changing time in CR2 file changes other info or confuses irfanview?

[Archive]

[Originally posted by marlow on 2007-10-12 15:29:14-07]

I just found exiftool and it looks very powerful & useful.

Using the Win32 exiftool, I'm trying to adjust only the times of Canon CR2 raw photo files by -58 minutes.

I used "exiftool -AllDates-=0:58 Img_1832.cr2"
The times are indeed changed and the photo files seem okay when I load them into photoshop. However, things are very strange when I merely open the photos with irfanview: It looks like a lot of other info has been changed:
First, when irfanview opens the image, it looks like it is loading only the thumbnail, no longer the full image. Irfanview's image properties reports:

--------------  Original ------ Modified

Compression:    none     ------ none

Original Size: 1536x1024 ------ 160x120 Pixels

Print size:    21.3 x 14.2 ---- 2.2 x 1.7 inches

No. Unique colors: 293207 ----- 14330

Disk size:     7.73 MB   ------ 7.73 MB

Irfanview knows the full image file is there, but it somehow is just reading/displaying the embedded thumbnail.

Is there any way I can just make the 58 minute shift without changing whatever is now confusing irfanview?

THank you.

[Archive]

[Originally posted by exiftool on 2007-10-12 15:41:27-07]

I think this is a question for IrfanView since ExifTool does not change
the image data when modifying the meta information.  You should
send them a sample image and ask them why their software isn't
reading it properly.

This has been tested extensively with many other image viewers, so
I am surprised to hear about this problem with IrfanView.

I have seen problems like this in the past with image viewers that
take shortcuts instead of properly parsing the raw file format,
but I wouldn't expect this sort of problem with IrfanView.

- Phil

[Archive]

[Originally posted by marlow on 2007-10-12 19:00:11-07]

Thanks much for the further info.

In order to display Canon CR2 raw files, Irfanview requires and uses (in a plugin fashion) a half dozen dll files from Canon's proprietary image software. So there are unknown opportunities for trouble ;-)

I'll do some further digging around to see if I can figure it out, but cannot for a week or so till I return from some travel. This trip I'll be sure to set the *&#$% clocks in my cameras! In fact I'd better do it right now.

Thanks again Phil for providing such a powerful tool!

[Archive]

[Originally posted by exiftool on 2007-10-12 20:04:22-07]

I am surprised that IrfanView would have a problem if it is using
the Canon plugins, because I have personally tested edited CR2
images with the Canon utilities and have never seen a problem.

But obviously something is wrong.  However, I am confident that
the problem doesn't lay in exiftool.

- Phil

[Archive]

[Originally posted by exiftool on 2007-10-15 12:29:42-07]

I just downloaded IrfanView 4.0 and tested this out myself under Windows XP.

The problem is IrfanView.  I tried editing the file by hand to change nothing except
to move the preview image, and IrfanView no longer displayed the 1536x1024 preview.
So IrfanView is taking shortcuts and assuming a fixed offset for the preview, which of
course is an assumption that is easily broken (by editing the image, or even maybe by
updating the camera firmware).

I don't understand why IrfanView would do this, because you can either write the code
to parse the CR2 image properly, avoiding problems like this and having one code that
works for all models, or you can take shortcuts and have to update your code for each
new model that comes out, and have your code break whenever an image is edited or a
camera firmware update changes the image structure.  The speed benefits from taking
shortcuts have to be minimal, and couldn't possibly make up for the disadvantages.

I have sent a bug report and some sample images to IrfanView support, and we will
see how they respond.

- Phil

[Archive]

[Originally posted by exiftool on 2007-10-15 22:15:25-07]

Irfan has replied with this message:

Code:

> Please install latest plugins first.
>
> Then see in IrfanView options: properties->plugins.
> There are some CR2 options, uncheck the preview option and try e.g.
> half-size loading ...

I will try this myself when I get a chance.

- Phil

[Archive]

[Originally posted by exiftool on 2007-10-16 11:43:19-07]

I tried it, and it does allow you to bypass IrfanView's preview problem
somewhat, but in my opinion it isn't a real solution.  The real solution
would be for IrfanView read the preview properly, but it looks like that
isn't going to happen.

- Phil