Today on www.spaceweather.com there is a link to an interesting graph denoting the geomagnetic activity on a monthly basis.

Spaceweather says: “Statistically speaking, March is the most geomagnetically active month of the year; October is a close second. Although the reasons why are not fully understood, there is no doubt that equinoxes favor auroras.”

The activity on the sun has been in a pretty low state recently, but things are getting more active. A CME (Coronal Mass Ejection) may produce some good auroral viewing if a few variables line up. Be on the alert on March 16-17

This is also a good time to mention an article I wrote on how to photograph the aurora borealis with a digital camera. And, its a good time for me to review that article as well. Its amazing how easy it is to forget something on a dark night. Especially remember to take your filter off (if you have one on the lens), and do a focus accuracy check, either using the stars or some other bright solar object. These two are among my most popular mistakes. The latter in particular with Canon’s finicky focusing 24mm f/1.4L.

If any Nikon users have the new 24 f/1.4, I would be very keen to hear some feedback on its performance specifically with aurora or astrophotography.

People often ask when is the best time to view the aurora, and the chart shown here shows geomagnetic activity. However, the factor of weather will play a role as well. It would be interesting to see a chart that showed which months had the most clear nights, per a specific location. The arctic photo tour that Hugh Rose and I guide in October has yielded aurora photography every year for the past 8 or so, although some years are better than others. Still, working around cloudy skies and hunting for holes is not a small task.

My advice if you want to catch some possible action on March 16-17 is to plan on spending a 4 hour block of time outside, with camera ready. Statistics say that in general, from 10:00pm to 2:00am nets the best results, but in reality, you just have to be there and be ready!

I have not touched my camera since shoulder surgery, which was four weeks ago, and I just might give it a try during this potential aurora show.

The pursuit of northern lights photography led me to the purchase of Canon’s 24mm 1.4L, and the following updated version II of the same lens.   My comments are derived from experience with this lens in the field and are not a comprehensive review by any measure. Here is what Canon has to say about this lens.

“Canon’s newest fixed length L-series lens, the EF 24mm f/1.4L II USM, incorporates the newest in Canon lens technology for spectacular sharpness and impressive performance at all settings. It features two high-precision, large-diameter aspherical lenses for sharpness across the sensor, even in peripheral areas of full-frame sensors. Lens elements have a newly-designed anti-reflective SWC (Sub Wavelength Coating) that departs from conventional coatings by using an extremely fine structure that minimizes ghosting and flaring across the lens surface, regardless of the angle with which light enters or exits. It also features two UD lens elements to minimize chromatic aberrations, incorporates rear-focusing, ultrasonic, quiet and high-speed AF with full-time manual override. A circular aperture provides beautiful out-of-focus detail and offers legendary dust- and water-resistant L-series construction using only lead-free glass”

This paragraph is enough to get anyone excited about the lens. But certain aspects of aurora photography put the lens to test. Because I use it exclusively at f/1.4, I’m not much interested in how it performs at other f/stops.

Just a reminder when looking at the MTF chart: the left end of each chart represents the center of the lens and right represents the outer edge. It is clear that the new  lens comes in pretty sharp at f/8 (the blue line). But the black lines are what interest me since they represent the lens performance wide open, in this case f/1.4. The thick lines (solid and dotted) represent contrast, the thin lines (both solid and dotted) represent resolution (or sharpness). I’m trying to simplify this, since there is certainly more to say about an MTF chart (see more at luminious-landscape).

You can see that the black lines fall off considerably towards the outer region of the lens, although they are an improvement over the previous version.  Keep this in mind when looking at the images below, since the enlargement areas are in this outer range of the lens–more specifically the upper right corner of the frame in this case. Bright stars in general, but much more specifically in the outer region of the glass, grow some sizable wings and look like flying birds. The darker the night, the brighter the stars, and the more accentuated this appears. Additionally, a dim aurora generates a longer exposure, burning in more of the stars and further accentuating this artifact. This image was taken on a moonless night with a very dim aurora and represents the worst scenario for a good example. It was taken with Canon 5D Mark II, 30 seconds @ f/1.4, ISO 1600

Some may find this unacceptable. The problem is, there are no other f/1.4L lenses out there to choose from. I’ve went back and forth on whether I think I can let something like this slide, which would normally be totally unacceptable from the rigid criterion I generally use in judging landscape imagery. But shooting the northern lights is a different subject all together. Would I like a clean image all the way to the corners, of course.

Where the f/1.4 really shines is the obvious speed it delivers. A 30 second exposure at f1.4 of the aurora on a dark night is a 2 minute exposure with an f/2.8 lens. That is a huge time disparity, and the two captures can look very different–from the ability to capture aurora shapes to minimizing star trails. It is that ability that keeps this lens in my line-up. Additionally, I could capture 4 frames to 1 in this same situation, producing more images. I generally photograph with two bodies. One has the 16-35mm 2.8L and one with the 24mm f/1.4L II. Currently, I don’t shoot aurora higher than 1600 ISO, but that could change soon, and the ability to shoot at 3200 or 6400 ISO, could offer the option to use other lenses.

What about focus? I sent my lens off to Canon (with the body) to be calibrated, which they did on both the lens and the camera, in vertical and horizontal positioning. But, I still don’t trust it. From now on, my method of achieving critical focus is to use Live View and a loupe on the back of the LCD, just to be safe (see my previous post on that subject). There is too much effort that goes into shooting the aurora to end up with soft images. Additionally, it is always a good idea to check images occasionally by zooming in on the back of the LCD to confirm uniform sharpness.

So in summary:

• Is the new lens better than the old? Yes, from the review of my files it appears sharper.
• Is the new lens worth twice as much money as the old one? Probably. It depends on what you seek to achieve. It is to me because I’ll take the slightest bit of improvement.
• Is the new lens perfect? No

With the aurora, the drama of the scene generally wins out over a super technical review of the corners of the image. At least for most people. They are wowed by the scene much more than they are dissed by oddly shaped artifacts in the stars. So it is a compromise of sorts, and one I’m willing to accept right now anyway.

I was all ready to photograph the Gemenid meteor shower last night, but clouds moved in around midnight, which was a disappointment. However, on Sunday morning, I woke up to a faint aurora display, directly over my house. I grabbed my camera and took a few experimental shots. I say experimental because I was testing out using Live View to achieve critical focus on Canon’s 24mm 1.4L II. This lens has been very difficult to lock into focus when shooting the aurora. The regular method of pre-focusing the lens before dark, which has worked flawlessly on all my other lenses, has constantly failed with the 24mm 1.4. I’ve used Live View as an alternative to pre-focusing, but felt I needed some additional magnification to confirm sharpness on an object as small as a star Even when zoomed in to 10x on the LCD, as star is very small indeed. This is particularly true with fading eyesight acuity!

So I used an LCD loupe with a built in focus diopter. It works sufficiently to view focus sharpness, although, it is a little awkward to handle. I know that all things get much more complicated when the temps are very cold. But focus really only needs to be achieved once per evening (generally), so it is not an item that needs to be used often in this case. I could have used a smaller loupe, and might explore this further, but I wanted this Hoodman Loupe since it serves the dual purpose for use with video. And that I’m yet to experiment with.

The aurora intensity was pretty low, so my ISO was high and the exposure at 30 seconds. Additionally, with such a long exposure and dim aurora, I picked up a little light pollution from the nearby town lights. When working with these images in Lightroom, I was surprised at the effect of the clarity slider on the stars.

I’ll address some technical and optical issues of the 24mm 1.4L II in the next post, as I know that many of you have asked about that. One thing is for sure about that lens, it really shows the stars.

Clarity at Zero

Clarity at 100

What are the best night sky conditions in which to photograph the northern lights? It is a question that can be answered in variations, but I’ve resorted to the simplest answer…whenever the northern lights are visible! Brushing that comment aside, I really don’t think there are “best conditions”, it really depends on your interest. I’ve photographed the aurora under a full moon which casts light upon the landscape, and on a dark moonless night with the sky filled with stars. Both extremes, and all the variations in between render great shooting conditions.

There are however, a few things to consider, based on what kind of image you seek. A moon-less night will provide a star-filled sky, something amazing to behold indeed. Your foreground is likely to be very dark and depending on the location of the aurora, may or may not be suitable. If you are fine to exclude the overall landscape and perhaps silhouette a tree or something similar, it is less of a factor. And of course, if you shoot directly into the sky without any foreground at all, some great imagery can be captured. These conditions are edging towards the realm of astro-photography technique, and I won’t go into that here. In particular, if the aurora is quite bright on a dark night, gathering ambient light to give distinction to the foreground gets even harder. Bright auroras will call for a shorter exposure time, thereby limiting ambient light on your foreground. On average, the exposures will tend to be much longer on a night without the moonlight.

In contrast, on a moon-lit night your exposure will be considerably shorter due to all the ambient light cast from the moon (depending on its angle in the sky). In this case, strong aurora is helpful, dim aurora can lack definition and a longer exposure tends to render a very bright foreground. Additionally, you need to have a good grasp on your foreground subjects since they will be well lit. Using landscape elements to give a sense of anchor or place to the image is helpful. Keep in mind that your sky however, will lack that “starry, starry night” feel, and the strength of the subject is found in balance of the foreground and the sky. I’ve included a few examples here demonstrating the big difference in look between the two extremes.

Note the comparison in exposure times between the two spruce tree shots. The top frame was taken at 30 seconds, and the bottom one in effect at a 3 second equivalent since it was shot at f/2.0. That is a huge difference in time. If the aurora is active in shape and movement, you could capture 9 frames to 1 in the brighter conditions!

In summary here is a list of things to consider regarding the moon before embarking upon a night of aurora photography:

• What is the phase of the moon
• When does it rise
• Where does it rise
• Will you be shooting with the moon in your frame?
• Consider working with the moon light in the sky both just before it rises and just after it sets
• Moon shadow- know your landscape ahead of time and consider the angle of the moonlight on your subject.

There are some very cool and helpful Iphone apps for figuring moon and other celestial data out. I’m working on a “My favorite Iphone Apps” post and that will be forthcoming, highlighting the programs I find useful in the field.

People have a keen interest in the Aurora borealis images, so I’m posting another one from my recent Arctic photo tour. We had unusually warm temperatures, and in some parts of Western Alaska, all time record high temps were set. This is usually not favorable, since the snow melts and things look pretty brown. However, there is always a silver lining. The warm weather also means that the rivers have remained unfrozen for a little longer. And in this photo, it affords the chance for a beautiful reflection of the aurora in the water. Some of our other photo tour clients got some fantastic shots of this. At first I did not bring out my camera and tripod as I was helping the others. But I could resist no longer and ran to get my tripod and camera, I was a little late for the great stuff, but got a few nice ones.

On a more technical note, I used Canon’s new 24mm f1.4L II, a very fast lens. However, it is extremely difficult to achieve precision focus. My horizontal frames were soft but the vertical ones were pretty sharp. In my discussion with Canon CPS, they said that there are different vertical and horizontal focus adjustments on the camera and the lens. So, when I return from the next trip, the body and lens will go to them for tuning, and we shall see how much of an improvement results.

Each October, my friend, colleague and fellow guide Hugh Rose and I lead a trip of intrepid photo enthusiasts into Alaska’s arctic to chase its magical light. The aurora borealis, polar bears, arctic wildlife and other grand landscapes prompt many shutter clicks. The sights vary every year, in an amazing diversity of subject material. However, the two big lures, the poloar bears and the aurora borealis, at least to date, have been present every year. Due to a large degree of interest we elected to run two tours this year, so one more begins in a few days. On last Saturday evening, under rather warm conditions, we all spent the last night of the tour photographing the aurora, which filled the sky with waving light for more than three hours. This particular frame reveals a wash of red color that ironically was not very visible to the human eye. This can often be the case with red aurora, which happens much higher in the atmosphere, generally from 250-300 miles high, according to Dr. Syun-Ichi Akasofu who has written a helpful book on the aurora titled “The Northern Lights: Secrets of the aurora borealis” .

In order to capture this color, the key is to be aware of aurora shape and activity and of course shoot and review your images often. Digital camera’s have revolutionized and simplified aurora photography immensely, however, there is still an extensive checklist to go through before you begin. You can reference an article I wrote on how to photograph the aurora with a digital camera. I used Canon’s new 24mm f/1.4 II lens, which is a huge improvement over the previous version in sharpness. The aurora shape was relatively static, which served well for a long shutter speed of 30 seconds.

Even though I’ve seen and photographed the northern lights many, many times, they never cease to amaze me. It is one subject listed under the 7 Natural wonders of the world. And it gets my vote here as well. Alaska, with its northern latitude, is well situated for viewing this phenomenon throughout the dark winter months.

There are several important qualities to look for in a lens for photographing the aurora:

• Speed. Light gathering ability is important. A traditionally “fast” lens with an aperture of f/2.8 still requires shutter speeds in the 30 second range. F/1.4, however is four times faster and reduces this to around 8 seconds. A faster lens also tends to reveal more stars, and the faster shutter freezes the stars that would leave trails on long exposures.
• Wide angle. The aurora often spans a broad section, if not the entire area, of the night sky. Aurora photos are often taken in the 16-24mm range.
• Sharpness. This is a desirable trait for any lens, but even more important with aurora or astronomy photography. Many lenses are sharp stopped down, but an aurora lens must be sharp wide open. Also important is corner-to-corner sharpness and flat-field focusing. Some lenses, when focussed at one point in the center, will be focussed at a different point at the corners. This could go completely unnoticed indoors, where only one subject is intended to be in focus. However, the sky is all essentially an infinite distance away, so a lens must be able to focus equally at all areas of the frame.