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I'm shooting panoramas with a manual 8mm fisheye lens on my Canon 60D DSLR (APS-C, 1.6x crop factor).

Since the camera cannot talk to the lens, the exif data in the pictures is all wrong. I know how to fix the focal length using ExifTool, but I'm having trouble locating the proper tag to indicate that the lens is a fisheye.

Does anybody know which tag is used to indicate the lens type?

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Do you want to indicate the type of lens in general, or are you looking for a particular tag to indicate that this is a fisheye lens as opposed to a rectilinear lens? –  mattdm Dec 12 '11 at 3:00
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The latter, I want applications to automatically recognize the lens as a fisheye. –  Miguel Dec 12 '11 at 4:31
    
@Miguel have you attempted to contact the Hugin developers (launchpad.net/hugin)? Or looked at the source code yourself? –  drewbenn Dec 12 '11 at 20:46
    
I haven't looked at the source code yet, but it would be interesting to do that to determine how they obtain the lens type. Instead I'm currently exploring the idea of batch generating Hugin project files that link to my pictures with the proper lens settings. –  Miguel Dec 12 '11 at 22:14
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3 Answers

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I don't believe there is an "official" EXIF tag for lens type. As much as I know about EXIF (which admittedly isn't a ton), I believe Lens Type is a "maker note", or additional OEM-specific settings. I believe you can simply add a LensType tag and stuff the name of the lens in that tag. Most tools should recognize that.

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Thanks for your answer. I found the Canon specific LensType tag in the ExifTool documentation, but my lens isn't in the list. I can enter the description of my lens, but ExitTool apparently parses it and then finds the closes one from the known list. I'm starting to think I'm out of luck with this. –  Miguel Dec 12 '11 at 4:59
    
Does it have to be an Exif tag? I think IPTC has some gear-related tags that you might also be able to use. If IPTC tags are supported for whatever you use...tools or web sites...that might be an alternative. –  jrista Dec 12 '11 at 5:19
    
No, it does not need to be EXIF. I asked about EXIF because I expected this aspect of a lens would be covered somehow. I also looked at the IPTC and XMP tag lists and didn't find anything. Looks like you are right, the lens type is all there is, you just have to hope that tools interpret those types properly. –  Miguel Dec 12 '11 at 6:14
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The EXIF field you're talking about is the LensType field and the value is defined by the manufacturer of the lens. There are a couple of problems with that:

  1. The lens must be identifiable. Not all lenses can be, especially older ones, so you can't just put anything there. You could try to find the lens ID of a more modern equivalent, but it's not the same lens, so the EXIF won't be correct, just close.

  2. Some manufacturers re-use the ID. A prime example would be this shot of mine on Flickr. Here the focal length is measured as 400mm, but the lens info claims a 70-200mm f2.8. This shot was with the Sigma 120-400mm at 400mm and it shares a lens ID with the other lens (and another, for a total of 3). I happen to have both, a bit of a pain... It also makes Sigma look like morons, but that's a side note.

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It's frustrating, because my lens isn't old, just a manual non-canon brand lens (a Rokinon 8mm f/3.5). I actually don't care about showing the correct lens brand, I just want applications to identify it as a fisheye, so that it can be dealt with properly when stitching. –  Miguel Dec 12 '11 at 5:03
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As another poster has mentioned, this kind of data is more on a manufacturer by manufacturer level, and is not necessarily standardized. With that said, I have examples with a Canon camera and Canon lens that probably gives you at least enough to fill in some of the major blanks. Fill in as much or as little as you wish. I would start with the Lens Type in the first screenshot, and see if that provides enough data for the end result you are looking for.

enter image description here enter image description here enter image description here enter image description here

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I can enter all the details about my lens except the fact that it is a fisheye. Panorama stitching applications import the pictures and treat them as a normal lens for the stitching calculations. –  Miguel Dec 12 '11 at 5:14
    
@Miguel — applications aren't expecting to see EXIF data identifying the lens in this way, so they're not looking for it, so it doesn't matter what you put. I suggest you start a new question, something like "How can I get software XYZ to automatically handle images from my manual fisheye lens as fisheye images?" –  mattdm Dec 12 '11 at 12:21
    
@mattdm: the application in question is Hugin. It does get the focal length from the EXIF, but it marks the lens as normal. That prevents me from doing batch processing. I am now looking at how to address this in another way along the lines of your suggested question (generating a Hugin project with the correct settings). Thanks. –  Miguel Dec 12 '11 at 16:31
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