Yes of course, everone knows nconvert.exe.. don't you ?!.. o) Ok.. let's be serious.. o)
I had a test on my own, as you suggested and found out:
"SetAttr META *" does NOT remove the thumbnail and it does not remove all exif/meta information from a jpg either, just a subset.
Following information is still present after running setattr, but I guess the command just isn't meant to remove every single bit of information from jpg-files.
[ Overview ]
Program: Not defined
White Balance: Auto
Flash: Flash did not fire
[ JPEG ]
Application Segment 0 (JFIF): 0x00000006
Application Segment 1 (Exif): 0x00000018
Encoder: Independent JPEG Group library (used by many applications), Quality: 85
and maybe some other software or cameras
Encoder Signature: 98DEC36FE95ED7C1772D9ED67A67E260:221111
Color Mode: RGB color
Subsampling ratio of Y to C: YCbCr4:2:0
Encoding Process: Baseline DCT, Huffman coding
Bits per Sample: 8 bps
Image Height: 3000 px
Image Width: 4000 px
Number of image components in frame: 3 comp.
[ Image ]
Orientation of image: 0° (top/left)
Image resolution in width direction: 180 dpi
Image resolution in height direction: 180 dpi
Unit of X and Y resolution: inch
File change date and time: 2012-07-25 10:37:22
Y and C positioning: Co-Sited
Exif IFD Pointer: 0x0000023A
PRINT Image Matching: 0x000000AA
[ Thumbnail Info ]
Compression scheme: JPEG (old-style)
Orientation of image: 0° (top/left)
Image resolution in width direction: 180 dpi
Image resolution in height direction: 180 dpi
Unit of X and Y resolution: inch
Offset to JPEG SOI: 0x00002A44
Bytes of JPEG data: 6423 bytes
Y and C positioning: Co-Sited
[ Camera ]
Exposure program: Not defined
??? (8830): 1
Exif version: 2.3
Date and time of original data generation: 2012-07-25 10:37:22
Date and time of digital data generation: 2012-07-25 10:37:22
Meaning of each component: YCbCr
Image compression mode: 4 bpp
Maximum lens aperture: 3.36 Av (F3.2)
Metering mode: Unknown
Light source: Flash
Flash: Flash did not fire
Manufacturer notes: 0x000003D4
Supported Flashpix version: 1.0
Color space: sRGB
Image width: 4000 px
Image height: 3000 px
Interoperability IFD Pointer: 0x000029B0
Sensing method: One-chip color area sensor
File source: Digital Camera
Scene type: A directly photographed image
Custom image processing: Custom process
Exposure mode: Auto exposure
White balance: Auto
??? (A404): 0
Scene capture type: Standard
Gain control: None
Contrast: Normal
Saturation: Normal
Sharpness: Normal
[ Interoperability ]
Interoperability Identification: R98: DCF basic file (sRGB)
Interoperability Version: 1.0
[ JPEG File Interchange Format ]
JFIF Version: 1.01
Units for the X and Y densities: X and Y are dots per inch
Horizontal pixel density: 72 dpi
Vertical pixel density: 72 dpi
Thumbnail horizontal pixel count: Not set
Thumbnail vertical pixel count: Not set
[ PRINT Image Matching ]
PrintIM Version: Version 2.5
??? (0001): 0x00160016
??? (0002): 0x00000000
??? (0003): 0x00000064
??? (0007): 0x00000000
??? (0008): 0x00000000
??? (0009): 0x00000000
??? (000A): 0x00000000
??? (000B): 0x000000AC
??? (000C): 0x00000000
??? (000D): 0x00000000
??? (000E): 0x000000C4
??? (0100): 0x00000005
??? (0101): 0x00000001
??? (0110): 0x00000080
When run through "nconvert" what's left in the image-file is this, saving some 20-40kb (quite an amount of data, if you generate thumbnails for web-usage e.g):
[ Overview ]
nothing.. o)
So thanks, my question is answered.. o)