM

When transfering film to MiniDV, is the frame rate and or color of the origional film compromised at all?



Film is generally 24fps "progressive" which means the whole picture is displayed at the same time and not broken down to display as in NTSC or PAL tv systems. NTSC is 59.94 fields per second (2 fields make a frame) and pal is 50 fields per second. This is a analog compression technique and works by drawing half of the lines in a video picture "going down" and filling in the other half "going up" there were no LCD or Plasma, etc. displays when TV was invented and the up/down analogy is based on the electron gun sweeping across the phosper on a CRT.

Film scanning either uses a 3:2 pulldown or a transfer at 25fps to fit the natural film framerate into the way SD broadcast works. Despite the fact that DV is a digital format it has to work with the long established broadcast standards and recreates it's digital bitstream into a analog interlaced 720 pixel format (with 486 or 576 lines NTSC or PAL) this motion compensation and downres of the natural film picture and framerate is one component of "loss" inherent in the DV system.

16mm film is generally considered to be a 2K res format and even super8 is being scanned at 2K these days so many arguments can be hatched from the film res debate but 2K is 2048 x 1556 and DV is 720 x 480 so there is a significant loss of resolution, this is also why film transfered to SD can look so good because it is "supersampled" basically you are stuffing a 800lb gorilla in a 50lb box, google Nyquist for more info on this.

Film color is often represented at 16bit per channel precision (either in 16bit rgb or 10bit log) this is a representation of each color dye (red, green, blue) as a digital sample. Video works differently it makes a representation of the B+W image (the Y in YUV) and then uses two color difference signals (the U&V in YUV) to "hang" color on that framework. This is where the 4:4:4, 4:2:2, 4:1:1 numbers come from they represent how often a digital system samples each of the 3 pieces of the YUV component video signal. Full sampling is 4:4:4 or no information is thrown away. DV is 4:1:1 which means 3/4 of the color information is thrown away and instead of being sampled at 16bits per channel, or 10bits as in hi-end video, it is sampled at 8 bits. In order to make a initial bitstream which is ready to compress the "front end" of the DV system throws allot of information away.

The last compromise is the 5:1 compression which is applied to the incoming signal this compressor was designed a few years ago and there are more efficient compressors and the compressor has to be able to be stopped on an individual frame so as to facilitate editing, this is the big difference between Dv and DVD compression.

This is a simplified version of what's out there and the differences between DI style RGB representations of film and the video representations get much more complex. Dv looks good because it retains all of the sampling from the underlying B+W picture and tricks you by chucking much of the color, this is why DV looks much better in B+W than in color and also why it is a "clean" looking picture...Dv is much better than Hi8 but I feel not as good as BetaSP but it's cheap and universal and mostly easy to use.


Hope this helps.

-Rob-
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#4 Dory Breaux DP

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Posted 12 March 2007 - 11:19 AM

Film is generally 24fps "progressive" which means the whole picture is displayed at the same time and not broken down to display as in NTSC or PAL tv systems. NTSC is 59.94 fields per second (2 fields make a frame) and pal is 50 fields per second. This is a analog compression technique and works by drawing half of the lines in a video picture "going down" and filling in the other half "going up" there were no LCD or Plasma, etc. displays when TV was invented and the up/down analogy is based on the electron gun sweeping across the phosper on a CRT.

Film scanning either uses a 3:2 pulldown or a transfer at 25fps to fit the natural film framerate into the way SD broadcast works. Despite the fact that DV is a digital format it has to work with the long established broadcast standards and recreates it's digital bitstream into a analog interlaced 720 pixel format (with 486 or 576 lines NTSC or PAL) this motion compensation and downres of the natural film picture and framerate is one component of "loss" inherent in the DV system.

16mm film is generally considered to be a 2K res format and even super8 is being scanned at 2K these days so many arguments can be hatched from the film res debate but 2K is 2048 x 1556 and DV is 720 x 480 so there is a significant loss of resolution, this is also why film transfered to SD can look so good because it is "supersampled" basically you are stuffing a 800lb gorilla in a 50lb box, google Nyquist for more info on this.

Film color is often represented at 16bit per channel precision (either in 16bit rgb or 10bit log) this is a representation of each color dye (red, green, blue) as a digital sample. Video works differently it makes a representation of the B+W image (the Y in YUV) and then uses two color difference signals (the U&V in YUV) to "hang" color on that framework. This is where the 4:4:4, 4:2:2, 4:1:1 numbers come from they represent how often a digital system samples each of the 3 pieces of the YUV component video signal. Full sampling is 4:4:4 or no information is thrown away. DV is 4:1:1 which means 3/4 of the color information is thrown away and instead of being sampled at 16bits per channel, or 10bits as in hi-end video, it is sampled at 8 bits. In order to make a initial bitstream which is ready to compress the "front end" of the DV system throws allot of information away.

The last compromise is the 5:1 compression which is applied to the incoming signal this compressor was designed a few years ago and there are more efficient compressors and the compressor has to be able to be stopped on an individual frame so as to facilitate editing, this is the big difference between Dv and DVD compression.

This is a simplified version of what's out there and the differences between DI style RGB representations of film and the video representations get much more complex. Dv looks good because it retains all of the sampling from the underlying B+W picture and tricks you by chucking much of the color, this is why DV looks much better in B+W than in color and also why it is a "clean" looking picture...Dv is much better than Hi8 but I feel not as good as BetaSP but it's cheap and universal and mostly easy to use.


Hope this helps.

-Rob-


Oh dear, I actualy understood that. I must be hanging around these forums too much. The place I am looking at for the x-fer also can give me AVI or HDV files, would that help at all?

Thanks a bunch,
Dory
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#5 Robert Houllahan

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Posted 12 March 2007 - 11:33 AM

Oh dear, I actualy understood that. I must be hanging around these forums too much. The place I am looking at for the x-fer also can give me AVI or HDV files, would that help at all?

Thanks a bunch,
Dory



AVI can be allmost anything it could be uncompressed, it could be dv compression. HDV is a terribly compressed "hd" format both of these formats are transported over firewire so i would suspect that the facility is using a 8mm projector and some kind of firewire camera rig for a frame by frame capture, hence no real uncompressed video, etc...

Where are you located? there are many facilities which use real film scanning systems to do this work which will ultimately yield a better picture that a "film chain system" we are one of those facilities but there is Spectra and Pro8 in LA, fsft in seattle, us (cinelab) duart, debenham in the northeast US, and many more in europe using Rank or flashscan scanners...plus the cost is either the same or just a bit higher than a shop using a little projector/camera rig.

-Rob-
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#6 Dory Breaux DP

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Posted 12 March 2007 - 05:45 PM

AVI can be allmost anything it could be uncompressed, it could be dv compression. HDV is a terribly compressed "hd" format both of these formats are transported over firewire so i would suspect that the facility is using a 8mm projector and some kind of firewire camera rig for a frame by frame capture, hence no real uncompressed video, etc...

Where are you located? there are many facilities which use real film scanning systems to do this work which will ultimately yield a better picture that a "film chain system" we are one of those facilities but there is Spectra and Pro8 in LA, fsft in seattle, us (cinelab) duart, debenham in the northeast US, and many more in europe using Rank or flashscan scanners...plus the cost is either the same or just a bit higher than a shop using a little projector/camera rig.

-Rob-


I'm in Fort Bragg, CA. Its up by Mendocino on the north coast.
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#7 Michael Nash

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Posted 12 March 2007 - 05:55 PM

Also keep in mind that the transfer is never a "perfect" recreation of what's on the film -- it has to be interpreted in some way by the colorist as to what looks "right" on video. Unsupervised "best-light" transfers can sometimes be underwhelming, when that same footage in the hands of a good colorist with good equipment can look stunning.
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#8 Robert Houllahan

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Posted 12 March 2007 - 06:02 PM

I'm in Fort Bragg, CA. Its up by Mendocino on the north coast.



Well the magic of fedex can get your film anywhere overnight, check around or even check us out (banner on the right) to find a facility to do your process/transfer the right way.

-Rob-
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#9 Dory Breaux DP

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Posted 12 March 2007 - 06:26 PM

Also keep in mind that the transfer is never a "perfect" recreation of what's on the film -- it has to be interpreted in some way by the colorist as to what looks "right" on video. Unsupervised "best-light" transfers can sometimes be underwhelming, when that same footage in the hands of a good colorist with good equipment can look stunning.



Dont think that fits my budget.

Robert- your prices seem pretty good, I like the idea of having the discount for both proccessing and TC.
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Ritter Battery

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Media Blackout - Custom Cables and AKS

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Visual Products

Metropolis Post

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