Monday, 18 January 2010

Star Trail Photography - Some of the Problems

Image taken by Kristin Repsher at the
Bluedog Photography Star Trail Workshop Jan 2010

Star trails can be one of the most rewarding or disappointing photo shoots you can do.
We love them! What are some of the pit falls and traps of star trail photography and why do images not always turn out the way you would like?

Star Trails may take a lot of experimenting under different conditions.
Noise is the number one enemy you will encounter doing a long exposure star trail with digital cameras – one reason some drag out their film cameras for this type of image capturing. Every camera will have different noise at different times; you just have to find your limit.

Factors such as the night temperature can affect noise. On our Bluedog Star Trail Workshop last weekend it was a warm 23°C. As the temperature drops, the signal to noise ration improves, and your noise will decrease.

Noise will almost always be apparent if you expose for more than 10-20min. Different parts of your camera heat up and affect how the sensor works. Every camera is different and it also depends on the environmental conditions such as haze, dust, ambient light and temperature as mentioned above. On this particular workshop we had also had a grass fire earlier on close by.

Digital noise is more pronounced in the darker areas of an image than lighter areas.

If you experience noise try to do the following:
Use Noise Ninja and try different settings to reduce noise
Use an adjustment layer and increase contrast (reduce brightness of the image).
Use the foreground as silhouette only.

A note about dew. Some of us experienced dew building up on our lenses towards the end of the star trail. This is very common and caused by the amount of humidity in the air. To overcome this use a sock wrapped around your lens hood, or use a battery operated hair drier every 5 minutes to keep the lens warm. You can also use one of those hand-warmers that you put inside your gloves for winter activities. Wrap it around your lens barrel (or even inside of your hood).
Never use a lens cleaner to clean your lens during a shot.

The images below show an example of noise in a star trail. While noise is very evident at 100% magnification it is far less visible at screen view.

We hope this information is useful and you are inspired to get out and try more star trails in the future.
Cheers Garry and Danielle

Image by Garry Schlatter  magnified 100%

 Image by Garry Schlatter at screen view%

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