PANORAMIC IMAGE KIT (English)

[Japanese | English]

By Hirofumi Kasagi

Contents

◆ Motivation.

  1. Image Based Lighting
  2. What is needed to make an HDRI ?

◆ Set up.

  1. Materials
  2. Tools

◆ Make it.

  1. Set L-Frame on the head of tripod.
  2. Make a new head on the L-frame.
  3. Set the level meter on the L-frame.
  4. Make a round acrylic plate.
  5. Make a Fisheye mirror.
  6. Assemble Panoramic Image Kit.

◆ Use it.

  1. Take a photograph.
  2. How to make an HDRI.

Motivation

IMAGE BASED LIGHTING

Computer graphic artists frequently use a technique called IBL (Image Based Lighting).

IBL is a lighting technique that uses an image to calculate the intensity of ambient light like that from a computer-simulated sun or light bulb to light objects in a 3D world.

IBL generally uses HDRI (High Dynamic Range Imaging) for greater realism.

IBL is an important technique for greater realism, and involves HDRI.

Please examine the four pictures below.


The upper left picture is not made from IBL.

Let's compare the other pictures to it.

Upper right, lower right, and lower left pictures are made from IBL with HDRI.

In the upper right, notice that sample objects and shadows are tinted blue from the sky.

The lower left and right pictures are tinted green or red from the forest.

Moreover, the pictures were composited naturally from foreground 3D object and background landscape. These special effects are from IBL.

By the way, one can purchase HDRI data for IBL from online CG software shops, and one can also buy a camera which can take an HDRI.

However, such pictures and tools are expensive for personal use, because the equipment is marketed for research and development or CG companies, not for private experiments. There is not such a great demand for such tools, which drives their price even higher.

If you need a particular HDRI of a definite place; for example, your room, kitchen, or the neighborhood park you must take the pictures yourself.

Is it possible to make HDRI for IBL yourself?

Yes!

Actually, the above three sample pictures were made from HDRIs made by myself. Naturally, my HDRIs don't look as good as professional ones. However we can use it for IBL and get satisfactiory results. Moreover the cost of making a tool which can take pictures for HDRI is less than the professionals.

That is to say, anyone can make it if principles of HDRI and IBL are understood.

WHAT IS NEEDED TO MAKE AN HDRI?

To begin with, IBL is a technique that uses an image for calculating the intensity of light to light objects in a 3D world. Please refer to the sample image following.

An HDRI for IBL is required that can form a hemisphere to wrap around an object.

How do we take such a picture?

A fisheye lens is a wide-angle lens that takes in an extremely wide, hemispherical image. A camera equipped with a fisheye lens can take a picture suitable for making HDRI for IBL.

However, this technique is not so affordable, since a fisheye lens is generally expensive and can be attached only to a single-lens reflex (SLR) camera.

The goal is to capture the scene around an object.

The direct way is to use a camera equipped with fisheye lens, but it is not so affordable. How can one take a picture indirectly ?

By taking a picture of objects in mirror.

So this "Panoramic image kit" is based upon that idea.

Arrange the camera with a hemispherical mirror above it, and take a picture of image on the surface of the mirror.

This way is cheaper than buying a fisheye lens, and one can take a good picture for IBL.

Have fun making it!

Set up

MATERIALS

Material name Detail
[A] Level meter  
[B] L-frame (short) 40×40mm
[C] L-frame (long) 40×200mm
[D] Japanese ladle 360ml
[E] Rubber plate 1×150×150mm
[F] Alminium plate 1×100×300mm
[G] Clear acrylic plate 3×180×320mm
[H] Wing nut W1/4
[I] Washer W1/4
[J] Hexagonal bolt W1/4×20
[K] Polishing cloth (for metal)  
[L] Lens adapter LAH-DC20 (for PowerShot S3IS)
[M*1] Don't use it.  
[N] Flat head bolt 6×60mm
[O] Hexagonal nut 6mm
[P] Square nut 6mm

TOOLS

  Tool name
[1] Plastic cutter
[2] Scissors
[3] Phillips head screw driver (plus)
[4] Hand saw (for metal)
[5] Hand drill (for metal)
[6] Quick-drying glue
[7] Blade of drill (6mm)
[8] Rasp (for metal)
[9] Felt-tip pen (oil-based)
[10] Ball-point pen
[11] Compass
[12] Scotch tape
[13] Tripod
[14] Digital camera

Make it

1. SET L-FRAME ON THE HEAD OF TRIPOD

1a. Take the head off the tripod.

1b. Take off the screw which holds the camera to the head. We will use this screw later, so retain it.
1c. Thread the washer onto the hexagonal bolt, and screw it into the hole.

1d. Thread the hole of the short side of the L-frame sort through the bolt, thread the second washer, and attach it tightly with the wing nut.

2. MAKE A NEW HEAD ON THE L-FRAME

2a. Cut aluminum plate into width 80mm (green line), length 100mm (orange line).
2b. The edge of aluminum plate cut by the saw is sharp, dangerous for camera and hand.

Please scrape it smoothly with the rasp (metal file).

2c. Cut rubber plate to the same size as the aluminum plate.

2d. Clean the surface of rubber plate up, and apply a quick-drying glue.

Attach rubber over aluminum plate exactly, quickly, before the glue dries and leave it briefly.

2e. Carve vertical and horizontal lines (like a right picture) after rubber is glued to aluminum.

2f. Equip a drill bit (6mm) with hand drill, set its top on the mark, and drill a hole through it carefully.
2g. Cut the surface of rubber, like that in picture.
2h. Apply a quick-drying glue to the long hand of L-frame, wrap it over the rubber and aluminum plate, and let it dry.

I adjusted the hole of rubber plate to the second hole from top of L-frame, but you can choose another hole that you want to adjust for your camera.

2i. Another view.

3. SET THE LEVEL METER ON THE L-FRAME

3a. Set the level meter on the L-frame.

But if your tripod already has one, you need not attach another.

3b. Apply a quick-drying glue on L-frame (short) and set level meter on it.
3c. Adjust the hole of L-frame (short) to the hole of L-frame (long), and glue short frame on long frame. Keep holding with clip or hand until quick-drying glue sets.
3d. Finish setting.

4. MAKE THE ROUND ACRYLIC PLATE

4. Draw a circle along the edge of camera adapter with felt-tip pen (oil-based).

4b. Cut the acrylic plate with plastic cutter.

Be careful: if the surface of acrylic plate is scratched, the camera will take pictures with visual noise.。

4c. We don't know the center of this circle because it was drawn along the edge of the camera adapter.

Therefore, the next step is locate its center.

4d. Draw a circle on the paper.

4e. Set the compass point at the edge of the circle, and draw a half circle which crosses through the circle at two points.

Set the needle at another point on the circle, and draw a second half circle.

Two half circles should cross at two points. If those circles didn't cross at two points, please draw a half circle again.

4f. Draw a line through two points where two half circles cross.

Repeat. then there are two lines, and crossing at a point. This point is the center of the circle.

4g. Copy the center from the paper to the acrylic plate.

4h. Drill into the acrylic plate with the previously used 6mm bit.

Be careful: acrylic plate is not so hard, and cracks more easily than aluminum plate.

4i. Cut the corners of acrylic plate with plastic cutter.

4j. After that, scrape the edge of the round acrylic plate with rasp for metal.
4k. and scrape the hole in the center.
4l. Finally, polish the surface of the plate with a soft cloth.

5. MAKE THE FISH-EYE MIRROR

5a. Thread the round plate with flat head bolt (6mm×60mm) and washer. Attach it with the hexagonal nut.
5b. Apply a quick-drying glue on the edge of the camera adapter, as and glue it together.

Pay attention, the head of bolt turns below.

5c. Correct position is that shown in right picture.
5d. Cut off the handle of the ladle with the hand saw.

5e. Drill at the center of ladle with 6mm blade.

Be careful; the rounded surface is slippery.

5f. Polish the surface of it with the cloth for metal.

5g. Set a hexagonal nut at the middle of the flat head bolt.

Adjust the setting point to the range of focus by yourself.

If the length of the bolt (60mm) is too short, please change it to long one.

5h. Side view.
5i. Finally, fasten the mirror head with a nut.

6. ASSEMBLE PANORAMIC IMAGE KIT

6a. Attach fisheye mirror to the camera.

6b. Attach the camera to the L-frame with the screw which was left from tripod.

6c. If there is a gap between the camera and L-frame, thread some washer on the screw.

6d. Congratulations!

Let's take a picture with fisheye mirror.

Use it

TAKE A PHOTOGRAPH

When you take a photograph, change the focus to macro mode.

You have to try to adjust the focus point at the center of view.

If your camera has a manual focus mode, I recommend using it.

If you can select some ISO mode, I recommend to use low value mode, to prevent white out when you take a photograph of the surface which is on the mirror.

Sometimes, you take a picture in which you can see yourself.

The answers are to use a timer mode, or hide in the blind spot (below the camera, etc.)

I recommend a large size photograph;

High resolution makes a better image for IBL than low.

You should take some photographs at ±1 step brighter or darker than original. When you have two pictures which are taken at different exposures, you can make a HDRI. I if you have more photographs, can make a better HDRI.

Generally, I bracket five photographs (-2, -1, ±0, +1, +2) for making a HDRI.

How to make an HDRI

To make a HDRI, one need special-purpose software.

Now, there is some HDRI software which is free or commercial-for example, Photoshop (CS2), HDRI Shop, and so on.

There are many web sites which introduces how to use it and make HDRI.

I omit describing how to use those software.

Thank you for your reading.

Good Luck!