I have recently discovered DigiCamControl, a really good software to control and use the reflex camera from PC.
This is useful for Timelapses, HDR photography (and other kind of bracketing), and is also convenient for studio photography.
The software also supports liveview, which is handy when the camera is in nearly inaccessible position (for example close to the floor, or too high, or above a table pointing down vertically) because you can check composition watching the PC monitor instead of the optical viewfinder. But of course liveview in the PC is avaiable only for DSLR cameras that already have liveview(the ones that can use the LCD display as a viewfinder and usually can capture videos).
I have a Nikon D40 that like many other reflex camera do not have liveview so I tried to solve the problem.
Step 1: Ingredients
A small webcam
A computer, a desktop works but for portability better notebook or netbook,
also some tablets/smartphones have the ability to use external usb webcam, and some can also remotly control the DSLR by USB, but in this case you won't control the DSLR and view what's inside the eyepiece simultaneously, (because usually tablets/smartphones at best have just 1 USB host connector, maybe a powered USB HUB can solve this particular problem but the other problem is that usually on a tablet you can see only one app at a time.)
An angle bracket.
(the bracket should be inserted in the hotshoe, then the thickness and width must be suitable.
the length should allow the webcam to be placed right in front the optical viewfinder, if the right dimension are't avaiable take a longer one and cut)
in alternative to the bracket also a flat bar of aluminium, that will be bended as needed.
An alternative to the hotshoe mount a similar solution could also be connected to the tripod mount screw.(but in my case the hotshoe was much closer and alligned with the viewfinder, so I choose that)
As an option I also used an off-camera strobe extension cable (I-TTL) to be able to use the flash anyway(and because it spaced the angle bracket from the camera exactly and i was able to avoid cutting the metal bracket).
Step 2: Build
1) Insert the flash extension cable in the hotshoe
2) Insert a thin piece of plastic on the top of the flash extension connector(the camera end of the cable) to avoid shorting the hotshoe contact
3)Insert the angle bracket on the top of the flash extension connector
4)Clamp the webcam to the bracket.
Step 3: Using
1) Plug the webcam in the computer
2) Now aside the DSLR camera controlling software start the webcam software(I used Yawcam or AMCAP)
3) As you could notice in the pictures of the previous step the webcam is upside-down so in the webcam software change the settings(select flip vertically and flip horizontally or rotate 180° that is the same) to show the image correctly.
(then when choosing the webcam software consider that it must be able to flip the image)
4) Turn the lens on the webcam to focus the image.
Step 4: Possible Future Improvements Test (wireless and Better Portability)
There is an android app(free) named "IP Webcam" that let you see on an internet browser(or media players) on a PC or tablet what your smartphone is capturing if they are both connected to the same WiFi network.
So replacing the webcam with the smartphone I would be able to point the camera looking the smartphone display (almost like the reflex it had liveview on its own LCD), and I would be able to connect also the TABLET to the smartphone (and do it wirelessly)
and since it's possible to connect tablet and smartphone with ad-hoc wifi connection this is also possible in the middle of nowhere (a tablet is much more portable and flexible than a notebook and a wired webcam).
The devices used in the test are a smartphone Samsung Corby i5500(Samsung Galaxy 5) and a tablet Mediacom Smartpad 875s2
a problem to be solved is that the image captured by the smartphone is mainly black(being able to zoom only the interesting part would help)
another problem is that the smartphone's camera can't focus and then the image is slightly out of focus(the image obtained with the webcam is much sharper)