2014年5月24日 星期六
What is Video Scope? 介紹RGB色彩亮度在視訊示波器上的解讀
基本上在視訊示波器的幾項顯示畫面:
Waveform in Luma: Luma 指的是亮度，所以這時候的顯示提供影像畫面上畫面分佈的亮度狀況（Exposure 曝光或是亮度值），也就是以畫面的左到右來看畫面所在位置的亮度狀況，暗的亮度就往下到 0% Black 黑色，亮的亮度，就往上到 100% 白，超過就是曝光過多或是高亮度，這不僅僅是在調色時使用的亮度參考，這也在很多業務以及廣播級攝影機上具備的曝光亮度參考畫面，或者是在廣播級螢幕上也會有的功能，也就是如果亮度過高，或是想要在後期進行調光處理，就可透過這個顯示來進行光圈或是快門的感光調整，提供後期製作有亮部（White）或是暗部（Black）的動態調整空間，尤其是壓縮規格的影像記錄。
2008年3月14日 星期五
29.97/59.94 的由來
Ah, More Math! 29.97 and 59.94!
原則上，NTSC 的圖場率是每秒 1/60 格。（NTSC 為美國（含北美地區）、日本與台灣等地區的電視系統規格；圖場率，就是每秒可以呈現的影像格數）這個數值是根據在北美地區 AC 交流電源的頻率 60Hz 而來的。（台灣地區的交流電源頻率也是 60Hz； 1/50 或是 50Hz 是在 PAL 規格地區所採用的，例如歐洲、中國大陸等地區使用。）不幸的是，當初工程師在制定影像規格時只是針對黑白的影像訊號所設計的，並沒有針對彩色影像來作規劃。所以當彩色電視機出現時，才在訊號上做了一些改變。為了技術原則，調整比原來的格率還要再慢上 0.1% 的速率。這個工作方式超過 29.97fps，直到 59.94fps 的圖場率。
Originally, the field rate of NTSC was 1/60 of a second. This number was chosen to match AC power-line frequencies of 60Hz in North America (1/50 or 50Hz, in PAL). Unfortunately, the engineers who designed the specification did so for a black-and-white video signal, and they did not plan ahead for color. So when color television arrived, they had to make a change in the signal. For technical reasons, this turned out to be a 0.1 percent slowdown in the frame rate. This work out to 29.97fps, leading to a field rate of 59.94fps. (The actual calculation for frames per second is 30x1000/1001, which equals 29.97002997003. For fields, the calculation is 60x1000/1001, which equals 59.940059944006.)
The Article from Final Cut Pro Workflows - The Independent Studio Handbook, Focal Press
原則上，NTSC 的圖場率是每秒 1/60 格。（NTSC 為美國（含北美地區）、日本與台灣等地區的電視系統規格；圖場率，就是每秒可以呈現的影像格數）這個數值是根據在北美地區 AC 交流電源的頻率 60Hz 而來的。（台灣地區的交流電源頻率也是 60Hz； 1/50 或是 50Hz 是在 PAL 規格地區所採用的，例如歐洲、中國大陸等地區使用。）不幸的是，當初工程師在制定影像規格時只是針對黑白的影像訊號所設計的，並沒有針對彩色影像來作規劃。所以當彩色電視機出現時，才在訊號上做了一些改變。為了技術原則，調整比原來的格率還要再慢上 0.1% 的速率。這個工作方式超過 29.97fps，直到 59.94fps 的圖場率。
Originally, the field rate of NTSC was 1/60 of a second. This number was chosen to match AC power-line frequencies of 60Hz in North America (1/50 or 50Hz, in PAL). Unfortunately, the engineers who designed the specification did so for a black-and-white video signal, and they did not plan ahead for color. So when color television arrived, they had to make a change in the signal. For technical reasons, this turned out to be a 0.1 percent slowdown in the frame rate. This work out to 29.97fps, leading to a field rate of 59.94fps. (The actual calculation for frames per second is 30x1000/1001, which equals 29.97002997003. For fields, the calculation is 60x1000/1001, which equals 59.940059944006.)
The Article from Final Cut Pro Workflows - The Independent Studio Handbook, Focal Press
為什麼 Timecode 要從 01:00:00:00 開始計算？
How (and Why) to Start at 01:00:00:00?
If your show is going to hit air or even make that picky duplicator happy, your program should start exactly at the one-hour mark. This means you need to start your bars and tone at 58:30:00, giving you enough time for slate and countdown. (By the way, countdowns are only needed for programs going to air; they just annoy duplicators.)
Most DVCam and Mini DV machines don't allow you to stripe timecode with a preset number. To complicate things, Final Cut Pro doesn't allow you to stripe timecode onto your tape as you record your show (again, this is usually a function of the deck; they need a timecode-in capability)
Here's a trick we've used: The solution is to go "out of house" and have a friend with a deck that can generate timecode (or even a duplicator) create a couple of DV tapes with timecode that start at 58:00:00. Now you can simply clone the timecode from your DV camera to your DV deck. Make sure you're connected FireWire-to-FireWire, and start playback on the striped tape before you hit the Record button on the record deck. Waht you should get is a perfect clone of the timecode on the new tape.
You don't need to record the whole tape. Just take it to a few minutes past the one-hour mark. Using the Edit to tape command, you can target your In point at 58:30:00, perform an assemble edit, and you're golden.
Note: Be sure to give the Edit to Tape window a try and see if you can get desired results.
Article from Final Cut Studio on the spot, Focal Press.
要隱藏的部份
If your show is going to hit air or even make that picky duplicator happy, your program should start exactly at the one-hour mark. This means you need to start your bars and tone at 58:30:00, giving you enough time for slate and countdown. (By the way, countdowns are only needed for programs going to air; they just annoy duplicators.)
Most DVCam and Mini DV machines don't allow you to stripe timecode with a preset number. To complicate things, Final Cut Pro doesn't allow you to stripe timecode onto your tape as you record your show (again, this is usually a function of the deck; they need a timecode-in capability)
Here's a trick we've used: The solution is to go "out of house" and have a friend with a deck that can generate timecode (or even a duplicator) create a couple of DV tapes with timecode that start at 58:00:00. Now you can simply clone the timecode from your DV camera to your DV deck. Make sure you're connected FireWire-to-FireWire, and start playback on the striped tape before you hit the Record button on the record deck. Waht you should get is a perfect clone of the timecode on the new tape.
You don't need to record the whole tape. Just take it to a few minutes past the one-hour mark. Using the Edit to tape command, you can target your In point at 58:30:00, perform an assemble edit, and you're golden.
Note: Be sure to give the Edit to Tape window a try and see if you can get desired results.
Article from Final Cut Studio on the spot, Focal Press.
要隱藏的部份
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