Before your start, keep few things in your mind
1. In canon MTF graph blue lines represents image taken at F8 aperture
2. In Canon MTF graph Black lines represents image taken at MAX aperture.
3. Thick Lines = resolution
4. Thin Lines = Contrast
How to Read the Canon MTF Graph? (forget those blue lines of F8 aperture, see only black lines in the graph)
Sharpness of the image
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Thin black line / Resolution lines above 0.6 indicate good sharpness.
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The closer the thin black(Sagittal) line and the dotted black(Meridional) line together, the more natural the blurred parts of an image appear.
The more the S (solid line) and M (dotted line) curves are in line, the more natural the blurred image becomes.
Lens Edge Performance
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Lenses that demonstrate good edge performance have almost horizontal lines.
A Canon MTF chart is made up of 8 graph lines in two colours. The 4 black lines represent the lens’ performance at maximum aperture while the 4 blue lines indicate performance at f/8. Thick lines show contrast (10 lpmm) and thin lines resolution (30 lpmm). The lines representing sagittal detail are shown as solid lines. The lines representing meridional detail are shown dashed.
MTF Chart for Zoom Lenses
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For zoom lenses, chartsare provided for both the minimum and maximum focal lengths. The perfect lens would show both solid and dashed lines running horizontally across the top of the chart – in other words, showing 100% accuracy throughout the frame. In practice no such lens exists, so you will see some amount of variance with even the very best lenses on the market.