Final answer:
In a blue chroma key, blue objects become transparent because the technique removes the color blue. A blue filter absorbs all visible light other than blue light and allows only blue light to pass through. The color we perceive in an object, such as blue, is determined by the wavelengths of light the object reflects when illuminated by white light.
Step-by-step explanation:
What occurs in all blue objects in a blue chroma key is that they become transparent because the blue chroma key technique involves removing or keying out the color blue. This is commonly used in video production and photography to composite two images or video streams together based on color hues. The same principle applies to how colors are perceived in general, as the true color of an object is determined by its reflective characteristics. For instance, a blue object reflects the blue component of white light, making it appear blue to our eyes.
When it comes to the question of whether a blue filter absorbs or reflects blue light, it's important to note that a blue filter absorbs all visible light other than blue light. Therefore, it is incorrect to say that a blue filter reflects all other colors and absorbs blue. Instead, it absorbs other colors and transmits the blue component of the light, which is why it is used to allow only blue light to pass through.
Objects appear different colors depending on the light that shines upon them and the wavelengths of light they reflect or absorb. For example, when white light, which consists of all colors, falls on an object, the object absorbs certain wavelengths and reflects others. A blue object under white light will reflect blue light and absorb other colors, which is why we perceive it as blue. If this blue object were to be placed under blue chroma keying, it would blend in with the blue background and seem transparent in the final output of the video production.