Final answer:
Overdevelopment of the film during the processing stage leads to a straight, black border. Overexposure results in blown out highlights while underexposure creates dark and undefined images. Proper balance of shutter speed, aperture, and ISO is crucial for correct exposure.
Step-by-step explanation:
The processing error that causes a straight, black border is typically associated with the film development process in photography. Option 3: Overdevelopment of the film leads to a straight, black border.
This happens when the film is left in the developer solution for too long, which increases the density of the film's edges creating a black border. Overexposure in photography occurs when too much light is allowed to reach the film or sensor, leading to a photo that is too bright or even with areas that are "blown out," where detail is lost in the brightest parts of the image.
Conversely, underexposure happens when not enough light reaches the film or sensor, resulting in a dark and possibly indistinct image. It's critical to manage the balance between shutter speed, aperture, and ISO to achieve properly exposed photographs.