When loading model some of the requested fields contains wrong values or field is not returned.
Couple cases where that came up for every image/photo file:
whiteBalance (empty result)
fNumber (wrong value 0)
fileExtension (ReferenceError: Can't find variable: fileExtension)

Test code attaced

When checking with tracker-info of image all of those has valid value there:
$ tracker-info file:///home/tliljend/n900_images/20100902_039.jpg
Defaulting to 'files' service
Results: 23 for '/home/tliljend/n900_images/20100902_039.jpg'
'DC:Format' = 'image/jpeg'
'DC:Type' = 'Image'
'Image:Height' = '1440'
'Image:Width' = '2560'
'Image:Date' = '1283459116'
'Image:CameraMake' = 'Nokia'
'Image:CameraModel' = 'N900'
'Image:Orientation' = '8'
'Image:ExposureProgram' = 'Not defined'
'Image:ExposureTime' = '0.030303030303030304'
'Image:FNumber' = '2.8'
'Image:Flash' = '0'
'Image:FocalLength' = '5.2'
'Image:ISOSpeed' = '123'
'Image:WhiteBalance' = 'Auto white balance'
'File:Name' = '20100902_039.jpg'
'File:Ext' = 'jpg'
'File:Path' = '/home/tliljend/n900_images'
'File:NameDelimited' = '/home/tliljend/n900_images/20100902_039.jpg'
'File:Mime' = 'image/jpeg'
'File:Size' = '480666'
'File:Modified' = '1283448316'
'File:Accessed' = '1283506623'