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On 8/9/19 12:47 PM, Russell Reiter via talk wrote:<br>
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<div dir="ltr" class="gmail_attr">On Fri, Aug 9, 2019, 8:58
AM James Knott via talk, <<a
href="mailto:talk@gtalug.org" target="_blank"
rel="noreferrer" moz-do-not-send="true">talk@gtalug.org</a>>
wrote:<br>
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<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">On
2019-08-09 08:03 AM, Russell Reiter via talk wrote:<br>
> This problem is amplified by making a copy of a copy
of a copy etc. <br>
<br>
That is certainly the case with analog, but with digital
the copies<br>
should be exactly the same, even if on a different media.<br>
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<div dir="auto">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.</div>
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When you say keeping your photos in the raw format you are opening
up a few other questions.<br>
First. If the photos are film based then over time your master image
will fade and any copying will result in some form of loss.<br>
If your using most phones/cameras you have no actual access to the
raw images unless you start hacking so that your first image is
already a less than exact copy of the intensity of the raw pixels in
the sensor.<br>
<br>
Once you have an image file then copying will almost always result
in a perfect copy of the original.<br>
Bit error rates in copying and storage are exceedingly low and there
are numerous methods to decrese the risk go insanely low levels.<br>
Data loss in modern computer systems during copy is much more of an
academic discussion than a real life discussion.<br>
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<div dir="auto"><a
href="https://en.m.wikipedia.org/wiki/Lossless_JPEG"
target="_blank" rel="noreferrer" moz-do-not-send="true">https://en.m.wikipedia.org/wiki/Lossless_JPEG</a><br>
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It is not clear in the referenced article that lossless JPEG is a
lossy compression scheme.<br>
It may work as well as any of the popular compression schemes like
Huffman or LZP where data can be compressed and exactly restored.<br>
All compression schemes take advantage of some kind of pattern in
the data once the data does not match that pattern then often the
compressed data can be larger then the raw data.<br>
There is no compression scheme that will guarantee compression of
any arbitrary data stream.<br>
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<div dir="auto">Humans lose thousands of skin cells a day, yet
the fabric of the persona stays the same. I think photo data
is a little the same, a few stray bits lost here or there
won't change the picture that much. However it is possible to
corrupt that significant bit which would make decoding the
picture impossible.</div>
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Raw digital photo images as an array of RGB pixels will be very
tolerant of bit errors without destroying the whole of the image.<br>
GIF or JPEG compression has the downside of being sensitive to
errors and will not fail gracefully but given the reliability of
digital copies I would be hard pressed to say that it is less
reliable than a photo in a drawer.<br>
<br>
Data loss by accident is way more likely than data loss due to
bit-rot.<br>
<pre class="moz-signature" cols="72">--
Alvin Starr || land: (647)478-6285
Netvel Inc. || Cell: (416)806-0133
<a class="moz-txt-link-abbreviated" href="mailto:alvin@netvel.net">alvin@netvel.net</a> ||
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