Meteorite photography, HDR, HDRI, pictures, images, photos

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HDRI-Meteorite photography
Meteorites pictured with High Dynamic Range Imaging

Unclassified heavily regmaglypted 5.7kg stone meteorite from Northwest Africa (Inventory # B-0235). The images shown were produced with the aid of a set of techniques known as High Dynamic Range Imaging (HDRI or HDR). HDRI is used to accurately represent the wide range of intensity levels found in real scenes ranging from direct light to shadows. This result is achieved by combined rendering of 3 to 9 individual images of the same scene that vary in exposure. Although HDRI is commonly used to produce interior or landscape images it certainly qualifies as well for macro purposes. Accurately used it brings out depth and plasticity of a meteorite superior to a concventional image.

Shown above is the bracketed exposure series on which the composite image is based. The five shots were taken in raw-format and with an exposure value interval (EV) of 0.5 (Camera Pentax K20D, lens: Sigma 50mm F2.8 Macro). The middle exposure is the desired exposure and is likely how this scene would normally be presented. The exposure far left is 1 EV lighter, showing some detail in the cast shadow regions. The exposure far right is 1 EV darker, showing some detail in brightest parts of the scene. This shows how a composite image can retain the interesting details from all five exposure settings.

The example images of this 1,138g Chergach meteorite (Inventory # B-0228) show that HDR imaging is also suitable to highlight texture details on the fusion crust of meteorites. The wider dynamic range of the HDR image allows a darkening of the reflexes on the crests of the flow lines and a lighting of the shadowy valleys between the ridges.

The bracketing series below shows the individual exposures of one of the above composite images. The image far right was taken after a change of the lighting and was added to achieve better contrast to the background. If secured that the camera as well as the motif can not move then images may be rendered via HDR software that were taken under different light situations. For this purpose a robust tripod with a solid ball coupling is recommended.

The HDR image below shows a 35.30g individual of the Camel Donga meteorite from Western Australia. The reflecting enamel like surface of fresh eucrites is particularly hard to photograph. Usually light reflected from the shiny crust leads to harsh contrasts that hardly allow any detail to emerge from surface regions either too light or too dark. HDR offers a way to reduce these contrasts by extending the dynamic range to a level compareable to the scenery the human eye would see.

Image below: detail of the fusion crust on the 35.30g Camel Donga Eucrite. Although the quality of the HDR images suffer when displayed on the computer screen, this picture gives some idea of the potential HDR imaging has to offer to meteorite photography.

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