-3db

Bill Ravens · May 13th, 2008, 09:22 PM

works great as long as the dynamic range of the scene is fairly forgiving, The problem with most inexperienced shooters, is that they really don't get when it's NOT ok. the problem I've found with this forum is that there's LOT of inexperienced shooters....LOL

Noah Yuan-Vogel · May 13th, 2008, 09:36 PM

So -3db definitely isnt the no gain? I wondered if maybe they just decided that noise was so acceptable at with some gain that they called +3db 0db and 0db -3db. i guess i just wasnt sure if it was even possible to actually apply negative gain to sensor output. how sure are we that -3b,0db,+3db,+6db etc actually refer to what the hardware is actually doing in absolute terms, and not just names they decided on? like for all we know sony engineers actually know what we call 0db gain as +11.4db (or some arbitrary number) and -3db as +8.4db, or is it common practice for this actual numbers to carry over to the end user? if someone has insight on this id be very interested to hear it. And if we can confirm that -3db is actually what it says it is or that the the changes we see between +3/0 and 0/-3 are actually different (lower latitude etc).

so if -3db causes clipping earlier, is it possible that it is just not calibrated correctly? maybe working in -3db requires different gamma/knee adjustments but will actually give greater latitude if set up correctly?

Leonard Levy · May 13th, 2008, 11:23 PM

Bill, That's a fascinating observation.

I've always assumed (and most people I know) that -3DB was a marketing gimmick. That the camera manufacturer in an effort to make the camera look faster than it really was arbitrarily picked a certain sensitivity with what they felt was an acceptable noise level and called it "0". Then to accommodate people who wanted less noise they invented -3DB which should have actually been "0". Thus most people i know always prefer to shoot at -3DB when possible. It also always been known tha one cameras noise at "0" might be the same as another's at -3 or another's at say +3DB.

However you are introducing an entirely different idea - that "0" might really be the ideal setting for a camera including both noise and dynamic range as well as other possible parameters. Interesting. I'd love to hear from a Sony engineer about this or perhaps Adam Wilt our resident tech guru.

The only exception I know of to the general rule to shoot at -3DB is the SDX900. All the techs I know soon discovered that the SDX lost dynamic range in the highlights at -3DB so we all stopped using it there. Hurt flesh tones in particular.

I guess I'll have to test for this.

Do you know of a place on the web that explains the SAW gamma patterns well? I'm used to judging gamma looking at a waveform of a chip chart but the SAW patterns are kind of greek to me.

Lenny Levy

May 13th, 2008, 09:22 PM	#16
Bill Ravens Join Date: Nov 2001 Location: santa fe, nm Posts: 3,264 Images: 10	works great as long as the dynamic range of the scene is fairly forgiving, The problem with most inexperienced shooters, is that they really don't get when it's NOT ok. the problem I've found with this forum is that there's LOT of inexperienced shooters....LOL

May 13th, 2008, 09:36 PM	#17
Noah Yuan-Vogel Major Player Join Date: Dec 2004 Location: New York City Posts: 613	So -3db definitely isnt the no gain? I wondered if maybe they just decided that noise was so acceptable at with some gain that they called +3db 0db and 0db -3db. i guess i just wasnt sure if it was even possible to actually apply negative gain to sensor output. how sure are we that -3b,0db,+3db,+6db etc actually refer to what the hardware is actually doing in absolute terms, and not just names they decided on? like for all we know sony engineers actually know what we call 0db gain as +11.4db (or some arbitrary number) and -3db as +8.4db, or is it common practice for this actual numbers to carry over to the end user? if someone has insight on this id be very interested to hear it. And if we can confirm that -3db is actually what it says it is or that the the changes we see between +3/0 and 0/-3 are actually different (lower latitude etc). so if -3db causes clipping earlier, is it possible that it is just not calibrated correctly? maybe working in -3db requires different gamma/knee adjustments but will actually give greater latitude if set up correctly?

May 13th, 2008, 11:23 PM	#18
Leonard Levy Trustee Join Date: Feb 2006 Location: USA Posts: 1,684	Bill, That's a fascinating observation. I've always assumed (and most people I know) that -3DB was a marketing gimmick. That the camera manufacturer in an effort to make the camera look faster than it really was arbitrarily picked a certain sensitivity with what they felt was an acceptable noise level and called it "0". Then to accommodate people who wanted less noise they invented -3DB which should have actually been "0". Thus most people i know always prefer to shoot at -3DB when possible. It also always been known tha one cameras noise at "0" might be the same as another's at -3 or another's at say +3DB. However you are introducing an entirely different idea - that "0" might really be the ideal setting for a camera including both noise and dynamic range as well as other possible parameters. Interesting. I'd love to hear from a Sony engineer about this or perhaps Adam Wilt our resident tech guru. The only exception I know of to the general rule to shoot at -3DB is the SDX900. All the techs I know soon discovered that the SDX lost dynamic range in the highlights at -3DB so we all stopped using it there. Hurt flesh tones in particular. I guess I'll have to test for this. Do you know of a place on the web that explains the SAW gamma patterns well? I'm used to judging gamma looking at a waveform of a chip chart but the SAW patterns are kind of greek to me. Lenny Levy