Irix 150 mm f/2.8 MACRO 1:1 Dragonfly
8. Vignetting
| Canon 50D, f/2.8 | Canon 50D, f/4.0 |
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As you see, there are no problems whatsoever. Even at the maximum relative aperture it would be difficult to notice any vignetting as it amounts to just 13% (−0.39 EV). Additionally it disappears completely on stopping down the aperture to f/4.0 where we got a result of 4% (−0.13 EV).
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How the situation changes when you progress to full frame? Let's find out.
| Canon 5D MkIII, f/2.8 | Canon 5D MkIII, f/4.0 |
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| Canon 5D MkIII, f/5.6 | Canon 5D MkIII, f/8.0 |
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In this case the results are distinctly higher. By f/2.8 you have to take into account brightness loss of 42% (−1.55 EV) in the frame corners. It is a worse result than 37% reached by the Sigma 2.8/150 Macro OS, but the difference is not especially big. When you stop down the Irix to f/4.0, the vignetting decreases to 23% (−0.77 EV). By f/5.6 that aberration reaches 17% (−0.53 EV), and by f/8.0 and f/11 apertures it becomes practically imperceptible, amounting to, respectively, 10% (−0.32 EV) and 5% (−0.16 EV).
| Canon 5D MkIII, JPEG, f/2.8 |
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