Focal Length in Exif Information
|
MacWilliam
Joined: 2005-04-16
Posts: 33 |
Posted: Mon, 2005-04-25 17:46
|
|
Gallery 1.4.4pl4 displays in photo properties: E.g.: Focal length : 77.0mm (35mm equivalent: 319mm) This is incorrect. The focal length of the lens was 77.0mm. Is this a setting somewhere? Complete photo properties are: File size : 169236 bytes |
|
Posts: 6818
Hello,
Gallery just get the data.
If its wrong it was written wrong.
Regards,
Jens
Posts: 33
Hi Jens,
Thanks for your reply.
Correct: it was written wrong, but where?
The calculation from the lens focal lenght (FL) to the 35mm equivalent must be based on the chip size: thus model / make.
50mm FL on a Canon 300D has a crop factor of 1.6, thus the 35mm equivalent is 80mm
With a Canon Powershot G6 a FL of 16mm equals a 35mm FL 80mm
The Exif version 2.2 holds only one value. The 35mm equivalent is calulated somewhere on the server. This piece of software assumes that I have a compact camera because of the wide angle.
With some other photo it says:
Focal length : 108.0mm (35mm equivalent: 191mm)
This is also not correct, because the 35mm equivalent should be:
1.6 x 108 = 173mm, but only because this camera has 1.6 crop factor.
Is there a setting somewhere?
Thanks again.
Posts: 33
Posts: 13451
Well, the only way of fixing that is to edit the exif info in the actual photo. Thats where Gallery gets the info from.
Posts: 33
Thanks for you reply.
The EXIF of the actual photo holds the Focal Lenght, but NOT the 35mm equivalent. It's added somewhere, after the upload.
(There is more added: The "file date" is also not in the EXIF.)
Any idea what I can do about it, because the info about the 35mm equivalent is incorrect.
Posts: 13451
MacWilliam, Gallery does no conversion of any of the exif data. Thats up to the binary file that extracts it from the picture. If you run Gallery 1.5, it also supports exiftools as well as jhead. Perhaps give that a try?
Gallery relies on whatever info the toolkit provides, so there is nothing we can do about what data is returned. If jhead is indeed reporting the wrong data, you should file a bug report with the jhead developer.
Posts: 33
Thanks H0bbel,
I'm using Gallery 1.4.4pl4.
As I understand I should check jhead.
Posts: 33
This is what Jhead says about it:
"Some Canon digital SLR cameras fail to encode the effective sensor resolution when shooting at less than full resolution, causing jhead to incorrectly miscalculate the 35mm equivalent focal length. Jhead usually gets blamed for this bug, but it is in fact a camera bug, and jhead can't do much about it"
OK, now I know where it is .... just have to find a solution ...
Posts: 13451
There we go, nothing anyone can _really_ do about it, it seems.
Hope I won't run into that when I get my new 350D...
Posts: 33
H0bbel. I guess this will be the case for every 350D ...
According to the maker of Jhead (Matthias Wandel) there is no way to solve this in Jhead.
"No, there isn't a way in jhead. Maybe gallery can be set to ingore it for certain makes of camra."
Is there a way that I can manipulate which information is shown in "photo properties" and thus remove the 35mm equivalent.
Can I manipulate the photo properties CSS and put this text in the background color?
Posts: 13451
MacWilliam, I'm sure that there are ways to manipulate the data when it's entered into the Gallery cache. I suggest you ask in the customizations forum, hopefully someone there can help you out.
Did you try to use exiftools instead? Does it generate the same result?
Posts: 33
Hi H0bbel,
I would like to try Exiftools and have found it.
(http://owl.phy.queensu.ca/~phil/exiftool/),
but I have no idea how to install this.
I'm new in Gallery and servers (just a simple Mac user).
Some hints would be very much appreciated.
Posts: 13451
My bad, it's exiftags ( http://johnst.org/sw/exiftags/ )
Posts: 33
Hi H0bbel,
Thanks. I've downloaded this "exiftags-1.00.tar.gz" and it contains a folder loaded with documents. It isn't just a binary which I can put in my \bin folder.
I've read the included "read me" but it's not clear to me how to get this working.
Some hints on how to proceed would be very much appreciated.
Posts: 1535
Download the tarball (note the correct usage this time, h0bbel... :P) and extract it using
tar xfz exiftags-1.00.tar.gzcd into the new directory it makes (exiftags-1.00) and type
makewait for it to compile, then typemake installIt oughta stick the new files (exiftags, exifcom, exiftime) into /usr/local/bin (at least, that's where they went in my distro).
Posts: 33
Thanks H0bbel for your help.
I guess I need shell access to my server for that.
I'm still figuring out how to do that.
I'm on a Mac and did everything with Gallery by browser or ftp until this moment.
Although the Mac OS X system is running BSD and I've got a terminal console on it, I have no clue about Unix.
I can always ask the hosting webmaster to do this for me ...
Posts: 13451
MacWilliam, I used the rpm files, so I don't know how to compile it. Not on OSX. http://exiftags.darwinports.com/ looks like there is a version available though.
Posts: 33
Thanks again.
The rpm files open Realplayer with me ;-)
Yep, it describes how to install it on my Mac.
I could run my Mac as a webserver then I guess.
I've entered a question in the Apple Discussions Forum on how to get shell acces from my Mac on the webserver. This is what I need I guess.
Posts: 13451
I asumed you ran it on a max, since you mentioned it. If not, ask your host if they can install it for you, as it doesn't seem like there are any precompiled, static, binaries of exiftags available.
Posts: 33
Thanks !