Compressed or uncompressed?

[mjh]

Advertisement (gone after registration)

The term lossless is silly

It is a useful and well-defined term, nothing silly about it. A lossless compression algorithm reduces the amount of data while leaving the information conveyed by the data exactly the same. A lossy compression algorithm throws away some of the original information for achieving (usually) higher compression ratios. Leica’s compression algorithm is of the lossy kind but its compression ratio isn’t significantly higher than that of lossless algorithms (but then its computational complexity is much lower which is the reason Leica did choose this algorithm in the first place).

 

It is easier to fix a uncompressed file than a compressed file.

While this is often true, there are exceptions to the rule. For example, a damaged file compressed using the lossless LZW algorithm may be difficult to restore while Leica’s lossy algorithm does not compromise recoverability an any way. If a couple of bytes get garbled you only lose a few image pixels, either with or without compression.

 

My understanding from Leica, is that on the M9 compressed file is 8-bit, and uncompressed is 14-bit. On 8-bit equipment, it is difficult to reproduce any difference.

Actually the uncompressed files are 16 bits per pixel, 14 of which being significant. Indeed it is difficult to show how the loss of information leads to any visible loss in image quality, but whether the image is eventually displayed using 8 or 16 bits isn’t really relevant, if only because you would have trouble distinguishing 2^16 levels of brightness. Having said that, it would always be beneficial to perform image manipulation within a 16 bit space; this applies to compressed and uncompressed images alike.

[stunsworth]

I use in-computer backup on another disk, which could be RAID, but I use Second Copy, and for external backup I use IASO.

 

Best Online Backup Software | IP-based Backup Solutions from IASO Backup Technology

 

They don't seem to show the price anywhere - other than to say it costs from 5 Euros a month.

 

How long does a couple of TB of data take to upload? What happens if they go bust?

[diogenis]

How long does a couple of TB of data take to upload? What happens if they go bust?

Let's say that you got 24mbps adsl

Usually this gives you a 1 Mbps upload speed

Or 1 Mbits per sec

Which equals to 1Mbyte per 8secs

Or 1Gbyte per 1000secs and finally 1Tbyte will take 1 million secs...

Quite a lot, but I would guess they would arrange another faster means for your original archive

[perb]

I had a quick look, and since I couldn't find any reference (sorry if I missed it), here is a link to one of the key threads on the subject in the M8 forum:

 

http://www.l-camera-forum.com/leica-forum/leica-m8-forum/85038-effects-compressing-8-bits.html

 

Please note that there are interesting posts not only at the beginning, so browse through to the end

 

Note also post #38 with lots of refs to further threads on the subject.

 

Regards

Per

[jaapv]

They don't seem to show the price anywhere - other than to say it costs from 5 Euros a month.

 

How long does a couple of TB of data take to upload? What happens if they go bust?

Long - but you only upload changed files. And if they go bust you look for another service...

[diogenis]

Also 1 gig can hold some 25 uncompressed photos @ 40mb each, so 1TB should hold some 25000 photos (approx.)