Category Archives: Image

The Elusive Milky Way – Capture an Image

Published: July 7, 2012
Last Updated: September 10, 2018

I assume you already read part one of this article which describes a bit about what the Milky Way is and what times and seasons are best for photographing the cloud-like expanse of innumerable stars.  In this installment we describe the equipment and settings you will need.

Just Ahead: A Universe of Possibilities

f/2.8, ISO 3200, 30 seconds, 16mm, post processed and combined with shots of the bridge that were lit with a spotlight.

Standard Capture

To get a passable or better image of the rather dim Milky Way you need:

  • A high performing low light camera (more on that in a moment)
  • A large aperture (f/2.8)
  • A wide angle lens. Ultra wide even.
  • A cool/cold night
  • As little city glow and moonlight* as possible – see below for an image taken in twilight
  • A solid tripod
  • Patience
  • To know where and when to look!

To get a recognizable Milky Way in a single frame, you’ll want to use somewhere between 2000 and 6400 ISO at f/2.8 or wider setting. That’s very high, and a wider aperture than many people have paid for.  You’ll also want to expose as long as you can before stars are streaking.  We recommend starting at 30 seconds, and reducing your exposure time if the streaking is objectionable. Below is an image taken when the rising moon was beginning to wash out the sky and this may be typical of attempting to capture the Milky Way in a less than ideally dark scenario. Just want a quick suggestion for settings:  Use these:

  • f/2.0; 24mm; ISO 6400; 15 seconds or
  • f/2.8; 24mm; ISO 3200; 25 seconds (or longer)
Group Hug

Moonlight and Twilight begin to overwhelm the Milky Way in Alabama Hills, California; 30 seconds, ISO 3200, f/2.8, 17mm

Some image degradation is to expected. For example vignetting and coma are both more obvious at lower f/stops. Coma is a comma or “bird-wing” like appearance of stars near the corners of the image.  Both coma and vignetting can be overcome by stopping down the shot – but resist the temptation because stopping down means losing some or perhaps all of the wispy milky goodness that you are trying to capture. Exposing longer will only help if you have some special apparatus (see Tracked Capture below). Are you wondering why exposing longer does not solve the problem? We have tackled the issue in two different styles: a cheerful allegorical example, and a recent math savvy explication.

What will an image look like captured with 3200 ISO? It may look like the image on the left below which is “straight out of the camera” – but perhaps not for you as this image was taken in a VERY dark sky area in Nevada.  On the right is the same Milky Way with some simple processing we will describe in the next installment.

SOOTC (and not SOOTC) [C_039467]

What is a “High Performing” Camera?

I qualified my statement earlier by indicating a high performing camera is needed for a standard capture like those I’ve shown above.  Since it would be impossible to keep an up-to-date list of the current high performing cameras, let me instead point out a few characteristics common to all high performers:

  1. Recent generation (2 or 3 years since introduction) is preferable because technology has steadily improved.
  2. Large pixels (to collect more light).  A common measure of the pixel size is in microns. Generally this puts full frame cameras ahead of cropped cameras.
  3. High “ISO at Unity Gain” – this is a measurement of the efficiency of the sensor. There are two good sources for this information: the DxO Sensor Scores and ClarkVision’s (older) tables.
Don’t be fooled by the highest ISO setting advertised. That number is completely meaningless.
As of August 13, 2018, the highest performers are listed by manufacturer and in order of performance. E.g. the Nikon D3s is better than the D800 – though the difference is small. Indeed, the D800 excels in some categories over the D3s. Cropped cameras are shown in italics – note that there fewer of them and none of the crop cameras exceed their full frame siblings. The first paragraph are the TOP performers. The next bracket list other cameras that “meet” our judgement of “good enough to photograph the Milky Way – with an appropriate lens. Note that the Cybershot DSC-RX1R ranks right after the Canon 1DX II – that’s quite a surprise –  it does have a fixed focal length of 35 mm, however.

TOP PERFORMERS

Pentax: 645Z
Hasselblad: X1D-50c
Sony: A7 III, A7S, A7R III, A9, A7R II, (Cybershot DSC-RX1R II – 35mm f/2.0 lens, A7S II)
Nikon: Df, D3s
Canon: 1Dx II

DECENT PERFORMERS

Nikon: D4s, D600, D800E, D4, D750, D610, D800, D810, D850, D5, D700, D3, D3X, D3300, D5200, D7100, D5100, D7000, CoolPix A, D3200
Canon: 1DX II, 5D IV, 6D II, 1Dx, 6D, 5D Mark III, 5D II, 1DS III, 1DS II, 5D, 1D III, 1D VI, 1D III, 1 D II
Sony: A7R, DSC-RX1R, RX1, A7, Alpha 99, Alpha 900, Alpha 850, A6000, Alpha 580, NEX-F3, NEX-C3, NEX-5N, NEX-3N, NEX-6, NEX-7
Leica: M Typ 240, X Vario
Phase One: P40 Plus, P65 Plus
Pentax: K-1, 645D, K-5 II, K-5 IIS, K5, K-50, K-01, K-30
FujiFilm: FinePix X100

Not in contention: any cameras by: Casio, Konica Minolta, Mamiya, Nokia, Olympus, Panasonic, Ricoh, or Sigma.

The list above shows all cameras having a DxO Sports (low light) score of 1000 or higher.

Cameras like the Nikon D90, Canon 1D II N, Phase One IQ 180, Canon 1Ds, Nikon D3100 and Leica M9 fall just below this threshold and may also be suitable.  The first eight Nikon models outperform the Canon 1Dx, and after the 1DX is the Sony A7R. The Fujifilm just barely cracks the list in 43rd and last place.

If you want the camera to cost less than $2,000 USD your current top choices are: Sony A7 III, Pentax K1, Nikon D610, Canon 6D II (or 6D).  If we were to make a recommendation, we’d recommend any of the full frame choices over the smaller sensor cameras.  Note that prices vary dramatically, and you may find used higher performing cameras for less than $2000. Beware of all Sony models, however, as they have had a long standing problem with “Star Eater” noise reduction problems. As of August 13, 2018, it’s not clear if they’ve actually fixed this problem on all of their models.

Stacked Capture

A “stacked” capture is what you may need to resort to if your camera performance is not so spiffy.  The approach applies astrophotography techniques to create a lower-noise version of an image.  The technique requires MANY shots of the same view. However using this approach you will want to avoid having anything but sky in your photo. Terrestrial elements will make stacking the image tricky.

Urban Milky Way [C_036919-23PSavg]The image at the left is a stacked capture to illustrate the point, however it was done with a high performing camera and only 5 images.  A lower performing camera will require as many as 20 or so captures to combat the noise. The method is described in my a “Astrophotography 101” Webinar and details are walked through in Astrophotography 301.  On the other hand, this image was captured in a location where the Milky Way was quite faint – alongside 7 million people in the San Francisco Bay Area so there is hope even where the Milky Way can only faintly be seen.

Details about the stacking method appeared in an earlier column as well as in an an earlier webinar.

Tracked Capture

The last way to get a great shot of the Milky Way is to track the sky with an apparatus called an Equatorial Mount.  By tracking the sky at the rate of the earth’s rotation you can lengthen a 20 second capture to perhaps a 60 second one. You can also use several such captures to create a stunning “Stacked Capture”. Again, however, shots which include the land are a bit harder to pull off unless you resort to layering. What do you need to do a tracked capture? We cover that in detail in the Astrophotography 101 Webinar, but in short, you’ll want an Equatorial Mount of some sort – not an Altitude-Azimuth (aka Alt-Az) mount! A device that looks intriguing and not terribly expensive is the Polarie.

Once you get that image (or those images), you will no doubt want to tease the most pleasing photo you can out of your data. That is a topic we’ll cover in the next installment: Processing your Milky Way images.

600 Rule?

You may have heard it elsewhere as the “600 rule”.  I first heard about the rule while visiting the Looney Bean in Bishop, California in 2008.  Five photographers sitting in a coffee shop poring over their laptops reviewing what they recently bagged are bound to start talking.  It was my good fortune that one of those present was the very talented Brenda Tharp who first quoted the 600 rule to me.

I, however, have repeated the rule as the “500 Rule” because I think 600 is overly optimistic.  What is the rule?  The rule states that the maximum length of an exposure with stars that doesn’t result in star streaks is achieved by dividing the effective focal length of the lens into the number 600.  A 50mm lens on a 35 mm camera, therefore would allow 600 / 50 = 12 seconds of exposure before streaks are noticeable.  That same 50 mm lens on a 1.6 crop factor camera would only allow 7.5 seconds of exposure.

But Wait. The Rule Isn’t All That Great!

The real number is quite subjective.  A little math reveals that on the Canon 5D Mark II (a full frame camera), with a 16mm lens a pin point star on the celestial equator moves from one pixel* to the next in 5.3 seconds.  But the 600 rule would allow 37 seconds of exposure and the 500 rule 31 seconds.  Both rules will produce streaks on the sensor! The visibility of those streaks will depend on the finished print size and viewing distance.  Print it large and stand close and the streaks will be obvious.

So what does a 30 second exposure look like at the pixel level:

3 Stars at 30 Seconds, 16mm on 35mm Sensor

Clearly those stars are streaking across about 5 pixels* just as the math would bear out.

What is going on here?  The Canon 5D Mark II images are 5634 x 3753 pixels* from a sensor that measures 36 x 24 millimeters. Dividing 36 by 5,634 reveals that the distance from the center of one pixel* to the next is a scant 0.00639 millimeters (or 6.4 microns).

The formula for calculating the distance in millimeters (d) that a star travels across a sensor due to the earths rotation looks like this:

d = t * f / 13750

Where t is time in seconds, f the effective focal length and 13750 is, well 13750.  I’ve simplified the above from the full equation. Is the math scaring you a bit… don’t worry… we’re almost done. Earlier we calculated the pixel* to pixel distance as 0.00639, what we want to find is how long (t) it takes for a star to move that far on the sensor.

0.00639 = t * f / 13750

Solving for f = 16mm we get a t value of 5.3 seconds as I asserted earlier.

But how does that calculate out on a different sensor, the Canon 50D, for example?

The Canon 50D has 4770 pixels across 25.1 mm or an inter-pixel* distance of 0.0053 millimeters.  Substituting into the earlier equation we find that a star marches across a pixel on the 50D with the same 16mm lens in 2.83 seconds.  With a 50mm lens on the same camera… the bad news is the star is speeding from one pixel* to the next in less than a second!

What does an image look like with a 30 second exposure at 16mm on a full frame camera? Remember that the streaks will be 40% longer on the cropped Canon 50D.

Milky Way over Black Rock Desert, Nevada

30 Second Exposure – a close look shows elongated stars.

Scaled down to only 16% of the original image size or seen from a distance no streaking is obvious! We will try not to twitch knowing – because we pixel peeped – that the stars are really dashes not nice round pinpricks of light. And indeed only the eagle eyed are likely to notice the dash-like nature of the stars until the photo is printed large, say at 20 x 30 inches.

What Can We Conclude?

  1. Streaking starts a LOT sooner than any rule you may have learned.
  2. The time it takes to streak depends on the inter-pixel* distance (sensor density / mm) and the focal length.
  3. How much streaking to allow depends on your aesthetic tolerances.
  4. You can not get more or brighter stars by exposing longer; starlight has already given up on one pixel* and moved on to the next in just a few seconds.
  5. The longer the focal length, the more impossible it becomes to prevent streaking.
  6. Gaps in your star trails may be unavoidable if the inter-shot delay (normally 1 second) is long enough to skip pixels*.

Final Note

I carefully added asterisks* to every location where I wrote the word “pixel” in a way that might imply your camera collects light in pixels. You might be wondering why I did that. The answer is: your sensor is comprised of sensels, not pixels. It takes 4 to 9 sensels to create a single pixel depending on the de-mosaic-ing algorithm your camera uses. Maybe you aren’t that picky, but I didn’t want to hear complaints from the purists.

I particularly relish this epiphany because I reported long ago that “longer exposures do not result in more stars“.  I just never got around to doing the extra bit of math – or the experiments – to prove out my assertions.

Real Final Note

A commenter has rightfully taken me to task by pointing out that the perception of a streak is dependent on many things other than just the actual sensor values recorded. In particular, if the image is not enlarged much some streaking will be scarcely or completely unnoticeable because the feature will be too small for the eye to perceive.  The problem with this assertion is that it assumes a lot of preconditions: e.g. how large the print is, how far from the print a viewer stands, and the subjective experience of the viewer.  My real world experience has led me to conclude that it is a reasonable goal to keep the streaking to 2 to 3 pixels or less because that will provide the greatest possible usable magnification (finished viewing size).  There would be no point to collecting a high megapixel image if you can not produce a print proportionately larger or more detailed than a lower megapixel image!

Here is an example that makes my point. I love this image captured on a Canon 5D Mark II. When printed at 20×30″ and viewed at 4 feet there is some streaking. Perhaps only a critical eye would notice, but even an untrained eye will notice when viewed from two feet away.

Famous III [C_035478]

Skies Ablaze – Capturing Fireworks

Pod People [C_033010]

Photo 1: Abstract Sausalito fireworks (aka Pod People)

Several times a year Americans (and others around the world) find an excuse to gratuitously burn large amounts of black powder in spectacular displays that serve no real purpose except to create awe and wonder. For that reason alone, I love fireworks.

Fireworks are an interesting subject for Night Photography and require a little patience and experimentation to do well. And I have found some new approaches to photographing fireworks that make them even more interesting – as shown in Photo 1, above. Yes… that is a firework burst!  For information on how I achieved that effect, see below.

Challenges with Fireworks

Fireworks come with their own set of issues. From the ephemeral nature of the light to the selection of a site to photograph them from.  I generally favor more distant locations where I am able to switch between telephoto and wide angle lenses to alter the composition of the shot.  At greater distances the flashes of the fireworks are also a little less challenging photographically.

Brief Intense Light

Firework bursts are brief lasting seconds or less, but surprisingly they are very bright. Because they are so brief catching them at just the right moment may at first seem daunting. As with all things night photography the camera is quite inadequate at metering or adjusting for fireworks in a way that will capture the drama and grace. So the first tip:

Tip 1: Stay in MANUAL mode and do not let the camera try to adjust anything.

I generally prefer settings that are approximately like this:  200 ISO, f/9, 10 seconds.  But may change those dramatically based on the outcome of a shot or two, and how much background I’m trying to grab.  For example, I will often choose shorter exposures at higher ISOs, and sometimes I use BULB mode.  More on that in a moment.

Location, Location, Location

As in real estate, location is everything. Fireworks, in my opinion look better against a city skyline, reflected in water, or next to the moon or a snowy mountain peak. But creating an exposure to include those background elements is tricky, sometimes very tricky.

Nearly every event in which fireworks are employed is massively crowded (think 4th of July) so finding a clear view and a safe hassle free space to set up a tripod takes a little creativity and patience. Fortunately fireworks can be viewed from near or far – and far is often a bit better.

Photo 2: Fireworks and the San Francisco Skyline

Weather may also be problematic – as in the San Francisco area where fog in the summer evenings and mornings is normal. Four years of shooting produced only one year with moderate haze (as in Photo 2). Two years were complete shutouts.  Photo 2 could be improved with a brighter background – either by taking a longer exposure at the time or by combining with an exposure taken earlier or later in the evening.

The minions in the Night Photography group were clamoring to shoot fireworks, but thrice burned equals twice shy despite a fantastic location found years earlier.

Tip 2: A good location is always the better choice. Location, location, location!

Composition

Wide shot or tight shot?

Photo 3: Tight coverage of a burst

Photo 4: Wide angle with pond and reflection

Straight shot or creative shot:

Photo 5: Changing focus during exposure

Fortunately there is no rule that says you can not try a number of different approaches in the same event – provided the event lasts long enough.  However it is best to start with trying to get a pleasing result that is conventional in nature that is, more like Photo 4, above.

Timing

As in comedy, timing is important.  Start the exposure too soon and you’ll catch the bright burst of the firework which may very well overwhelm the camera and produce a “white blob”. There are three approaches to the timing problem, and sometimes I use all three in the same night:

  1. Set the camera up with an intervalometer/locked remote shutter and just let it run.
  2. Manually release the shutter using a fixed exposure length as soon as you see a burst.
  3. Manually control the shutter in bulb mode.

The main reason to use a fixed exposure length is if you intend to stack or animate your photos – keeping the background exposures the same produces a more pleasing, flicker free result. However if your only goal is to “get the boom”, option 3 is probably the best.  I recommend shooting after the initial “boom” because what makes the firework appealing is the light spreading and then falling over time.  How long to expose depends on a lot of things, of course, including how bright the background is and how many fireworks are blowing up at a time.  The Finale is usually a good time to take your eye off the camera and enjoy the show because finale’s usually end up a washed out mess.

Tip 3: Start the exposure immediately AFTER the boom.

Creative License

So how did I get the strange effects in Photo 1 and Photo 5?  I adjusted the focus while exposing.  I have also played with the zoom while exposing.  In Photo 1 the shot started focused and I defocussed it.  In shot 5 it was the other way around – it started out of focus and finished less out of focus.

Once you start playing with the focus, do not expect to have sharp images which is why I recommend you get the conventional exposure first before you get all creative.

 

What is Special about the December 10th Lunar Eclipse?

The moon is in penumbra as it sets over the US Capitol Building, December 10, 2011

December 10th will bring us a total lunar eclipse visible from much of the United States. It will be the last such total lunar eclipse for the next 3 years.  The Eastern United states will get just a glimpse of the first umbral contact as the moon sets and the sun rises, but the Western continental US will see the moon totally eclipsed as it sets.  Get up at least an hour before sunrise to see it, and look low in the west.

What’s not clear is how visible the moon will be since twilight will begin to drown out the fully eclipsed moon for western observers. However if you’re a “Moon hunter” like I am, this eclipse provides a rare opportunity to catch the eclipsed moon together with features near the horizon – landmarks, mountains, etc and THAT is quite unusual.  The ideal place to be would be about one time zone west of the Pacific time zone… so perhaps those in the far western Canadian Provinces and those in Eastern Alaska and Hawaii will have ideal conditions. For them, there will be plenty of time to track the eclipse.

Many of those in the San Francisco Bay area are in for a big treat as the eclipsed moon will slip behind the South Tower of the Golden Gate Bridge – IF you can find the right spot to be.  Here is an approximation of what those with clear weather and good timing likely to see (except, of course it will be early twilight):

 

I wrote about this event previously.  If you’re interested in calculating these things for yourself, I have scheduled the next “Night Photography 111: Catching the Moon Webinar” for January 4, 2012 (webinar cost $25.11). What have the students said about this webinar?

  • Steven did an excellent job with the training. – Judy, San Jose, CA
  • Top notch, even for a novice such as myself. Wish it was longer, so much to learn – Jack, Los Angeles, CA
  •  Great presentation! Steven offers a perfect balance between inspirational shots, moon facts and figures, and calculations to make our own moon compositions.  – Phil, San Francisco, CA
  • Wow did I ever learn a lot. I have been trying to shoot the full moon every month this past year. Some pics were okay and some not. After this class, I feel like I have some new tools to plan my shots and get a lot closer to my vision of the shot or maybe realize it won’t work after all and revise accordingly. I am already planning for my next full moon.  – Marsha, San Francisco, CA
  • SteveC is a Great Teacher – Roger, San Francisco, CA

If you’re thinking that Astrophotography might be worth trying, my next Astrophotography 101: Getting Started Without Getting Soaked is December 20th (cost $36).

  • Excellent presentation – MUCH better than I expected. Steven really knows the material, and has it well prepared. – Burt
  • A lot of very good information presented in a way that a beginner can understand. I was pleasantly surprised to learn that astrophotography can be attempted for less than the price of a new lens.  – Phil
  • Excellent introduction to astrophotography. – Alan