45

This is the inverse of Is there any software which will set the EXIF Dates based on the file's modification date?, and I'm sure all of the programs listed there will apply. jhead Of these, for this very simple task, jhead is my suggestion. For example, the command jhead -ft *.jpg sets a bunch of files so that the file timestamp matches EXIF. jhead ...


36

This is most likely caused by entropy coding, which is the final lossless stage of JPEG compression, after the image data has been quantized to reduce its size. When a JPEG image is losslessly rotated, this final lossless encoding layer must be undone, the unpacked DCT coefficients shuffled around, and then the shuffled coefficients need to be entropy coded ...


34

In short: there is no reason to care about this value and it its presence does not make your file larger. identify -verbose filename(s) only displays the quality if the image uses the standard quantization matrix. You can use nonstandard matrix (-define jpeg:q-table=...) to make this value disappear. The quality will be, however still displayed when the (...


24

I went ahead and repeated the experiment to see if I could figure out what's going on. Procedure I generated a random 256-by-256 pixel RGB image using the "Solid Noise" filter in GIMP (Filters > Render > Clouds > Solid Noise...) using the default settings (shown below): And the result: Then I saved the image as a JPEG using the default settings: Then I ...


20

EDIT: This answer was posted before I knew that the files had increased in size by around 9 KiB (9055 bytes for the 256×256 image, 9612 KiB for the 512×512 image). In all likelihood, when you first rotated the image, Windows Picture Viewer did one (or both) of the following things: Added an EXIF tag that was not in the original JPEG image (perhaps the ...


20

Well, for one thing, all photos larger than 16 megapixels are resized to 16 MP — so, for many cameras today, that's an immediate, obvious drop in resolution. But all other photos are compressed too, using an optimizing compression algorithm. I don't think Google comes out and says exactly what they do, but it's probably their open source Guetzli algorithm. ...


19

Adobe's XMP metadata standard supports information defined by the Metadata Working Group (MWG), which includes a definition of how to store face tagged data. See: Adobe XMP: http://www.adobe.com/products/xmp/standards.html MWG: http://www.metadataworkinggroup.com/ where you can click on the specifications, download the PDF, and then look at page 51 ...


18

The Exif:ApertureValue is stored as an APEX value as mandated by various EXIF standards. The APEX system is a way to calculate exposure and works using base-2 logarithms. The use of base-2 means a rise of one in the value equates to a doubling, which we know as 1 stop; which makes it pretty handy for photographers if they're good with logarithms (which we ...


17

Yes, it is possible. But you should not do this. Being dishonest with your teacher is never a good move. If you have a mirrorless interchangeable lens camera with a large sensor, you may be able to convince your teacher that what you have is significantly close to a DSLR to work for the needs of the class. It's probably a good idea to ask exactly what she's ...


16

From the man page: -s (-short) Short output format. Prints tag names instead of descriptions. Add up to 3 -s options for even shorter formats: -s - print tag names instead of descriptions -s -s - no extra spaces to column-align values -s -s -s - print values only so, exiftool -s -s -s -...


16

When the engineers are designing a lens, the 70-300 is a target focal range they design to, but it's not important that they hit it exactly as long as it covers the advertised range. As they tweak the lens characteristics to get a suitably sharp and quality image for the target cost, the actual focal lengths may change slightly. Eventually, when everything ...


16

I don't know what is required to recognize the "foreign" image, probably something in the Exif... but for your goal, just create the image with your message, with appropriate background, and take a picture of it when showing on the home computer screen. Then it is already in the camera.


15

Using ExifTool, ShutterSpeed is not an actual tag within the file, it's a tag derived from several other values (See Extra Tags). That's why it's grouped under Composite Tags when you follow ExifTool FAQ 3. As you discovered, the actual tag you want to write to is EXIF:ExposureTime using ExifTool.


14

Using Picasa (3.8) it's very easy to either shift or set the date of a batch of photos. And it's cross-platform (Windows, OSX and Linux) and free. And no terminal fiddling... Open Picasa Select your photos Click Tools > Adjust Date and Time Fill in as required (see screenshot)


14

Most of the time you have more use of the position from where you took the photo. If you know from where the picture was taken, you can often from the photo see exactly which direction the camera was pointed. If you know the position of the subject, you might be able to see approximately which direction it was taken from, but seldom the exact position. Of ...


13

Privacy reasons are certainly the main concern. The second concern is bandwidth. Stripping EXIF information makes images considerably lighter at web-sizes. This makes it a better experience of 99% of viewers who do not care about how the image was made. Lastly, the information may not exist. A lot of images on the web are composites, be it HDR/Exposure ...


13

For whatever reason, the ColorSpace tag is not very useful in EXIF. The only standard values are 1 (sRGB) and 65535 ("uncalibrated"). All other values are reserved. Some cameras use them to mean Adobe RGB or something else, but this is non-standard. Apple is, in fact, using Something Else, and that's found elsewhere in the metadata. With ExifTool, looking ...


13

Experimentally (on my EOS 70D), this is the beginning of the exposure, and not the end. But: this seems truncated to the second it depends how accurate is the time of the camera (before doing this I carefully set the time on my camera, but I doubt I can do better than half a second) ... not speaking of clock drift if it hasn't been set recently IMHO a ...


12

The first thing I did not know from the beginning was that keywords are hierarchical. Based on your question, I see you know that so you are already ahead of where I started. Other than that: Make clear a hierarchy that has an unambiguous meaning even at the expense of being redundant. For example, city hall can be anywhere but montreal city hall has to be ...


12

Irfanview and jhead will both do what you want. Both free. Links to both below. jhead is command line driven or can be called by other processes. Irfanview version can be invoked from a command line or internally in a batch or on a file by file basis. Example below for Irfanview shows how to copy in either direction: Irfanview Allows GUI or command line ...


12

It is sadly impossible to to prove when an image (or any file for that matter) originated. It is possible (if the author wants to) to prove that a file existed prior to a given time by signing the file from a third party time stamping server (through which the third party proves that the file existed at the time of the signing) but such information is not ...


12

ExifTool is a cross-platform tool which will work from the Windows command line. It is very powerful, with a perl-based syntax allowing comparison of various metadata. In a directory full of JPEG files, this command will print a list of all files where the beginning of the filename does not match the year from the date-taken EXIF value: exiftool -d "%Y" -...


12

This isn't metadata that can be stripped. It's an analysis of the compression calculated from the quantization tables. When it's comes back unknown, the jpeg was compressed using a program that isn't known to identify. See this SuperUser answer. Edit: Upvotes for @szulat answer, much more detailed than mine.


11

Yes, this capability exists to some extent, but not through "signing" the image in the normal sense. It's based on the sensor noise patterns. Jan Lukáš, Jessica Fridrich, and Miroslav Golja (and a few others) at SUNY Binghamton have done work relating to two fields - identification of digital cameras using sensor noise patterns and identification of digital ...


11

Photoshop Lightroom does this with the "map" tab. Here is an example of my shots mapped with it: You can download a free trial from Adobe or purchase it for $100-150USD.


11

Your camera saves this information, which we call "metadata" (because it is data about the data captured in the photo itself — one level beyond, or meta), in every file. There are many utilities which can read and display this. I'm not aware of any software designed for photography which doesn't — that'd include Adobe Photoshop and Lightroom, Picassa, and ...


11

As the author of StolenCameraFinder, I am somewhat biased ;) Both sites have published success stories. Here are my success stories, and here is one from CameraTrace. I actually have more stories in my email, I'm just pretty rubbish at typing them up ;) With both sites, you can run searches for free manually, just try them out and see what results you get. ...


11

The EXIF standard describes the DateTimeOriginal tag simply as "the date and time when the original image data was generated." It gives no guidance about what event (e.g., shutter released, shutter open, shutter closed, sensor read, post processing) should be used to determine the value. As mentioned in a comment, the best way to find out how your camera ...


10

Yes, they can sign images. This should prove authenticity although a team claims to have cracked Canon's implementation. Another team did the same for Nikon. So this is like most digital security issues, it will prove authenticity or monumental effort to circumvent it ;)


10

For instance, sensor noise should be rather consistent if the photos were taken with the same camera, pretty much like firing a handgun and the bullet gets unique marks. Bingo - that's right on the money. There are two aspects research aspects that I'm familiar with when I worked in this area in 2006-2007. The first was the identification of the make and ...


Only top voted, non community-wiki answers of a minimum length are eligible