There are some EXIF editing tools out there, but I'd advise against it. You'd be better off choosing an available, but unused, metadata field, like something in the IPTC or xmp, and posting that info in that field. That's all outside the realm of jAlbum, however - jAlbum isn't the tool for doing things like that.
Getting it properly labeled in Turtle, however, would be quite a challenge. I don't think the skin gives you that much flexibility.
We don't know what the metadata field is called - Laza was just providing a hypothetical example. The field could have any one of a thousand different names.
If you have an image that has the lens manufacturer recorded in the file metadata, add it to a jAlbum project. Right-click the thumbnail and choose List metadata. That will show you all of the fields that jAlbum can extract from that image file. If you see the lens manufacturer listed there, write down the name of the metadata field. You can then tell the skin to display that field in the photo info.