If you want to change the resolution of existing layers without changing the dimensions of the file, you need to use the Quality option in the Edit Menu. Using the Resolution option will change the dpi (dots per inch), but it will also change the file dimensions. 

This is sometimes desirable when opening digital photos for the first time as they are usually rather large in size, but have a low resolution. Increasing the resolution of files such as this will also reduce the dimensions. This is because you are putting more pixels into an inch (or centimetre) and therefore the pixels are becoming smaller, bringing the file size down.

Essentially, the Resolution option will retain the same number of pixels in the file, whereas using the Quality option will adjust the number of pixels in the design accordingly.

How to change the quality of layers

1. Activate all of the layers in the file and either select Quality from the Edit Menu, or click on the above Quality icon in your toolbar. The following window will open:
   
   
2. Click on the Scale pop up bar and select /2 to divide the current file resolution in half.
   
   
3. Make sure Selected Layers and Editing are checked and click on Set.
    
   • Selected Layers - if you only have a few layers selected in your file, only those layers will be affected by the changes made in this window. If this option is not ticked, all layers in you design will have the changes applied to them.
   • Editing - means the resolution at which you edit the design. If any layers in your design have a higher resolution than the selected editing quality they have their pencils removed (indicating that they are not active). This is because you cannot edit a layer that has a higher quality than your editing quality. If you were able to edit the layer, not all the high resolution pixels would be drawn on, resulting in an unwanted dotty effect.

Changing the resolution of a file

Changing the resolution of a file using the Resolution option in the Edit Menu will change the dimensions of the file too.

1. Go to Edit Menu > Resolution. The following sheet will appear:
   
   
2. Enter the resolution you need your file to be in both he Across and Down dialog boxes. If you are a weave designer, you may have a different resolution in the Across and Down dialog boxes in order to comply with the sett of the design. 

Why does my resolution change when I create new designs?

Occasionally, the resolution of a file will change slightly when a new file is created. For example, the file below was created at 1 cm across and down, with a resolution of 300 dpi.  When we look at the resulting resolution in the Layers Palette, we can see that the resolution has rounded to 299.72 dpi.

This is because a resolution of 300dpi does not work mathematically in a file which is sized using centimetres. You are asking the software to put 300 dots per inch into 1 centimetre.

If you divide your 300 dpi (dots per inch) by 2.54 - the number of centimetres in an inch, the answer is 118.11. Because you cannot split a pixel, the ultimate resolution rounds slightly to accommodate the file size.

If it is important to you to retain the resolution, you need to use one which works perfectly with your file size. The easiest way to do this is to work in dpc (Dots Per Centimetre) if your files are sized using centimetres and dpi if you size your files in inches, or select a dpi which divides perfectly into a round dpc measurement.

For example, 254dpi is 100 dpc.  508dpi is 200 dpc.

If the resolution is more important than the dimensions of your file, you can Maintain Resolution when you create new files. This will retain the resolution you set, but adjust the size of your document accordingly.