Promaster spectrum 7 Auto Teleconverter

The Promaster Spectrum 7 Auto Teleconverter for Canon is designed to double the effective focal length of Canon EF and EF-S lenses while maintaining automatic functions. Here is a detailed overview of its features, performance considerations, and usage tips:

Key Features:

1. Compatibility: Designed for use with Canon EF and EF-S mount lenses and cameras. Ensure your lens is compatible, as not all lenses perform optimally with teleconverters.
2. Magnification: Provides 2x magnification, effectively doubling the focal length of the attached lens. For instance, a 100mm lens will function as a 200mm lens.
3. Automatic Functions: Maintains electronic communication between the lens and camera, preserving autofocus (depending on the lens and camera model), image stabilization, and automatic diaphragm control.

Performance Considerations:

1. Image Quality: Using a teleconverter typically results in some reduction in image quality. This includes potential losses in sharpness and contrast, as well as increased chromatic aberrations. The impact varies with the quality of the teleconverter and the primary lens.
2. Aperture Reduction: The teleconverter reduces the maximum aperture of the lens by two stops. For example, a lens with a maximum aperture of f/2.8 will have an effective maximum aperture of f/5.6 when used with this teleconverter. This reduction in light can affect exposure settings and autofocus performance.
3. Autofocus Performance: Autofocus speed and accuracy may be affected, especially in low-light conditions or when using lenses with smaller maximum apertures. Some camera bodies might disable autofocus with maximum effective apertures smaller than f/5.6 or f/8.