salam
I have a Canon iVIS HF S21 High Definition 64GB Dual Flash Memory Camcorder and want to know can I use it for making chroma key? I have heard about "Chroma subsampling" and want to know does this camera has this feature?
http://en.wikipedia.org/wiki/Chroma_subsampling
Answer
i have been in the television broadcast engineering for 30 years and i have never heard this referred to as "over-sampling". here is the wiki definition of over-sampling - http://en.wikipedia.org/wiki/Oversampling
so while despite getting the name of the process wrong, some of the information concerning chroma sampling (not over sampling) is correct. a point, aka a pixel, does not have a bandwidth, so no matter how many times you take a sample you will get the same value, until the pixel is refreshed for the next video frame.
sampling when dealing with digital video means how many samples you take compared to the colorburst frequency used in analog video (yes digital has not yet escaped its analog roots). in the early days of digital video, the only purpose for digital was to make lossless videotape recordings of analog video. so in order to make conversion of digitized analog video, you had to sample at least 3 times the subcarrier rate to preclude aliasing. D2 and D3 sampled at 3x. But instead of sampling composite video, what if you sampled 3 component video, and wanted to preserve luma resolution at better than broadcast resolution (4.2 MHz) then the sampling rate is standardized at 4x subcarrier. while component does not have subcarrier modulation, sampling at an even multiple of the subcarrier rate leads to more precise conversion back to analog composite video which does have subcarrier. Broadcast chroma resolution is less than the luma, 1.6 MHz for the I vector and 0.8 Mhz for the Q vector. This means that I and Q chroma can be sampled at 2x subcarrier and still make a better than analog broadcast resolution conversion back to composite video. this is where the specification of 4:2:2 sampling comes from.
4:2:2 is the standard for Digital Televison broadcast. Inside a television studio, high end cameras (the $100,000 kind) sample at 4:4:4 for the purpose of getting the best chroma key result. Standard broadcast grade cameras (and camcorders) sample at 4:2:2 so they can be used directly for digital television transmission. these are the $20,000 class cameras.
When digital video was created for consumer use, starting with miniDV, one simple and virtually loss free compression was to reduce the chroma bandwidth to 1.6 MHz for both components by sampling at 4:1:1 This provides broadcast like analog chroma resolution while using only half the chroma samples used for digital television. All, i repeat all, consumer cameras whether miniDV, dSLRs, HDV, AVCHD, cellphone ad naseum sample at 4:1:1, this includes the canon you are asking about. 4:1:1 video has sufficient chroma resolution to perform very good chroma key, every bit as good as broadcast television equipment in the analog TV days.
What makes for a good chroma key camera in the consumer digital era is the codec, or to put another way, the compression. miniDV uses only 6:1 compression, so it is at the top of the heap when it comes to chroma key use. cheap SD memory card cameras can run compression as high as 200:1, so chroma keys works poorly. your canon camera employs a lot of compression but most of that is temporal. so as long as your subject does not move, the key will be satisfactory. with a moving subject, resolution blurs and so does your key.
i have been in the television broadcast engineering for 30 years and i have never heard this referred to as "over-sampling". here is the wiki definition of over-sampling - http://en.wikipedia.org/wiki/Oversampling
so while despite getting the name of the process wrong, some of the information concerning chroma sampling (not over sampling) is correct. a point, aka a pixel, does not have a bandwidth, so no matter how many times you take a sample you will get the same value, until the pixel is refreshed for the next video frame.
sampling when dealing with digital video means how many samples you take compared to the colorburst frequency used in analog video (yes digital has not yet escaped its analog roots). in the early days of digital video, the only purpose for digital was to make lossless videotape recordings of analog video. so in order to make conversion of digitized analog video, you had to sample at least 3 times the subcarrier rate to preclude aliasing. D2 and D3 sampled at 3x. But instead of sampling composite video, what if you sampled 3 component video, and wanted to preserve luma resolution at better than broadcast resolution (4.2 MHz) then the sampling rate is standardized at 4x subcarrier. while component does not have subcarrier modulation, sampling at an even multiple of the subcarrier rate leads to more precise conversion back to analog composite video which does have subcarrier. Broadcast chroma resolution is less than the luma, 1.6 MHz for the I vector and 0.8 Mhz for the Q vector. This means that I and Q chroma can be sampled at 2x subcarrier and still make a better than analog broadcast resolution conversion back to composite video. this is where the specification of 4:2:2 sampling comes from.
4:2:2 is the standard for Digital Televison broadcast. Inside a television studio, high end cameras (the $100,000 kind) sample at 4:4:4 for the purpose of getting the best chroma key result. Standard broadcast grade cameras (and camcorders) sample at 4:2:2 so they can be used directly for digital television transmission. these are the $20,000 class cameras.
When digital video was created for consumer use, starting with miniDV, one simple and virtually loss free compression was to reduce the chroma bandwidth to 1.6 MHz for both components by sampling at 4:1:1 This provides broadcast like analog chroma resolution while using only half the chroma samples used for digital television. All, i repeat all, consumer cameras whether miniDV, dSLRs, HDV, AVCHD, cellphone ad naseum sample at 4:1:1, this includes the canon you are asking about. 4:1:1 video has sufficient chroma resolution to perform very good chroma key, every bit as good as broadcast television equipment in the analog TV days.
What makes for a good chroma key camera in the consumer digital era is the codec, or to put another way, the compression. miniDV uses only 6:1 compression, so it is at the top of the heap when it comes to chroma key use. cheap SD memory card cameras can run compression as high as 200:1, so chroma keys works poorly. your canon camera employs a lot of compression but most of that is temporal. so as long as your subject does not move, the key will be satisfactory. with a moving subject, resolution blurs and so does your key.
Photoshop CS/Photoshop Elements and Photoshop Lightroom Differences?
Jessica
Okay, I have always used Photoshop CS, currently I'm still using CS3 because I refuse to upgrade. I'm going to be getting a new computer soon and I want a professional program but I don't necessarily need CS. I've never had the chance to use Elements or Lightroom and am looking at this as a cheaper option to replace my CS. I do not have the registration code for mine anymore as I just had it with my ex and it was his program. I do not plan to be asking him for his registration code, so I'd like to know my limitations with Elements or Lightroom.
Currently I mostly use it to create things like RP sigs for my roleplays and character based stuff. The one things that is a necessity for me is to be able to make transparent backgrounds. So yeah I just need to know what limitations I might have for designing simple stuff for online. I also need text. Again I have never use either of these programs.
And yes I know I can give the trials a run, but I just want to know where to start at.
Answer
If you don't have a DSLR camera, don't bother getting Lightroom. Its main strength is organizing and enhancing collections of raw format images. It isn't designed for cut-and-paste editing.
Photoshop Elements should be fine for your needs. It doesn't have any of regular Photoshop's vector tools (aside from basic Shapes), nor advanced features like channel editing, non-RGB color modes, or the "natural" brush engine. However, core features like layers and blending modes are all there. It is also a lot less expensive than regular Photoshop, usually around $100.
There are less expensive options, including open source software like GIMP and Paint.NET.
If you don't have a DSLR camera, don't bother getting Lightroom. Its main strength is organizing and enhancing collections of raw format images. It isn't designed for cut-and-paste editing.
Photoshop Elements should be fine for your needs. It doesn't have any of regular Photoshop's vector tools (aside from basic Shapes), nor advanced features like channel editing, non-RGB color modes, or the "natural" brush engine. However, core features like layers and blending modes are all there. It is also a lot less expensive than regular Photoshop, usually around $100.
There are less expensive options, including open source software like GIMP and Paint.NET.
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Title Post: Does my camera have proper Chroma subsampling?
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Rating: 92% based on 9788 ratings. 5 user reviews.
Author: Yukie
Thanks For Coming To My Blog
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