"Missing" frames in Trimmer

ds wrote on 7/5/2011, 10:19 AM
I captured lightning at 60i HD 24bps and can step single frame in the timeline and see single frame lightning. However in Trimmer, some lightning is not visible. I verified that I am indeed stepping a single frame at a time. At one lightning strike, in Trimmer, I can see a very faint "hint" of lightning that is clearly visible in the timeline.

Is there a setting that would account for the Timeline/Trimmer difference?

Comments

Steve Grisetti wrote on 7/5/2011, 11:51 AM
Are your project properties set up to exactly match your video? (For example, if your camcorder is shooting 1920x1080 AVCHD, did you select that as your project settings when you set up your project?)

Also, in your project properties (select Properties under the Options menu), what have you got set as your Deinterlacing Method?
Tim L wrote on 7/5/2011, 4:06 PM
[IMG=http://i262.photobucket.com/albums/ii106/timlan635/TrimmerLightning2.png]

Sorry, I couldn't resist...

(Clicking the lightning bolt just clears the "trimmer history" -- the drop-down list of clips most recently loaded into the trimmer, in case you want to go back to something you had in the trimmer a little bit ago.)

Anyway, my guess is that the trimmer window is probably only showing you one "field" of the 60i frame, and the lightning was captured in the other field.

In NTSC 60i video, there are (roughly) 30 "frames" per second, and the even lines of a frame come from one 1/60th of a second exposure, the odd lines from a different 1/60th of a second exposure. (I don't recall which is first -- odd or even.)

I'm guessing for efficiency the trimmer is showing only odd or even lines, and your lightning bolt was captured in the "other" field. (The lightning strike itself is only about 30 millionths of a second long.)

If your camera is CMOS it gets a little more complicated than that because CMOS imagers have rolling shutter read-outs, so you could have part of a lightning bolt in the top half of the even lines, and the other part in the bottom half of the odd lines (or vice-versa). The exposure of each scanline in a CMOS imager is sequential and isn't simultaneous with all the other lines in its field like it is with a CCD.
ds wrote on 7/6/2011, 5:50 AM
Good Humor, Tim. Thanks for the ideas and info about CMOS sensors.