Understanding PNG Files


I have always saved my JPEG photos as PNG as I understand JPEG is a compressed file but PNG is lossless so I thought it would be better. Am I right? Or should I just leave them as JPEGs straight from the camera? I noticed when I used Lightroom, it would see the JPEG’s but not the PNG files. Was it trying to tell me something? —Peter D’Mello, via email

This story was originally published in December 2013.

Both PNG and JPEG compress the data, but PNG is essentially lossless compression. JPEG will give you a much smaller file size, but the compression occurs at the cost of some details. However, it is advisable to avoid the PNG format for a number of reasons. Firstly, it is a format that is primarily optimised for graphics, not photographs. In that sense, if you are saving a picture for the Web, a PNG file may be a good option, but then, for most practical applications, JPEG or TIFF are better formats. Most basic image-editing software—including some highend ones like Adobe Photoshop Lightroom, do not recognise the PNG file format. Since the format is not a dedicated photo format, it does not support EXIF information and colour profiles too.

A better solution would be to set the camera to save in the RAW format, which is the original data file of the image as seen by the camera. RAW is lossless and allows more scope for tonal, white balance and other adjustments. Once you have finished editing, you can then save in either JPEG or TIFF format.

Tags: Question of the Day, JPEG, compression, TIFF, PNG files