All digital SLR cameras today come with a built in light meter. The TTL, or Through The Lens meter is a crucial tool that helps you get exposures right. However, it is only a tool and it can and does give you wrongly exposed photographs is you follow its readings like a holy book! Let us look at spot [...] submitted: 5 years and 1475 days ago
In this page we discuss lens testing (actually, testing complete photographic systems) using the Koren 2003 lens test chart, which has continuously varying spatial frequency. You can download, print and assemble it yourself. This approach is primarily intended for film images, but Imatest Log frequency analyzes digitized images of the chart described further.
What is the aperture of our cameras? What is the use of setting a large or small one?
Letâ€™s dive into those mysterious numbers and find out what they mean. Think of the aperture as the opening of your lens. Light arrives and its photons are focused onto the sensor by the lens. The incoming analog signal gets then translated into digital numbers and written on the memory card.
The first problem we need to look at is, how close the lens will focus. Lenses have a minimum focus distance which varies considerably from lens to lens, some longer zoom lenses have a 'macro' setting and will focus quite close but most lenses will not focus close enough to take the picture on the right.
Tilt shift lenses enable photographers to transcend the normal restrictions of depth of field and perspective. Many of the optical tricks these lenses permit could not otherwise be reproduced digitallyâ€”making them a must for certain landscape, architectural and product photography. The first part of this tutorial addresses the shift feature, and focuses on its use for in digital SLR cameras for perspective control and panoramas. The second part focuses on using tilt shift lenses to control depth of field.
Sigma makes some interesting lenses for digital SLR cameras. They also produce some of their own digital SLR bodies with a class-unto-itself new type of sensor. Sigma is mainly known as a third-party lens manufacturer, producing lenses in mounts compatible with the major brands: Canon, Nikon, Pentax, Sony, Olympus. They offer high-quality glass in many of the popular focal lengths which, in many cases, are at more affordable prices than the specific manufacturerâ€™s offerings.
This article covers every current Sigma product.