Metadata

Learning goal

You will be able to read, edit and check before sharing the information a photo file carries alongside the image. You will tell apart the EXIF information the camera writes by itself, the geotag a phone adds, and the keyword and copyright information you write; you will see why setting the camera's clock correctly protects your date folders; you will learn from the EXIF information of your own frames, especially the exposure compensation values; and you will make it a habit to remove the location when sharing a photo, so as not to reveal by accident where your home is, where a child is, or where a person you photographed lives.

The question

A day after getting the frame where she blew out the candles, your aunt shares it on social media. In the evening a cousin calls you: they downloaded the photo's file, opened the file information on their computer, and a map came up; on it, a small pin standing right in the garden of your grandmother's house. In the same window it also says which camera and which lens the photo was taken with, at what time, its aperture and its shutter speed.

What hidden information is inside a photo? Where does this information, which someone looking at the image can't see but which goes everywhere with the file, come from, what is it for, and when does it turn into a risk? In this lesson we will talk about the information a photo carries outside the image: metadata.

Context

Think of a letter. The paper inside the envelope is the real text; but there is information on the envelope too: the sender's and recipient's addresses, the date of the stamp, the post office's postmark. Someone reading the letter usually doesn't look at the envelope; but the envelope can tell more clearly than the text where, when and to whom the letter went. A photo file is like this too: the image is the letter, the metadata is the envelope.

This envelope is usually a helper. It is what builds the date folders, lets you find a photo years later with a word, and helps you learn from your own shoots. But the address on the envelope, when the photo passes into other people's hands, can also reach people you don't want it to. This lesson teaches reading the envelope, editing it, and tearing it up when needed.

Simple explanation

What information is inside the file?

Metadata is data about data: not the photo itself, but the information that describes the photo. The camera writes part of it by itself. Among this information, called EXIF, are the model of the camera and the lens, focal length, aperture, shutter speed, ISO, exposure compensation, white balance, whether the flash fired, the date and time of the shot, and often the camera's serial number. Phones and some cameras that connect to a phone also add a geotag, that is, the latitude and longitude of the place where the shot was taken.

Part of it you write. A keyword is a short word you add to a photo to search for it later: "birthday," "garden," "candle," "grandma." Copyright information is the line that states the photo's owner and its terms of use: your name and a copyright notice. On many cameras you can write this information into the menu once and have it added to every frame by itself. Editing programs often write additions like keywords and star ratings for RAW files to a small side file that sits next to the file; when moving the RAW, you need to move this side file along with it.

What is metadata for?

Metadata's quietest but most important job is the date. The date folders you built in the previous lesson rely on the camera's clock. If the camera's clock is wrong, or the time zone wasn't changed on a trip, photos land on the wrong day. If you use a camera and a phone together in the same shoot, there is a simple way to sync their clocks: at the start of the shoot, take a photo with both devices of a screen showing the same time; correcting the difference later becomes easy.

EXIF is also a way of learning from your own shoots. When you read the settings of frames you like, you see which aperture and shutter speed you chose in a particular light, and where you set exposure compensation. When you compare two portraits shot in the same window light, you may notice that in the frame where your dark-skinned friend's face came out detailed you set compensation to plus, and in the frame where your light-skinned friend's forehead didn't blow out you set it to minus. This record lets you know what to set and why on your next shoot, not from memory but from your own experience.

What do you watch for when sharing?

A geotag is usually recorded with a precision of a few meters. A photo you took at your home, at a child's school or at a friend's door can, when its file is downloaded, also give that place's address. Some sharing services delete the location information of uploaded photos, some don't; sending a photo by message as a document, on the other hand, usually carries all the metadata as it is. Rather than trusting what each service does, it is safer for you to remove the information before sharing.

There are two ways for this: turning off location recording in the phone's camera, or using the option that removes location information when exporting. Most editing programs offer, during export, the option to delete the location and other personal information and leave only the copyright information. This care isn't only for yourself: when the face of a person you photographed and the location of their home come together in the same file, who that person is and where they live is revealed in a moment. You also need to decide with this in mind whether to write people's full names in the keywords.

Visual evidence

After your cousin's call, you write to your aunt and ask her to take down the post. Then you open the original of the candle frame in the editing program and look at the metadata window: the date and time are right, focal length 35 millimeters, aperture f/2, shutter speed a sixtieth of a second, ISO 3200, exposure compensation plus two-thirds of a stop, and also the garden location added by the camera paired with your phone. When you look at the other frames from the same night, you see that in all the frames where your uncle's face came out cleanest the compensation was on plus, while in the child's frames facing the lantern it stayed at zero; you now know what to watch for at the next dinner.

You add the keywords "birthday," "grandma," "candle," "garden" and a copyright line with your name to the frame. In the export window you tick the remove location option and produce a new copy, and send this copy to your aunt. When you open the copy's file information, the map window is empty, but your name and copyright line are in place. You also write the copyright information once in the camera's menu; from now on every frame will be born with your name.

Common mistakes

Summary

Metadata is the information a photo carries outside the image: the EXIF the camera writes, the geotag a phone adds, and the keyword and copyright information you write. A correctly set camera clock protects the date folders, keywords let you find a photo years later with a word, and EXIF, with values like exposure compensation, lets you learn from your own shoots what showed a face well on every skin. Removing the location before sharing, on the other hand, is the simplest way not to reveal by accident where you and the people you photograph live.

Mini assignment

In this assignment you will open and edit the envelope of your own photos.

1. Check the clock and time zone of your camera and your phone; take a photo with both devices of a screen showing the same time and note the difference between them.
2. Open three frames you like in an editing program and compare their EXIF information, especially the exposure compensation values.
3. Add three or four keywords and a copyright line with your name to one shoot; set the copyright information in the camera's menu too.
4. Look at the location information of a photo you took with your phone; then check that the map stays empty in a copy you exported with the location removed.

Check yourself

• Is your camera's clock right, and do you know the difference between the two devices?
• From the EXIF information, were you able to work out where you set compensation in frames that showed faces of different skin tones well?
• Did the last photo you shared have location information?

Glossary

Mini quiz

1. Which of these does the camera write by itself as EXIF information?

• A) Aperture, shutter speed and ISO
• B) The keywords you added
• C) The photo's title
• D) The place where the photo was shared

2. If the camera's clock is set wrong, what breaks the most?

• A) The photo's colors
• B) The photo's sharpness
• C) The date folders and which day the photos land on
• D) The file's size

3. When you send a photo by message as a document, what usually happens to the metadata?

• A) It is deleted by itself
• B) Only the copyright information stays
• C) The location information is encrypted
• D) It is carried as it is

4. You want to learn from the portraits you took of two friends, one dark-skinned and one light-skinned, in window light. Which value in the EXIF is most useful to look at?

• A) The camera's serial number
• B) The exposure compensation value
• C) The file's name
• D) The location information

Answers

1. A — The shooting settings are written by the camera; keywords and the title are information you add.
2. C — Date folders rely on the camera's clock; a wrong clock lands photos on the wrong day.
3. D — A file sent as a document usually carries all the metadata as it is.
4. B — The compensation value shows where you set the exposure in the frames where the face came out detailed.

Summary card

• Metadata = the envelope: EXIF (camera), location (phone), keyword and copyright (you).
• The clock has to be right; sync two devices with a photo of the same screen.
• Learn from EXIF: where was compensation in the good frames?
• Move a RAW's side file along with it.
• Remove the location before sharing; don't reveal the address of the people you photograph.

Bridge to the next lesson

Over a whole evening, you placed your photos in date folders, wrote their keywords and added your copyright line; all of it sits on a single disk in your computer. If one morning you turn on the computer and the disk doesn't work, where do all that order and all those years go? The next lesson talks about backup and the 3-2-1 rule, built on three copies, two different media and one copy kept somewhere else.