Learn About Mac Image File Formats

Hi, this is Gary with MacMost.com. Let me tell you about different image formats that you may come across while working on your Mac. 

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So whether it's a photo you've taken with a digital camera, an image you've scanned in, an image you've taken with your iPhone, or perhaps an image you've downloaded online it's going to be in a specific file format. Each image format is good for some things and not for others. So first let's start with the most common format you probably already know. It's JPEG.

JPEG files are for photos. It's what's called a lossy compressed format. Lossy meaning that you lose some of the quality whenever you save a JPEG file. For decades cameras have saved files as JPEG files. As a result you get a much smaller file than if the file had the exact color for every single pixel of the photo. The compression is really all designed around photos. So it doesn't really work well for graphics. If you have a graphic, like the company logo or a background or an illustration. A lot of times there are some solid colors in there and maybe a very limited set of colors. JPEG's are meant to work with photos where just about every pixel is a different color of some kind. One interesting thing about JPEG is you can use different compression amounts whenever you compress an image and it's a lossy type compression you're always trading quality for file size. A smaller file will mean lower quality. A larger file will mean higher quality. 

So Apple started using an alternative to JPEG about five years ago called HEIF or HEIC. The HEI stands for high-efficiency image. The F is either for file or format or file format and the C is for Container. In most cases they're interchangeable although Containers can contain several images so they're used for things like Dynamic Desktops where there are several images in one file or for live photos. These files use a newer, better compression algorithm so you can have better quality with the same file size that you had with JPEG. Or have the same quality but a smaller file size . In other words a 2MB JPEG is not going to look as good as a 2MB HEIF file. In general these files are going to be smaller so it's going to take up less space in your iPhone, less space on your Mac, less space in iCloud or anywhere that you store the images. So that sounds great. But there is one problem. Because this is a newer format older devices may not be able to open them. If somebody you send a HEIC file has an older device or they are running an older version of their software or operating system they may not be able to do anything with those images since they're stuff predates when these files were being widely used. But that's typically not a problem because when you share a file from Apple's Apps, like you're going to send somebody an image in Messages or in an email, it typically converts to a JPEG image. It's usually doing this anyway just to create a smaller file than the original and it will also save it out in a JPEG format so more people can access it. Then in years to come it will become less and less of a problem as most computers can use this format. 

You may read somewhere that HEIC is a proprietary Apple format. That's not true. It's a standard format that Apple is using. 

So another format you may run into is the GIF format. GIF. Now let's get the pronunciation question out of the way. Is is JIF or GIF? There are people that go either way. It probably doesn't really matter right, but I'm going to say GIF because as a guy named Gary I've got to go with GIF. Now GIF files are really made for graphics. So things like logos and illustrations. They are not made for photos. If you try to save a photo as a GIF file you may be able to get decent quality but the file size is going to be huge because the way GIF's compress is lossless. It's trying to save the exact color of every pixel. So it's looking for large areas of solid colors that it could describe the area as all being the same color rather than having the color for every single pixel. That's not going to happen in a photo. So a photo saved as a GIF file is going to be huge or it's going to be really bad quality. When you save a GIF you can often compress it at that point by sacrificing quality. But the GIF file itself is going to have exact pixels with exact colors at every location. 

Now another confusing thing about GIF files is sometimes when people say GIF they are really talking about an animated GIF. This is a special type of GIF file that has several frames in there and that can be run as an animation. So chances are if somebody said take a look at this funny GIF they're talking about an animated GIF. If somebody says use this GIF as my logo on the website they're talking about a still image GIF. 

Now a more modern way to save graphics files is using PNG. PNG is a lossless format that still has compression in it. So it is still trying to identify pixels that are similar and make a smaller file. But every pixel is saved perfectly. So you're going to get large files if you try to save photos as PNG files. But they are great for graphics. Also in addition to saving the color for every pixel there also could be a transparency level saved for every pixel. So you can have a semi-transparent images. So a circular logo, for instance, can actually be transparent outside of the circle. So they are ideal for layering graphics in graphic's apps or in video apps. Often when I do a tutorial on creating a semi-transparent overlay to use in a video I'm using a PNG file. You can export PNG files from graphic's apps, illustration apps, and even things like Keynote to create graphics that have some areas that are transparent and some that are opaque. 

Now another format that you may come across is RAW. RAW isn't actually one format. There are different types of RAW formats for different camera makers. So Sony and Cannon and other camera makers will have different formats. There's also an Adobe Photoshop RAW format. There's also the RAW format you get when you take RAW photos on your iPhone. Basically what they all have in common is they are saving the exact data that's coming off of the photo. When you take a photo using an iPhone or camera and it saves JPEG it's making decisions on the fly about things like exposure and colors that will make a good looking image. But that is kind of baked into the final JPEG and then compressed to give you a smaller file. A RAW photo is saved without any of that. So you get a much larger file but it has got all the original data from the photo there. So the advantage is you do a lot more with a RAW photo. But a disadvantage is you have to do a lot more with a RAW photo. You can't usually just take a RAW photo and send it to somebody. It's going to be a huge file and it's not going to look great. You're going to want to look at it in the Photos App, in Adobe Lightroom, in Photoshop. In whatever app you're using for images and actually make adjustments to it which will allow professional photographers make better photos. 

So if you're using RAW photos, of course, you're not worried about file size. You're going to be spending a lot more to store these files and you're not worried about getting the file image right now because you're planning on actually looking at the image and making adjustments later on. 

There are other formats as well. You may come across TIFF files which are lossless files. Very large. They perfectly save images but you don't see them too much anymore. If you're doing a graphics file that's going to be lossless then you're probably going to be using a PNG today and if you're taking a photo and you want that to be lossless you're probably doing a RAW photo. 

Another format you may see is PSD. That stands for Photoshop Document. That's a file format that's proprietary to Adobe Photoshop although there are lots of other apps that can open PSD files. They can have layers and they can have all sorts of adjustments and other data in the file format. So you typically only deal with PSD's if you're using Photoshop or if somebody you're working with is using Photoshop and sends you one of these. 

So I hope this gives you insight into what these different file formats are used for and why you may come across them when working on your Mac. Thanks for watching.