Posted by Frank Winters on November 21, 2008 at 11:48 AM
I just converted a RAW file to TIFF using Canon's RAW processor. The resulting file is a 68 Mp TIFF file. The camera is a Canon G9 -- a 12 MP file.
My question is -- why is the TIFF so large? What is being added?
Thanks,
Frank
Posted by Steve Foss on November 21, 2008 at 12:09 PM
When I convert a 12 Mp 5D image at standard size from RAW to TIFF using ACR at 16-bit color, I get a 72 Mb file, so your 68 Mb is not surprising.
Posted by Robert Fisher on November 21, 2008 at 12:12 PM
I think you might be confusing terms a little bit, Frank. The RAW is a 12MP file but the TIFF is likely a 68MB file. Megabytes, not megapixels. The size of the G9 RAW file is probably around 12MB.
RAW files contain only luminance information and one colour value at each pixel location. That individual pixel site colour information is then interpolated into an RGB value at each pixel, thereby increasing the colour information at each pixel in the processed TIFF. RAW files are also slightly compressed while your TIFF files likely aren't. Your G9 RAW files are also likely only 12 bit files. Those are being interpolated up to 16 bit as TIFFs and even though the extra 4 bits is only being filled with zeros, that still takes up space and increases file size.
Posted by Guy Tal on November 21, 2008 at 12:31 PM
Robert gave you part of the answer but the missing factor is that raw files are compressed and standard TIFFs are not (you can compress them when saving from Photoshop, but Canon's DPP doesn't offer this option as far as I know).
Also, there is no such thing as a 12-bit file. Files are created in bytes. Anything requiring values in the 0-255 range can use a single byte (or 8 bits) per value. Anything requiring values between 0-65535 will use 2 bytes (or 16 bits) per value. This latter category covers 12-bit and 14-bit readings as well as 16-bit readings. Any bits not used are simply set to 0. This allows 12-bit files to compress better than 16-bit files but in uncompressed form the files will be the same size.
Confusing enough?
Guy
Posted by Robert Fisher on November 21, 2008 at 1:19 PM
Discussion
4 repliesMy question is -- why is the TIFF so large? What is being added?
Thanks,
Frank
RAW files contain only luminance information and one colour value at each pixel location. That individual pixel site colour information is then interpolated into an RGB value at each pixel, thereby increasing the colour information at each pixel in the processed TIFF. RAW files are also slightly compressed while your TIFF files likely aren't. Your G9 RAW files are also likely only 12 bit files. Those are being interpolated up to 16 bit as TIFFs and even though the extra 4 bits is only being filled with zeros, that still takes up space and increases file size.
Also, there is no such thing as a 12-bit file. Files are created in bytes. Anything requiring values in the 0-255 range can use a single byte (or 8 bits) per value. Anything requiring values between 0-65535 will use 2 bytes (or 16 bits) per value. This latter category covers 12-bit and 14-bit readings as well as 16-bit readings. Any bits not used are simply set to 0. This allows 12-bit files to compress better than 16-bit files but in uncompressed form the files will be the same size.
Confusing enough?
Guy