Image size is directly related to image resolution i.e. the higher the resolution, the bigger the file size

The Relationship of Image Resolution To Image Size

Calculating Image Size

The > the bit depth, the > the number of tones (grayscale or color) that can be represented. 
(W x H x BitDepth) / 8 bits/byte = (W x H x BitDepth) x 1 byte/8bits
When planning for shoots with a DSLR or other digital camera, make sure you have enough capacity on your SD card. For commercial and wedding photographers who need to shoot non-stop, a fast write operation and high capacity storage device is ideal. (Photo Source Panasonic)

Reasons To Shoot In High Resolution

(L) 4928 pixels (horizontal) at 300% magnification. (R) 1200 pixels (horizontal) at 300% magnification. At higher resolutions, you can get better details when zooming in. At lower resolutions, the image gets more blurry and loses plenty of details when zooming in. This is even worse when the low resolution image uses a lossy compression algorithm.
(L) 4928 pixels (horizontal) at 1300% magnification. (R) 1200 pixels (horizontal) at 1300% magnification. When further magnifying or up scaling a lower resolution image, the “staircase effect” or jagged edges start to appear and the image becomes less clear, more blurry. This is the result of aliasing, and photo editing software use a technique called anti-aliasing to minimize this. The higher resolution image on the other hand, appears more detailed even at higher zoom. Although the pixels become noticeable at close distance to the eye, it does not matter from a large distance. For example, when viewing a billboard display, the users will not notice the pixels that much but will instead see the larger scaled image without the aliasing and blurry effect. Commercial and advertisements shoot in high resolution for the purpose of blowing the image up or scaling it for large prints.

The Uses For Low Resolution

For web content (e.g. lookbooks, e-commerce catalogues, portfolios, etc.) the image resolution does not have to be so high. For one thing, it won’t fit on screen if your display is only 1080 pixels wide, while the image is over 4000 pixels wide. Instead the images are resized to appear on the website to fit. Users can still download the original image in its original resolution.

Summary

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Vincent Tabora

Editor HD-PRO, DevOps Trusterras (Cybersecurity, Blockchain, Software Development, Engineering, Photography, Technology)