Lens review
Canon EF-S 18-135 mm f/3.5-5.6 IS
8. Vignetting
No surprise here. At 18 mm and by f/3.5 the vignetting reaches a high level of 44% (-1.7 EV) and after stopping down to f/4.0 it decreases to 38%. The aberration is still noticeable by f/5.6 where it amounts to 22%. On further stopping down we see some improvement but it is rather slight because by f/8.0 we noticed the vignetting level of 20% and by f/11 it reached the value of 19%.
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The situation improves a lot at 35 mm focal length. At the maximum relative aperture the brightness loss in the frame corners gets to 27% (0.92 EV). On stopping down to f/5.6 the vignetting becomes hardly bothersome because it reaches just 16% and by f/8.0 it decreases to an imperceptible level of 10%.
When we lengthen the focal length further, some serious troubles with vignetting are back. At 70 mm and by f/5.6 the light fall-off in the frame corners is 36% (-1.31 EV). Fortunately this aberration decreases very quickly on stopping down, by f/8.0 amounting to 17% and by f/11 -to only 10%.
The results at 135 mm are even a bit worse. At the maximum relative aperture we must cope with the vignetting level of 40% (-1.5 EV) and by f/8.0 its value is still 22%. Only the usage of f/11 and f/16 apertures release us from this problem because the brightness loss in the frame corners amounts there to 13% and 8% respectively.
To sum up in this category the Canon 18-135 mm IS didn’t impress us much. However, to be honest, we didn’t expect to be impressed at all.
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