Remove Horz. Bars in dark shot

HeeHee wrote on 4/30/2002, 10:43 PM
I have some footage of a wedding shot 10 years ago with a VHS camcorder. The camera did not have a light source and the footage is of the reception dance with the lights down real low. The original is very dark. I can use the Brightness/Contrast FX to brighten the video to an exceptable level, but then I get these blueish scan lines across the screen. There is about 9 of these bars. It also gets a bit grainy. Does anyone know of a filter or FX that would fix this. I have tried adjusting HSL & Color Balance, but all these do is change the color of the bars.

Comments

SonyEPM wrote on 5/1/2002, 8:57 AM
what did you capture this video with?
Former user wrote on 5/1/2002, 10:24 AM
You might try using the CURVE tool (I think that is what is called). Using this tool you can adjust what constitutes black. You can maybe bury the blue lines by making the curve such that they become black lines. You will also lose definition on anything else in this luminance area, but it will be a tradeoff.

Dave T2
BillyBoy wrote on 5/1/2002, 4:17 PM
Forget adjusting brightness and contrast. The "secret" is such controls are only included in image/video editing software because people not knowing any better expect to find them. No professional would ever fiddle with constrast and brightness alone and if used maybe a few points in either direction at most.

The short reason why is doing so effects ALL the pixels in the image instead of targeting just the ones out of range which is the proper correction. I can still remember seeing Russell Brown, (one of the orignal Photoshop Team resident gurus) shaking his finger and scolding and harping away on this topic, probaby his number one pet peeve in several TV computer shows from years gone by.

Anyhow... the far superior method is adjusting levels and curves. Since your primary adjustment will be trying to adjust for an overly dark shot begin with levels. While a cheat fix itself, nudging the gama upwards can works wonders all by itself. Try going from the default 1.000 to maybe as high as 1.200. Combine this tweaking with minor adjustments of the four other levels. Next adjust curves. Check for a earlier article I wrote under my old nick WVG on how to make a "S" curve. While that post mainly concerned a washed out image and boosting contrast, you can also add brightness to the highlights of an image by first putting a set point near the mid range to prevent altering midlevels and shadows then experiement with adding a set point in the upper 1/4 of the curve (upper right) of original line shown then moving the set point you added up and to the left. Combined with adjustment of levels you'll see how far you can take it without running into the problem you did. Before trying be sure to remove the FX brightness/contrast filter.
HeeHee wrote on 5/2/2002, 11:21 PM
BillyBoy,

Your suggestion seams logical. I will give that a try.

HeeHee
HeeHee wrote on 5/2/2002, 11:24 PM
Capture was done from a VCR thru an ATI AIW Rage 128 Pro via composite connections. This is not the real promblem, but contributes. The root cause is a combination of old technology VHS camcorder, old tape, poor lighting, etc......
HPV wrote on 5/3/2002, 6:46 PM
It might be a ground loop problem. Do the bars roll thru the screen ?

Craig H.