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):
...
- 21.6k
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 ...
- 4,583
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 ...
- 5,045
27
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 ...
- 32.2k
27
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:
...
- 5,512
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 > ...
- 543
25
votes
Accepted
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 ...
- 32.2k
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, ...
- 143k
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 ...
- 9,539
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 ...
- 32.2k
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 ...
- 3,663
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 ...
- 143k
17
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 ...
- 1,192
17
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 ...
- 174k
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 ...
- 32.2k
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 ...
- 12.9k
14
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 ...
- 311
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 ...
- 143k
14
votes
Accepted
Does the EXIF data "DateTimeOriginal" get recorded at the start or end of the exposure?
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 ...
- 5,512
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 ...
- 658
13
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 ...
- 3,663
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 ...
- 20.3k
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 ...
- 32.2k
12
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 ...
- 3,663
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'...
- 3,663
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 ...
- 325
11
votes
How can I extract just the value of a tag without the name using exiftool?
Use -b:
$ exiftool -b -make x.jpg
From the man page:
-b (-binary)
Output requested metadata in binary format without ...
- 403
11
votes
Accepted
What does a pair of numbers in parentheses mean as a focal length value in metadata?
Values in Exif metadata can be stored as various data types, including ASCII text strings, "short" or "long" integers, or "rationals". A short integer is stored in two bytes; a long integer takes four ...
- 143k
11
votes
How can I rename files to match their EXIF "created date"?
For simple things where the flexibility, power, and complication of ExifTool aren't necessary, I like to use the tool jhead. It's a command-line tool available for Linux, Mac, and Windows.
...
- 143k
11
votes
How to efficiently stop metadata being in my photos?
Your camera does not have the option to disable Exif. I know of no camera that has the ability to enable and disable the saving of metadata.
Some old cameras from the 1990s do not save Exif metadata.
...
- 26.8k
Only top scored, non community-wiki answers of a minimum length are eligible