View Full Version : EXIF Thumbnail

10.02.2009, 05:17 PM
My camera's EXIF shows a thumbnail is present, but when I try to view the embedded thumbnail in a program like XnView, it doesn't recognize it. What is this thumbnail then?

Thumbnail: -
Compression - 6 (JPG)
Orientation - Top left
XResolution - 72
YResolution - 72
ResolutionUnit - Inch
JpegIFOffset - 703
JpegIFByteCount - 12300
YCbCrPositioning - Co-Sited

15.03.2009, 08:32 PM
Looks like a thumbnail to me Skippybox. Why not have a look in Wildbit Viewer. The EXIF info there includes the thumbnail.
You have to be careful with programs like XnView that cache the thumbnails. After you change the option you need to clear the cache, exit the program and re-open before you see the changed thumbnail.
Worth making a test jpeg by copy and pasting something completely different over one of your camera images and saving that. Then you can see quite easily whether it is showing your pasted image or the original EXIF thumbnail.

16.03.2009, 04:34 PM
Tried Wildbit, and it appears to be a thumbnail. In XnView I have caching disabled, but still, the little embedded thumbnail icon does not show. Have a test with this picture for yourself in XnView. What could be going on? Is XnView just no good?

21.03.2009, 05:13 PM
Sorry Skippybox, I have been busy for the last couple of days and have not checked all the postings. I took your image and pasted part of another on top and saved that with EXIF data. That way I could tell what was derived from the image and what from the EXIF data.

When looking at the EXIF data in Wildbit the original embedded thumbnail was still there. With the cache turned off and cleared, I could then view a thumbnail either original or reduced from the image by turning the Extract from EXIF data option On and Off. That all works as advertised.

Doing the same in XNView though I could not find any way of viewing the original embedded thumbnail whatever I did. So, yes, I agree this EXIF extraction of thumbnails does not appear to work in XNView.
I did check in Wildbit again later to make sure that the original EXIF thumbnail was still there.

IrfanView of course also shows a reduced version of the main image as a Thumbnail all the time, but does not claim to do otherwise.

21.03.2009, 06:52 PM
That is perfectly understandable, which is why I reminded you, in case you were overlooking it. Thanks for confirming that XnView is the flaw here. Perhaps I will report this abnormality. Strange, in that most other photos from other cameras show the thumbnail OK.

21.03.2009, 10:34 PM
Maybe the purpose of allowing EXIF extraction is just to supply a thumbnail as quickly as possible, so is designed to use whatever method will do it fastest. That would then depend on file size.
If so, then your assumption of always seeing the EXIF thumbnail when the option is checked may be wrong.

21.03.2009, 10:59 PM
That is an interesting perspective that I had not thought of. However, the embedded thumbnail of the images you gave me (Statue and Pavement) are shown, and they are much smaller both in dimensions and filesize. Wouldn't smaller files take longer to decompress anyhow?

22.03.2009, 04:57 PM
That is an interesting perspective that I had not thought of. However, the embedded thumbnail of the images you gave me (Statue and Pavement) are shown, and they are much smaller both in dimensions and filesize. Wouldn't smaller files take longer to decompress anyhow?

I would imagine that smaller files decompress faster. As I recall those two images had EXIF rotation. Perhaps it is quicker to use the EXIF thumbnail then since it is already rotated upright. You will probably have to join the XNView forum to find out more about how it works.

23.03.2009, 08:14 PM
While smaller files may decompress faster, I was really referring to higher compressed ones. Cameras do have several compression offerings. Mine has two; I'm using the better quality one. So, I would think less compression, faster load time? That would lend to your theory, but so far resaving the image has not forced the thumbnail either.

I don't think this whole "quickness" idea is true, as there really is no evidence of it. The dialog nor the help file mention anything about substitutions of this nature either. But, you know how those things are. I will try the forum.

Actually, your embedded thumbs are not already rotated, only when :eek: auto-rotate is enabled.

27.03.2009, 05:35 PM

Update: Well two people have confirmed it now, including the program author. But, then the moderator noticed something interesting.

jhead.exe -st "thumbnails\&i" *.jpg produced:
Nonfatal Error : '2008.11.06 (006).jpg' Illegal number format 32 for tag 010f

JPEGsnoop v1.3.0 revealed:
*** Marker: COM (Comment) (xFFFE) ***
OFFSET: 0x00003415
Comment length = 18
Comment=Camera .MISC

NOTE: JFIF COMMENT field is known software
Based on the analysis of compression characteristics and EXIF metadata:

ASSESSMENT: Class 1 - Image is processed/edited

The real problem though Mij, is that the JPEG is not JFIF-compliant (JPEG File Interchange Format), because it is a popular JPEG-DCF (Design rule for Camera File system) file. My file is missing the APP0 marker for JFIF and uses only the APP1 marker instead, for DCF. So, I guess XnView is not DCF-aware, and strictly interprets JFIF JPEGs. The thumbnail though, seems to be the only thing not detected. Obviously, if both markers were present in the proper order, it would be detected by XnView. Most software should be able to handle this incompatibility in my file, but it appears XnView has not updated the code to accept such files. Apparently, WildBit has.

27.03.2009, 08:29 PM
Nice to know why. Does it give you a way forward though?

27.03.2009, 09:14 PM
Hopefully this will draw attention to the flaw in XnView, and it will be solved in a future version if the author so desires.

Of course, this is a flaw in the design of several cameras. Now, I could use a program like JPEG-JFIF Repair (http://www.tow.com/software/jpeg-jfif_repair/), but it is only available for the Mac. :( Still, it would be a big effort.

Someone has suggested transplanting good EXIF to each image using jhead, then rebuilding the thumbnail using XnView or some other software. But, that would be silly to make a giant duplicate set of all my pictures. It is also yucky since the EXIF wouldn't even match. Can you imagine?

So, I can either wait, use another program that can accomodate the DCF standard, or forget about this. While not a solution, maybe I'll get a new camera soon. :D

28.08.2009, 07:15 PM
Well, I decided to just get a new camera (http://en.irfanview-forum.de/vb/showpost.php?p=24534&postcount=11)!