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Template for measuring scan lines
I did a search and didn’t quite find the answers I was looking for. I know there is a plugin for FCP, but this seems like something simple.
We need a way to measure scan lines, mainly for the “Paid for by…” in political advertisements. I was thinking about making a template in Photoshop with a semi-transparent grey bar that is 20 scan lines high and just overlay it in FCP to ensure the text meets the minimum size. My question, how do I know my grey bar is exactly 20 scan lines high? Obviously I have an image in Photoshop 720×486. Does that mean each line or pixel is one scan line?
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4 Replies
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[Eric Nicastro] “My question, how do I know my grey bar is exactly 20 scan lines high? Obviously I have an image in Photoshop 720×486. Does that mean each line or pixel is one scan line?”
Right.
Make your bar 720×20 in photoshop.
rafael -
That’s what I figured I could do. But here’s my next question. I was doing research on the FCC’s website about political advertisements (https://www.fcc.gov/mb/policy/political/candrule.htm). It says “The sponsor shall be identified with letters equal to or greater than four percent of the vertical picture height that air for not less than four seconds.” Are they referring to the visible screen size of 486 or the actual screen size with areas not seen of 525?
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Hi Eric,
On the NTSC 525 lines, there are some lines with no picture information (Vertical interval). You have 486 “active lines”. Part of those lines are also reserved for VITC, test signals, etc, so you end up airing some 480 lines (then TV sets will crop the picture further, but this will be up to the model/brand. DVDs will crop the picture on compressing too)Your titles needs to be at leas 4% of that high (480), so 19.2 scan lines. To measure the high in FC, the 720×20 pixels will do the job.
rafael -
But when you throw in up-conversion/down-conversion and letterbox/pillarbox, the picture height can be anywhere from 480 to 1080 to 360. 360 would be the case if the station has an HD channel, and up-converts/pillarboxes SD material, which is then down-converted and letterboxed by someone with a regular standard-def 4:3 TV receiving over-the-air, or through a cable/satellite provider. And WHO KNOWS if the HD channel will get center-cropped or letterboxed downstream for by the providers – or both, according to broadcast flags in the signal (if such a system is arranged between the local station and the cable/satellite provider). But as long as the FCC’s rules are followed (how do they measure against their specs anyway?)… *shrugs shoulders*
Tim
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