Introduction

When transfering a reference photo onto the drawing surface in a larger scale it is best to use either the so called grid method or a projector to help with the proportions. Here is the quickest and easiest way to create your own grid overlays in Photoshop.

Creating the Grid

First, load your reference photo into Photoshop and go to EDIT->IMAGE SIZE and uncheck "Recalculate Image", set the resolution to 300 DPI. Set the width/height units to cm or inches, and type in the dimension of your actual drawing. For example, if you want your drawing to be 100 x 70 cm, set the width and length there to 100 x 70 cm.
Hit OK.
Next, create a new image FILE->NEW... Set the image dimension to the size of your grid, for example 6 x 6 cm or 2.5 x 2.5 inches. Make sure you have the same DPI resolution that you set earlier with your reference image. Choose a white background and hit OK.
Unlock the layer by clicking on the lock symbol. Now add an FX layer to that layer and choose OUTLINE. In the menu set a pixel width of around 4, set the position to inside, opacity to 100%, and the color to black. Hit OK.
Now choose "SELECTION->COLOR RANGE and click on the white background. Press OK and then press DELETE to remove the background. Next, choose SELECTION->DESELECT ALL
Go to EDIT->DEFINE PATTERN and name it the size of your grid, e.g. 6x6cm.
Now go to your reference image, select the FILL tool and in the menu bar at the top change it from FOREGROUND to PATTERN. Choose your pattern from the dropdown menu that just appeared. Finally, press anywhere in your image to fill it with a (in our example) 6 x 6 cm grid. Done.


Drawing the Grid Onto the Drawing Surface

Using a ruler, measure and mark 6 cm (or 2.5 inches) intervals continuously at the top and bottom, and at the sides of the drawing paper. Draw the grid lines by connecting the marks. When drawing with charcoal, use a Derwent Light pencil. For graphite, use a blunt HB pencil. Do not use any other pencil for the grid! Don't erase the grid after transfering the drawing. Derwent Light / HB pencil will just disappear during the shading and blending process. With charcoal, erase the parts of the grid before shading and blending white charcoal though.

It's best to clean your ruler or bar before and afterwards to avoid dirtying your drawing surfaces by accident.

If you made a mistake, use a clean kneadable eraser and dab lightly over it to remove the charcoal.