Lock Stock and 2 smoking barrels

2 replies [Last post]
jamiewamie
Offline
Joined: Sep 18 1999

In premiere (or other) does anybody know how the tinted high contrast look was achieved in Lock Stock and 2 smoking barrels and all the trendy TV adverts in the UK etc etc ??

Ideas?

Thanks in advance

Jamie

Christian Lett
Offline
Joined: Apr 26 1999

"Lock Stock" was shot on super 16mm film which gives it different characteristics to video in terms of contrast, etc. From what I've seen, it's quite easy to change the colour balance and contrast of video in a NLE system - try experimenting with a short clip and then apply it to the whole movie. I also heard that adjusting the gamma of an image makes it look more "filmic".

Christian.

------------------
Christian J. Lett
[email=clett@nationalexpress.co.uk]clett@nationalexpress.co.uk[/email]

Christian Lett After Effects and Maya Artist www.quarterlightpictures.com

Alan Roberts at work
Offline
Joined: May 6 1999

This is an interesting one, and was to be the subject of an article I intended to write for CV. Bob turned down the first offering (on Depth of Field) because it was too mathematical, but that's the only way I can explain mathematical problems. Anyway.....

Film records light by generating density, linearly proportional to incident light. Density is additive so we have a logarithmic recording medium. It goes wrong at very low and very high light levels, so we have a transfer characteristic (density vs light) that is straight apart from flattening at top and bottom.

TV cameras are truly linear. They make voltage that is linearly related to incident light. They have "gamma-correctors" that apply a transfer characteristic to try to make it look more like a power law.

Displays (specifically crts) have a power law transfer characteristic, over the range of brightnesses used for direct viewing, the law is about 2.35, so we can use the equation:
Light = Volts ** 2.35

The human eye has a non-linear resopnse as well, the CIE specifies a human response curve in the L* formula and quotes a power law of 0.33, but with an offset in the curve limiting the slope at black to about 9 rather than infinity which would be implied by a true power law.

Film matches the eye nicely over a huge range of exposure, and, by a curious coincidence, the transfer characteristic of the typical crt is almost exactly the inverse of the response of the eye. So we can say that density in film is perceptually linear, as is the drive voltage for the crt. That's very handy because it means that any distortion to the video signal is not made more visible by it's position in the contrast range; noise is evenly spread.

So the target for a video camera to look "realistic" is to make it's transfer characteristic (gamma) a power law, with no limiting slope at black. Broadcast cameras specify that limiting slope to be 4.5, the UK has a spec (BBC and ITVA) of 5, and most broadcast cameras can achieve that. Domestic cameras rarely get better than 3 or 3.5 times near black, so pictures look black-crushed and oversaturated, with colours pushed towards their nearest primary or secondary colour. Simply raising the gain of the transfer characteristic near black will make the camera look "more like film".

Another problem is the handling of highl-lights. Film does it gently, coping with several stops of overload, domestic cameras simply clip at 100%. Broadcast cameras have "knee" circuits that allow contrast compression of highlight overloads, up to 2 or 3 stops, and this alos helps to make video look like film.

I could go on in this vein for hours, but it really needs graphs and pictures to make it all clear. I can't do that here. This is a huge subject that I can't do justice on a forum.

Hope that helps a little.