Information contained in the MakerNote EXIF Tag of the Nikon 990 digital camera

The Nikon 990 stores images using the "EXIF" JPG format. One of the tags that it records is the MakerNote tag (Tag 0x927C). Although there is no official specification for the format of the data contained in this tag, it appears that the Nikon 990 (and other digital cameras) record (more or less) standard EXIF (Image File Directory Entries) data in this tag, containing manufacturer and camera-specific information. Thus the Maker-Note data is an Image File Directory (IFD), which contains several IFD Entries.

However, none of the tags contained in these IFD Entries is defined by the EXIF specification; Thus, determining their meaning requires trial-and-error research. So far, I've been able to decode most of the 16 entries and my results are listed below. For several of the tags I've included "Others?" to indicate that there may be other values that the camera records, but I haven't done exhaustive testing to confirm the values.

Please send any corrections or modifications to If you have any information on the MakerNote tag for other cameras please send it along and I'll include it in Thumber.

Tag Name
Data Value*
0x0001 Unknown 7 - undefined 4 Usually (always?) 0,1,0,0
0x0002 ISO Setting 3 - unsigned Short 2 0, 100 = ISO 100
0, 200 = ISO 200
0, 400 = ISO 400
0x0003 Color Mode 2 - ascii string varies COLOR, B & W, (others?)
0x0004 Quality 2 - ascii string varies NORMAL, FINE, BASIC (others?)
0x0005 Whitebalance 2 - ascii string varies AUTO, WHITE PRESET, (others?)
0x0006 Image Sharpening 2 - ascii string varies AUTO, HIGH, (others?)
0x0007 Focus Mode 2 - ascii string varies AF-S = Single autofocus
AF-C = Continuous autofocus
0x0008 Flash Setting 2 - ascii string varies NORMAL, RED-EYE, (others?)
0x000A Unknown 5 - unsigned rational 1 Always (?) 8832/1000
0x000F ISO Selection 2 - ascii string varies MANUAL = User selected
AUTO = Automatically Selected
0x0080 Image Adjustment 2 - ascii string varies AUTO, NORMAL, CONTRAST(+), B & W, (others?)
0x0082 Auxiliary Lens 2 - ascii string varies OFF, FISHEYE 2, WIDE ADAPTER (others?)
0x0085 Manual Focus Distance 5 - unsigned rational 1 Distance in Meters if focus was manually selected, otherwise 0
0x0086 Digital Zoom 5 - unsigned rational 1 Digital Zoom Factor
e.g. 140/100 = 1.4x digital zoom
0x0088 AF Focus Position 7 - undefined 4 0,0,0,0 = Center
0,1,0,0 = Top
0,2,0,0 = Bottom
0,3,0,0 = Left
0,4,0,0 = Right
0x0010 Data Dump 7 - undefined 174 varies
* Shows observed values and likely interpretation for data contained in these tags. These is not meant to be an exhaustive listing

Credits: Thanks to Olivier Scherler and TsuruZoh Tachibanaya for decoding the auxiliary lens tag.
Additional information: