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Auto CHDK to Exif Question

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Offline Sow.N.Reap

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Auto CHDK to Exif Question
« on: 06 / August / 2009, 02:52:55 »
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Why are there 2 different numbers for Exposure Time?

Here's what it reads .. the CHDK shutter speed was set at 1/8000 using Powershot S5is:

[Composite] ISO: 100
[EXIF] ISO: 100
[MakerNotes] CameraISO: 100
[MakerNotes] ExposureTime: 1/8192
[MakerNotes] ExposureTime: 1/6747
[MakerNotes] FNumber: 2.8
[MakerNotes] FNumber: 2.8
[EXIF] UserComment: 1.72
[] caption-abstract: -

If I "patch it", it uses 1/8192 which I assume would be the more accurate one???

Also, is there anyway to keep it from putting the Subject Distance into the User Comment field? I see it's putting the number into the Exif Subject Distance which is good but I don't need or want it in the comments also.

Are there any other programs that can quickly write the CHDK values into the Exif?

Thanks in advance to anyone that can enlighten me.

Canon S5is .. My Flickr page

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Offline Anaglyphic

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Re: Auto CHDK to Exif Question
« Reply #1 on: 06 / August / 2009, 17:15:23 »
Hi.

I don't know about enlightening you, but I think I can explain what's going on.

But first, I've never seen or used "Auto CHDK to EXIF tool" but I can guess what it does... (is that thing even around anymore, the link on the Software wiki page leads to a 404 at zshare, and wasn't this Barney's, and de-sticky'd a while ago??)

Yes, the former is probably the correct one, and the reason it's not exactly 1/8000th is the maker notes values are calculated via the APEX system and not from a look-up table. IIRC the field for Maker Note #22 is the shutter speed you set, regardless if the camera you have can shoot at that speed or not. That's part of the problem, you have to know the limitations of your model; just because it says it shot at ISO 10 and records this in the tag, doesn't make it so.

That program is probably a front-end to exiftool, I'm sorry I don't know it, maybe someone else can help, I'll just pretend you're using exiftool directly. You can have duplicate tag names, as well as tag numbers, I don't know how to do it with "Auto CHDK to EXIF tool" but you'd add -D (decimal) or -H (hexidecimal) to your exiftool command line so you can differentiate tags... something like: exiftool -D -G -a some_image.jpg/crw/dng. You'll notice that the one you want is the highest number, #22 vs. the other Canon:ExposureTime values (#6 I think), so this will be read as 'the' value when you query that tag.

So to change the EXIF:ExposureTime to match the Canon maker note, just do: exiftool '-canon:exposuretime>exif:exposuretime' some_image.jpg/crw/dng (note the quoting, and experiment on images you don't care if you lose the tag info.) This will result in the new exif & composite values being 1/8192th as you'd expect; check it with: exiftool -shutterspeed some_image.jpg/crw/dng.

re: the comment problem; that's something that this "Auto CHDK to EXIF tool" thing is doing, normally the comment is blank straight out of the camera... to blank the comment field for all images in a directory with exiftool, do (in that directory): exiftool -comment= *.jpg/crw/dng

Have fun, and hope this helps...
Since we cannot know all that there is to be known about anything,
 we ought to know a little about everything.
-- Blaise Pascal

Re: Auto CHDK to Exif Question
« Reply #2 on: 06 / August / 2009, 17:49:33 »
is that thing even around anymore, the link on the Software wiki page leads to a 404 at zshare, and wasn't this Barney's, and de-sticky'd a while ago??)

If you want to play with it, get it here


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Offline Sow.N.Reap

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Re: Auto CHDK to Exif Question
« Reply #3 on: 06 / August / 2009, 21:35:44 »
Thanks for the explanation, Anaglyphic. You are correct that the Auto CHDK to Exif is a front end for exiftool & it was Barney's. It does make it much easier to update the exif tags with it when doing a lot of photos. I may try exiftool by itself though so I can learn it better. And your info helps with that.

I'm still learning how to use my S5, CHDK & manual settings & having the correct info in the exif sure helps.

It took me a bit to find the program. The link on the Wiki does need to be updated. Microfunguy posted a new link but I think I got it from a different one.

The one good thing about it putting that number in the comment is that I found out the iMatch is reading the Canon Maker Note for Subject Distance wrong. I'll have to let Mario know so it can be corrected.

I appreciate all the help.
Canon S5is .. My Flickr page


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Offline fe50

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Re: Auto CHDK to Exif Question
« Reply #4 on: 07 / August / 2009, 01:52:36 »
It took me a bit to find the program. The link on the Wiki does need to be updated. Microfunguy posted a new link but I think I got it from a different one.

...there's a safe place for such CHDK files, the link is also there:
Quote
Note2:an alternative download location can be found here: ? http://drop.io/chdksoft
I replaced the zShare link with a direct link to the drop...

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Offline Sow.N.Reap

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Re: Auto CHDK to Exif Question
« Reply #5 on: 07 / August / 2009, 02:33:26 »
Quote
Note2:an alternative download location can be found here: ? http://drop.io/chdksoft
Yep .. the "drop" link is where I downloaded from. For some reason Firefox didn't have that download in my history & I couldn't remember what it was. Thanks Fe50.


Canon S5is .. My Flickr page

 

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