LensTip.com

Lens review

Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM

28 February 2015
Arkadiusz Olech

7. Coma, astigmatism and bokeh

The coma is the most acute at the shortest focal length where it remains very visible. Fortunately at the longer end the situation improves greatly and the influence of coma on the shape of the diode becomes negligible.

Nikon D7000, 18 mm, f/3.5, center Nikon D7000, 18 mm, f/3.5, corner
Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh
Nikon D7000, 50 mm, f/4.8, center Nikon D7000, 50 mm, f/4.8, corner
Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh
Nikon D7000, 100 mm, f/5.6, center Nikon D7000, 100 mm, f/5.6, corner
Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh
Nikon D7000, 200 mm, f/6.3, center Nikon D7000, 200 mm, f/6.3, corner
Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh
Nikon D7000, 300 mm, f/6.3, center Nikon D7000, 300 mm, f/6.3, corner
Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh


The astigmatism, understood as an average difference between vertical and horizontal MTF50 values, is very low in the 18-200 mm range, reaching just 3.6%. That aberration becomes noticeable only at the maximum focal length, where it is 12%.


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The appearance of defocused images for a megazoom lens can be called sensible. Only the rim of the ring, increasingly intensive on stopping down, sticks out. The mechanical vignetting is not especially annoying because the ring is truncated in the corner only at the maximum relative aperture.

Nikon D7000, 100 mm, f/5.6, center Nikon D7000, 100 mm, f/5.6, corner
Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh
Nikon D7000, 100 mm, f/8.0, center Nikon D7000, 100 mm, f/8.0, corner
Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh
Nikon D7000, 100 mm, f/11.0, center Nikon D7000, 100 mm, f/11.0, corner
Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh Sigma C 18-300 mm f/3.5-6.3 DC MACRO OS HSM - Coma, astigmatism and bokeh