How do different images from the same camera vary in file size?

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Wouldn’t a camera with a constant resolution capture images of the same quality and therefore file size? How is it possible that some images on my camera can be 1.5 MB, and others 2.5 MB?

In: Technology

17 Answers

Anonymous 0 Comments

Cameras use image compression algorithms to keep the files small, and the less information a picture contains, the better these compression algorithms work.

If some of the picture is black for example, the algorithm can just say ‘the upper half is all black’ instead of saving the color of each pixel in that area. And if it only contains a limited number of colors, that also helps.

If you want to try it out, take a picture in a perfectly dark room or cover the lens with something that blocks all light, and you will see that the file that comes out is much smaller than a normal photo.

Blurry images also tend to contain less information and are easier to compress, so if you take multiple photos of the same object, the ones with the smallest file size also tend to be the worst ones in terms of quality/sharpness.

Anonymous 0 Comments

Basically, most images are in a compressed format. If a photo has a huge amount of pixels of the same color in a given area, the file format can record this as one piece of information. It’s like when you’re remembering a phone number: it’s a lot easier to remember a sequence if you have two or three numbers that are the same in a row. So, a picture of a blue sky is going to be smaller than a picture of a Jackson Pollock painting.

Anonymous 0 Comments

There are two types of file that come from a camera, the raw file, and a processed file.

You’re right in that the raw file will always be the same size because each pixel has information.

The processed file (commonly .jpg or similar) has been processed by the camera or phone to be _much_ smaller. Say you took a picture with some sky in it that is a huge swathe of blue. Your phone notices that and takes some shortcuts to the information it saves, rather than saving information for each pixel.

Edit: spelling

Anonymous 0 Comments

Everything with images is compressed, otherwise the filesize is ridiculous, so the difference comes from which picture is better compressed there probably some algorithm that determines the minimum quality loss and so the camera compresses the file until that quality is reached

Anonymous 0 Comments

think of it the same as painting a picture. if your painting has one large swathe of paint you can go over it in one stroke of the paint brush it is done. if your painting has lots of fine details you need to go over it again and again with different strokes to get all the different colored details. in this analogy each paint brush stroke is a piece of memory.

so a picture of a blue sky with a white mountains underneath my only have two main strokes and say eight accent strokes of shadows on the mountains, making relatively small photo memory wise. a photo of a rose bush requires dozens and dozens of strokes to save all the details of the shadows, leaves, flowers, etc. and will have a much bigger memory size.

Anonymous 0 Comments

You’re painting right. And you use cheap shitty paint or canvas. Sure it could look ok. But it you need to restore it or make changes later it’s probably gonna end up turning to shit.

But use good paint equipment and a good canvas you can do lots of more cool shit.

Camera formats work the same. Use a shitty format to save space. But you loose ability to play with the image. Use a good format and you can do some really cool things with it.

Anonymous 0 Comments

Compression, imagine you have 10 pieces of paper, and they’re all red, you could describe them as

I have 1 red paper
I have 1 red paper
I have 1 red paper
I have 1 red paper
I have 1 red paper
I have 1 red paper
I have 1 red paper
I have 1 red paper
I have 1 red paper
I have 1 red paper

Or you could just say “I have 10 red papers”, you’d convey the same message, but the message itself wouldn’t be as big, however if all your papers have different colors then you’ll actually have to describe each one of them individually and there’s no way for you to compress that, swap papers with “pixels” and factor in position and that’s pretty much how compression works

Anonymous 0 Comments

If you were to use no compression, then sure, every picture would be the same size. For every pixel, you would need 3 bytes of information (or more with more colour depth). Your 2.5MB file wouldn’t even be a full megapixel.

Instead, we use compression algorithms to reduce the amount of data we need to actually hold. We can do things like only store the difference between one pixel and the pixel next to it, since those tend to be very similar values.

The algorithms for good compression can get very complicated very quickly. There are also two forms of compression — lossy and lossless. With lossless compression, you can get the raw file back in its exact format. With lossy compression, you get something that isn’t pixel perfect compared to the original, but (ideally) a human eye can’t tell the difference.

Anonymous 0 Comments

Files from cameras are almost always compressed, which basically just looks for data that’s repeated in the image and only remembers it once, saving space. The more repeated data in that specific image, the smaller the file size will get.

Further more, most consumer cameras use “lossy,” compression, such as `.jpeg`. The actual process is pretty complicated, but in simplest terms it removes data from the image that you won’t notice is missing, saving tons of space. Downside is it makes professional work a little harder, but that’s fine if your just uploading to Instagram.

Anonymous 0 Comments

An uncompressed raw file will always have the same file size, as it saves the same data for the same amount of pictures. However most raw files are (lossless) compressed and include other information beside the picture info.

However most pictures you’ll come across won’t be in raw format. They’ll be things like jpg, png, gif. They can reduce the file size immensely, but the way they achieve that is very different.
Jpg is the most common format. If you want to see how it works I can recommend [this video](https://www.youtube.com/watch?v=fRjFwTbJfes). It has a very good way of showing how it all works.