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Old Jan 18, 2010, 6:44 PM   #1
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Default Nikon 5000 and reported lens in showphoto

Hello all a bit late but best wishes for 2010


I have a D5000 and a Sigma AF 70-300mm F4-5.6 DG MACRO F /nikon

Photos taken with this combo and shown in Showphoto
give as lens-info Sigma 70-300mm F4-5.6 APO DG MACRO HSM

On the lens barrel no APO

So where is D5000 getting this lens info ?
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Old Jan 18, 2010, 6:56 PM   #2
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The developers are looking at proprietary maker notes information stored in an image's metadata (a header in the image files). Basically, a lens reports itself in some manner (via an ID).

The camera is then storing that ID in the maker notes section of the EXIF in the image's header. The digiKam developers are probably using a table to translate the ID into the description you see for the lens when using showFoto.

Chances are, the same ID is being used for more than one version of a similar lens (IOW, they probably don't have a way to narrow it down to your specific lens as far as APO versus Non-APO, etc.).
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Old Jan 18, 2010, 7:05 PM   #3
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P.S.

Another good tool you can use that is capable of interpreting a lot of the proprietary tags in the maker notes section of the EXIF is PhotoME. They don't have a Linux version of it. But, it runs fine under Wine in Linux, as long as you install the Microsoft GDI+ library you'll see on the download page for it, too.

http://www.photome.de/
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Old Jan 18, 2010, 7:21 PM   #4
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If you look on this page, you can see some of the tags that one of the libraries (Exifv2) being used by showFoto and digiKam can interpret for Nikon models. Scroll all the way down to the bottom and you'll see a section labeled "Nikon Lens Data 3 Tags".

http://www.exiv2.org/tags-nikon.html

Those are the lens related tags used by your Nikon model. You'll see a tag for a Lens ID Number (a byte). Once showFoto gets that Lens ID number from an image using the Exifv2 library, they're probably matching it up to a description they have stored in table somewhere to give you the description you see in showFoto for your lens.
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Old Jan 18, 2010, 8:00 PM   #5
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The camera retrieves the lens' ID number and stores it in the makernotes portion of the EXIF data, as JimC has stated, but the lens manufacturer assigns an ID to the lens, not the camera manufacturer. It is probable that Sigma has simply assigned the same ID to two very similar lenses.
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