In my last post, I discussed the relative frame sizes of 35mm still film and 35mm motion picture film, and how this relates to the depth of field of the two formats. I mentioned that imager size and depth of field have an inversely proportional relationship. I find that a lot of people know that this is true, but are confused as to why this is. I was confused by it myself for a long time, and I have never seen it explained in a very clear way, so I am going to try to explain it. If I end up just confusing you further, well that's the chance you take by reading this blog.
If you've ever taken a photography class, or read a book about photography, you no doubt learned the three variables that affect depth of field: focal length, distance to subject, and aperture. Ok, so what about format (sensor size)? How does that come into play? Well, chances are you don't remember hearing about that one, because it's not really a variable. If you are shooting on 35mm film, you're only concerned with the depth of field of 35mm film. When you're taking a picture, chances are you're not going to grab a camera that shoots in another format just because you want more or less depth of field, the way you might change the aperture or choose a different lens for that reason.
HD capable DSLRs seem to be everywhere these days, with projects ranging from low-budget feature films to primetime network television programs taking advantage of the cameras. They offer HD imaging with cinematic 35mm depth of field in a tiny package at a bargain-basement price. What's not to love?
As an HD DSLR owner myself, I will be talking a lot about these cameras on this blog, but in this post I would like to focus (no pun intended) on that cinematic depth of field. After all, this is really what sets these cameras apart from pretty much any other HD camera even remotely in the same price range.
There seems to be a lot of confusion about the term "full frame sensor". I would like to try to clarify this concept, specifically in terms of how it relates to what are no doubt the two most popular HD DSLRs, the Canon 5D Mark II and the Canon 7D.