image conversion: size questions

[stefano adami]

I tried to export a series of raw images to jpg. Raw are 3906x2602, 9MB.

First strange thing is that Jpeg size are around 9MB (like raw) with a
compression quality set to 75.

So I tried to reconvert image (jpg->jpg) with quality set to 80 and now
images are around 1,8MB (a correct and appropriate size in my opinion),
but digikam displays a 16KB size and had apparently lost all images info
(this sounds like a bug).

It's normal that a 75 quality jpg is bigger than a 80quality jpg?
 
 
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On Wednesday 17 June 2009 15:15:25 stefano adami wrote:

> I tried to export a series of raw images to jpg. Raw are 3906x2602, 9MB.
>
> First strange thing is that Jpeg size are around 9MB (like raw) with a
> compression quality set to 75.
>
> So I tried to reconvert image (jpg->jpg) with quality set to 80 and now
> images are around 1,8MB (a correct and appropriate size in my opinion),
> but digikam displays a 16KB size and had apparently lost all images info
> (this sounds like a bug).
>
> It's normal that a 75 quality jpg is bigger than a 80quality jpg?

For me it looks like first compression wasn't 75 but 100. That could give such
results.

Normally with 75 jpeg artifacts are clearly visible in many parts of image. If
there is no such thing it wasn't 75 :)

m.
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