False sensitivity - When 0db is NOT 0db

[Paul Anderegg]

I need something to rant/complain about at least once a day. Today, it is false camera sensitivity figures. You know all those Panasonic and JVC cameras that give great f11-f13@2000 sensitivity figures with s/n ratios of 60db? Well, that is all a sham.

When you see a Sony camera that says f12@2000 and 60db, that is actually what you are getting. When you see a Panasonic or JVC camera stating the same, it is a flat out lie. Why is this? Well, those brands have a standard and extended/low light mode. What you get in STANDARD/NORMAL mode is that sweet 60db s/n, but in actuality, you only get that at around f8@2000, like a Betacam from 1993. Where do those higher f11-f13@2000 numbers they advertise come from? When you switch to the more sensitive mode, the camera is GAINED UP 6db, but the viewfinder will show 0db instead. So any gain value you see is on top of that added base 6db. Obviously, if you add 6db of gain to 0db, that 60db s/n ratio is then compromised, and you will have noise at 0db.

On an old Panasonic HPX2000 (f10@2000 NTSC) you could toggle on a "line mix" function which did exactly the same thing, added 6db of gain underneath everything else, but they didn't go around advertising the camera as f14@2000! With Sony kicking ass with low light sensitive noiseless cameras, the competition has no choice but to lie and fudge their figures to make sales. I tested this out on a JVC HM890, and set each mode with 6db offsets. Toggling between standard 6db and extended 0db produces no change in picture. If you shot in standard mode, you are shooting on an f8@2000 camera.

OK, enough ranting, that stupid f number thing is annoying me because I hate gain noise and shoot everything in the dark. This isn't a play on ISO rating, it is a comparison of Sony vs the other manufacturers. :-)

Paul

[Andrew Smith]

Rant is appreciated! It's good to find out these things and I'd be sure that the issue is of genuine public interest to our community here.

Andrew