One of the more apparent differences between film and digital video is the way the cameras handle depth of field. Film cameras have allow for a shallow depth of field (resulting in only the subject area being is in focus), while video cameras offer a larger depth of field (resulting in everything being in focus). To achieve a shallow depth of field with digital video camcorders a depth of field adapter is generally used. Before you rush out to purchase an adapter you should ask yourself if you really need one.
Before you decide if you need one, you have to understand exactly what you are purchasing. A depth of field adapter is not a quick solution. It will not provide perfect results once you install it. They are a tool like any piece of video equipment in your arsenal. This tool, like any, requires mastering. It will take time and practice to achieve the results desired from an adapter. With that said and adapter should not be an impulse by nor one you should rush to buy/build. I will say for most videographers it is a fun tool to experiment with.
Ok, so you decided you want to go for an adapter. The first thing you should do is research. They're are many high-end commercial solution that cost $1000+, however there are also as many 'DIY" versions on the market ($150+) and tutorials for building your own DIY adapter. I can say i have seen footage from many of the 'DIY' adapters and they can be very comparable, if not superior, to commercial solutions. This is why research is the key. You can search sites like Vimeo.com for HD footage from most of the adapters out there. There are also many comparison videos there as well. While researching adapters keep in mind that there are 3 types of adapters; static, spinning, and vibrating. Static is fine, but you run into trouble with keeping the internal ground glass(heart of the adapter) clean, which results in noticeable artifacts and patterns in your footage. The solution is to add movement to the ground glass...hence the vibrating and spinning adapters. Spinning adapter are larger and use a rotating disc as the ground glass, this can actually cause a 'pumping' focus effect if not aligned correctly. Vibrating adapters are my personal choice. They actually vibrate the ground glass, usually in a slight circular, pattern. The vibration is very slight, but enough to make any dirt on the ground glass disappear. Usually vibrating adapter allow for speed adjustment which provides you with even more control.
Okay so you decided you want an adapter and you understand the basics of each type, now what? Now you decide if you want to attempt to build on yourself or purchase one. Purchasing a DIY vibrating adapter will run you at least $250 (most likely more), while a commercial version will be at least 3x as much. Building your own sounds like a cheap route to go right? Well, not exactly. Unless you have the parts available to you at a local store (most likely not) you will probably end up sourcing them online. And you can find great prices online, however, since there really isn't a one-stop shop for parts, you have to factor in shipping. Which really ranges greatly from store to store. This will make a vibrating DIY adapter about $100 - 200 easy. However there are a few creative solutions utilizing PVC pipe and other easy to get parts from local stores. Tutorials for these can be found at here.
I hope this helps, also don't forget to figure in lens support and a tripod into your budget...once you start experimenting with the actual adapter you will understand why these might be needed.
