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Author Topic: General question about in-camera pre-processing of sensor data in RAW files  (Read 3751 times)
AFairley
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« on: September 16, 2010, 02:33:51 PM »
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Olympus has released its E-5 camera, which has a weaker anti-aliasing filter, and uses the in-camera processing chip to (apparently) address moire problems that may result, as well as "Fine Detail Processing technology, utilizing a sophisticated algorithm to deliver all the information from eachimprove image quality" -- at least in JPEG output.  This has resulted in some discussion on other forums about whether this new and improved image processor has any effect on the RAW images, i.e., is there any processing of the raw file prior to being written to the card.  A lot of people have weighed in on the issue, but I have not seen any link to any authoritative source as to whether there is any image processing performed on RAW files before they are written (as opposed to operations designed to write the sensor data in a manner that conforms to the raw spec, embed as-shot and camera data in the appropriate sections of the file etc) -- jsut the usual assertions on either side made with the usual absolute certainty.  I figured that if I could get the straight dope anywhere, it would be on this forum.  So I'm asking -- are operations that can affect final image quality performed on the sensor data stream before the data is written to the card?  Thanks
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madmanchan
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« Reply #1 on: September 24, 2010, 09:39:07 PM »
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Most image data is processed in some way before the data is written out to the raw file. The degree of processing and the type of image operations depends on the camera make and model.
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feppe
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Oh this shows up in here!


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« Reply #2 on: September 25, 2010, 05:27:08 AM »
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Identical question was asked very recently, and the responses echo Eric's: it depends on the manufacturer and model. So it can be and is done, but getting a confirmation from the manufacturer on what or even if something is done before the RAW is written is another matter.
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BartvanderWolf
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« Reply #3 on: September 25, 2010, 09:32:55 AM »
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Olympus has released its E-5 camera, which has a weaker anti-aliasing filter, and uses the in-camera processing chip to (apparently) address moire problems that may result, as well as "Fine Detail Processing technology, utilizing a sophisticated algorithm to deliver all the information from eachimprove image quality" -- at least in JPEG output.

To put it plain and simple, Aliasing cannot be undone after is has been recorded. Aliasing artifacts are larger than the finest detail that the sensor can reliably resolve (Nyquist limit) and are blended in with real lower resolution detail. No way the two can be separated after the fact (unless there is prior knowledge what is recorded where and at which magnification). What can be done, is reducing the visibility of some of the aliasing artifacts, but with it comes a loss of real detail that was resolved accurately. For some structures that will be hard to see, for others it will be a net loss.

As other have answered before me, what actually gets recorded in Raw is not disclosed.

Cheers,
Bart
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hjulenissen
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« Reply #4 on: October 18, 2010, 05:08:22 AM »
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As other have answered before me, what actually gets recorded in Raw is not disclosed.
A fair guess would be that at least anything that is individual for that camera (e.g. calibrated on the assembly line) is processed even for raw files.

-h
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