Having taken a photograph for use as reference material in your painting, you will probably want to edit it so that it is easier to use. This you will probably do using Photoshop.
Here is an example, and common, workflow:
- Take photo and save as jpg, tiff or whatever.
- Use crop tool to change the dimensions of your image. This can crop the image and also embiggen it.
- Move the grid from this file by following the directions embedded in it.
- In that file there is a grid. Follow the directions to resize the grid to your needs.
You now have a working file. Edit your PS file in the way that you need. You will require a painting surface the same proportions as your PS file. Follow the directions at the bottom of this page to make a surface in matching proportions. Draw a grid on your surface and transfer.