SIGMA 18-250mm F3.5-6.3 Macro DC OS HSM Lens for Nikon

Sigma have made the 18-250mm more compact and thus more portable than its predecessor Click here to view larger 18-250mm f/3.5-6.3 DC Macro OS HSM Produced in their legendary Aizu facility in Japan, Sigma presents their 18-250mm f/3.5-6.3 DC Macro OS HSM zoom lens. Building on 50 years of innovation in precision optics design and craftsmanship, the 18-250mm is a versatile super zoom lens and direct successor to the widely acclaimed Sigma 18-250mm F3.5-6.3 DC OS HSM. Evolving from the success of its predecessor, the 18-250mm sets a new generation’s high zoom ratio by achieving improved image quality, a significantly reduced size and an advanced close focus capability. With its ability to cover such an extreme range of focal lengths, this lens makes a great all-round offering to any budding photographer. By using the innovative Thermally Stable Composite material, the 18-250mm is 25% lighter than its predecessor Click here to view larger The Lens Design Design features make up the foundation of the Sigma 18-250mm lens. Measuring 7.4cm x 8.7cm and weighing just 470g, the 18-250mm is both more compact and 25% lighter than its predecessor. Sigma have achieved this incredible weight reduction by using a new lighter material called Thermally Stable Composite (TSC) instead of much heavier Polycarbonate. This innovative material has a thermal shrinkage level equivalent to aluminium and has little contractility, even when subjected to sharp temperature changes. The 18-250mm features Sigma’s dedicated Optical Stabiliser system (OS). The system offers an effective blur correction of 4 stops, helping to stabilise the image and counter shake. It is also linked to the viewfinder, allowing for more accurate previews and thus in focus images. Working alongside the OS is Sigma’s in-house developed inner focussing system, which both eliminates the need to extend the barrel, reducing light loss, and the need to rotate the front lens. In staying fixed, the front lens can accommodate a petal design hood (included) that helps to counter light related issues such as glare. The inner focussing system also allows for the use of Circular Polarising filters. The lens also features Sigma’s exclusive Hyper Sonic Motor (HSM) which works to auto focus images in a fast, accurate and silent manner. All the above features combined give the lens an extraordinary ability to produce in focus images whether at close or long ranges. The final design feature on the 18-250mm lens is a greatly improved bayonet mount. Sigma manufacture the mount from speciality treated brass, the result of which create a more solid and rust resistant connection between camera and lens. From Macro to Telephoto By covering such a broad range of focal lengths, the 18-250mm lens is capable of taking many different types of images and therefore accommodating many different types of user. With a fixed minimum focusing distance of 35cm throughout the entire focal range and a maximum reproduction ratio of 1:2.9, the lens performs well at taking close up images regardless of the distance between subject and lens. At the lower focal length settings (18-30mm) the lens acts like a Macro and reproduces detailed wide angled images of close up subjects. Then simply zoom in a little and the lens automatically turns into a standard-medium range telephoto. Finally, increase the zoom to the maximum focal lengths and it becomes a full telephoto lens allowing you to pin point a specific area within a landscape or scene and reproduce it in stunning close up detail. Higher F stop numbers as well as OS technology enhance the performance of the lens for long distance photography. One SLD and three aspherical lens elements counter various optical aberrations and increase light transfer to the sensor Click here to view larger The Optical Composition In all forms of lens construction, Sigma puts the highest emphasis on the quality and craftsmanship of the internal optics. As a result, the 18-250mm incorporates a set of cutting edge and unique optical features which work to create bright and sharp images, at all focal lengths. One out of a total sixteen lens elements, is manufactured from Special Low Dispersion (SLD) glass, renowned for its high resolution and light transmission properties. It works in conjunction with three aspherical lens elements (one double sided) to counter various colour and optical aberrations throughout the zoom range. The configuration also ensures that all levels of distortion are corrected. The resulting images speak for themselves in terms of sharpness and resolution. Super Multi Layer coatings work to eliminate flare and ghost irregularities Click here to view larger The lens incorporates a 7 blade diaphragm which produces a desirable blur (bokeh) effect on out of focus areas. The diaphragm also smoothes out intense back lighting, making them appear as rounded highlights as opposed to areas of over exposure. This effect helps to over emphasise the foreground subjects and smooth out the background, creating a well balanced image. Finally, Sigma applies Super Multi Layer coatings to all lens elements, which work to create an optimum colour balance by reducing the damaging effects of ghost and flare. The coatings also help to maximise light transmission to the DSLR’s sensor. A Lens Most Applicable For...... Packing so many focal lengths and optimising features, the Sigma 18-250mm replaces the need to carry several lenses making it the ultimate “all in one” DSLR lens. The compact size, 25% weight reduction and a zoom lock function, make the lens extremely portable and ideally suited to travel as well as general day use. With ability to instantly switch from a telephoto to macro lens and assisted by various features, it is suited to a wide range of specific uses from close-up wildlife photography, landscapes as well as long distance pursuits. The OS system and HSM also ensure that the lens performs well when composing handheld shots both near and far. If you are tired of carrying around and continuously interchanging your lenses to get the right shot, then the Sigma 18-250mm is a perfect all round solution for you.

High Performance, Compact, High Zoom Ratio Lens designed exclusively for digital SLR cameras

By revolutionizing the optical and structural design of the Sigma 18-250mm F3.5-6.3 DC OS HSM, this new lens achieves a compact size and a minimum focusing distance of 13.8. New material, Thermally Stable Composite (TSC) maintains its structure and has little contractility especially in varying temperatures, is incorporated into the lens barrel. It is convenient when you wish to keep your equipment to a minimum and yet still be prepared for all opportunities and situations, such as travels.

A wide range of photography is possible in one lens

Covering wide angle 18mm to telephoto 250mm, this versatile lens designed exclusively for digital SLR cameras, is suitable for all-purpose photography including landscape, sport, and macro photography. It is convenient when you wish to keep your equipment to a minimum and yet still be prepared for all opportunities and situations, such as travels.

Excellent for macro photography

Close-up capability is improved with the minimum focusing distance of 13.8 throughout the entire zoom range, and maximum magnification ratio of 1:2.9. In APS-C size equivalent, macro photography with approximately 1:2 magnification ratio is possible. In addition, with this lens, the size and flaming of subjects can be adjusted by rotating a zoom ring, making macro photography easier than using fixed focal macro lens. For further convenience, the maximum magnification ratio at each focusing distance appears on the side of the lens barrel.

Revolutionizing the design foundation results in compact size

Optimization of the power arrangement by such things as incorporating double-sided aspherical lenses, and reexamination of design, the filter diameter size is reduced. This compact size lens has the approximately 13x high zoom ratio with the filter size of diameter 62mm, and dimensions of diameter 2.9 x Length 3.5. It ensures portability and overall ease of use, making it perfect for travel and leisure photography.

New material TSC (Thermally Stable Composite)

The new material TSC (Thermally Stable Composite), which has little contractility especially in temperature changes, as well as maintaining firmness, is incorporated into the lens barrel. Compared to Polycarbonate which is generally used, TSC has higher elasticity by approximately 25%. Since thermal shrinkage is low, it has high affinity to metal parts which contributes to high quality product manufacturing. It also contributes to the parts such as the zoom ring and scaling to be slimmer

Lens Construction

In a conventional lens, focusing requires an extension of the entire lens or the front lens group. However, to better accommodate autofocusing mechanisms and closeup photography, a need has arisen for lenses that do not change their length during focusing or suffer from focus-dependent variation in aberration. Therefore, Sigma has developed focusing systems that only move elements within the lens barrel. These incorporate smaller and lighter moving lens elements which help improve auto-focus speed. With their unchanging barrel length and small variation in the center of gravity, these lenses also enhance balance and stability for the photographer. Furthermore, since the front of the lens does not rotate, polarizing filters can be used with extra convenience.

MTF Chart

MTF (Modular Transfer Function) is one of the measurements that evaluates a lens' performance, and it contrasts sensitivity at different spacial frequencies. The horizontal axis is in millimeters and shows the distance from the center of the image toward the edges, and contrast value (highest value is 1) is shown in the vertical axis.

The readings at 10 lines per millimeter measure the lens' contrast ability (red lines), repeating fine parallel lines spaced at 30 lines per millimeter measure the lens' sharpness ability (green lines), when the aperture is wide open. Fine repeating line sets are created parallel to a diagonal line running from corner to corner of the frame, are called Sagittal lines (S) and sets of repeating lines vertical to these lines are drawn, called Meridional (M) line sets.

Distortion

effective distortion: When you take a picture of a lattice pattern, it will appear as the blue dotted line shows. the red line illustrates how the lattice pattern will appear in the actual picture when any lens distortion is taken into account.

relative distortion: In this chart, the horizontal axis shows the ideal image height (the distance from the center to the edge of the image [mm]). The vertical axis shows the extent of distortion. The extent of the distortion is represented by how much Y, which is the actual image height, grows (or shrinks) against Y0 which is the ideal image height.

Extent of distortion: D[%]=(Y-Y0/Y0)x100

When you take the picture of a square object, if the distortion amount show a minus value, the image will be seen as expanded (Barrel distortion). If the distortion amount is a plus value, it will be seen as a recessed (pincushi on distortion). When the distortion value is close to 0, the appearance of distortion is very minimal.

Vignetting

The horizontal axis shows the image height (the distance from the center to the edge of the image [mm]). The vertical axis shows the amount of light in the image (based on the amount of light in the image center being 100%). If the peripheral amount of light is lower than the center, the four corners of the image will be darker (vignetting).