Image Processing Priorities: Resolution VS Quality

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Introduction

I have been hosting my photographs on my personal website for a long time. However, it is not quite possible to host the original photographs because of their large file sizes. So I usually resized the original photographs to a smaller resolution, typically from 50 Megapixels (8640x5760) to 3 Megapixels (2160x1440), and the JPEG file size would reduce from around 20-30 MB to around 2-3 MB.

I felt that those photographs hosted on my website do not look sharp enough on my high resolution 4K (3840x2560) monitor. But I was not able to further increase the resolution because the larger file size will slow down the website loading too much. There is also an additional option to reduce the photograph file size by reducing the JPEG quality, but I did not even try that because I was afraid that the resulting photographs will look bad.

It turns out that I was wrong. By balancing the resolution and JPEG quality, the photographs could look much better than what I had on my website and the file sizes will remain almost the same. In this blog post, I would like to share some of my experiment results on one of my original photographs.

Image Processing Priorities: Resolution VS Quality

Image Processing Procedures

I used ImageMagick on Ubuntu 24.04 LTS to process the original photograph.

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$ convert --version
Version: ImageMagick 6.9.12-98 Q16 x86_64 18038 https://legacy.imagemagick.org
Copyright: (C) 1999 ImageMagick Studio LLC
License: https://imagemagick.org/script/license.php
Features: Cipher DPC Modules OpenMP(4.5)
Delegates (built-in): bzlib djvu fftw fontconfig freetype heic jbig jng jp2 jpeg lcms lqr ltdl lzma openexr pangocairo png raw tiff webp wmf x xml zlib

The following commands were used for generating the processed photographs of different resolutions and JPEG qualities.

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IMAGE=DSC09742.JPG
IMAGE_RESOLUTION_LIST=(8640x5760 7680x5120 4320x2880 2160x1440)
JPEG_QUALITY_LIST=(10 20 30 40 50 60 70 80 90 95 99)
IMAGE_BASE_NAME=$(basename $IMAGE .JPG)
for IMAGE_RESOLUTION in ${IMAGE_RESOLUTION_LIST[@]}; do
    for QUALITY in ${JPEG_QUALITY_LIST[@]}; do
        convert $IMAGE -resize $IMAGE_RESOLUTION -quality $QUALITY ${IMAGE_BASE_NAME}_resized_${IMAGE_RESOLUTION}_${QUALITY}.JPG
    done
done

The file sizes of the processed photographs are summarized in the following table.

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$ ls -lh
total 135M
-rw-rw-r-- 1 leimao leimao  22M Oct 11 07:14 DSC09742.JPG
-rw-rw-r-- 1 leimao leimao 169K Oct 12 15:59 DSC09742_resized_2160x1440_10.JPG
-rw-rw-r-- 1 leimao leimao 208K Oct 12 15:59 DSC09742_resized_2160x1440_20.JPG
-rw-rw-r-- 1 leimao leimao 239K Oct 12 15:59 DSC09742_resized_2160x1440_30.JPG
-rw-rw-r-- 1 leimao leimao 264K Oct 12 15:59 DSC09742_resized_2160x1440_40.JPG
-rw-rw-r-- 1 leimao leimao 288K Oct 12 15:59 DSC09742_resized_2160x1440_50.JPG
-rw-rw-r-- 1 leimao leimao 315K Oct 12 15:59 DSC09742_resized_2160x1440_60.JPG
-rw-rw-r-- 1 leimao leimao 355K Oct 12 15:59 DSC09742_resized_2160x1440_70.JPG
-rw-rw-r-- 1 leimao leimao 425K Oct 12 15:59 DSC09742_resized_2160x1440_80.JPG
-rw-rw-r-- 1 leimao leimao 609K Oct 12 15:59 DSC09742_resized_2160x1440_90.JPG
-rw-rw-r-- 1 leimao leimao 868K Oct 12 15:59 DSC09742_resized_2160x1440_95.JPG
-rw-rw-r-- 1 leimao leimao 1.6M Oct 12 15:59 DSC09742_resized_2160x1440_99.JPG
-rw-rw-r-- 1 leimao leimao 317K Oct 12 15:59 DSC09742_resized_4320x2880_10.JPG
-rw-rw-r-- 1 leimao leimao 439K Oct 12 15:59 DSC09742_resized_4320x2880_20.JPG
-rw-rw-r-- 1 leimao leimao 531K Oct 12 15:59 DSC09742_resized_4320x2880_30.JPG
-rw-rw-r-- 1 leimao leimao 607K Oct 12 15:59 DSC09742_resized_4320x2880_40.JPG
-rw-rw-r-- 1 leimao leimao 680K Oct 12 15:59 DSC09742_resized_4320x2880_50.JPG
-rw-rw-r-- 1 leimao leimao 760K Oct 12 15:59 DSC09742_resized_4320x2880_60.JPG
-rw-rw-r-- 1 leimao leimao 897K Oct 12 15:59 DSC09742_resized_4320x2880_70.JPG
-rw-rw-r-- 1 leimao leimao 1.2M Oct 12 15:59 DSC09742_resized_4320x2880_80.JPG
-rw-rw-r-- 1 leimao leimao 1.8M Oct 12 15:59 DSC09742_resized_4320x2880_90.JPG
-rw-rw-r-- 1 leimao leimao 2.8M Oct 12 15:59 DSC09742_resized_4320x2880_95.JPG
-rw-rw-r-- 1 leimao leimao 5.6M Oct 12 15:59 DSC09742_resized_4320x2880_99.JPG
-rw-rw-r-- 1 leimao leimao 662K Oct 12 15:58 DSC09742_resized_7680x5120_10.JPG
-rw-rw-r-- 1 leimao leimao 936K Oct 12 15:58 DSC09742_resized_7680x5120_20.JPG
-rw-rw-r-- 1 leimao leimao 1.2M Oct 12 15:58 DSC09742_resized_7680x5120_30.JPG
-rw-rw-r-- 1 leimao leimao 1.4M Oct 12 15:58 DSC09742_resized_7680x5120_40.JPG
-rw-rw-r-- 1 leimao leimao 1.6M Oct 12 15:58 DSC09742_resized_7680x5120_50.JPG
-rw-rw-r-- 1 leimao leimao 1.8M Oct 12 15:59 DSC09742_resized_7680x5120_60.JPG
-rw-rw-r-- 1 leimao leimao 2.2M Oct 12 15:59 DSC09742_resized_7680x5120_70.JPG
-rw-rw-r-- 1 leimao leimao 3.0M Oct 12 15:59 DSC09742_resized_7680x5120_80.JPG
-rw-rw-r-- 1 leimao leimao 5.1M Oct 12 15:59 DSC09742_resized_7680x5120_90.JPG
-rw-rw-r-- 1 leimao leimao 8.0M Oct 12 15:59 DSC09742_resized_7680x5120_95.JPG
-rw-rw-r-- 1 leimao leimao  16M Oct 12 15:59 DSC09742_resized_7680x5120_99.JPG
-rw-rw-r-- 1 leimao leimao 781K Oct 12 15:58 DSC09742_resized_8640x5760_10.JPG
-rw-rw-r-- 1 leimao leimao 1.1M Oct 12 15:58 DSC09742_resized_8640x5760_20.JPG
-rw-rw-r-- 1 leimao leimao 1.4M Oct 12 15:58 DSC09742_resized_8640x5760_30.JPG
-rw-rw-r-- 1 leimao leimao 1.6M Oct 12 15:58 DSC09742_resized_8640x5760_40.JPG
-rw-rw-r-- 1 leimao leimao 1.9M Oct 12 15:58 DSC09742_resized_8640x5760_50.JPG
-rw-rw-r-- 1 leimao leimao 2.2M Oct 12 15:58 DSC09742_resized_8640x5760_60.JPG
-rw-rw-r-- 1 leimao leimao 2.7M Oct 12 15:58 DSC09742_resized_8640x5760_70.JPG
-rw-rw-r-- 1 leimao leimao 3.7M Oct 12 15:58 DSC09742_resized_8640x5760_80.JPG
-rw-rw-r-- 1 leimao leimao 6.3M Oct 12 15:58 DSC09742_resized_8640x5760_90.JPG
-rw-rw-r-- 1 leimao leimao  10M Oct 12 15:58 DSC09742_resized_8640x5760_95.JPG
-rw-rw-r-- 1 leimao leimao  20M Oct 12 15:58 DSC09742_resized_8640x5760_99.JPG

Original Image

This is the original photograph of resolution 8640x5760 that we will process.

Original Image, Resolution 8640x5760, Quality 100, Size 22.0 MB

Resolutions

On a 4K, 3840x2560 monitor, I noticed some details are lost due to interpolation when the photograph is resized to 2160x1440. For photographs whose resolution is higher than the monitor resolution, I could not tell if there is any difference between the original and the processed photographs. The processed photograph of resolution 4320x2880 and JPEG quality 99 has a file size of 5.6 MB.

Processed Image, Resolution 8640x5760, Quality 99, Size 20.0 MB Processed Image, Resolution 7680x5120, Quality 99, Size 16.0 MB Processed Image, Resolution 4320x2880, Quality 99, Size 5.6 MB Processed Image, Resolution 2160x1440, Quality 99, Size 1.6 MB

JPEG Qualities

I noticed that the JPEG quality does not affect the details of the subject at all. It mostly affects the color accuracy, especially the background colors. But the difference is hardly noticeable until I reduced the JPEG quality to 50 or below. The processed photograph of resolution 8640x5760 and JPEG quality 60 has a file size of 2.2 MB.

Processed Image, Resolution 8640x5760, Quality 99, Size 20.0 MB Processed Image, Resolution 8640x5760, Quality 95, Size 18.0 MB Processed Image, Resolution 8640x5760, Quality 90, Size 13.0 MB Processed Image, Resolution 8640x5760, Quality 80, Size 6.3 MB Processed Image, Resolution 8640x5760, Quality 70, Size 3.7 MB Processed Image, Resolution 8640x5760, Quality 60, Size 2.2 MB Processed Image, Resolution 8640x5760, Quality 50, Size 1.9 MB Processed Image, Resolution 8640x5760, Quality 40, Size 1.6 MB Processed Image, Resolution 8640x5760, Quality 30, Size 1.4 MB Processed Image, Resolution 8640x5760, Quality 20, Size 1.1 MB Processed Image, Resolution 8640x5760, Quality 10, Size 781 KB

The Sweet Spots

The existing processed photograph I used has a resolution of 2160x1440, JPEG quality of 99 (ImageMagick default), and a file size of 1.6 MB.

Processed Image, Resolution 2160x1440, Quality 99, Size 1.6 MB

The new processed photograph I want to use should have a file size close to 1.6 MB as well and should look better than the existing one. I found two sweet spots that meet the requirements. One has a resolution of 4320x2880, JPEG quality of 80, and a file size of 1.2 MB. The other has a resolution of 7680x5120, JPEG quality of 50, and a file size of 1.6 MB. I could hardly tell the difference between these two photographs and the original one on my 4K monitor.

Processed Image, Resolution 4320x2880, Quality 80, Size 1.2 MB Processed Image, Resolution 7680x5120, Quality 50, Size 1.6 MB

Image Processing Priorities: Resolution VS Quality

https://leimao.github.io/blog/Image-Processing-Priorities-Resolution-VS-Quality/

Author

Lei Mao

Posted on

11-09-2025

Updated on

11-09-2025

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