Doc -- you are one person who probably knows the answer to this. Why the f*** are so many videos on You Tube too dark? Is there something about doing vidcaps that leads to this? I'd use even more vids on my blog, except so many are barely viewable.
The reasons are that (1) because of the way human vision works, most compression systems put fewer bits into differentiating the darker parts of the video; and (2) because of the way human vision works, the response curve for intensity is also weighted toward bright things. Put these things together and once you start with dark video and compress and recompress it, it gets driven toward dark at an alarming rate, and it can't be recovered, 'cause there aren't very many bits representing the dark parts.
Even a simple operation like averaging 9 pixels together in a grid to create one small pixel will tend to lose brightness because the dark pixels, sadly, have more "weight" in the calculation - not because averaging doesn't work - but because you're averaging non-linear values.
http://www.youtube.com/watch?v=-6yL_tMUDps
The video above is disturbingly dark. It shouldn't be but since it has no doubt been through several rounds of compression before we see it, it's had a lot of subtlety in the dark range removed. Sad.
(One more thing - if you're watching on an LCD that is a few years old - well, they get dimmer as time goes by. That does't help.)
I like!
ReplyDeleteDoc -- you are one person who probably knows the answer to this. Why the f*** are so many videos on You Tube too dark? Is there something about doing vidcaps that leads to this? I'd use even more vids on my blog, except so many are barely viewable.
jack
Namaste!
The reasons are that (1) because of the way human vision works, most compression systems put fewer bits into differentiating the darker parts of the video; and (2) because of the way human vision works, the response curve for intensity is also weighted toward bright things. Put these things together and once you start with dark video and compress and recompress it, it gets driven toward dark at an alarming rate, and it can't be recovered, 'cause there aren't very many bits representing the dark parts.
ReplyDeleteEven a simple operation like averaging 9 pixels together in a grid to create one small pixel will tend to lose brightness because the dark pixels, sadly, have more "weight" in the calculation - not because averaging doesn't work - but because you're averaging non-linear values.
http://www.youtube.com/watch?v=-6yL_tMUDps
The video above is disturbingly dark. It shouldn't be but since it has no doubt been through several rounds of compression before we see it, it's had a lot of subtlety in the dark range removed. Sad.
(One more thing - if you're watching on an LCD that is a few years old - well, they get dimmer as time goes by. That does't help.)