[Digikam-users] 100% magnification for JPG and DNG (RAW)

[Gilles Caulier]

2010/3/13 Rei Shinozuka <shino at panix.com>:
> I am running digiKam 1.0.0-beta5 currently on Ubuntu 9.04, but the
> behavior I am about to explain has been with me well before digiKam
> version 1.0.

Go imediatly to 1.1.0 release. beta5 is too old and a lots of bugs
have been fixed. Note that 1.2.0 release will be done in 2 weeks.

>
> When I set my camera to take JPG and DNG (RAW) simultaneously, the
> camera deposits both JPG and DNG files of the same image capture on the
> SD card.
>
> In Digikam, I find that JPG will zoom to 100% (keystroke "1") as
> expected, but DNG will zoom far less.  In fact, I must zoom DNGs to 207%
> to achieve the same magnification as 100% in JPG.  When I click on an
> image in an album, the JPG would come up and say "Zoom: 21%," and the
> identical image as DNG will say "Zoom: 43%." (also just over 200% of the
> JPG)    Somehow the scaling in DNG is confused.
>
> Digikam sees the files:
>
> Type: RAW Image file (DNG)
> Dimension 3,920x2,638 (10.34Mpx)
> Bit depth: 16 bpp
> Color mode: Uncalibrated (RAW)
>
> Type: JPEG
> Dimensions: 3,936x2,624 (10.33Mpx)
> Bit depth: 8 bpp
> Color mode: YCbCr

You cannot compare. In preview mode, RAW can be loaded differently :
JPEG preview embedded (reduced size compared to RAW), or 1/4 raw
demosaiced version. For performance reason, in all case, it's not full
RAW size image.

With JPEG, libjpeg provide a way to load a downscaled version too. In
1.1 release, preview has a label over the image to indicate if you see
a downscaled version. Note that you can change this behavior in
digiKam setup dialog.

Only Editor will load full image size version.

Look this Light Table screen-shoot in action displaying this
annotation on the right top corner of preview area :

http://www.flickr.com/photos/digikam/4327772558/sizes/o/

best

Gilles Caulier