43 votes

How to check if a photo is edited (even basic edits like exposure and white balance)?

Being slightly harsh, competition rules like that show that the organisers don't really understand how modern cameras work. A very high level and simplified view of how a camera makes a image (JPEG): ...
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  • 19.8k
41 votes

If an image is rotated losslessly, why does the file size change?

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 ...
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34 votes
Accepted

Remove "quality" property from JPG

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 ...
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  • 4,845
28 votes
Accepted

How can I extract just the value of a tag without the name using exiftool?

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 ...
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  • 140k
26 votes

If an image is rotated losslessly, why does the file size change?

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 > ...
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25 votes

Can Exif data be copied completely from one image to another?

I suggest using the excellent exiftool by Phil Harvey: exiftool -TagsFromFile fromImage.jpg toImage.jpg See also questions 8 and 9 at the Exiftool FAQ if you're copying tags between certain RAW ...
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  • 31k
25 votes

What are ways to record who took the pictures if a camera is used by multiple people?

There isn't really any surefire way, other than meticulous bookkeeping, or following consistent habits. Some ideas: Use your mobile phone to take images of the rear LCD info page showing the file ...
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  • 31k
22 votes

How can I rename files to match their EXIF "created date"?

ExifTool is pretty much the Swiss army chainsaw for doing these kinds of things. It has a steep learning curve, but once you're over it, the kind of renaming you're after is a snap: exiftool -d '%Y%...
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  • 5,392
21 votes
Accepted

Google Photos high quality backup -- how does Google achieve great compression and am I losing some data?

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, ...
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  • 140k
20 votes
Accepted

How do XMP files encode aperture?

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 ...
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  • 9,430
20 votes

If an image is rotated losslessly, why does the file size change?

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 ...
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  • 31k
19 votes
Accepted

How to edit the shutter speed value in metadata?

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 ...
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  • 3,309
18 votes

Is it possible to make a photo's EXIF look like it was taken with a DSLR?

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 ...
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  • 140k
17 votes

How to check if a photo is edited (even basic edits like exposure and white balance)?

Submissions for these types of contests, and even some news agencies, require photos to be submitted as straight-from-camera JPEG files, not as exports of RAW images. This is usually enough to satisfy ...
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  • 31k
16 votes

How is actual focal length greater than focal range of lens?

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 ...
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  • 1,174
16 votes

Is there a way to write a "foreign" image so a Fujifilm X camera will display it?

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 ...
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  • 12.5k
16 votes
Accepted

How can I decode information on back of printed photo?

Those appear to be codes from a Fuji Frontier automatic film processing lab machine or one of its older predecessors. Such machines were/are popular at mass retailers who did/do one hour photo ...
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  • 168k
14 votes
Accepted

Which color space is used by my iPhone 8 photos?

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 ...
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  • 140k
14 votes

What are ways to record who took the pictures if a camera is used by multiple people?

Nikon D3400 (and, I assume, other models) lets you select the active folder to store files in. Just change folders when you change photographers. More generally, you can use two memory cards and ...
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13 votes
Accepted

How can the aperture value written in Exif be larger than the nominal limit of the lens?

You are confused because ApertureValue and MaxApertureValue are APEX values, not F-stops. An F-stop of 1.8 is equivalent to an APEX aperture value of about 1.695994. (The formula is Av=log₂A², where ...
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13 votes

Does the EXIF data "DateTimeOriginal" get recorded at the start or end of the exposure?

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 ...
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  • 16.3k
12 votes
Accepted

Software to cross-check EXIF date taken vs date in filename?

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 ...
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  • 140k
12 votes

When is each of these EXIF date & time variables created, and in what circumstances do they change?

You are correct about the [File] tags, they are info about the file from the underlying filesystem. Create Date/Time is the timestamp for when the file was created. I believe that File Modification ...
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  • 3,309
12 votes

How to add author and other properties to PNG files?

Edit: This answer is out of date. As of July 2017, PNG supports EXIF chunks. exiftool can edit PNG chunks, but Windows explorer apparently still does not support PNG chunks. See comments by posfan12 ...
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  • 31k
12 votes

Why don't Exif tags contain time zone information?

EXIF v2.31 (p49) defined time-zone offset fields in 2016 and the XMP time-zone guidelines (p33-34) also consider time-zones. The implementation in cameras and programs is rather minimalist at the ...
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  • 271
12 votes

Remove "quality" property from JPG

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'...
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  • 3,309
12 votes

What are ways to record who took the pictures if a camera is used by multiple people?

One solution that might work if you don't switch too frequently: Take a selfie whenever you take the camera. Then you know all following pictures have been made by the person of the most recent ...
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  • 305
11 votes

How can I see the photo settings like f-stop, ISO etc. of a image?

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 ...
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  • 140k
11 votes
Accepted

Do web-based photofinder services for stolen cameras work?

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 ...
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  • 5,956
11 votes

How to remove orientation attribute from the photo without touching other exif-data?

You can use exiftool to remove the orientation tag: exiftool -Orientation= /target/dir/or/File Replace /target/dir/or/File with the files and/or directories you want to process. If run under Unix/...
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  • 3,309

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