Making your Reference Probes
One very important part is making the reference probes you need later for matching color, contrast and brightness. What exactly are these reference probes, what is the sense and for what do you need these in your 3d application ?
These probes are original shots from your location and your background image you use in the viewport in your 3d software. Therefore you have to recognize, that exactly from your bg-images you have to make the probes. It´s the same like a professional photographer is working on a set. He is measuring the light and tries to get some references about light intensity, light color and contrast. Exactly this is such a very important point to match your 3d objects with your bg image.
Remember, that you will fail to match your 3d scene with your bg image without these very important values. This is the main reason, why many people fail matching 3d objecs with free downloadable hdri´s. Without the probes, it seems to be impossible to match the color and reflection perfect. You will try but without success. But with using your probes, it will be granted that you can match.
If you have made your reference probe, you can load it into your 3d software and put it onto your viewport . In this new scene file, you can create a 3d sphere directly beside the real photographed sphere, the reference probe. Now you have to choose the right angle and camera perspective from your virtual 3d camera. Remember, this has nothing to do with matching colors, it´s only a try to get the right perspective and angle on your virtual 3d camera. So you will get the right setup for your skylight and reflection.
And now it´s time to make your reference probes
These shots are nothig more than your bg images you want to use for your 3d render. But it´s very important, that you put your sphere with your linkage on the photo. I could find out, that it´s very good if the half of your image will use the sphere. Below the images from my probes.
Now let´s start with the first probe, the silver reflection sphere. Now make the setup from your camera, so that you can see your sphere in front of you. Like the images above.
Now use the automatic on your camera, so you will get automaticly the shutter speed and f-stop from your camera. Write down and remember these both values, and switch to your manual modus and set your shutter speed and f-stop to the same value, you´ve got before from your automatic modus.
Now the setup is finished. Get sure that the sphere is sharp in focus and click - make a photo.
Well done, now you have made your first reference probe, in this case your reflective reference probe. Every digital camera will let you know the shutter speed and f-stop from your image you have made. So you can control, if the manual image has the same values like the automatic modus.
Your second reference probe will be the next, and it´s the same way like we did it with the reflective reference probe. But in this case, you don´t use the reflective sphere, you have to use the white one. This sceond probe, is for matching brightness, contrast und saturation as also for the depth of the shadow.
If you want you can make also a probe with a black sphere, or the grey one. Every refernece probe will help your later for color matching. I recommend you to make a grey matte reference probe too. To use white alone, can make you troubles. Your white could be to bright, so that you will get troubles with matching your virtual 3d scene. With the matte grey sphere you will have less risk.
Now you have made your reference probes, but don´t forget to make your bg image without any sphere on it. This will be your bg image in your render scene you want to match with your 3d objects. Get sure, that you photograph your bg image with the same values of shutter speed, f-stop, perspectice, angle and focus.
If you have done all your images and saved on your harddisk, you have finished the part of making your reference probes.
Assembling with HDR Shop
If you have saved your images to your harddisk, open HDR-Shop. Create--> Assemble HDR from Image Sequence
The following image pops up:
Now load every single image into HDR-Shop. Get sure that you only choose the images you have made from your reflection sphere in step 2. In my case, I made 6 images and usually you get a very good result with six images.
Load Images
Camera Responsive Curve: This setting is very important. Choose the right value, the gamma curve from your camera. For the gamma curve you will find many technical papers, and you can get very easily confused. But the gamm-response curve is very simple. If the gamma value is higher, you will get more contrast into your image. But it depends on the gamma curve from your camera, because every camera has different settings. If you are in luck, you will find the gamma curve from your camera in your manual, than you can choose this value. In my case I have a gama response curve from 1.25. I could also find out, that you will get much better results in rendering, if your HDRI looks like a little bit "washed out", with less contrast. HDR-Images with a high contrast will bring you big parts of noise, and color distortion, because the contrast is to strong.
Calculate Scale Increments
The software calculates automaticly the scale increments. So it´s not necessary to use your own settings. I always choose the automatic calculation for that. Press "Calculate", and than "Generate Image".
Now a new image opens, and you can see your first own generated HDR-Image. Click the middle mouse button, so you can move the image.
With View--> Zoom out / in you can fit the image to your canvas. With + / - you can switch between the different f-stops. Chose the one that will fit best to your real life scene, and click
Image-->Pixels-->Scale to current Exposure
now you have set this f-stop to your favorite one, and this will be used in your 3d software after loading the image.
Select-->Draw Options-->Circle
With that option, we want to select the sphere only. Now click Select-->All. You can see a line which you can select and fit to your sphere. We want to crop the sphere. Image-->Crop
Image-->Panorama-->Panoramic Transformations
Will bring you to the following image:
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