Image Export Tips

The maximum file size for an image to upload to bla.st is 30KB. bla.st supports JPEG, GIF and PNG file types. But how do you choose which to use?

Choosing between JPEG, GIF and PNG

The goal is to produce the best quality image with the lowest file size possible. JPEG files work best for photographs, while GIF and PNG files work best for images with sharp text, line drawings, and flat colour.

1. Photograph image JPEG best option, at 70% quality	2. Flat Colour text and Logo GIF best option, with 256 colours	3. Photograph AND flat colour and text in the same image JPEG best option, at 80% quality

If the image is mainly a photograph as in 1, exporting as JPEG is your best option.

If your image contains only flat colour, text, or a line drawing as in 2, using GIF produces a sharper, cleaner image than JPEG will.

If your image contains both photographic elements AND flat colour or text in the same image, as in 3, using a JPEG at a slightly higher quality setting works best.

Exporting in Adobe Photoshop or Adobe Photoshop Elements

There are two ways to export image files in Photoshop. The traditional method is to use the "Save As..." menu option.

From Photoshop v5.5, a new menu option called "Save For Web..." is available, and this is what we recommend using to export your images ready for bla.st.

Here are two examples showing the "save for web" panel, with descriptions of each below.

To save as a JPEG file, select JPEG in menu labelled A.

Use B to select the quality of the JPEG. Use between 65% and 85%. Less than 65% will worsen the quality of the file too much. More than 85% will increase the file size dramatically with very little visual benefit.

While experimenting with the settings, the file size C will update. Our goal is to create a file less than 30KB

Any other settings should be set as shown, in particular make sure "progressive" is off, and "optimized" is on.

To save as a GIF file, select GIF in menu labelled A.

GIF files don't have a quality setting like JPEGs, instead you can choose how many colours are in the file (B). The fewer colours, the smaller the file size. Normally it is fine to leave this at 256.

Again the file size will be indicated at C. Compare this to the JPEG file size, and look at the image quality to decide which format will work best. You can also try PNG-8 and PNG-24 from menu A, and see what the file size produced is.