The Starry Sky

Canon EOS 20D, Sigma 12-24mm f/4.5-5.6 EX DG HSM, 30" f/4.5, iso 400, tripod. Dolomites, Italy.

The Three Peaks of Lavaredo are some of the most famous mountains of Dolomites. In the first weeks of october, I led two workshops in that area: from Misurina, we reached the Locatelli hut. The hut is already closed in october, but there is an alway open winter room for six persons, where we slept. The first day was very foggy, but the fog gradually disappeared during the night and when we get up, two hours before sunrise, the sky was cloudless. The air was cold and clear. The light of the waning crescent Moon was pretty dim, so the stars were shining brightly...what a vision!

I mounted the Sigma 12-24 and the 20D on my sturdy Gitzo 1548 tripod. The landscape was really dark so it was really difficult to compose the photo...we turned off the flashlights to get used to darkness. I choose to use the 12mm focal lenght to include as much sky as possible into the composition, and to use the zoom at its brightest aperture (the Sigma is f/4.5 at 12mm, while it is f/5.6 at 24mm). It was impossible to focus in the complete darkness so I set the the lens near infinity...the 12mm has a pretty wide depth of field even at f/4.5, so I had some margin of error. I checked the sharpness in the LCD screen at the maximum magnification and I adjusted the focus until the photo was in sharp focus.
The camera was set in evaluative metering, but in these situations the meter don't give acceptable results, so I turned the camera in M (full manual) mode. I begun by trying an exposure of 30" f/4.5 ISO 100, but the photo was pretty dark (I checked the exposure with the histogram), so I set the exposure to 30" f/4.5 ISO 400, and the image turned out correctly exposed. I could have taken the same image with an exposure of 2 minutes at ISO 100, but here I preferred to raise the ISO because I wanted to capture the stars as points, not as star trails.

To get the best from this image, I had to spend a little of time with Photoshop. First, it was necessary to remove the noise - a dark scene photographed at ISO 400 is very noisy! Then, I used the Layer Mask and the Levels to brighten up a little the foreground, so the mountains are not just black silouettes, they show a glimpse of detail. Last but not least, I applied a local contrast adjustement in the sky to enhance the brightness of the stars: I selected the sky and I applied the Unsharp Mask with Radius 20 pixels and Amount 30%. With these values, the Unsharp Mask enhances the contrast of the photo instead of enhancing the detail (I don't recommend to use this technique with all your photos since sometimes it creates artefacts, but is some situations it really helps the photo).

Night photography is always a challenge - but it is a neat experience, and some times the results are very rewarding.

Risposte e commenti