That's not strictly true, but it's good enough for this purpose (for more on MTF see ). So what does this tell us? Well, the you can think of the red lines as showing contrast and the green lines showing resolution. Real lenses never have an MTF of 1.0 when diffraction is included. Sometimes the plots exclude diffraction and in that case the numbers are higher and often react 1.0 in the center. The MTP plots below include the effects of diffract ion. The special elements of low and anomalous dispersion glasses help to minimize chromatic aberration. The second to last element is FLD, a type of glass with similar properties to Fluorite (anomalous dispersion). The second and third (large) elements are SLD (super low dispersion) glass and there's a smaller SLD element around the middle of the lens. Sigma 150-600/5-6.3 DG OS HSM C (Contemporary) Optics In addition to these functions, the USB Dock system can be used to correct and front or back focus you find (I didn't find any, but it's possible some photographers using different camera system might). These users defined settings can then be accessed and the C1 and C2 custom functions. This software an update the lens firmware, but it can also modify the lens focus speed, the Stabilization characteristics and can get a user defined focus range. This is a system which connects the lens to a PC running the Sigma USB dock software. These can be used in conjunction with Sigma's USB dock. You will also see another set of switches marked "Custom", with positions "off", "C1" and "C2". You may see different numbers, depending on how steady your hands are! The viewfinder image is quite "fluid" even when stabilization is active, but the system words well, giving at least 2 stops of stabilization at 600mm and at least 3 stops at 150mm by my measurements. There are three stabilization (OS) settings, Off, Normal (stabilized on two axes) and Panning (stabilizes on one axis). If you know the approximate distance of your subject you can speed up AF search by limiting the range to 2.8m to 10m for subjects that will be close, or 10M to Infinity for subjects you know will be far away The first is 2.8m to Infinity (the full AF range). The Sigma 150-600/5-6.3 DG OS HSM C (Contemporary) has three focus ranges. There are three focusing modes - Manual, AF (with full time manual focus option available) and a "manual override" mode in which manual focus takes precedence over autofocus at all times, even during the autofocus process and during high speed continuous shooting. Sigma supply a rubber band which fits in the gap left when the tripod ring is removed (a mice tough). This makes the lens slightly more comfortable to hand hold. The tripod ring can be removed from the lens if you are sure you won't be using a tripod. There are no click stops to guide you when switching from horizontal to vertical orientation. Rotation isn't particularly smooth, but it's not bad. One thing to note is that if you grip the focus ring tightly, the focus action gets even stiffer, to the pint of binding, so a loose grip on the ring is recommended It's fairly small and it's quite stiff, which can make the final small adjustments (when manually focusing using Live View and 10x magnification) a bit tricky. The manual focusing ring (which sits between the zoom lock and the controls in the image above) isn't the best feature of the Sigma 150-600/5-6.3 DG OS HSM C (Contemporary). The rotation of the zoom ring is in the same direction as that of Canon EOS lenses (opposite to the direction of rotation of Nikon Zoom Lenses). There is a zoom lock at the 150mm position to prevent the zoom from extending when the lens is being carried. The zooming action is stiff enough that there is no "zoom creep" even with the lens lend vertically. It is possible to "push-pull" zoom, but I don't think the lens was really designed with this in mind. Zooming action via a rotating ring is quite smooth. The Sigma 150-600/5-6.3 DG OS HSM C (Contemporary) feels has a composite metal/plastic construction, but it doesn't feel "flimsy" in any way. Sigma 150-600/5-6.3 DG OS HSM C (Contemporary) Construction and operation Notes: DG = full frame coverage OS = Optical Stabilization HSM = Hyper Sonic Motor Sigma 150-600/5-6.3 DG OS HSM C (Contemporary) Specifications In this review I will concentrate mainly on the Sigma 150-600/5-6.3 DG OS HSM C (Contemporary) lens in a Canon EOS mount. I have now had a chance to use all three lenses and compare them with each other. Last year Sigma announced two 150-600mm lenses, the Sigma 150-600/5-6.3 DG OS HSM C (Contemporary) at a price similar to that of the Tamron lens, and the Sigma 150-600/5-6.3 DG OS HSM S (Sports) at a price almost double that of the Contemporary lens. In late 2003 Sigma introduced there Tamron SP 150-600/5-6.3 Di VC USD lens and I reviewed it her last year Sigma 150-600/5-6.3 DG OS HSM C (Contemporary) Hands on review
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