EXIF inconsistency

[Guest]

Archived from groups: rec.photo.digital (More info?)

This seems very strange, and I'd appreciate any suggestions as to the
cause please.

In IrfaNview 3.95 I viewed a JPG. First the original HD file and then
the identical file burned to a CD with Nero. All EXIF entries are
identical *except* the following 3 (and the File path of course):

Value........
EXIF Tag From HD From CD
--------- ------- -------
ExifImageWidth 1360 2048
ExifImageHeight 2048 1360
InteroperabilityOffset 531 582

I don't know what 'InteroperabilityOffset' is, but I can say that the
HD version is correct and the CD version incorrect on the first two
entries, as this was a photo in portrait mode.

FWIW, here are the other identical tags:

EXIF Tag Value
-------- ------
Make SONY
Model CYBERSHOT
Orientation Top left
XResolution 72
YResolution 72
ResolutionUnit Inch
DateTime 2004:04:05 11:18:48
YCbCrPositioning Co-Sited
ExifOffset 224
ExposureTime 1/626 seconds
FNumber 5.60
ExposureProgram Normal program
ISOSpeedRatings 100
ExifVersion 0210
DateTimeOriginal 2004:04:05 11:18:48
DateTimeDigitized 2004:04:05 11:18:48
ComponentsConfiguration YCbCr
CompressedBitsPerPixel 2 (bits/pixel)
ExposureBiasValue 0.00
MaxApertureValue F 2.83
MeteringMode Center weighted average
LightSource Auto
Flash Not fired
FocalLength 9.20 mm
FlashPixVersion 0100
ColorSpace sRGB
FileSource DSC - Digital still SceneType A directly
photographed image

I've also emailed IrfanView's author.

--
Terry, West Sussex, UK

 

[Guest]

Archived from groups: rec.photo.digital (More info?)

"Terry Pinnell" <terrypinDELETE@THESEdial.pipex.com> wrote in message
news:kf0tt0tvbdmsk4jcambfeubigbs9eklu9d@4ax.com...
> This seems very strange, and I'd appreciate any suggestions as to the
> cause please.
>
> In IrfaNview 3.95 I viewed a JPG. First the original HD file and then
> the identical file burned to a CD with Nero. All EXIF entries are
> identical *except* the following 3 (and the File path of course):
>
> Value........
> EXIF Tag From HD From CD
> --------- ------- -------
> ExifImageWidth 1360 2048
> ExifImageHeight 2048 1360
> InteroperabilityOffset 531 582
>
> I don't know what 'InteroperabilityOffset' is, but I can say that the
> HD version is correct and the CD version incorrect on the first two
> entries, as this was a photo in portrait mode.
>
> FWIW, here are the other identical tags:
>
> EXIF Tag Value
> -------- ------
> Make SONY
> Model CYBERSHOT
> Orientation Top left
> XResolution 72
> YResolution 72
> ResolutionUnit Inch
> DateTime 2004:04:05 11:18:48
> YCbCrPositioning Co-Sited
> ExifOffset 224
> ExposureTime 1/626 seconds
> FNumber 5.60
> ExposureProgram Normal program
> ISOSpeedRatings 100
> ExifVersion 0210
> DateTimeOriginal 2004:04:05 11:18:48
> DateTimeDigitized 2004:04:05 11:18:48
> ComponentsConfiguration YCbCr
> CompressedBitsPerPixel 2 (bits/pixel)
> ExposureBiasValue 0.00
> MaxApertureValue F 2.83
> MeteringMode Center weighted average
> LightSource Auto
> Flash Not fired
> FocalLength 9.20 mm
> FlashPixVersion 0100
> ColorSpace sRGB
> FileSource DSC - Digital still SceneType A directly
> photographed image
>
> I've also emailed IrfanView's author.
>
> --
> Terry, West Sussex, UK
>
FWIW, my camera (S1 IS) puts the orientation (P/L) in the EXIF file and
displays the thumbnail oriented correctly (viewfinder/LCD screen) when
reviewed in the camera. Some other software also automatically rotates
(JAlbum, for one). Although I use IrfanView for quick viewing and slide
shows on my PC, I use either Exifer (which shows 35mm 'equivalent' focal
lengths/viewpoints? with the zoom multiplier relative to the shortest focal
length & the digital zoom multiplier seperately) and Exif Viewer, which
doesn't how the real zoom multiplier but does have the useful picture
comparison & statistics options.
http://www.exif.org/ is a useful site for info :-
"EXIF.org is a site dedicated to EXIF and related resources. EXIF stands for
Exchangeable Image File Format, and is a standard for storing interchange
information in image files, especially those using JPEG compression. Most
digital cameras now use the EXIF format. The format is part of the DCF
standard created by JEIDA to encourage interoperability between imaging
devices. "

 

[Guest]

Archived from groups: rec.photo.digital (More info?)

Terry

>>In IrfaNview 3.95 I viewed a JPG. First the original HD file and then
>>the identical file burned to a CD with Nero. All EXIF entries are
>>identical *except* the following 3 (and the File path of course):

I'm not sure what you mean when you say the "identical" file. Is it just a
straight copy of the jpeg file onto CD or did you use some photo-aware
package to make the CD copy?

If you just did it by, say, dragging and dropping the HD file into Nero, no
way can the EXIF data be different. Applications like Nero just copy files
as lumps of arbitrary data and wouldn't recognise an EXIF header if one
jumped out and bit it. A file copied to CD by Nero should be byte-for-byte
identical to the original.

>>I don't know what 'InteroperabilityOffset' is...
The header information on a photo contains a number of data structures
called "Image File Directories" (IFDs). Each IFD can contain an arbitrary
number of items. Information tends to be grouped into different IFDs
depending upon type. For example, there are separate IFDs for information
pertaining to the main image and the thumbnail (if present). All the camera
settings (exposure etc.) will be in another IFD called, surprise surprise,
the Camera Information IFD.

One of the IFD's is called the "interoperability IFD" and contains,
according to the EXIF spec, "tags which store information to ensure
interoperability" (whatever that means).

The Interoperability offset is simply the offset of the interoperability IFD
within the jpeg file, telling processing software where to find this data.
Quite _why_ I should want to find the interoperability IFD I don't know,
because I've never found any useful information in it.

When creating a photo file, application software and cameras have a lot of
flexibility what to store where in which IFD, and the order of the data.
Applications and cameras can also insert arbitrary "padding" into the file
between data blocks. Cameras frequently do this to keep important
information at fixed offsets. This helps to keep the camera firmware
simpler and therefore smaller.

It is therefore possible for the "same" photo with the "same" header info to
have wildly differing file sizes and/or to store the header information in
completely different orders.

>>EXIF Tag From HD From CD
>>InteroperabilityOffset 531 582

What this says is that the Interoperability IFD is 51 bytes further up the
file on the CD compared with the file on the HD. This implies to me that
some sort of photo-aware application package has processed the file before
it was stored on CD.

Keith