ガイド
画質を落とす画像圧縮の失敗例
画像をぼやけさせる圧縮ミスと、避けるための基本ルールを解説します。
圧縮は軽量化のための手段です。見た目が悪くなる場合はワークフローの見直しで改善できます。
Mistake 1: compressing without resizing first
Large dimensions plus strong compression can still look bad and stay heavy.
Resize to real display width before adjusting quality.
Mistake 2: using one quality value for every image
A universal setting rarely works across photos, screenshots, and graphics.
Test by content type instead of forcing one number.
Mistake 3: checking only at extreme zoom
Zoomed inspection can hide how files look in actual layout.
Always review images where users actually see them.
- Check mobile first.
- Review text in screenshots.
- Confirm skin tones and edges look natural.
Mistake 4: repeated re-export cycles
Saving the same lossy image many times can stack quality loss.
Keep a high-quality source and export web versions from it.
Mistake 5: ignoring format fit
Wrong format choice can force aggressive compression.
Use formats based on content needs, not habit.
Common situations
- Blurry blog screenshots.
- Noisy product photos.
- Over-compressed hero images.
- Inconsistent image quality across pages.
Small fixes make a big difference
Set simple compression rules and compare output in real page context before publishing.