Editing, changing, and adding exif data

pittendrigh · Post by **pittendrigh** » Wed Jan 20, 2016 7:35 pm

Is this off topic here? Questions about how to edit change and add exif information in jpegs or pngs?

When I make an N-exposure focus stack I shoot in Nikon Raw format with a StackShot focusing rail. Then I hand edit one raw image in the stack manually by manipulating the UFRAW GUI. Then save a ppm file. Then I use UFRAW batch processing to apply the same editing changes to all other raw images in the stack, and then use ImageMagick to convert all raw images to *.tif format on the fly (and then use ZereneStacker on the tifs, and then Gimp to make a final jpeg or png). ZereneSTacker is very good software, by the way. StackShot gets an A+ too.

However, in the batch conversion from RAW to TIF I lose all exif information for each new tif in the sequence. Hence my final jpeg has little to no exif information, which I would like to have (various online photo contests, for instance, refuse images without embedded exif stuff).

Is there a convenient GUI based debian linux compatible tool that edits exif? Adds new fields, which are now missing? So I could hand edit exif data inside my final jpeg?

I'm trying to fight my way through command line perl exiftool library, which could be incorporated into a script. But adding new fields is escaping me so far.

rjlittlefield · Post by **rjlittlefield** » Wed Jan 20, 2016 11:21 pm

What new fields do you want to add?

--Rik

pittendrigh · Post by **pittendrigh** » Thu Jan 21, 2016 5:14 am

rjlittlefield wrote:What new fields do you want to add?

--Rik

DateTimeDigitized, ExposureTime, and FNumber, FocalLength all of which are new in the sense they aren't there any more, because they were stripped out earlier in the process, when ImageMagick converted raw to tif. I might add a truly new file like Author too, if I knew how.

Perhaps there is a way to convert raw to 100% jpeg, so editing power is not lost. Which would be a conversion that probably would transfer exif

rjlittlefield · Post by **rjlittlefield** » Thu Jan 21, 2016 1:21 pm

For restoring old tags that got stripped by raw conversion, take a look at the -tagsFromFile option of ExifTool.

For adding a new tag, take a look at http://owl.phy.queensu.ca/~phil/exiftool/examples.html, for example

Code: Select all
exiftool -artist=me a.jpg
Writes Artist tag to a.jpg. Since no group is specified, EXIF:Artist will be written and all other existing Artist tags will be updated with the new value ("me").

Beware, it is easy to get lost in the details.

There is an index to the tag names recognized by ExifTool, at http://www.sno.phy.queensu.ca/~phil/exi ... index.html. The ones for EXIF are at http://www.sno.phy.queensu.ca/~phil/exi ... /EXIF.html.

Note that "Author"-- the one you said you were thinking about -- is not included in that list. There is one named "XPAuthor", but I'm not sure whether "author" would be accepted as a shorthand for that. And if it is accepted, I don't know whether XPAuthor would do what you intend.

Note also that similarly named tags may appear in other wrappers at the same time. For example http://u88.n24.queensu.ca/~phil/exiftoo ... tcuts.html mentions IFD0:Artist and IFDO:XPAuthor, described as "common metadata tags found in IFD0 of TIFF-format images."

It sounds to me like you may be thinking also about the IPTC tags. See http://www.sno.phy.queensu.ca/~phil/exi ... /IPTC.html for some more information about that. The IPTC Field Reference Table at https://www.iptc.org/std/photometadata/documentation/GenericGuidelines/index.htm#!Documents/fieldreferencetable.htm describes a field named "Creator", which apparently has synonyms "Author","Byline", and "Photographer".

All that said...

Experimentally, I find that it works to simply say

Code: Select all

exiftool -author="Rik Littlefield" foo.jpg

The resulting file is shown by Photoshop with me listed as "Creator" in the IPTC section. But if I do an exiftool -a -u -g1 foo.jpg to see where the tag actually went, it's listed by exiftool as "Author" in the XMP-pdf section.

In general, my experience is that trying to micromanage the metadata can be extraordinarily complicated and difficult to understand. At one point I discovered that a single particular image file contained three different tags for shutter speed, all with slightly different values! <Insert here, rude noise expressing confusion and frustration.>

What I currently do in Zerene Stacker is to have ExifTool and its -tagsFromFile option simply copy all existing tags from one source file to the output. Trying to make sense of the morass would require more intelligence and energy than I have available right now.

--Rik

pittendrigh · Post by **pittendrigh** » Thu Jan 21, 2016 4:07 pm

OK. I'm getting it. Thank you.

You cannot use the output from the command-line `exif` on any existing image file to find a list of Tag names or values you can actually work with.

exif will, for instance, display the exif tag FNumber as F-Number. And F-Number cannot be used as input to exiftool.

exiftool -s src.jpg .... will display tag names and values in the formats you can use.

That's what was killing me. Now it's easier.