On Fri, Aug 9, 2019, 12:51 PM James Knott via talk, <
talk@gtalug.org> wrote:
On 2019-08-09 12:47 PM, Russell Reiter wrote:
> There is a possibility that keeping your photos in raw form will
> protect from major copy errors, but in all situations of moving bits
> in a data stream, there is the possibility of transient error. Jpg was
> considered lossy as it could not fully recreate the the full raw data.
> 25mb or more of raw image data per image is, or was, a hefty size to
> move across the bus in early days, much less across the internet. Now
> we have so called lossless JPEG, however its accuracy is based on
> predictive sampling rather than a pure collection of bits per pixel.
Jpegs are not copies. They are manipulated to save space. When you
copy a file, that is do not modify it, then the copy should be an exact
replica. If you're really worried, you can use shasum etc. to ensure
integrity of the copy.
Jpegs are an exported file format created from aggregated image data collected by the CCD. They are digital files and subject to transmission errors just like any other signal. My 13 megapixel phone saves image data directly as a jpg file. Sure the raw data has been manipulated before writing the original, but that is much different than having an image recorded using raw format and then exporting a copy in a lossy format in order to save space.