35mm adapter question

[evolvnyc]

I know there's lots of discussion about the "best" 35mm adapter, but as I'm new to them, I wonder: Do ALL 35mm adapters have glass in them? Obviously, you are adding a 35mm lens to the equation, but are there differences in glass in the adapter itself? I ask because, as a still photographer, it is of great importance to know what's going in front of your expensive glass (in the case of the DVX, it's Leica...) So my question is: does anyone know of 35mm adapters which contain no glass, aside from the lens you will be adding to the mount?

 

[DavidChia]

Go here and read this and you will understand why there is a piece of ground glass inbetween your camera lens and 35mm lens

http://www.mediachance.com/dvdlab/dof/index.htm

 

[dbarak]

All need the ground glass (or equivalent).

Think of it this way -- your DVX lens is normally shooing a three-dimensional world and applying its own depth of field to the image. In the case of the camera, it's deep depth of field. Now, with a 35mm camera, the depth of field is generally less than with a video camera because the imaging plane is bigger. What you're doing with your video camera, when you're using an adapter, is essentially taking a picture of a two dimensional picture. The 35mm lens is projecting a (relatively) shallow depth of field image onto the ground glass, and your video camera is in turn just taking a picture of that image. Without the ground glass, you wouldn't get the depth of field effect.

Yep, there are differences in the quality of the ground glass, depending on the material and how it's treated. My adapter (a Redrock M2) uses a plastic ground "glass." Beyond the material, I don't know much about how it was made. Other adapters use real glass, and some home-built adapters use wax (I'm not sure how that works).

Keep in mind though, that there are three ways that I know of to utilize the ground glass. One method is static, which means the GG just sits there. The potential problem with this is that ground glass inherently has a grain pattern, and since the grain isn't moving, you could possibly notice it in your images. Some adapters are built so that the ground glass vibrates (up and down, left and right, but obviously not forwards and backwards, or that would affect your focus), and some adapters are built so that the ground glass is rotating. Keeping the grain pattern moving pretty much makes it disappear.

So, the ground glass is needed. It's primarily just a matter of quality. Although I do have an idea for an adapter that doesn't use a traditional ground glass...