What is Lossy Compression? A guide for creatives.
Take a lot of photos? You’ll know that digital storage space fills up quick.
Lossy compression can trim excess data from your images, so you can fit more on your hard-drive, website or cloud storage. This makes it a potentially useful tool for your digital photography kitbag — but is it always the right way to go?
If you’re at a loss when it comes to lossy compression, this guide’s here to help. We’ll run through its pros, cons and meaning— and give you some useful tips for compressing your own images.
What is lossy compression?
By definition, lossy compression removes background data and approximates certain details of an image file — making it smaller and easier to handle, store or send.
However, in return for a more manageable file size, you will lose data — permanently - hence the term ‘lossy’.
Lossy compression examples.
The effects of lossy compression aren’t always immediately noticeable. In fact, they sometimes aren’t visible at all. But if you look closely, you might be able to spot differences between compressed and non-compressed images. These can be subtle or more readily apparent, depending on the photo and the extent of the compression.
Take the two lossy compression examples below.
The original (above) is around 9.5 MB, while the compressed version beneath is approximately 500KB. On the face of it, they seem pretty similar. But if you look at the second image, you can see how the compression has pixelated and flattened the moody shading of the original.
This might be bad news if you’re a fine art photography specialist looking to show off your digital photography portfolio at its best. But you might get away with it if you’re displaying a small image or thumbnail online - sharing photos on your blog for example.
In the below pictures, you can see a more extreme example of compression:
On this standard-issue office stock photo, we reduced the image size from 3.32 MB to 95.3KB. This means that the image resolution and even colours have seriously deteriorated. Be aware too: following compression, if you didn’t keep the original, you wouldn’t be able to restore the image to its former glory either.
The good news is you’ll mainly discard metadata and background details that the end-user probably won’t notice. But if you compress your images too often or too much, the depth, quality and nuance of your original can suffer.
What is lossy compression used for?
Lossy compression makes it easier for you to upload, download, save, store and transfer your images. If you handle, edit and share images every day, this can save you a lot of time and space.
It’s also a very useful tool for web performance. To create an engaging, accessible website, you need great images — but photos, graphics and logos can slow down page load times. By compressing your files, a personal website or online client showcase can get eyes on it without risking technical issues or before users quit in frustration.
Advantages and disadvantages of lossy compression.
When it comes to lossy compression, for every pixelated image, there’s a faster load time. So, you need to find the sweet spot in between.
Let’s go through the upsides and downsides in more detail so you can strike the right balance.
Why is lossy compression beneficial?
- Easy image storing — Lossy files are often smaller than lossless alternatives — freeing up useful space on your server, hard-drive, cloud or smartphone. If you take hundreds of snaps on a regular basis, this form of compression really is your friend.
- Smooth image transfers — It can be a struggle to send large files to a client or move them around effectively. With lossy images, you can make uploads, downloads and transfers simple.
- Solid image quality — By and large, lossy compression can produce an image with passable or even unnoticeable differences from the original. It’s all about balance.
Faster website load times — Reducing resolution and file size means that your images will load quicker online. This can make your website more user-friendly and even and improve search engine rankings too. - Customisable and simple — Whether you use Photoshop or a native computer programme, it’s normally pretty easy to customise your compression for different purposes. Sometimes, this is as simple as sliding a scale or selecting a box for high, low and medium rates. You can also install plugins that compress your images automatically.
Lossy compression disadvantages.
- Loss of detail — When you compress an image, you can lose nuance, colour and depth. This can be fine for everyday web use, but if you’re using your photo in a bid to turn heads, the image might fall flat.
- Irretrievable data loss — When you use lossy compression, you can’t retrieve the data. You’ll need backups if you want to restore your image to its original quality.
- File limitations — Once you’ve compressed your image file, there is only very limited potential for editing, post-production and archiving. Any photo perfectionists out there should take note!
- Lack of control — Digital cameras sometimes compress image data automatically. Similarly, continued edits, saves and resizes can deteriorate your file automatically without input.
Learn more in our guide to lossy vs. lossless compression.
Lossy file formats.
There are a number of different ‘lossy files’ that commonly use - and are suited for - this kind of compression. Here are the main ones you might come across.
- JPEG — This standard image file is the go-to choice for non-transparent online images. JPEG files are favour for their handy size and metadata — which stores info on where and how the picture was taken.
- HEICs — Apple’s answer to the JPEG. While technically a lossy file format, HEIC actually retains edit data, so you can reverse changes.
- glTF — A standard file format for 3D scenes and models; sometimes known as the “JPEG of 3D”.
- MP3 — A standard audio file, often out of favour with the most discerning audiophiles due to lossy compression. Just like a compressed image, compressed audio can remove the ambience and richness from the original recording.
- JPEG 2000 — This next-gen JPEG format offers flexibility between lossless and lossy compression. JPEG 2000 files allow users to save their files as the uncompressed RAW files, as well as sharable JPEGs.
- WebP — Google introduced this file format to replace web mainstays like JPEG, PNG and GIF. WebP files support lossy and lossless compression.
- TIFF — With their high resolutions, transparency and flexibility, TIFF files are a common file format for graphic design and high-resolution imagery. They offer creators a choice between lossy and lossless.
Choosing the right file type can make all the difference to your image. Compare different image files and find the best one for the job.
Is JPEG lossy or lossless?
JPEG files are one of the most popular, widespread digital photo/still image file types going. Central to its success is lossy compression. This is because the JPEG generally maintains a decent quality image for the end-user, at an efficient level of memory for the creator. As a result, savvy JPEG creators can balance data loss with image quality as they see fit.
How to use lossy image compression on your photos.
There are a number of ways to compress your images using the lossy method. Let’s take a look.
- CMS — Some content management systems use lossy compression as standard. This helps improve page performance. You can tweak compression rates by modifying the code in some cases.
- Free tools —There are plenty of third-party apps out there that can compress images for you. These can follow a simple drag-and-drop functionality and allow you to customise your compression levels.
- Plugins — These automatically compress images and use the smallest version for your website. Plugins offer customisation, support for different files, plus bulk-compression capabilities to help you to optimise your images on the fly.
- Presets — Some cameras and software can compress lossy files automatically. This can be useful, but worth checking before you start snapping.
For the best results, you’ll need a specialist tool. Image editing software like Photoshop and Lightroom Classic allows you to customise your compression and closely monitor the results. You can then fine-tune the image to offset any loss of detail or depth.
Top tips for lossy compression.
When used wisely, this kind of compression can be a great addition to your digital toolkit. Here are a few tips:
- Strike the right balance between size, data and quality. It’s easy to do this with Adobe Photoshop’s tools or when compressing images with Adobe Lightroom Classic .
- Remember to test. Experimenting with different settings can help you to find the optimal size image for each format. You can also test for web performance to ensure your site will run smoothly after publishing your images.
- Use plugins that compress images on external servers. If the plugin runs on your server, it might slow down your site.
- Optimise for web. With Photoshop, optimal compression is a one-click job. When you’re saving your images, simply click ‘optimise for web’ and we’ll take care of the rest.
- Use the right formats. Sometimes, you might find that different lossy formats suit different devices, browsers and programmes. Often, native file formats like HEIC or WebP are the most efficient files for the job.
As the leading providers of image editing software, we have everything you need to compress, optimise and enhance your images.
Check out:
- Adobe Photoshop — This icon of image editing makes lossy compression a breeze.
- Photoshop Lightroom — Once you’ve finished compressing, tweak your image for maximum impact.
- Photoshop Express — Resize, compress and edit images on the go using just your mobile.
- Photoshop Lightroom Classic — The desktop app for powerful edits. Get the best from your compressed images.
Lossy compression: FAQs.
When would you use lossy compression over lossless?
If you want to reduce your files by a greater size and they can handle the dip in detail, lossy compression is great for saving on storage - and for faster webpage loading too. Lossless compression, by contrast, might not save as much storage space as you hoped for.
Is lossy compression more effective?
Lossy compression is effective in reducing file sizes and allows for greater customisation. However, while this can be extremely useful, drops in detail may be noticeable - so it may not be as effective for professional showcases.
Does lossy compression reduce quality?
By and large, lossy compression may not noticeably reduce your image quality. However, if you compress your images by too much or do so repeatedly, then you might see pixelation and loss of detail. For everyday web use, this is often a price worth paying for faster load times. But if you’re looking to display your very best work, then it might not be the best way forward.