fuchs-photography

Fuchs-Photography
Photos 2004-2010

Test: Chromatic Aberrations and what F number works best for a lens

Chromatic Aberrations, also called "colour fringing" is a problem one faces with almost every lens given the circumstances. Low F-number, wide angle and high contrast will most of the times lead to the problem. So how bad is in fact with my lenses and interesting to know especially, how does the 1,4 x converter (Sigma APO TELE CONVERTER 1,4x EX DG) affect the Tele "Sigma 100-300mm F4 EX DG APO HSM IF" ?

Following a Test of:
(Pictures shown are taken without any filters or Photoshop modification)

18mm	Sigma 18-50mm 3.5-5.6 DC
50mm	Sigma 18-50mm 3.5-5.6 DC
100mm	Tokina AT-X AF 100mm / 2,8 Makro Pro D
300mm	Sigma 100-300mm F4 EX DG APO HSM IF
420mm	Sigma 100-300mm F4 EX DG APO HSM IF together with Sigma APO TELE CONVERTER 1,4x EX DG

1) Sigma 18-50mm 3.5-5.6 DC at 18mm (shown in 150%)

F3,5	F5,6
F8,0	F11
F16	F22

Its very obvious, the Sigma Kit lens shows its worst side in the wide end (18mm) in low F-number. At F8,0 is starts to show decent results in CA and sharpness wheras at F16 and higher the edges are becoming fuzzy. This is a quite typical behavious for "low" quality kit lenses. Then again, once you know and work around these limitations you can get decent pictures even with this chaep and light lens also.
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2) Sigma 18-50mm 3.5-5.6 DC at 50mm (shown in 150%)

F5,6	F8
F11	F16
F22	F32

At 50mm the lens does not seem too susceptible to CA but also here the sharpest result is achieved at around F8,0.
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3) Tokina AT-X AF 100mm / 2,8 Makro Pro D (shown in 150%)

F2,8	F3,5
F4,5	F6,3
F8,0	F16
F22	F32

The Tokina 100mm Macro shows heavy CA when open at F2,8 and F3,5 but then gets significantly better, being also very sharp at F6,3. On the other end it loses sharpness slighly starting at F16 getting quite blury at F32.
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4) Sigma 100-300mm F4 EX DG APO HSM IF at 300mm (shown in 150%)

F4,0	F6,3
F8,0	F11
F16	F32

The Sigma 100-300mm Tele is not suspectible to CA. Pictures above show no real sign of CA nor do any of my other pictures shot over the last weeks. It is already very sharp open at F4,0 but gets a bit fuzzy in the end.
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5) Sigma 100-300mm F4 EX DG APO HSM IF together with 1,4 converter at 420mm (shown in 150%)

F5,6	F8,0
F11	F16
F22	F45

The Sigma 100-300mm Tele together with the Sigma 1,4 converter is still a pretty good option for a long Tele. Autofocus still works very good even in bad light. Not as brilliant as without but still comparable with other lenses for example the Kit lens. As shown on the picture above when wide open at F5,6 (due to the converter you lose one F-stop) it tends to have some CA which is also present at some bird shots I took over time. But it never shows significantly. I managed to get some quite sharp shots (all at 420mm) even with the converter but overall as expected they are a bit soft compared to ones taken without the converter.

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