When saving images in TIFF format many software offers to choose image compression for your files. You may wonder which is better, LZW, ZIP, or JPEG or maybe you always keep the default option, which is “None”, because you are afraid that the compression you choose may degrade the quality of your images.
First, let’s clarify that both LZW and ZIP are lossless types of compression, which means they reduce the file size of an image but do not reduce the image quality. This process is reversible and the image can be resaved with a different compression algorithm or without any compression with the same quality as the original. This is similar to compressing other file formats with ZIP archiving software – all information is there but the file is just smaller.
Contrary, JPEG is a lossy compression algorithm which will result in image quality reduction, although it may not be noticeable with the bare eye. Moreover, each time you resave your TIFF file with JPEG compression, even when the quality level is the same, the file gets smaller and you are losing quality. This process is irreversible because some data from the original image file is stripped out and lost forever each time you compress the image.
On a personal note, I don’t see a reason to save TIFFs with JPEG compression. If you don’t mind a little quality reduction and just want smaller file sizes, you may as well save the images as JPGs. The file size should be smaller than with TIFF.
So, you can safely use either LZW or ZIP compression. But the question is which is better? Because the quality of the image is unchanged, the best algorithm, in this case, will be the one that produces the smallest files. Both of this algorithms will produce different results for the same image, in most cases just slightly different.
A good way to see the difference in file size reduction between LZW and ZIP is to use both these options on various types of images and compare the results. It is important to test multiple files because the level of compression is dependent on the image content. Images with lots of details, rich textures, and high color depth may not compress very well. Images with plain backgrounds and large areas of solid colors will be reduced in size significantly.
Images with different content and their compression levels. A person with a phone: No compression – 21.5 Mb, LZW compression – 9.8 Mb. Roll of film: No compression – 20.7 Mb, LZW compression – 4.1 Mb. Street lamp: No compression – 16.5 Mb, LZW compression – 5.3 Mb.
Select a dozen images with completely different content and save them with both LZW and ZIP compression to see which results you like better. What is not to like about having smaller files of absolutely the same quality as the big ones? You will see that both types of compression work great.
However, each time you save or open compressed TIFF files, the software you use will need some time to compress or decompress your images. When you have a large number of large files to process – the time can be significantly greater than processing images without any compression. But this is a small price to pay for all the space you can save using TIFF image compression.