This study will describe you easy step by step how you can make your own hdri images, and use for your render to get a photorealistic look.

Chapter Overview 

1. Preparations
2. Making your own HDRI probes
3. Making your reference probes
4. Assembling with HDR-SHOP
5. Matching HDRI-Reflection
6. Matching HDRI-Skylight
7. Final Render
8. Post with Photoshop

Preparation

I don´t want to talk about mathematic, technic and function about HDRI. I will describe the practical use. An HDRI (High Dynmaic Range Image) is a shot from one image with different shutter speed. Every single image with all the different shutter speed were merged to one single image and saved as .hdr file. Years ago, the film industry recognized that this is a way to catch different levels of light, which is useful for rendering.

Which things are needed for using the HDRI-Technic ?

a) a digital cam
b) 3 spheres with a radius from 10 bis 30cm, and of it
- one silver, full reflective, mirroring sphere
- one white, matte sphere
- one grey, matte spherel
c) a tripod for your cam
d) a kind of tripod for your spheres
e) a white board
f) a little table
g) your laptop
h) the software HDR-Shop (download from Paul´s website www.debevec.org)
i) one free or for commercial use 3d software
j) a render

The following image shows all needed instruments for making the HDR Images. Except the cam, we needed to make this photo.

Cam: If you have the choice you should choose a digital cam with remotecontrol. So you can connect your cam with your laptop. If you don´t have this feature, than it would be good to have a timer on your cam.

That´s important, because I could see, that you can get lot´s of distortions in your image, because your hand isn´t still enough for a longer shutter speed. Without that, it´s not possible to get a 100% sharp HDRI.

Sphere for the probes: The probes are nothing more than simply spheres you can get in every super market store. If you ask for spheres which you can use in the garden for your roses, than you are on the right way. I could also see, that you can use spheres you usualy find on christmas trees. In my case, I used simple spheres, which you can open. The core is hollow and not massive.

It is important that you will get three spheres, witht the same dimension and size, but with different materials and colors. Following is the description of things you will require in this...

1. Sphere: It´s the mirror/reflection sphere and the material looks like a flat mirror. This sphere reflects the environment and you use this for the reflection probe.
   
   
2. 3 Spheres: One sphere should be white and the other one grey. The basic material should not reflect. An addition would be a black sphere, but with white and grey you will get great results.
   
   
   
3. The Tripod: The tripod should fit to your cam. It´s important that not every easily gust of wind will blow your tripod away.
   
   
4. The Tripod for your spheres: This is a very creative point. A very good solution is a sunning screen, which are very cheap to get. And it´s important that you have a linkage or something like this. In this you can fit a round bar and fit the sphere on it.
   
   
5. White Board: The white board will be used for the white alignment.
   
   
6. Little Table: A little table where you can put your laptop on, it´s really I can recommend.
   
   
7. Laptop: Required any description ?
   
   
8. HDR-SHOP: The HDR Shop you can download for non commercial use free from www.debevec.org. There are other software packages out you could use, but in this tutorial I will use HDR-SHOP only.
   
   
9. Free or Commercial 3D software: As instance, Blender is a free software you could use. Other solutions are 3dsmax, Cinema 4D, Lightwave, Maya, Softimage, etc.
   
   
10. Render: Usually you will get with common 3d software packages render systems. But also you can get render plugins like Splutterfish Brazil or V-Ray from Chaosgroup.
    
    

Making your own HDRI Probes

a) Location: Think about where you want to make your snapshots and what you want to photograph. For your first try I would recommend to choose a simple living room before you try an exterior shot. You should get ready with your cam and software. For this study I´ve choosen a simple possibility, that means, the final shot should record the environment and a 3d object.

b) White Balance: Before you start shooting your first images, you should make a white balance. How to do that, you should read in your manual of your camera. For that, use the white board.

c) Setup your tripod, the spheres and your camera: Put the camera on your tripod. On the same height and 1 meter in front of your camera, you position the linkage with the silver reflection sphere. Your camera shows direclty to the sphere (front view). Now put the camera 1 meter in front of your sphere, and watch out that you will get the same height as the sphere. You should see the whole sphere on your camera. For that, select the right zoom. Now get sure, that you can make the photo with your remote control, and that you have activated your automatic modus. So you can see if your sphere is 100% sharp and correct on your photograph.

If this photograph is perfekt, choose on your camera the best pixel solution. Now change your modus to manual, and choose for each photo a different shutter speed. The basics about photography you should know. If the shutter speed is longer, more light comes on the image, and so it will get much brighter. If the shutter speed is too long, you run in danger to get distortions on your image. To avoid that, you use the tripod. Of course, you have to see the shutterspeed dependent to the f-stops. The f-stop defines the radius of the hole to the lens.

For your HDR-Images it´s enough if you make 6 to 8 images. What does this mean for the praxis ? Make your first image, with a very long shutter speed, as instance 10 seconds. You will see, that the image get extrem bright. And you should know, that a good HDR Image has a bride range or even a high range of light information, that gets from bright to dark. So don´t get confused about that, it´s okay. Important are the different shutter speeds and there unit steps between. In the praxis I could see, that it is very good if you have 4 steps between your shutter speed range. As instance, 10 seconds for your first image, and the second shot you make with 4 seconds, and so on.

Take a look on the images which will show you excatly the values.

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