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Old Oct 4, 2002, 3:45 AM   #1
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Default What is ment by

I have see the word "raw" from the camera on the forum from time to time.
What does that mean? I have an older Sanyo digital camera VPC-X350 and it has three ways to take pictures, the first is 768x1024, that one uses more space on the smart media card, the second one is also 768x1024, it uses less space in the SM card, I can't see any differance between the two on my monitor. And the third one is something like 640x480, forgot the exact numbers, gets confusing, anyway that last one I CAN see that on the monitor as less resolution.
Is the first one, the one that uses more space on my SM card the "Raw"?
Thanks for any help on the confusing question.

[Edited on thep31. 18, by Bill Benson]
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Old Oct 4, 2002, 4:32 AM   #2
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RAW is simply the raw data as it comes directly off the CCD, no in-camera processing is performed. Typically this data is 8, 10 or 12 bits per pixel. The advantage being that file sizes are considerably smaller (eg. 2160 x 1440 x 12 bits = 37,324,800 bits = 4,665,600 bytes), the image has not been processed or white balanced which means you can correct the image, and it's a better representation of the "digital negative" captured. The disadvantage is you can't open these image files with a normal photo package without using an "acquire module" (a plugin, typically TWAIN, which can open / process such images).

Advantages of RAW format
*A true "digital negative", untouched by cameras processing algorithms
____ *No sharpening applied
____ *No gamma or level correction applied
____ *No white balance applied
____ *No colour correction applied
*Lossless yet considerably smaller than TIFF
*Records data over a wider bit range (typically 10 or 12 bits) than JPEG or 8-bit TIFF

Disadvantages of RAW format
*Requires proprietary acquire module (typically TWAIN) or plugin to open images
*Images can take 20-40 seconds to process on an average machine
*No universally accepted RAW standard format, each manufacturer (even each camera) differs.

[Edited on 5-10-2002 by ajitkataria]
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Old Oct 4, 2002, 9:25 PM   #3
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I'd like to add to ajitkataria's reply...

Most camera's save shots using JPEG file formats. JPEG is a file format that allows for variable quality and a small file size. It is however a 'lossy' file compression scheme - once a file is saved some of the information is lost and you can't get the original file back from the compressed copy.

RAW format is a compressed format that isn't lossy, a lossless format. All the information is kept during the the compression.

TIFF is format that is uncompressed, it creates a very large file.

What your camera is doing is saving the larger files in a higher quality JPEG file - less compression, more detail, larger file size. Based on the dpreview site your camera doesn't save a RAW format file.

I find the name 'RAW' to be a misnomer - it isn't the raw file info - it's a compressed format. It's also a pain that the format isn't standardized like JPEG or MPEG formats.

hope this helps
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Old Oct 5, 2002, 12:40 AM   #4
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The RAW format in my Dimage 7 is not compressed and I doubt if any RAW format files are. The size corresponds to the color depth of the bayer pixels which makes it somewhat smaller than a same size TIFF image though it actually has more color depth. There are lossless forms of compression including a TIFF format but I haven't seen them used a lot.
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Old Oct 5, 2002, 7:43 PM   #5
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Thanks everyone for the help, I think I understand it a little better now. I don't believe I have to concern myself with this on a consumer grade camera.
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Old Oct 16, 2002, 12:19 AM   #6
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Just to add a little more information. Raw files are sometimes compressed and sometimes not, depending on the manufacturer's whims. Either way they are in a loseless format which, with proprietary software, allow setting whitel balance, contrast, sharpness, etc., after the capture.

The Canon RAW files for the EOS-D30 and D60 are in a proprietary format with the CRW extension. With the Canon EOS-1D the RAW files are in a compressed TIFF format with the TIF extension. Nikon, on the other hand, uses a proprietary NEF format for the same purposes.

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