If you wear glasses, it can be difficult to see all of the viewfinder image clearly. A correction lens may help. The lens slips over the existing eyepiece lens so that you can view the image without wearing your glasses.
This fits most EOS digital cameras (the exceptions are the EOS-1D Mark III, 1D Mark IV, 1Ds Mark III, 1D X, 5D Mark III, 5D Mark IV, 5DS, 5DS R, 7D and 7D Mk II, where dioptric lens EG is needed, and EOS 3, 30, 33, 5, 50 and 50E, where dioptric lens ED is needed). It is available in ten strengths: -4, -3, –2, –0.5, 0, +0.5, +1, +1.5, +2 and +3 dioptres. It can be used with Rubber Frame EB, EC or EF, which provides a soft rubber surround to prevent the scratching of spectacle lenses.
Please note that the Canon dioptric lens E requires a separate rubber frame as follows:
Rubber frame Eb:
EOS 5D, 5D Mark II, 6D, 6d Mark II, 7D Mark II, 10D, 20D, 30D, 40D, 50D, 60D, 70D, 80D, D60.
Rubber frame Ec:
EOS-1D, 1D Mark II, 1D Mark II N, 1Ds, 1Ds Mark II.
Rubber frame Ef:
EOS 77D, 100D, 200D, 300D, 350D, 400D, 450D, 500D, 550D, 600D, 650D, 700D, 750D, 760D, 800D, 1000D, 1100D, 1200D, 1300D, 300V, 300X.
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.