Archived posting to the Leica Users Group, 2006/12/20
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]"Put Windex" ---------------- > When I first read Brian's comment about an IR problem I thought no > way. Then the more I thought about it the more I thought it might be > possible. Now I don't know anything about photo sensors or amplifiers > in the visible light range, but I do know about RF amplifiers, > detectors and amplifiers in general. Since the M8 sensor is allowing > a much greater frequency bandwidth from Uv to IR, the power to the > amplifier increases and creates an increase in distortion and makes > the amplifier much easier to overload. In order to avoid overload the > signal to the amplifier is reduced by gain reducing the circuit. The > amount of gain reduction (AGC) is controlled in the design of the > amplifier The design curve of this AGC system can be developed in the > lab on a test bench by duplicating the actual operating conditions of > the total system. However this is under ideal conditions using test > generators of the input spectrum of concern, visible light. However > if the incoming spectrum in the finished product is greater than what > the design model was set up for, you can go into an overload > condition. However it is not that easy to develop a perfect AGC > system. If you gain reduce the system too much, you introduce noise. > That may be what the increased noise is from in the higher ISO > ranges. The system may be in an over AGC'ed mode and still not fully > getting out of overload. The amount of AGC is also probably > controlled by the ISO setting. Dropping the ISO and then decreasing > the exposure would certainly reduce noise, but also increase the > likelyhood of overload. > > Please forgive my ramblings. I'm still thinking like an engineer. It > makes sense to me, though. > > Len > > > On Dec 20, 2006, at 11:10 AM, Frank Filippone wrote: > > > Then the 486 filter should fix the issue......it would kill the IR > > components......easy to test for..... > > > > Frank Filippone > > red735i@earthlink.net > > > > Given that candles are a strong source of IR, I would guess that > > this is almost entirely an IR problem. > > > > > > > > _______________________________________________ > > Leica Users Group. > > See http://leica-users.org/mailman/listinfo/lug for more information > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information