Astrophotography is a specialized type of photography that entails making photographs of astronomical objects in the sky such as the Moon, Sun, planets, stars, and deep sky objects such as star clusters and galaxies.

Effective astrophotography requires the use of many of the following techniques:

- Mounting the camera at the focal point of a large telescope
- Film emulsions with low light sensitivity or specialized CCD cameras
- Very long exposure times and/or multiple exposures (often more than 20 per image).
- Accurate tracking of the subject to compensate for the rotation of the Earth during the exposure
- Use of filters to reduce background fogging due to light pollution of the night sky.

History

The first astrophoto is attributed to John William Draper, who took a photo of the moon in 1840. His son, Henry Draper, later became the first person to photograph the Orion Nebula in 1880, which was essentially the first deep sky astrophoto.

Today, astrophotography is a fast growing hobby that is popular among photographers, amateur astronomers, and hobbyists of all ages.

Amateur Astrophotography

Although the description above suggests that astrophotographs can be made only with expensive equipment by observatories or photographers with extensive experience; in fact, surprisingly good quality photographs of the night sky can be made by almost anyone using readily available single lens reflex 35 mm film cameras, digital cameras, inexpensive dedicated astro cameras to off-the-shelf webcams.

Photographs using exposures lasting several minutes or even hours will show long star trails (because of the Earth’s rotation). Some astrophographers do this on purpose for the desired effect. Most astrophotographers avoid this blurring by either using a short exposures on a stationary mounted camera, or by using a motor-driven telescope mount, in order to keep the stars as points of light in the final photograph.

Difficulties

There are several unique problems with photographing very faint objects, and taking such photographs from a moving platform (Earth) adds to the complexity.

* Astro subjects can be extremely faint - much fainter than the naked eye can see. In many cases the photographer can not see the subject being photographed.
* The spectra (color) of many astro subjects are difficult to record. Some are near the infrared, or require special filters to be separated from the background light.
* The Earth is constantly rotating. When imaging through a telescope or long focal length lens, the effect of Earth’s rotation will ruin an image within a fraction of a second, if nothing is done to compensate for it.
* Camera tracking platforms and/or telescope mounts are expensive, take time to set up, and can be difficult for a beginner. Special guiding techniques and error correction programs are required to ensure that the camera tracks the sky perfectly.
* Long exposure will lead to excessive noise for non-cooled digital cameras; active cooling and stacking can help to reduce this problem. For film based imaging, film will show reciprocal failure, that means the sensitivity to light of different wave lengths appears to drop off as the exposure time increases, which also leads to color shift in the image.

Technorati Tags: astrophotography, digital photography, photo news, photo contest, digital camera review

FISH EYE LENS is a wide-angle lens that takes in an extremely wide, hemispherical image. Originally developed for use in meteorology and astronomy and called “whole-sky lenses”, fisheye lenses quickly became popular in general photography for their unique, distorted appearance.

They are often used by photographers shooting broad landscapes to suggest the curve of the Earth. Hemispherical photography is used for various scientific purposes to study plant canopy geometry and to calculate near-ground solar radiation.

The focal lengths of fisheye lenses depend on the film format. For the popular 35 mm film format, typical focal lengths of fisheye lenses are between 8 mm and 10 mm for circular lenses, and 15-16 mm for full-frame lenses.

All the ultra-wide angle lenses suffer from some amount of distortion. While this can easily be corrected for moderately wide angles of view, rectilinear ultra-wide angle lenses with angles of view greater than 90 degrees are difficult to design. Fisheye lenses achieve extremely wide angles of view by foregoing a rectilinear image, opting instead for a special mapping (for example: equisolid angle), which gives images a characteristic convex appearance. A panorama by rotating lens or stitching images (cylindrical perspective) is not a fisheye photo.

TYPES OF FISH EYE LENS

Circular

The first types of fisheye lenses to be developed were “circular fisheyes” - lenses which took in a 180-degree hemisphere and projected this as a circle within the film frame. Some circular fisheyes were available in orthographic projection models for scientific applications.

Full-frame

As fisheye lenses gained popularity in general photography, camera companies began manufacturing fisheye lenses that enlarged the image circle to cover the entire 35 mm film frame. Because of this, the picture angle produced by these lenses only measures 180 degrees when measured from corner to corner.

The first full-frame fisheye lens to be mass-produced was a 16 mm lens made by Nikon in the late 1960s. This is the type of fisheye most commonly used by photographers. Digital cameras with APS-sized sensors require a 10.5 mm lens to get the same effect as a 16 mm lens on a camera with an image sensor the size of a 35mm film image.

Focal length

The widest lens ever produced was a 6 mm circular fisheye made by Nikon. Initially designed for an expedition to Antarctica, it featured a 220-degree field of view, designed to capture the entire sky and surrounding ground when pointed straight up. This lens is still manufactured by Nikon upon special order, and is used nowadays to produce interactive virtual-reality images such as QuickTime VR and IPIX.

Because of its very wide field of view, it is very large and cumbersome - weighing 5.2 Kg (11.5 lb) and having a diameter of 236 mm (9.3 in). It dwarfs a regular 35mm SLR camera and has its own tripod mounting point, a feature normally seen in large long-focus or telephoto lenses to reduce strain on the lens mount because the lens is heavier than the camera.

Technorati Tags: digital photography, lens, fish-eye lens, photography equipment, photo news, camera review

Canon today announces the launch of the 12x optical zoom, 8.0 Megapixel PowerShot S5 IS. The new compact inherits optical Image Stabilizer (IS) technology, professional-grade optics and extensive movie functions while introducing a host of new features designed to increase the photographer’s success rate.

Powered by Canon’s DIGIC III image processor, Face Detection Technology improves focus, exposure and flash output for people shots while the new Red-Eye Correction feature effectively solves red-eye problems in captured photos. An increased sensitivity range of ISO 80-1600 complements the optical IS system for extended low light performance.

Other key advancements include a larger, higher resolution 2.5” vari-angle LCD, additional shooting modes and extended video recording. The compact design incorporates a new hot shoe that provides compatibility with selected Canon EX Speedlite external flashes, adding to an accessory list that includes Wide, Tele and Close-up converter lenses.

Feature:

• 12x optical zoom lens with Ultrasonic Motor (USM) and UD lens
• Optical Image Stabilizer
• 8.0 Megapixel CCD
• DIGIC III with advanced Noise Reduction technology and Face Detection for stills and movies
• Red-Eye Correction in playback
• 2.5” high-resolution vari-angle LCD
• Long-play VGA movies with stereo sound and Photo in Movie
• 22 shooting modes including full manual control and 0cm Super Macro
• High ISO 1600 and Auto ISO Shift
• Compatible with Wide/Tele/Close-up converter lenses and Canon EX Speedlite flashes

Look for Canon Powershot S5 IS at our ONLINE CAMERA STORE.

Discuss this news & share your opinion on our PHOTO FORUM.

Read the full review of the Canon Powershot S5 IS.

Technorati Tags: Canon Powershot S5 IS, photos, photography, images, digital cameras, tripods, lenses