The Sigma 18-50 comes with a large aperture zoom and it is specifically designed for digital SLR cameras with at least 20 cm of focusing distance. This makes it a great choice for close up photography. This lens combines the hybrid aspherical lens technology with the glass mold one to offer high quality images, peripheral brightness and a compact structure.
In terms of sharpness, the Sigma 18-50 comes with a sharp image quality at different focal lengths. However, the sharpness will lower when you open up the lens to f/2.8, especially at the corners. For this reason, you should stop down to f/4 in order to bring the sharpness in focus. The sharpness gets better to about f/11, but after that it starts to decrease because of diffraction. At f/22, the images are not as sharp, and it is even worse as compared to when the Sigma 18-50 lens is put on wide open.
The focal length of the Sigma 18-50 will keep the image quality under strict control. The users will also benefit from the macro feature which allows the users to get very close to the subject. Some of other benefits they will enjoy include the lightweight and small size of the unit, which allows them carry it without any problem.
The users will also enjoy a correction of the color aberration, thanks to the presence of the SLD (Special Low Dispersion) and ELD (Extraordinary Low Dispersion) glass. It also comes with a multi layer coating that is characteristic of most Sigma lenses. The coating on the Sigma 18-50 will help in the reduction of flare and ghosting, making sure that the images are of high quality. The two aspherical glass elements will also help in the correction of distortion, allowing users get the best photos.
In terms of sharpness, the Sigma 18-50 comes with a sharp image quality at different focal lengths. However, the sharpness will lower when you open up the lens to f/2.8, especially at the corners. For this reason, you should stop down to f/4 in order to bring the sharpness in focus. The sharpness gets better to about f/11, but after that it starts to decrease because of diffraction. At f/22, the images are not as sharp, and it is even worse as compared to when the Sigma 18-50 lens is put on wide open.
The focal length of the Sigma 18-50 will keep the image quality under strict control. The users will also benefit from the macro feature which allows the users to get very close to the subject. Some of other benefits they will enjoy include the lightweight and small size of the unit, which allows them carry it without any problem.
The users will also enjoy a correction of the color aberration, thanks to the presence of the SLD (Special Low Dispersion) and ELD (Extraordinary Low Dispersion) glass. It also comes with a multi layer coating that is characteristic of most Sigma lenses. The coating on the Sigma 18-50 will help in the reduction of flare and ghosting, making sure that the images are of high quality. The two aspherical glass elements will also help in the correction of distortion, allowing users get the best photos.
The presence of the inner focusing system is a useful feature that will prevent the front element of the lens from rotation. This allows the users of Sigma 18-50 lens to make use of the petal-type of lens hood as well as the circular polarizing filters.
This unit is suitable for the professional photographer as well as the amateurs. It can also be used in low existing light and at a maximum range. With its fast and quiet auto focus, the users will have a smoother time in operating the zoom and focus rings. The only problem with the Sigma 18-50 is that it does not have the Optical stabilization, which could help users without steady hands.
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