Digikam image re-compression - is it reliable?

[Amos Shapira]

Thanks.

They are in JPG, not RAW. exif is copied over.
Minimal compression setting (whatever that means on the camera's user
interface).

My takeaway from your answer is, as usual - "it depends". Most of the
photos were takens in typical opportunistic "catching the kid doing
something funny" reasonable light situations, were additional artefacts are
less likely to happen. I also don't plan to blow them up to huge sizes.

For now it sounds like a +1 for re-compression of normal-light photos.

Thanks.

--Amos

On 20 June 2012 13:30, Marc Volovic <marc at bard.org.il> wrote:

> You do not say whether the originals are in JPG formst or in RAW format.
> If the latter, they contain a lot of information that can be safely
> discarded (it is used for photo-processing which - in re-compressing - you
> have decided to forgo.
>
> If your originals are JPG files, the re-compression is just that. Now, a
> JPG compression on JPG compression adds more artefacts, depending on what
> has been photographed.
>
> And, you will not be able to enlarge and print anything really huge.
>
> C'est touts.
>
> M
>
>
> ---MAV
> marc at bard.org.il
>
>
>
>
> On Wed, Jun 20, 2012 at 6:13 AM, Amos Shapira <amos.shapira at gmail.com>wrote:
>
>> Hi,
>>
>> I'm preparing a disk-on-key with family photos to send to my mum and
>> noticed something a bit unexpected.
>> Most of the photos were taken with a Canon EOS 300D, maximum resolution
>> and minimum compression.
>> Some were taken with Android phone and iPhone 4.
>> I use Digikam on Debian to manage my photos.
>> The total space of the original images (including movies, which weren't
>> touched) was ~7.6Gb.
>> The total space after re-compression using default parameters (75%, JPEG,
>> no resizing) - < 1Gb.
>>
>> I think I saw before that simple re-compression saves a lot of disk
>> space, but this is about 90% reduction (take into account that this
>> includes copied untouched .mp4 movie files).
>> From eye-balling the images on the computer screen (24", 1920x1280) they
>> look just fine. They are going to be printed on regular sized photo paper,
>> not made into bus-stop posters or anything.
>>
>> Am I missing something? Should I still send the larger images (I think I
>> can just barely fit them into an old 8Gb disk-on-key) or will the smaller
>> ones do fine?
>>
>> It also makes me wonder about my own photo stash - it takes a few dozens
>> of Gb's now. If I can recompress them without losing noticeable quality
>> (assume I never intend to display/print them larger than an A4 page) then
>> this could save me a huge amount of disk (+backups, handling, easier
>> shipping to relatives on the other side of the world etc).
>>
>> Thanks,
>>
>> --Amos
>> --
>>  [image: View my profile on LinkedIn]
>> <http://www.linkedin.com/in/gliderflyer>
>>
>>
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>


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