When choosing the electromechanical components, you need to have some idea of what the mechanical requirements are.
So lets think a little about the actuator that would move the camera up/down. How much does the camera weigh? How much will the rest of the assembly that you move up/down weigh? How much do you need to be able to move the camera up/down? This things will have an interrelated effect on the actuator you choose. For example, let us say you have a 1lb. camera, and need to move it +/- 1.5 ft. The easiest solution is then an actuator rated for a the weight of the camera, plus the mounting assembly. Note that you will likely need to increase the force capability as you need to think about how fast you need to move the camera up/down. Remember that F=ma, so if you need to accelerate / decelarate quickly, the force requirments of the actuator go up. Then once you know the force needed, then you can think about the travel. In this case you need a total travel of 3ft. My guess is that an actuator capable of the force required, at a 3ft travel, may be sort of expensive. You may then say, well lets use mechanical advantage with a linkage that then increases your travel. Note that this will likely force the total weight of the camera assembly up, and remember that if you then design a mechanical advange of 3, that the forces from the weight of the camera and platform on the actuator will be increased by at least 3x, and likely a bit more, as no system is 100% efficient. (Our old friend friction comes into play.)
So, you can iterate on a couple solutions, while looking at total cost, in an effort to minimize the total solution cost, so that you can build the thing. Then you can come up with a best guess on where the sweet spot is for cost of that solution.
Do this in other areas as well. Do you need to know the position of the actuator? How will you do so? How will you determine if the camera must go up/down? Can you determine if your feedback system will implement a proportional response, or will it be a up-off-down control loop? etc.
My guess is that you will need to find specs for a variety of types of actuators, with different force, response, and travel requirments, and then use that to choose the device. Note that the optimal solution may even include one device with a long travel with slower response, and a shorter throw device with fast response.
There are many more variables here than you've thought about. This will be plenty challenging for you! In engineering, lots of times you aren't the expert... until the end of the project where you have become the expert!