فروش لنز و فلش حرفه ای sigma - تهران

فروش يك لنز ژاپني sigma nikon اكبند زير قيمت
فلش مدل ef-500 dg super adi
لنز مدل 1:4 apo dg hsm
Sigma APO 100-300mmd 1:4apo dg hsm
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Here is a lens from Sigma that fits into the medium to long telephoto range and is a step up from the average 70-300mm models. It sports a constant aperture of f/4 and Sigma’s HSM autofocus motor. We take a look at how it performs.

Sigma 100-300mm f/4 APO DG HSMSpecification

Focal length 100-300mm
Max aperture f/4
Min aperture f/32
Construction 16/14 elements/groups
Closest focus 1.8m
Reproduction ratio 1:5
Filter size 82mm
Dimensions 92.4x227mm
Weight 1.44kg
Price (SRP) £899

Build and handling
The lens is one of Sigma’s EX range and is finished in their matt black with white engraving and a little gold for the logos. This finish has proved to be quite hard wearing and is certainly quite smart in it’s looks. There is an AF/MF switch in the usual place and the lens comes supplied with a tripod collar that is Sigma’s quick release design that I have expounded on before in these pages. Next comes a 35mm wide zoom ring, three quarters of which has a comfortable ribbed rubber finish. It is marked at the 100, 135, 200, 250 and 300mm points and is torqued very slightly on the stiff side, giving the impression that it is built to last.
A neat, flush, distance window separates this from the larger (75mm) manual focus ring which is again covered for three quarters of its length with a matching rubber ribbing.

Autofocus is achieved with HSM, Sigma’s hypersonic system that is both quick and virtually silent in operation. The lens stays the same length throughout both focussing and zooming, and without the front element rotating, making life for filter users easy with the 82mm filter thread. Also supplied with the lens is a front lens hood that is more or less a bucket shape with the slight exception of a small cut-out to stop vignetting at the wider setting. The hood is a nice, snap bayonet, fitting that stays in place during use.

The lens is also compatible with Sigma’s EX Teleconverters and retains autofocus when used with the 1.4X version.

Optical quality
As could be expected of a modern zoom lens design, this one is fairly well put together. Even the mathematically challenged can see that the zoom ratio comes in at 3:1 and this is the accepted limit where compromises in design start to raise problems. Things like distortion are well controlled and measured figures of –0.1% (barrel) at the short end and 0.45% (pincushion) at the full stretch of the lens are negligible and cannot be seen with the naked eye.

The new digital coating Sigma have applied to all of their lenses, to cut out light reflected back from digital sensors bouncing around inside the lens, has had the added benefit of improving contrast and the same is true of this optic. Resolution is pleasing and the performance in this department is very close across the frame with very little drop-off towards the edges. A bonus for users of full frame equipment.

The one area where there is a slight disappointment is in the control of Chromatic Aberrations (CA). There is no evidence anywhere in the range at the centre of the frame; however, at the longer focal length the anomaly does start to creep in at the very edges. Most of the time, and under a lot of circumstances, it would not be noticed, but it is there.