SEPT 2011 IMAGE OF THE MONTH
CONTINUED: E-LETTER #13
IMAGE OF THE MONTH
Elk Lake Nebula was one of those, “I almost tripped over this one” kind of experiences. Before turning in for the night, I walked out of the cabin we were staying in at Elk Lake, on the Cascades Lakes Highway, in the vicinity of the Three Sisters Wilderness area, with the intent of simply making sure our kayaks and canoe were tied off and secure. When I stepped from the trees to the lakes edge I was confronted with one of the best Milky Way displays I have seen in sometime. Not only were the stars spectacular but the nebula and stars were reflected in the perfectly calm waters of the lake. It was almost 11pm and the moon had been down for about an hour so the night sky was clear and dark. I knew instantly there would be no sleep until I had bagged this trophy scene.
My wife took one look at me as I looked at the sky, then the lake, then the sky, then the lake, and she simply said, as she touched me on the arm. “I’m going to bed; don’t wake me when you get done”. She knows me better than I do myself sometimes.
Within minutes I had my gear at the shoreline and realized there were too many trees overhanging the lake where all the boats were stowed. After a middle of the night hike both right and left along the shoreline I found the perfect spot with enough of a clearing to provide only a hint of tree boughs to barely frame the heavens for the shot I had in mind. I knew almost instantly that this shot would have to have a foreground to set the stage and anchor the image given the power of the Milky Way and the reflections on the lake itself. It only took a few minutes to untie the canoe and shove off onto the still calm of the lake, which was riddled with heavens reflections. A quiet paddle along the shore brought me to my chosen location. In no time I had the canoe secured, the tripod up and camera and operator all ready to begin the shoot.
When I initially began shooting PinPoint Star images it was a real struggle. I experimented with every aspect of what my equipment would allow me to do and drew on my 40+ years of experience and I still ran into dead end after dead end. Only after changing camera bodies and lenses did I find success. I now shoot all my pinpoint star images with my Nikon D700 and almost always use my fixed f-2.8 12 to 24mm wide angle lens. I say almost always, on the lens selection, primarily because I discovered that the length of my exposures was dictated by the focal length of my lens. As a general rule, if I am shooting a star scene similar to the Elk Lake Nebula image, with a really wide (14mm) lens I’ve learned that I can make exposures up to BUT NOT LONGER THAN 25seconds. Over 25 seconds and the stars begin to elongate or stretch and don’t show as well as a pinpoint presentation. I also learned that the longer the lens (more telephoto) the shorter the exposures have to be.
Now for the other pieces of the puzzle. What about your ISO setting and what F-Stop should you be using?? Let’s go back to the Elk Lake image. For that image and for most of the moonless Milky Way images I have done over the past two or three years I have found that a really high ISO and very large F-Stop are the ticket. The Elk Lake image was shot at an ISO of 6,400 with an F-stop of 2.8 for 25 seconds. *(I’m guessing, when it comes to F-Stops, that you know the smaller the number (like f-2.8) the larger the diaphragm opening. Which also means the larger the number (like f-16 or 22) the smaller the opening in the F-Stop diaphragm. The smaller the F-Stop number the more light gets to the film, or sensor. Well, I think you get the point.
So, when we use a high ISO, that adjustment to the camera means the camera is MUCH more sensitive to the light in the scene. An ISO or 200 is twice as sensitive (or records twice as much) as an ISO of 100. So, you do the math to figure out how much more light, or sensitive your camera is at an ISO of 6,400 verses an ISO of 100. When you add all three components together. The ISO, the large opening F-Stop and a time exposure you can pretty quickly see how much more capability your camera will have in low to very low light situations.
That capability isn’t necessarily free. There is a price to pay for such sensitivity and the end product ends up being “NOISE” in your images. Noise is essentially artifact, much like Grain was in the film days, which degrade the sharpness of your images. In some cases it can really be a killer and in others it can pass for “it’s ok” images.
The camera industry has worked overtime to find ways t lessen the noise in low light level imagery. Almost every pro-summer and pro camera on the market has software built into the camera to mathematically minimize and reduce the noise footprint in low light level photography. As luck would have it one of the best in this arena is the Nikon D700. The combination of the full size sensor and the noise reduction capabilities of the camera make it the perfect tool for the task at hand.
Now, back to the shoot…………..Initially, I ran three or four test shots to determine my best exposure to capture the essence of the Milky Way. I wasn’t sure if I was going to have to shoot multiple exposures to capture the correct light levels with the lit trees around the Elk Lake Lodge and or the deep shadows and darkness in the immediate foreground including the shore line, canoe and some of the lake itself. Surprisingly, I found I could capture the entire scene, less the foreground, with a single exposure. So what to do about my canoe. Well, that was an easy fix as well. I just painted it with light.
I knew from experience that shining my headlamp on the canoe, no matter how briefly would be overkill. So, I decided to use bounce fill light for the foreground. I found that shining my headlamp behind me and moving it around to light the limbs, trees, and branches etc of the trees behind me that the reflected light seemed to barely light up the scene foreground with a nice, soft, diffused glow.
Once I chose to use that lighting technique the next question was…How much bounce light was needed to balance the canoe and foreground with the lake, lodge and sky. During four 25 second exposures, that were programmed to capture the lodge, horizon and sky, I painted the trees behind me for 3, 5, 7 & 9 seconds. Under close scrutiny, with my trusty loupe, it was clear that 3 seconds is all I needed. Now the puzzle was solved. All I had to do was; lock the mirror up, open the shutter for 25 seconds and paint the trees behind me for a 3 second burst of rapidly moving light pointed behind me into the forest.
I knew I wanted only a hint of detail in the foreground. I didn’t want the canoe to compete with the Milky Way as my Center of Interest. After dialing in all the parameters of how to capture the scene before me, and about 4 or 5 shots into the shoot I witnessed the most amazing shooting star I have seen in quite some time. Unfortunately, I thought I had missed it as I was sure I was between images when it lit up. Imagine my excitement when editing the images I found a perfect record of the shooting star in one of the best exposed images of the night. On reflection I now realize that I had actually opened the shutter and was in the process of recording another 25 second image when I thought I had only clicked once to raise the mirror before the actual exposure. Yeah, it is easy to loose count sometimes but on this one it was a wonderful surprise that buyers, viewers and collectors will enjoy for years to come.
The final image was post processed from the single RAW file. I did make three different Master Working files from the original. One for the Milky Way, one for the horizon and one for the canoe and foreground. With some gentle adjustments and tweaking the three were easily layer masked together to preserve the best of the entire image and the end result is a great companion to my Nocturnal Cascades image that has been my, run away, best seller for the past two years. Good things really do come from the heavens.
Thanks for sticking with it through this kinda lengthy explanation.....................Vern