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
Inside of a camera, there is a chip called a sensor that has a bunch of tiny little dots on it. These dots are referred to as pixels. When you take a photo, the processor inside the camera records the exact amount of red, green, and blue light hitting each pixel. This information is then sent on for further processing. First, image corrections might be applied, like correcting the colors in an image based on the lighting in a room, or brightening up darker parts to make the picture look a bit better. Second, the camera will usually compress the image into a JPEG file.
A JPEG file is just a way to compress a photo down so it takes up less space on a device’s storage. The data coming off of a camera’s sensor is about 30-40MB which doesn’t seem that big by today’s standards, but back when digital cameras were first becoming popular, the biggest memory cards you could buy were only around 32MB in size, which wasn’t big enough to hold even a single photo! So, a bunch of scientists got together and created some amazing math that is really good at compressing an image to the point where it doesn’t appear much different to a human but is still a small fraction of the size of the original.
To compress a photo, the JPEG algorithm first reduces some of the color information stored about a photo. The human eye is more sensitive to difference in brightness than it is to differences in color, so for most people, it’s perfectly okay to just throw some of that color information away to save space. Second, the JPEG algorithm will reduce “high frequency” changes in image information. This means that frequent and drastic changes in color between pixels will get thrown out, and an average color will be used instead. This is perfectly OK for most applications, since most people don’t notice too much of a difference unless they look extremely closely at an image. Finally, the JPEG algorithm compresses the image even further by encoding it in a way that the total amount of duplicated data is reduced. For example, a solid-color wall might get reduced to an entry in the file that says “This part of the image to this part of the image is all just the same color blue”. This same process is repeated a bunch, with all kinds of similar-looking parts of the image getting compressed down. What you’re left with is an image that is missing some of the fine details, but is a much smaller file size than it was before.
This type of compression is called “Lossy” because some of the information that was captured is just thrown away entirely with no way to ever get it back. If you’re just taking pictures of a vacation to show your friends or post online, lossy compression is totally fine, and well worth the trade-off to most people.
But, if you’re a professional photographer, you might not be too happy that some of the information about a photo you’re taking is just getting lost, and you might not be too happy with the image adjustments that a camera makes automatically. After all, you might be able to do a better job at adjusting the photo than the camera, and you definitely don’t want to lose any information! So, a RAW photo just saves all of the information that comes off the sensor directly to a file with no further processing and no compression of any kind. It’s then the responsibility of the photographer to go back and edit the photo in a program like Photoshop, applying all the corrections and adjustments they want to get the image looking exactly how they want it to look.
Latest Answers