On 2007-01-17 19:25:34 +0000, Andy Burns said:

Colin Wilson wrote:

Aren't they supposed to provide photos now to prove you were there ?

How does that prove when/or for how long you were there?

Are .jpeg compressed photos accepted as "evidential quality", one of my
local authority customers seems convinced they need to use .tiff files
instead.

There's a lot of information and misinformation surrounding this whole area.

For example, at one point, some clever dick lawyer managed to get his
client acquitted of some charge involving CCTV evidence because the
electronic compression used was MPEG. The encoding scheme for this
involves both spatial and temporal compression - i.e. compression
within frames and also of changes between frames using lossy
algorithms. His argument was that because of this, it could be
possible that some evidence information could be lost in the temporal
compression from frame to frame. The argument is bogus in reality, but
the technically illiterate judge/jury bought the argument. There
was then an uptake of Motion JPEG (M-JPEG) compression because that
does not use temporal compression nad is lossless in the time sense.
Nonetheless JPEG is, in general, lossy so one wonders why arguments
haven't been made there.

TIFF is generally accepted as more universally useful for quality imaging.