Does the JPEG file size accurately reflect the image quality?

It is possible that your previous conceptions are wrong with JPEG images. After this article, you can save quite a bit of storage!

The relationship between JPEG file size and image quality is often understood by people in the sense that 'the heavier the file, the higher the quality '. But really, things are not quite so.

The compression ratio during JPEG conversion from RAW files is low, the finished JPEG images will be of better quality and larger capacity but not synonymous with 'the heavier the better '. In fact, the lowest compression ratio ( equivalent to the heaviest file capacity ) is really unnecessary.

Does the JPEG file size accurately reflect the image quality? Picture 1

The features of our human eyes have a certain threshold and that will help you save quite a bit of memory each time you choose to select the compression ratio when converting RAW to JPEG. Now, no more, now let's learn more in detail with the actual examples below!

The perception of one's image is oriented

JPEG as everyone is so familiar, is a lossy image compression algorithm, which cuts off information from the original RAW image. The color information of the light from the RAW image will be processed to cut off the excess parts to reduce the size of the image.

The garbled information is calculated based on human cognitive ability and visual, eye and brain systems. People are truly a magical creature, our visual system provides information about the brain and the human brain that can compensate for the missing information itself and even create even the information itself. still not real. The information that the brain creates itself will follow a certain rule and therefore the image of the person is oriented.

In fact, please look at the image below. Most people observed 2 triangles and 3 circles even though all 5 shapes were defective. Thus, the process of recognizing human images is a process oriented, helping us to place structures on unclear information to receive them in the way that the brain wants.

Does the JPEG file size accurately reflect the image quality? Picture 2

JPEG works the same way. The parts of the information that are garbled by our compression algorithm, the visual system, and our brain reproduce the missing parts. However, JPEG is not just a format name but JPEG is also the name of the compression standard.

Therefore, the results of the process of running uncompressed compression algorithms vary depending on the different programs of different vendors. Therefore, it is possible to have the same lighting conditions, the same subject that two companies like Canon and Nikon produce 2 JPEG images with very different styles.

Factors affecting image quality when performing compression

During compression, a number of factors are used for the purpose of reducing image capacity such as resolution or DPI index, long size x width in pixels and compression ratio. All three factors affect the final image quality more, of which the most important are the two factors of image size in pixels and compression ratio.

The size is long and wide in pixels

All digital photos have the size of the image in pixels, such as 1024 x 768 pixels, 800 x 600 pixels . That is the length and width of the image in terms of the number of pixels displayed on the screen. at 100% display level.

Thus, a smaller image will of course have a lower memory capacity than a larger image with a larger pixel size. For example, if the same compression ratio, an image of 1,024 x 768 will be larger than an 800 x 600 image, simply because a larger image has more internal pixels. Simple is that.

DPI Index - Dot Per Inch

This index really has little effect on the size of the finished product unlike the pixel size index of the image. An image is 1024x768 in 300 DPI and 100 DPI has the same storage capacity. This indicator is only meaningful when you use photos to print, and when using digital photos to share via the web, e-mail, this index is not important.

Compression ratio

This ratio determines whether the algorithm will trim less or more information. The low compression ratio will make the image retain more information while heavier and higher compression ratio will cut more and keep the image size lighter. However, no matter what compression ratio you choose, the image will be cut off even more or less.

That's why a 4.0 MB RAW image after JPEG compression will only have 1.5 MB. Thus, the high compression ratio will result in lighter, but lower quality images, the only problem is the question: ' How much is moderate? 'and we'll find out the answers later in the article!