From the DTO archives, this short course will teach you how to combine two pieces of photo reference. There are many subtle factors to combining multiple photos into one scene.
You will certainly have to sync up the perspectives from both photos. This course will help you to figure out how to map horizon lines and vanishing points. You will also learn the importance of matching light sources. This course will help you to create a believable illustration.
The lessons in this course were filmed back in the beginning, when the original Drawing Tutorials Online was launched. The video quality is not great, however the lessons are valuable, enjoy.