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DOF: Depth of Field Using 35mm Lenses Continued…

Building the First Model Prototype

So now that we know what we will be building, we have to get everything we need together.

Maxwell already has the fake CD clouded on one side making it the perfect alternative to ground glass.


You may have an old CD player, like this one lying around in a garage or a basement. If one is not available to you, you could try to find a cheap one at a thrift store or from a friend.


Finding someone to assist you, is a great way to make this a more entertaining project. And finding an assistant who doesn’t misplace or try to take your supplies is always a good thing.


Now the CD player can have a “second life”.


Three screws held together the motor piece that we need to the body of the player.


The lens and laser have been taking out, and the remaining piece is what we need.


The bottom lens cap piece of the lens will hold the lens and the board together and still allow it to be taken off.


In order for light to pass through the cap, obviously a hole needs to be made in the cap.


Three boards with holes cut out of them, mentioned in the previous page, are needed.


Now with everything we need, let’s put it together.

First, the motor from the CD player needs to be attached to the board. The rubber silencers can also be used.


Second, with the lens in position, the next board is attached to the lens cap. And if you look through the lens onto the CD (ground glass), you can see the mirrored image.


 The last and final board can then be attached. This is the board that will connect to the video camera through the macro lens. Once the battery is connected, we are ready to conduct the first experiments.



The main objective is to determine the distances so the whole range of focus of the lens can be used.

You can figure this out with the lens distance from the CD (ground glass). Carefully, this should be set, so the whole focusing range of the lens can be reused. An easy way to find the right distance is to focus the lens to infinity and aim the whole mechanism towards an object far away and look through the back at the CD (ground glass). It’s not possible for the image to already be in focus, so we have to change the distance between the lens and the CD (ground glass) with the screws in order to focus it. In doing this the mechanism is now calibrated so that it can focus on infinity.

With zooming, the distance from the CD (ground glass) to the macro lens is not extremely sensitive when we determine that we can focus with the camera from that distance. To avoid getting a vignette effect, we can zoom in or out. If there is a problem with focusing, the camera must be removed from the CD (ground glass), until you are able to focus. The macro lens can make the distance shorter.

In one evening this model took about two hours to build.

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