Image guides
The background knowledge you need to get the most out of the tools. We start with the problems people actually get stuck on: choosing a format, how file size relates to quality, and ID photo specifications.
JPG vs PNG vs WebP vs AVIF — Which Image Format Should You Use?
JPG vs PNG vs WebP vs AVIF compared: compression, transparency, color depth, file size and 2026 browser support, plus the best format for each use case.
How Image Compression Works — Resolution, Quality, Chroma Subsampling and Metadata
The five factors that decide photo file size, and the order to adjust quality and resolution to hit a target like 200KB with the least visible quality loss.
ID and Application Photo Size Guide — Korean Passport, ID Card, Driver's License, Civil Service Exam, Q-Net and US Visa
Official photo specs for Korean passports, ID cards, driver's licenses, the civil service exam (137×177px, under 350KB), Q-Net and US visas (600×600px, 240kB).
What Is a HEIC (HEIF) File? iPhone Settings, Opening HEIC on Windows and JPG Conversion Quality
Why iPhones save photos as HEIC, the Most Compatible and transfer settings, how to open HEIC on Windows and Android, and what changes when converting HEIC to JPG.
Photo EXIF Metadata and Privacy — How to Check and Remove Location Data
What EXIF records in your photos (GPS location, device, time), how to turn off or remove location on iPhone, Android and Windows, and a checklist before sharing.
How to Watermark Photos — Placement, Opacity, Tiling and Copyright Notice Wording
Pros and cons of corner, center and tiled photo watermarks, placement that resists cropping and AI removal, opacity and size tips, and copyright notice examples.
How to Split a Photo into an Instagram Grid (3×N) — 3:4 Grid Ratio and Posting Order
How to split one photo into a 3×N Instagram profile grid: tile ratios for the 2025 3:4 grid, original size math, posting order, and fixes for misaligned seams.
How to Remove a Photo Background Cleanly — AI Segmentation vs. Matting, Shooting and Touch-Up Tips
How AI background removal works (segmentation vs. matting), how to shoot for cleaner cutouts, fixing hair and transparent edges, and saving as PNG or white JPG.
Resolution, DPI, cm and Pixels Explained — "How Many Pixels Is 3×4cm at 300dpi?" Conversion Table
How pixels, DPI (PPI) and cm relate, the conversion formula, print vs. screen, pixel tables for ID photos, prints and A4, and how big a phone photo can print.