What exactly is happening to a Raw photo when it becomes a JPEG and what about Raw photos are so preferable for photo editing
In: 239
The simplest explanation is that a JPEG is an image, where every pixel’s color and brightness is defined. A Raw photo is not an image, per se, it’s a file that contains all the data collected by the camera. You can then take that data and turn it into a JPEG by selecting how you want to render that data, so it’s infinitely flexible, whereas a JPEG is already an image where those decisions have been made (either automatically by the camera or by a user during editing).
JPEG mainly compresses data by using a set of 2D cosine waves to approximate an image. This may sound ridiculous at first, but a surprisingly low amount of cosine waves with different frequencies and amplitudes are necessary to approximate a function. (This process is called a Fourier Transform).
If the colors in the image varies greatly, the approximation will perform worse.
Various other alterations to the colors of the image will also occur that enables a better approximation.
All of this reduces the quality of an image, which is not preferable when you want to layer on even more edits with your photo editor.
JPEG mainly compresses data by using a set of 2D cosine waves to approximate an image. This may sound ridiculous at first, but a surprisingly low amount of cosine waves with different frequencies and amplitudes are necessary to approximate a function. (This process is called a Fourier Transform).
If the colors in the image varies greatly, the approximation will perform worse.
Various other alterations to the colors of the image will also occur that enables a better approximation.
All of this reduces the quality of an image, which is not preferable when you want to layer on even more edits with your photo editor.
JPEG mainly compresses data by using a set of 2D cosine waves to approximate an image. This may sound ridiculous at first, but a surprisingly low amount of cosine waves with different frequencies and amplitudes are necessary to approximate a function. (This process is called a Fourier Transform).
If the colors in the image varies greatly, the approximation will perform worse.
Various other alterations to the colors of the image will also occur that enables a better approximation.
All of this reduces the quality of an image, which is not preferable when you want to layer on even more edits with your photo editor.
ELI5:
Raw is the entire lego set, with extra pieces that came in the box and the instructions.
JPEG is the completed set glued together and nothing else.
Raw lets you change it, read the instructions and see more about how it was made, but takes more space.
JPEG you can add to it a little bit, but you can’t go back once you glue it together unless you keep a copy. any extra info is lost.
Saving an image as a jpeg throws away most of the information that the image originally had, in order to make the file size smaller. A RAW image file has all of the information that the camera can provide.
If you want to edit the image later, to tweak the colors or remove redeye or whatever, you want to use the RAW version that has all of the information. If you edit (and then resave) jpegs, you’re losing _more_ of what little of the original information was still in the jpeg. Do this too many times and your picture becomes horribly blocky and blurry like an old meme that’s been passed around too many times.
ELI5:
Raw is the entire lego set, with extra pieces that came in the box and the instructions.
JPEG is the completed set glued together and nothing else.
Raw lets you change it, read the instructions and see more about how it was made, but takes more space.
JPEG you can add to it a little bit, but you can’t go back once you glue it together unless you keep a copy. any extra info is lost.
ELI5:
Raw is the entire lego set, with extra pieces that came in the box and the instructions.
JPEG is the completed set glued together and nothing else.
Raw lets you change it, read the instructions and see more about how it was made, but takes more space.
JPEG you can add to it a little bit, but you can’t go back once you glue it together unless you keep a copy. any extra info is lost.
A lot of people have mentioned that jpeg is “lossy compression”. This means that there is a lot less information than in the raw image.
What other people have not mentioned yet is why jpeg looks so good _despite_ so much information being discarded.
Your eyes are pretty good, but they aren’t perfect. You will have experienced this when looking at something which is far away, like a mountain. You don’t feel like you are missing out on anything, but to see distant details you know that you will need binoculars.
What jpeg does is remove the information that you would only perceive in an image if you zoomed into it. If you don’t zoom in, you will not know it is missing.
If you are a professional photographer, you want this information (that you can’t normally see) because the processing you might want to do could bring that information into the perceptible range.
You can try it yourself. Take an image and save it as a JPEG with extreme compression, and then zoom into it. You will see the artefacts introduced by the lossy encoding.
A lot of people have mentioned that jpeg is “lossy compression”. This means that there is a lot less information than in the raw image.
What other people have not mentioned yet is why jpeg looks so good _despite_ so much information being discarded.
Your eyes are pretty good, but they aren’t perfect. You will have experienced this when looking at something which is far away, like a mountain. You don’t feel like you are missing out on anything, but to see distant details you know that you will need binoculars.
What jpeg does is remove the information that you would only perceive in an image if you zoomed into it. If you don’t zoom in, you will not know it is missing.
If you are a professional photographer, you want this information (that you can’t normally see) because the processing you might want to do could bring that information into the perceptible range.
You can try it yourself. Take an image and save it as a JPEG with extreme compression, and then zoom into it. You will see the artefacts introduced by the lossy encoding.
Latest Answers