Some of the photos uploaded to our website have used the .png image format (Portable Network Graphics) rather than the .jpeg image format (Joint Photographic Expert Group) . 

The .png image format is most appropriate for logos, icons, charts, graphs and screenshots. When used for photos it results in excessively large files which will slow down page-loading for website visitors.

The .jpeg format (as the name suggests) is preferable for photos because there is a good balance between the image size and its quality.

Please use the .jpeg image format for photographs.

You can convert any .png images to .jpeg prior to uploading.  If you do not have software to do this, there are many free online conversion services such as https://png2jpg.com/