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Old Feb 5, 2004, 10:33 AM   #41
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Default Sorry, this does not make any sense to me

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Originally Posted by Panasonic
OK guys, I'm sorry it took so long but I have an answer on this ongoing discussion. During this time what is taking place is not exactly noise reduction. As we know, the output from each individual pixel differs slightly and those differences will be more visible as the length of the exposure and CCD temperature increases.

Officially itís called CCD compensation. The output variations that normally occur would be more visible at higher temperatures with longer shutter speeds. This characteristic is not a defect. On the FZ10 it kicks in from the 1/2 second shutter speed.

The time to detect and compensate the pixel variations is nearly equal to shutter speed that is selected. So when the shutter speed is set to 4 second, the camera will need a total of almost 8 seconds in order to detect and compensate pixel levels.

With some stretch of the imagination we might consider an error in pixel levels as ďnoiseĒ so your preliminary labeling of this as noise reduction was not that far off. But to be specific, this operation does differ from true noise reduction.
Sorry, this does not make any sense to me.

As a long time software developer with some relevant experience (not a lot but enough to know what I am talking about) I see no reason for the processing time of the final picture to be equal to the shutter time when the ficture was taken, particularly since:

1) The delay is unaffected by the subject of the shot. A dark frame, a white page or any other shot results in exactly the same delay.

2) The same effect is observed with the 2MP FZ2 and the 4MP FZ10.

3) The Venus engine is fast enough to do a JPEG compression of 4 full frames in 1-2 seconds.

4) This explanation does not mesh well with the results of the experiments that were performed by myself and others.

The only logical explanation for the delay being equal (or nearly equal) to the shutter time is that the camera is taking another "shot" at that time (with a closed shutter).

Now, whether the camera uses the result of the 2nd "shot" for "dark frame subtraction", "CCD compensation" or any other technical (or marketing) phrase is a matter of terminology.

I strongly suspect that what we have here is a classic example of miscommunication and use of internal terminology. Especially since a Google search for "CCD compensation" does not turn up anything relevant.
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Old Feb 5, 2004, 3:20 PM   #42
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Alex,
I have no reason to question the information I received. It's direct from the designers and I believe they have a fairly good knowledge of the product. Aside from correcting some grammar, that's the RAW data!

Issue closed - next!
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Old Feb 5, 2004, 3:58 PM   #43
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Quote:
Originally Posted by Panasonic
Alex,
I have no reason to question the information I received. It's direct from the designers and I believe they have a fairly good knowledge of the product. Aside from correcting some grammar, that's the RAW data!
Well, somebody misunderstood the info and I apologize in advance if that was me.

So to make sure we are on the same page I will ask for one clarification:
Does the camera take another "shot" with the shutter closed (a dark frame) in order to perform the "CCD compensation" that you referred to or does it not?

No matter what your answer will be, I will thank you for the information and will not bother you on this subject again.
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Old Feb 5, 2004, 5:10 PM   #44
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Alexo, as has been mentioned it the thread already, what you suggest appears to be exactly what is happening. The CCD needs to take a second "picture" with the shutter closed so that it has a frame of reference to the first picture. If the first shot was 8 seconds and the second only 1 second, then the CCD would not be charged equally and there would be a noise discrepancy in the two frames. Bob's explanation of what is happening was already known to most of us, I'm sure yourself included, I just wanted to know at what shutter speed the "process" began. I think that had already been answered by Karl and Charlie. Thanks for confirming our results Bob.
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Old Feb 5, 2004, 8:50 PM   #45
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Thanks - you are very welcome. I don't mean to be "short", but there is so much wheel spinning going on. Given the very limited time I can devote to participation, to see the same issue being rehashed can get frustrating. Before you know it, opinions morph into reality. Your understanding is very much appreciated.
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Old Feb 5, 2004, 9:04 PM   #46
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I'm new to this group, but I agree. Thanks you!
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Old Feb 6, 2004, 11:20 AM   #47
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What Panasonic Bob wrote sounds technically correct. There are two components to what one would normally think of as noise. The variation in gain, that presumably is fairly constant over a short period of just a second or two, and a smaller random error that isnít constant and represents true electrical noise.

Having said that, Panasonicís comments are perhaps a little misleading. The result of this variation in gain between what should be identical photo diodes, looks the about same as true noise in the image. The practical problem is that diodes as small as those in the FZ10 are not as equal as one would like. As can be seen in images at higher ISO values compared to cameras with larger sensors. Name it whatever you like.
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