DSC07567

We can create a sort of photographic camera with a digital scanner and a camera obscura.

DSC07571

If we want to focus close objects, we have to build a camera obscura with a sliding part.

DSC07580

We have built a camera obscura of black foam core cardboard with a base of 20 cm x 28 cm and a height according to the focal length of the lens, 20 cm.

DSC07587

We are using a bi-convex lens with a focal length of 200 mm and a diameter of 50,8 mm.

DSC07581

So the height of the camera obscura must be 200 mm = 20 cm. When the sling part is closed, the lens will be focused to the infinity.

DSC07596

This is what our scanner + camera obscura looks like

DSC07601

The scanner + camera obscura does not give any visual reference to focus the object, so we have to apply the formulas you can find in the paper: «How to calculate the focusing distance».

 How to calculate the focusing distance

formula2

This is the formula, where f = focal length, s = the distance from lens to the object (focusing plane) and Δx = the sliding distance.

 If our globe sphere is placed 100 cm to the scanner and the focal lenght is 200 mm = 20cm, the result is 20 X 20 / 100 - 20 = 5 cm

If our globe sphere is placed 100 cm to the scanner and the focal length is 200 mm = 20cm, the result is 20 x 20 / 100 – 20 = 5 cm. The sliding distance is 5 cm.

Save0005--

With a Canonscan LiDE 35 scanner we got this image (a bright, sharp enough, white and black image).The scanner specifications are:
Scanning Element: Contact Image Sensor (CIS)
Light Source: Three-colour RGB LEDs.

We tried the Canonscan LIDE 35 scanner with a image outdoors...

We tried the Canonscan LiDE 35 scanner with a image outdoors…

But we got this image (too much light for this kind of sensor, we guess)

DSC07613

Now, we are going to use the formula the other way round. We place the sliding part at 15 cm from the scanner and…

formula1

we apply this formula, where f= focal length= 200mm = 20 cm, and Δx (the sliding distance)= 15 cm. Then, 20 (20 + 15) / 15 = 46,666 cm. So the globe sphere has to be placed 46,6 cm from the scanner.

Imagen 003-

With an Epson Perfection 1650 scanner we got this image (a dark but sharp colour image). The scanner specifications are:
Photoelectric device: Colour CCD line sensor
Light source: White cold cathode fluorescent lamp

Imagen 011+--

The same image amplified

DSC07634

The darkness of the indoor image made us have a go with a outdoor image

DSC07637

We fixed a lens hood to protect the camera from the sun

Imagen 013

And we get this image

Imagen 014

The same image amplified

Some further information: