In the film world, we speak of "latitude" when referring to the range of brightnesses, or stops, that it can handle with reasonable visible results. I've heard said that film has about 8 stops of latitude, while video has only about half that much. But I can never figure out how to tell the latitude of a particular video camera, short of doing some complicated waveform monitor tests that I know nothing about. So here are the questions:

What is the specification that relates to the equivalent latitude of a CCD? I'm assuming that latitude is a characteristic of the CCD itself, so is there any improvement in latitude between an analog and a digital camera with the same CCD? Do the multiple-CCD cameras provide greater latitude? Is the tape that the signal is recorded on a factor? (I assume minimal in the digital case)

Thanks for your help.

-- Carlo Federiconi (cprf@jps.net), October 16, 1999

Answers

If you mean latitude, as in tolerance for over or under exposure, the nvideo's tolerance is zero. With film you can shine more or less light through it when you print it and muck with contrast by deliberately exposing for it. The final print from a negative (or reversal original) contains a narrower range of shades than the negative does.

Video is digits. White is 255 & black is 0 (sort of). (more numbers for broadcast digital but the same white-black range). The total range is on the tape and that is it. There are methods for changing gammas, colour casts, white and black levels etc. in postproduction but it is nowhere near as flexible as film. End of story. Expose properly for the look you want.

Exposure range is the difference between what is recorded as black and what is recorded as white. Cameras these days are tons better than they used to be. The first time I picked up a VX1000 I was stunned by its exposure range. 3 CCD cameras would have better resolution at the black and white extremes than 1CCD. Different cameras would have different 'looks' and expensive ones would have adjustments for the 'look'.

Broadcast tape formats have better brightness/colour detail at the extremes (well, everywhere actually) because they record more detailed data. Digibeta etc records 10 bits, whereas DV records 8, for each colour pixel. the pixel resolution is much the same, although compression is a big factor there.

Lighting for video has always been less contrasty than film, as a general rule, but it does depend on what you're looking for. The Sony digibeta toys have all sorts of gamma controls etc. and can look like film when they get to a TV.

Experiment.

:-) Ewen

-- Ewen Wallace (walkabout@freeuk.com), November 11, 1999.