Making RTIs
What can go wrong,
what can be fixed
Materials
- Camera, lens
- Camera remote or mirrorless app
- Tripod
- Lamp
- Reflective sphere
- Background
- Ruler
- Software
A decent setup
Zoom
Having the correct optics is important
to make use of the full resolution.
Light
Use a dark room with a small, bright light.
Reflective sphere
- Shiny black
- Size: ~200 pixels
Too big causes shadows, too small can't tell light direction - Placement in the corners
Pay attention where the shadows will fall, both object->sphere and sphere -> object - Half sphere if you can: easier to place, less shadows
- Multiple spheres if you can
software will be able to estimate light position in 3d and compensate
Background material
- Opaque
- Dark
- Microstructure
Best are cloth or rough cardboard.
Camera setup
RAW
PROS: can fix exposure and white without losing quality
CONS: space on SD, shoot time, conversion to JPEG
Manual mode
- White balance
- Exposition time
- Diaphragm
- ISO
- Focus
All these parameter must remain consistent across shots.
White balance
A correct white balance preserve the original look of the object.
Invest some time to get it correct at shoot time.
Exposure
The exposure must be able to accomodate razing light and front light.
Rule of thumb: pick 45 degree light.
Focus
Can be challenging to have all of the object in focus, and can't be fixed later!.
Close the diaphragm to increase the depth of focus, don't overdo as image quality suffers: diffraction.
Execution
Keep the camera still!
If the camera moves between shots the RTI will be blurry, even if each photo is perfectly in focus.
This problem can be fixed later most of the time, but takes a lot of work.
Light directions
From left to right: horrible, decent, good, dome
The light directions should be uniformly sampled.
Distance
- Too far: the camera or the tripod will cast shadows on the object
- Too close: the lighting will be not uniform
- Keep the distance of the light consistent
Software
