I have just made a little progress on this issue. So I will post a BRIEF description of what I have found. There is more to learn, and maybe I can get around to this another time.
There are at least two metadata standards:
- IPTC: the International Press Telecommunications Council standard.
Tags saved with Gwenview is only possible within Gentoo GNU/Linux when it has been compiled with certain USE flags. I won't get into this now. Also, I don't know how to go about doing this, yet, with Ubuntu or other distributions.
I finally experimented with tags today. They were apparently saved as IPTC tags, not visible in the utility "exiftags" which I think is hardwired for a standard set of tags, to allow reading and maybe manipulation of exif tags of a few types in image files, maybe to change a date, I don't know.
Another application is "jhead." With jhead, I was able to add an exif tag, "Comment", with my own comments. This tag is readable in jhead, at least. And jhead also saw the IPTC tag I stored in the same image using Gwenview.
Other programs I am using are
- shotwell -- good for importing files into a date tree from an SDCard
- Picasa -- good at organizing, but has those sad volatile meta data. Unfortunately Google, written originally in GNU/Linux, has not provided native GNU/Linux ports of this. It runs on top of Wine. Not completely acceptable yet. Maybe good for uploading, if I get into that.
- digikam -- I will experiment, but previously had some issues. First, will it import to the same tree as shotwell? I saw a comment on the Inet that Digikam uses IPTC metadata. Interesting.
- gwenview (KDE4) -- does a lot, and because it's local (on the HDD) and is native, it is pretty attractive. It's gymnastics with tags are so far useful. Saves tags in IPTC format.
- some gnome tools?
Here are some commands with jhead:
- to add a comment:: jhead -ce <path to file>
- to read the metadata (exif and IPTC):: jhead <filename>
- to see other options:: jhead -h
Here are the comments from an image I worked on today:
~/WB/org $ jhead ~/Pictures/2012/03/22/img_0592.jpg
File name : /home/deckert/Pictures/2012/03/22/img_0592.jpg
File size : 130820 bytes
File date : 2012:03:22 08:38:06
Camera make : Canon
Camera model : Canon PowerShot SD1100 IS
Date/Time : 2012:03:22 08:38:06
Resolution : 2048 x 1536
Flash used : Yes (manual, red eye reduction mode)
Focal length : 18.6mm (35mm equivalent: 117mm)
CCD width : 5.72mm
Exposure time: 0.017 s (1/60)
Aperture : f/14.0
Focus dist. : 0.45m
ISO equiv. : 100
Whitebalance : Manual
Metering Mode: pattern
Comment : Tripod used, Crab Cove
======= IPTC data: =======
Keywords : tripod
A more complete readout of standard exif tags is found with "exiftags". No custom or comment exif tags were seen.
~/WB/org $ exiftags ~/Pictures/2012/03/22/img_0592.jpg
Camera Model: Canon PowerShot SD1100 IS
Equipment Make: Canon
Camera Software: Picasa 3.0
Maximum Lens Aperture: f/4.9
Sensing Method: One-Chip Color Area
Lens Size: 6.20 - 18.60 mm
Firmware Version: Firmware Version 1.00
Owner Name: Alan and Fe
Image Orientation: Top, Left-Hand
Horizontal Resolution: 180 dpi
Vertical Resolution: 180 dpi
Image Created: 2012:03:22 08:38:06
Exposure Time: 1/60 sec
ISO Speed Rating: 100
Lens Aperture: f/14.0
Exposure Bias: 0 EV
Flash: Flash, Compulsory, Red-Eye Reduce
Focal Length: 18.60 mm
Color Space Information: sRGB
Image Width: 2048
Image Height: 1536
Exposure Mode: Auto
Scene Capture Type: Standard
Unique Image ID: 5b5bfc656e8e1824c2814e2936491976
Focus Type: Close-Up (Macro Mode)
Metering Mode: Evaluative
Shooting Mode: Manual
Image Size: Unknown
Focus Mode: Single
Drive Mode: Single
Flash Mode: Red-Eye Reduction (On)
Compression Setting: Normal
Macro Mode: Macro
Subject Distance: 0.450 m
White Balance: Custom
Exposure Compensation: 3
Sensor ISO Speed: 160
Image Number: 100-0592