If you're like most photographers, you think there are three factors affecting depth of field. In that case, you would be incorrect - there are indeed four factors affecting depth of field. Do you know what they are?
In this video Mat Marrash covers the four factors that contribute to depth of field. Moreover, he provides some useful education to better understand how they work together to create the desired effect. In addition, for those photographers who shoot large format or utilize lenses or cameras with tilt capabilities, Marrash discusses how a photographer may take advantage of front or rear movements to affect depth of field in creative ways.
Personally, the depth of field, tilt, and shift capabilities of a large format camera is why I got into 4x5. The full frame equivalent to the standard 4x5 lens (e.g., 210mm f/5.6) is a 56mm f/1.5 which may not sound like much but the fact of the matter is that most people would agree that there's something particularly special to large format images (particularly when it comes to portraits). When you start playing around with front standard movements, that already razor-thin depth of field can make some very creative looks.