MACRO 105mm F2.8 EX DG OS HSM

A New Standard for Macro Photography

Equipped with SIGMA OS optical stabilisation, this macro telephoto lens is capable of delivering images at a 1:1 reproduction ratio and incredibly sharp freehand.

The low dispersion glass elements that make up the SIGMA MACRO 105mm F2.8 EX DG OS HSM perfectly correct different chromatic aberrations by limiting the scattering of light inside the lens.

Specifications

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).