DVL-Digest 467 - Postings: Index BLACK BALANCE? SDTI XL1 resolution BLACK BALANCE? - "Perry" Whilst a couple of folks explained what it did, they did not explain why you have to do it. CCDs are analogue devices that rely upon detection of tiny amounts of charge to signify light. This charge is detected by measuring the current to neutralise the charge. When they are in the dark, they still pass some current (known surprisingly as 'dark current') which will depend upon temperature. This has to be offset in the processing so that true blacks can be shown correctly. This is what is happening when the Black Balance process is invoked, the lens will be automatically capped as the first part of the process. Perry Mitchell Video Facilities http://www.perrybits.co.uk/ SDTI - "Perry" A little story to indicate Apple would have to go some to replicate SGI's presence: A couple of years ago I was shooting around the ITN facility in London. We were taking a break in the main equipment room, watching their current on-air output, and I asked the engineer with me where the station graphics came from; "you're sitting on it!" It was an SGI box the size of a small refrigerator! Perry Mitchell Video Facilities http://www.perrybits.co.uk/ XL1 resolution - Perry Mitchell This crops up every few months, and I always repeat the cry: 'there are lies, damn lies and camera resolution specs!' The XL1 is well known for having interleaved G and R/B chips. This gives apparent higher resolution when looking at a black/white resolution chart but would not necessarily give commensurate results when shooting real life scenes. The actual numbers for the resolution will vary wildly depending on the exact method used to measure it, so can really only be used for comparison when issued by an independent test lab. Even then, resolution has to be considered alongside anti-aliasing measures which will reduce resolution but can greatly improve the clarity of the picture. It is also common practice on consumer equipment to roll off the high frequencies at increased gain settings, and to also cut the response in the shadows (known as coring) both of which give apparently improved noise. For me these type of processing tricks lead to a particular 'consumer' look that is a dead give-away compared to a fully pro camera. (diese posts stammen von der DV-L Mailingliste - THX to Adam Wilt and Perry Mitchell :-) [up] |
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