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BPD_1938

Playing with the light. ND Filters.

Most good modern DSLR’s have a good amount of Dynamic Range (DR), DR is the measurement from the brightest to the darkest a sensor can capture in one image, beyond this range highlights will be blown and dark shadows will yield no detail. It is normally measured in Exposue Values (EV). A Good sensor will be at least 12, and maybe as high as 16.

But what do you do if the image you are trying to capture has more DR than my sensor can capture? Well there are a number of ways to deal with this, these are the most common:

  • Take multiple exposures to combine into one image, either as a composite merge or a high dynamic range shot (HDR), later models can do HDR in camera.
  • Add additional light to the scene.
  • Use filtering effects to modify the light being exposed.

BPD_1948HDR and adding light are fairly common, but using filters is not very common for night sky photography and Aurora’s. The reason it is not popular is that adding filters reduces the amount of light entering the camera, resulting in either having to use higher ISO settings or longer exposures.

However given the right circumstances using a filter can have great results. I like to use them for shooting Aurora’s provided the Aurora is very bright and it has minimal movement. If the Aurora is bright I don’t need to increase my ISO, and minimal movement like beams in the Aurora will mean I can increase the exposure time a little without blurring any details.

I have found that using a 0.9 (3 stop filter) helps significantly with exposure compensation, balancing out the light Aurora in the sky to darker foregrounds. Not only does it help with the balance and bringing out blacks, but it effectively gives your sensor a 3 stop advantage.

A sensor that can shoot 14 stops of DR is suddenly equivalent to 17.

Suddenly I’m no longer dealing with those horrible black dark areas where the noise hides.

Iron Pot Pano Small.

“Someones up late”.

Iron Pot AuroraHad one of those nights last night where I could just not sleep, so I decided to head out and see if I could get a nice shot on a beach where I recalled someone had built a makeshift stick “hut”.

The beach faced north, so I knew if the Aurora Australis was active I’d have to do at least a 200 degree panorama to get it all in. In the end it was only four shots with my 16-35 lens.

I have titled it “Someones up late”.

Shot shows the Iron Pot lighthouse at the mouth of the Derwent River in Storm Bay with Bruny Island to the right (Tasmania). Pictured to the left is a single shot from the same location a little further down the beach.

'Working Late', Aurora over Mortimer Bay, Tasmania.

Oblivious to the lights.

IMG_7875When your out shooting late at night you have a lot of time for thinking during exposures and between shots, especially if your by yourself. I often think of all those people at home, watching TV, or asleep in their beds, oblivious to what is going on around then, and the silent lights that weave across the night sky above them.

I think the mood in this shot sums up how I often think of those people. They are inside, working away or watching some program on TV. Meanwhile outside the lights are dancing in the sky and the stars are shining brightly on a perfectly clear and moonless night.

The picture was taken in Mortimer Bay (Tasmania). The photograph to the right was taken only a stones throw from the boat shed when the Aurora was a little more active.

Night Focus, Easy As….

Okay so we have all sat in the picture theater and thought “Focus FOCUS”, and maybe recently you started to shoot at night only to find your camera was not up to the task.

“Yer, my camera won’t focus, so how do you focus to infinity at night?”

Most cameras are not designed to focus in extreme low light, and will require manual intervention, switch the lens from Auto to Manual focus mode.

“Ok, so my lens is now in manual mode and I set the focus to infinity but it’s still blurry?”

This is normally the case as the infinity mark is almost never perfect, think of it like the pirate code, that is more a “guide”.

“You mean I can’t focus at all at night?”

There are a number of ways to get perfect focus in the dark, here are the 2 easiest.

1. If your camera supports live view use it. Set you lens to manual focus, and focus to infinity, then using live view and zoom (normally 10x) you should be able to locate a distant light on the horizon or bright star you can adjust the focus on to get it perfect. This will require some practice and stars or faint objects may only work on better / later model cameras and lens with larger apertures like f2.8 and lower.

2. If your camera does not have live view then during the DAY have your camera focus on a distant object in auto focus mode (something on the horizon), then looking at your lens note where the focus mark is, it should be near infinity, but it probably wont be exactly on it. Take note of the location, or place some masking tape next to the mark and mark it with pen so you can manually move the focus back to this spot later. Repeat this a few times to confirm the mark. Now at night set your lens to manual focus and move the focus to your recorded mark. This method is not as good as the one above as lenses have a little bit of “play” or tolerance, but it should be more than good enough for infinity focus.

There you have it two ways to get perfect focus in the dark. – Cheers.

Aurora Australis

Aurora AustraliaMy experience with the Aurora.

I have shot a few Auroras now, most at fairly low light levels when compared to those at very high or low latitudes. I have shot a nunber at around 42 degrees south from Tasmania, and here are my tips for shooting Auroras that are just visible to the eye.

Light, it’s all about light. The fastest glass is going to give you the best results, why? Auroras are funny things, large light curtains that slowly move and weave across the night sky, in order to get the best picture you need to “stop” or have as little movement in the curtains as possible. There are only two ways to do this while keeping your exposure short, either you increase your ISO or you open you lens f-stop to allow more light in. Increasing the ISO is not ideal as it adds more noise, and only the best cameras will have usable low light pictures at high ISO’s

The picture above was shot at ISO 800 for 2 mins at f4 with a 17-40mm, in this example you can just start to see start trails, and the aurora is flat with little variation across the color bands. f4 on this lens was the max f-stop for light. If however I had used a 24mm f1.4 I would have been able to reduce the time period by 3 stop or an exposure of 15 seconds @ f1.4 at ISO 800. This would have given the same overall exposure but allowed for more variation and exposed the ribbons better.

So, get the fastest glass you can afford, and this is sometimes a trade off with focus length. For example 16-35mm f2.8 v’s 24mm f1.4, the 24mm is going to allow a lot more light in, but will not be as wide as the 16-35, and the cheaper 17-40mm f4 is going to allow even less in. Another option is the Sigma 20mm f1.8 if you can handle it’s softness.

What else do I need to know? Well, don’t try shooting an aurora near other light sources, such as cities. If you moon is up, and all but a slither then forgot it, it’s going to wash your aurora shots out. Use a good tripod, I can’t stress it enough, don’t buy a cheap flexible tripod for low light photography. the slightest movement is going to wreck your shot. You can used ND grads, and they will help to even out brightness. Know where infinity is on your lens, as you may not be able to see enough to focus. Some cameras show stars in live-view zoomed in and you can focus on them, or a light source far in the distance.

Night Photography, Nikon v’s Canon

Fort Direction Sunset

I have been a user of the 5D mark II since the day it was released, well almost. It’s a great work horse, delivering consistent images regardless of the situation. Then along comes the Nikon with the D800, and it’s smaller brother the D600. Are they any good for landscapes compared to the Canon? After some very extensive research on the web (hours of reading articles), I decided to move to Nikon, with the D800 being all the rage. So I borrowed a friends D800, and a D300s to do some basics comparisons and to get used to the Nikon bodies. What I will discuss here is how Nikon compares to Canon for low light landscape photography. The types of light levels I’m discussing are around 30sec / f2.8 / 1600ISO.

The D300s I was considering for a second body, as is of the same era as the 5D mark II. It was useful to confirm the D800’s metering as discussed below.

Live View

Canon has always had a good live view system, particularly with the frames per second delivered to the LCD on the rear of the camera. The first thing I noticed with Nikon was increased noise and significantly reduced frame rate when viewing zoomed in content on the Nikon, particularly in low light. The combination of these two factors made it very difficult to focus the camera, and I stress ‘very’, with the Canon I could focus on a star for example, while with the Nikon the frame rate was so low it was very difficult to focus, not impossible, just frustrating. I did however like the inbuilt level feature. Insuring the horizon is level at low light can be difficult.

Exposure

I’m sorry, but the Nikon is next to useless for getting the exposure anywhere near correct at extremely low light. In very low light conditions the Nikon did not meter anywhere near correct, and was metering at least 3.5 f-stops below the Canon. Having said that the Canon was also metering low as well and I was clearly in the manual settings / try and see space. It could be that Nikon allows significantly more light in through the view finder? It was nice to see that the D800 did have a shutter for the viewfinder, which was a welcome relief from the rubber boot / strap cover. To be fair on the Nikon the conditions were well outside of normal photography, and even the Canon was struggling, but closer to the mark.

Color Balance

The Canon always delivers good color balance, and very rarely do I have to set it to daylight or any other setting, even when shooting at night. The Nikon however was struggling and needed to little more help to get the balance correct, most of the pictures were turning out a very dark blue. Having said that, this is not a major issue as I always shoot RAW, and this can easily be corrected in post. Most likely the slight color balance issues were getting worse at lower light: “The D800 was noticeably sharper, while the Mark III produced more accurate colors, with a superior white balance system.” – http://www.digitalcamerainfo.com/Features/Head-to-Head-Nikon-D800-vs-Canon-5D-Mark-III.htm

Long exposure artifacts

When taking very long photos the D800 was introducing a lot of random white spots into photos, I would not consider them to be “hot” pixels, but they were quite strange. a quick Google search later and I discover it’s a nice feature: http://scottreither.com/blogwp/2012/07/01/nikon-d800-e-long-exposure-issues-problems-2/ & http://www.flickr.com/groups/1567431@N22/discuss/72157632780538698/ are two such examples.

 

Conclusion:

I think this video shows most of the points above: http://vimeo.com/42381520. You can clearly see the under exposure, incorrect color balance, and some noise being introduced, even at 1/50. Extend that to a 5 min exposure and it all goes pear shaped.

There is no doubt that during the day or in moderately low light the D800 will perform as well a a 5DmX, if not better. However at extreme low light I do not believe the D800 is the best choice. It’s clear, at least to me, that this is pushing the camera to it’s limits. So for the time being I will hold onto my 5DmII, and hope that Canon will introduce some of the new options in their next 5D body, along with maybe a few more Mega Pixels.

 

Also, D300s Frames Per Second?

This is completely not related, but a surprise to be sure. We all like to get the best out of our gear, so I always set my camera to 14-bit RAW were possible. With the D300s I noticed something interesting, the factory setting is only 12-bit RAW, thus allowing up to 7.5fps dependent on other settings. However increasing the quality to 14-bit RAW reduced the fps to 2.5 max (ouch). I rarely shoot more than one frame at a time and could not care less. However  I wondered if this was just a marketing “trick” from Nikon’s to make the camera look better than it really is? How fast would a Canon body be at 12-bit RAW?