Designed for the EOS-1D Mark III, 1D Mark IV, IDs Mark III 1D X, 1D X Mark II, 5D Mark III, 5D Mark IV, 5DS, 5DS R, 7D and 7D Mark II and available in 7 strengths: –4, –3, –2, 0, +1,+2 and +3 dioptres. Each lens comes complete with a rubber frame and is ready to attach directly to the viewfinder eyepiece. The lens slips over the existing eyepiece mount so that you can view the image through the viewfinder without needing to wear your glasses (corrects minor defects only).
EG frames are fitted with release grips which must be pressed before the frame can be removed from the camera. This is an improvement on the Adjustment Lens E which slides on and off the viewfinder with no lock.
We covered dioptric lenses in the 'Eyes Right' article in the January-March 2011 issue:
Dioptric correction lenses date back to the days of film cameras. Apart from the EOS 1, 1N and 1V, these cameras do not have built-in correction. Instead, Canon produces a range of adjustment lenses which slip over the viewfinder eyepiece. The lenses are available in different strengths, from -4 dioptres (for short-sightedness) to +3 (for long-sightedness).
All EOS viewfinders, for digital and film cameras, have a built-in correction of -1 dioptre. This is because many people either suffer from slight short-sightedness, or will do in the future. If you have good eyesight the -1 dioptre lens should not cause any problems. Your eyes will automatically adjust to take account of the built-in lens, and you should not even notice.
There are three ranges of Canon dioptric adjustment lenses: Adjustment Lens E, Adjustment Lens Eg and Adjustment Lens Ed.
You will notice that there is no -1 dioptre lens in any of the ranges. This is because the designation is not the power of the dioptric lens itself, but the power when it is attached to the viewfinder.