Black Cardboard Tutorial -- How to deal with high contrast scene

We usually use graduated neutral density filters to take a picture with high contrast
range. If you are standing in a location with contrasty lighting --for example, a forest
on a bright sunny day-- you can see detail in both the darkest shadow areas and the
brightest highlight spots simultaneously. But its result is fixed depending on what kind
of filter you use. Considering of the contrast area is higher than a 8-stop range. How
do you deal with this range in one scene ?
This tutorial will introduce a new method instead of using flters to take a picture in
high contrast range. If you have already manipulated the black cardboard. You can take
a shot like eye seeing 12 - 14 stops, even more.
Before you practice this tutorial, you should prepare a thick black cardboard first.
For a sunset picture, we can separate the picture to light and dark area.
If we get a exposure time for the high light area is 0.5 sec and the dark area is 6 secs.
The detail steps as below:
1. Put the black cardboard on the border between two areas that you can see from the finder.
2. Adjust the shutter to 6 secs, cover the light area with black cardboard.
3. Shake black cardboard on the border between two areas quickly.
4. Release the shutter.
5. Shake the black cardboard 6 - 0.5 = 5.5 secs to let the dark area expose.
6. Move black cardboard up quickly to let light area expose.

If you have been familiar with the above steps. You can try to use M shutter mode to
control the shutter by yourself totally. And follow the final step, you have to use
black cardboard to cover the lens very quickly. For some practice, you can handle
1/8 sec. And more practice, may you can handle 1/16 sec or 1/32 sec. For more advanced
skill, you can shape of the black carboard for you need to cover the light area.

PS. Black cardboard method originates from the dark room to control the film exposure.

If you have any question, please feel free to ask me ^__^.