Category Archives: Composites

Advanced Star Trail Tricks

Published: Oct 11, 2012
Last Update: February 14, 2018 (remove Flash)

I have been playing with Star Trail processing for quite a while.  Ever since I wrote the StarCircleAcademy Stacking Action I’ve been tweaking processing to try different things. Sometimes failure is inevitable, sometimes… well, you’ll see.

First, you may want to look back through my earlier columns on shooting and processing star trails because this is not a primer on star trails – it builds on what I’ve previously written and this is not a good place to try to understand what stacking is.

Second, please understand that I use a variety of tools but almost all of my more successful endeavors end up as layers that are combined in Photoshop (CS5 at the moment).  You could combine your layers in GIMP if you don’t have Photoshop, but you’ll be out of luck if you try to use Lightroom.

Here are my star trail effects:

  1. Smoothee – Averaged sky and/or foreground to reduce the grittiness that sometimes results from brighten stacks. I’ve been espousing this for quite a while. See the Simple Astrophotography Processing Technique.
  2. Blobulous – stars at the beginning (or end) of a trail are made to stand out from the rest of the trail.
  3. Comets – star trails appear to grow brighter and the end of the trail looks like the nucleus of a comet.
  4. Streakers – Like comet only the trails are longer
  5. Blackened – A clever trick removes sky glow from light pollution, the moon, or twilight.

And of course you can make “Blobulous Comets” and “Blobulous Streakers” and “Blackened Smoothee Comets” and more.

Building Blocks

To creatively combine exposures, I usually create the following stacked frames.

  • Dark (Darken in Image Stacker/StarStax)
    The darkest elements emerge – especially the hot pixels
  • Brighten (aka lighten) stack
    The Brightest of everything is present, including hot pixel and more noticeable noise
  • Average
    Contrast is reduced, smoothness increased.
  • Additive (called “Stack” in Image Stacker)
    Hot pixels become really bright.
  • Scaled (called Stack/Average in Image Stacker)
    Allows some increase in brightness but more smoothness, too. Experiment with different divisors.

Normally I create all of these combinations using Image Stacker against my JPG files because it is really easy to do.  I end up with a set of frames something like these although I’ve significantly brightened them so that they are easier to see.

Smoothee

In a Nutshell: Combine the Average stack over the Brighten stack using Normal mode at 45% opacity.

I’ll start with the Smoothee technique since it’s probably the easiest to do and perhaps the easiest to understand.  The problem with “Brightness” (or lighten as it’s called in Photoshop) is that it will also pick up all the hot pixels, and the brightest bits of noise.  Averaging on the other hand tends to smooth out everything except for truly hot pixels since most noise is random. By putting an averaged stack as a layer over the brighten stack and then adjusting the blending modes and opacity you get a smoother sky and foreground.  Exactly what settings to use depend on the images, but surprisingly many of the blending modes for the Average layer work here including Darken, Multiply, Overlay, and Normal. The starting place for Opacity is about 45%.

Hint: You can also use an Additive stack instead of the average stack but usually only the Normal blend mode will work.  For even more fun combine the Additive stack and the Average stack.

For additional smoothness you can also subtract the “Darken Stack” while adjusting the opacity to prevent halos and weirdness.

Blobulous

In a Nutshell: Add one of the single frames more than once.

What do “Blobs” look like? Like this…

“Fat Star” processing.

There are two ways to produce “Blobs”. One way is to add “Comets” to a smoothed star trail. The other is to simply pick an image (usually the last one in the set) and add it in using “Add” or “Screen” mode. To make the blob more pronounced duplicate the last frame so it’s added twice. BUT remember when you add in any single image the hot pixels are going to come out… and even more so if you add an image twice.

Comets and Streakers

These two techniques require some fancy stacking techniques. Fortunately I’ve created an action to do all the fancy stuff.  I’ll be rolling out the action and the explanation to my Photo Manipulation Webinar participants first <NOTE: The Advanced Stacker PLUS action has been released and is available for purchase in our store>.

Oh, here is a peak at what the Comet action looks like:

What's The Point?

And here is what an animation of comets might look like:

Star Rise

 

Settings

I know you’re going to ask so let me save you some typing. Except for the “Comet” image above, all images used in these illustrations were taken during the Ancient Bristlecone Pine Workshop in the Patriarch Grove on White Mountain, East of Bishop, California.

The 34 or so images that I’ve combined in the examples above were all taken with the following settings: Canon 50D, ISO 400, f/3.5, 79 seconds, 10-22mm lens at 15mm.

Dark Frames And Your Night Photography

In an upcoming webinar (Down with the Noise) I explain a lot about noise: causes, contravention and cures. This is a bit of a prelude and addresses the questions:

  1. What is a dark frame?
  2. What do I do with my dark frame?
  3. What do I do if I don’t have dark frame(s)?

What Is a Dark Frame?

A dark frame is one or more images taken at the same exposure length, ISO and ambient temperature as the light (normal) frames but with the lens or body cap on the camera to prevent any light from reaching the sensor. When doing many kinds of night and low light photography dark frames can be quite helpful. And when doing star trails or other night imagery dark frames may save your bacon. A dark frame is what your camera does after a long exposure when long exposure noise reduction is turned on. But you’ll be far more efficient if you take those frames yourself. If you’re taking 100 light frames, e.g. for a star trail, you can take 3 or four dark frames and waste 50% less time (and not have gaps!)

Contrary to popular belief dark frames and long exposure noise reduction do little to reduce the random noise that is present in every exposure. That random noise is most pernicious in dark photos and shadow areas.  Dark frames, however are good for the following things:

  1. Reducing or eliminating hot pixels and amp glow
  2. Removing any “bias” in your image – that is bringing the black back.
    Want me to translate that: an unexposed area on your sensor should read as “0,0,0”  for Red, Green and Blue but I will bet you you don’t get zero!

This would probably be a good place to show you what a dark frame looks like. But you’ll be disappointed. Dark frames are usually quite black.  So instead of showing you JUST the dark frame, here is the dark frame boosted to show the speckles from hell – though they may not be obvious. Here I have made the speckles more obvious by boosting the darks using Curves in Photoshop. At this level of detail there are not any obvious hot pixels.

Dark Frame Overview – Boosted to show details. Note where the markers are – they are shown in the next frames.

And next is the same dark frame zoomed to 3200% unaltered. Hover your cursor over the image to see the same area boosted using curves.

Single Dark Frame (Linear Mode) Unmodified – or cursor over to see boosted version.

When inspected carefully, and with the dark level significantly increased it is possible to notice the hot pixels and possibly banding in a dark frame.  While there were plenty of red speckles and obviously green and blue as well in my stable of dark frames, the “hot pixels” didn’t leap out at me.  If you look carefully at the image you’ll notice I also used the color sampler tool to provide RGB values for 3 different locations on the image.  Of note is location 1 where the R (red) value is 14.  What is particularly worrisome about that value is that even after the entire frame has been boosted to the equivalent of 1.6 stops, you’ll notice that a value of 14 is still larger than all three colors at spot 3. After boosting, that red pixel really stands out with a value of 44.  Our first take away is that boosting the brightness boosts the noise.  The second thing to notice is that the red spot is NOT a hot pixel.  How do we know? Compare 4 dark frames (all boosted)

Boosted Dark Frame                             Click these–>   Frame 1 ~ Frame 2 ~ Frame 3 ~ Frame 4

Takeaway 2: There really is randomness!

Now that we have noticed the randomness, we realize that if we average enough of these frames together we can get the average “bias” – that is the amount of offset above zero in the image.  And if there are hot pixels, the good news is they will be in there too.

But How Do I Use a Dark Frame?

The simplest answer is to feed your dark frame(s) to a program that already knows what to do with them like StarStax, StarTrails or Image Stacker.  But you can do it yourself, and perhaps more elegantly using Photoshop.  How?  Place the dark frame as a layer over the image you want to correct and change the blend mode to Subtract (or difference). Adjust the opacity of the blend until it looks just right.

But I Did Not Take a Dark Frame, Now What?

All is not lost. If you have enough frames you can create a unique kind of dark frame. I took over 300 28-second exposure for a star trail along Lake Gaston in North Carolina.

In the image below I created the top frame using the Brighten mode in StarStax. I could just as easily have created the top frame using the StarCircleAcademy Stacking Action.

I used Darken mode to create the middle frame by feeding it my 100 darkest images. Using Darken mode as the stacking option means that hot or stuck pixels that are in every image as well as the lowest value of sky glow will be collected into a single result.

I then loaded the light (Brighten Mode) and the dark (Darken mode) frames into Photoshop. I placed the dark image over the brighten stack and changed the blend mode to Subtract.

What Happened Here?
Dark Frame Substitute process

Several interesting things happened:

  1. The hot pixels were almost completely annihilated
  2. The sky gradient caused by lights glowing in the distance was also almost eliminated.
  3. The contrast in the sky and elsewhere was improved
  4. The red bias on the railing was mostly removed.

A few less desirable things happened, too. The bright red glow on the railing once subtracted caused some of the railing to turn green. And the subtraction created some “holes” and “halos” in the image – especially where the brightest lights are found.  With some minor touch up, most of those issues can easily be fixed.

Is this the end? By no means! There are a LOT more interesting techniques to follow. Stay tuned.

SHARE this on Facebook or Google+ You know you want to help your friend out anyway, right!?

Painting with Light

Originally Published: Sep 18, 2012
Last Updated: May 11, 2016

Cascade of Stars [C_049409+12]

A Flickrite asked me a question:

 I’d like to know how long do you shine the light or use flash when you are shooting

I was really tempted to give the answer “as long as I need” but I’d just seem cruel to answer the question that way.

The truth, however is “as long as it takes”. Eric Harness, one of my partners in the Star Circle Academy endeavor uses a quite different technique than I do. He prefers to reduce the ISO and paint with light for the entire length of the exposure.  I like to keep painting short and purposeful. Each strategy has its strengths and weaknesses.

How Long?

Voyage into Pointy Land [C_061012]Painting for best effect is a knack, not a science.  You just have to try it and refine your technique based on your results.  Remember to check not just the LCD, but also your histogram when deciding how well you’ve done.  Here are some important points that will influence both the method and how long you will paint with light:

  1. Check your ISO and f/stop.  The lower the ISO or higher the f/stop the longer you will have to paint and the brighter the light has to be.
  2. The distance to the things being painted (due to the inverse-square law). You may spend a fractional second on a granite boulder nearby and long slow seconds on dark, light-eating evergreens in the distance.
  3. Brighter lights require less painting but a more deft hand.
  4. Ocean foam or white water in a waterfall will reflect a lot more light than lava rock – you have to paint the rock much longer.  A still pond or lake require a LOT more light than you would expect. The reflectivity (texture) of the surface matters quite a lot.
  5. It is harder to be precise with wide beams, but easier to uniformly illuminate.
  6. Spotlight or narrow beams make it easier to highlight specific things – but also makes blow outs and hot spots harder to control.
  7. When trying to highlight a certain thing or reveal some shadow detail you will need more light.
  8. House in the Wood [C_049613-17]Often there is too much to paint in a single shot. Using stacking techniques you can paint the scene in sections – and even in different light knowing that they are easily combined later. Or you could expose longer and try to get it “all in” but it is hard to get it just right like that.

Power and Direction

I think most people overpaint – they make the subject stand out too much or blow out the details.  Neither of these are blown out, but they have obvious hot spots.
Beholders of the Galaxy [C_061001] vs Anticipation [C_050158]

  • Don’t paint “head on”. Paint at a 30-45 degree angle to the camera view – and even from behind the subject for rimlight.
  • Consider painting from both sides to fill in shadows – but paint less from one side than the other to keep the scene from looking flat.
  • Be mindful of the color you are painting with and the thing being painted.  Bluish LED lights produce a very different feel from warmer incandescent light
  • Be cognizant of the color “bias” due to existing light.
  • If you use a flash, set it on manual and don’t try to expose all at once. Tilting the flash upward helps to even out the exposure.
  • When painting with a bright light, quick movement is essential. Continuous circular motion helps prevent hot spots.
  • Sometimes you can get more even and pleasing light on what is in front of the camera by painting the ground or rocks BEHIND you – much like bouncing a flash off an interior wall.
  • For dimmer light slow methodical movement is better.
  • Moonbow with Character(s) [C_039385]Try throwing in some color!

Star Man and Perseus [C_059960-1]

Tools

About now you may be wondering what flashlight(s) to get.  We can’t really answer that, however we do suggest you snag the following:

  1. A BRIGHT light (120 lumens or better)
  2. A SPOT light (one with a very narrow beam)
  3. An incandescent light
  4. A broad, dim light (like a keychain light)
  5. Colored lights (red, amber, blue, purple) or some cellophane or gel.

Sooner or later you’ll be like us and carry EACH of the above. Oh, and don’t spend a lot!  Get some cheap stuff – like you find at the checkout counter in a hardware store.

Nonetheless here is a list of our favorite illumination toys. Some or all of them may no longer be available.

The Elusive Milky Way – How to Find It!

Last revised: July 5, 2018
Original Publish Date:  June 26, 2012

This is Part 1 of a multi-part series on finding and photographing the Milky Way.  From November through February it is impossible to spot the densest part of the Milky Way because the sun is hovering there. Read on for more information.

What IS the Milky Way?

Path of the Milky Way West-to-East

The Milky Way in Summer from Horizon to Horizon

We are located in a corner of the heavens of a galaxy we call “The Milky Way.” The Milky Way stretches all the way across the sky and some part of the Milky Way is present every night – indeed EVERY star you see in the sky is located within our Milky Way.   Most people, however, think of the Milky Way as the cloud-like stretch of stars from the constellation Scorpius (aka Scorpio) to the constellation Cygnus – particularly the part nearest to Sagittarius.  I’ll try not to be too poetic, but when you have clearly seen the Milky Way, it is hard to describe how awesome it is without breaking into song. In ideal conditions the diffuse light of the Milky Way can cast a shadow on the ground!  Unfortunately there is little chance that you will ever see that shadow because most accessible places in the world are mildly to HORRIBLY light polluted. Constellations that are found in the Milky Way include:  Perseus (off the bottom), Cassiopeia (near the bottom in the picture above-left), Lacerta, Cygnus (near the center), Aquila, Sagittarius, Ophiuchus and Scorpius (very top).  Those in the Southern Hemisphere will also find Norma, Circinus, Crux, and Carina.  There is a faint portion of the Milky Way visible in Puppis, Canis Major and the bow of Orion. Look carefully at the image above and you’ll see a bright “smudge” in the center of the bottom fourth of the image. That is one of our sister galaxies known as Andromeda. The galaxy gets its name from the constellation in which it is found.  With an unaided eye it is readily possible to spot Andromeda in a dark sky. With binoculars Andromeda is observable even in a suburban area. In the southern hemisphere two additional sister galaxies called the Large and Small Magellanic clouds are easily seen. On a dark clear night it is easy to observe the lack of stars in the broad band of wispiness that forms the Milky Way. But the dark void is not due to the absence of stars. The void is due to immense inky dust lanes that obscure the stars!

When to See the Milky Way

The sun is in the constellation Sagittarius in December so during November, December and January it is impossible to view the richest part of the Milky Way.  October and February are generally impossible, too. The optimum viewing time in the Northern Hemisphere is in the summer when the sun is on the opposite side of the sky. Unfortunately summer in the Northern Hemisphere is also when hot, stormy, cloudy weather is doing its worst and also when the nights are the shortest. Those in the Southern Hemisphere have an advantage – longer and cooler nights during winter mean the air is clearer. Using a simple tool called a planisphere it is easy to predict when and where to look for the dense part of the Milky Way. But what must also be factored in is the location and phase of the moon. The time of year and the direction of the least light pollution also frame the parameters for getting the best view of the Milky Way. Generally the dense part of the Milky Way is best viewed when it is as high as possible in the Southern sky. Facing south during April and May the pre-dawn hours are best. From June to early August the best time is near midnight, though the Milky Way will be visible almost all night. From Mid August through September the best time is soon after the sun has set and the sky has grown dark. Below is an illustration that may help you. It was created for 38 degrees North latitude, but will serve the middle of the United States, Southern Europe, Northern China, Japan, and any location at a similar latitude very closely.  The farther North you go, the lower in the southern sky the Milky Way will be.  If you live above 65 degrees north, you will never see the Milky Way core because it never rises above your local horizon. The circle in the image below indicates the star Alnasl in the constellation Sagittarius. Above Alnasl (the spout of the teapot) is the center of our Milky Way Galaxy.

The Milky Way as seen from Mid-Northern Latitudes

The Milky Way as seen from Mid-Northern Latitudes Facing South. Click for a larger illustration

Best Times To Spot the Milky Way

Month Best Time (Local Time) Moon Phase*
  January IMPOSSIBLE
  February Difficult. Before sunrise (late February only) 3Q to New
  March Difficult. Before sunrise New to 1Q
  April 4 AM to Sunrise New to 1Q
  May 3 AM to 6 AM New to 1Q
  June 10 PM to 2 AM New
  July Sunset to Midnight 3Q to New
  August Sunset until 10 PM 3Q to New
  September Sunset until 9 PM 3Q to New
  October Difficult: Sunset (early October only) 3Q to New
  November IMPOSSIBLE
  December IMPOSSIBLE

*1Q means first quarter moon (half full). In its first quarter the moon rises around noon and sets near midnight. 2Q is a Full moon. Nearly full is called a Gibbous. It is nearly impossible to see the Milky Way when the moon is near full. 3Q is the third quarter (also half full) moon which rises near midnight and sets near noon. New means the moon rises and sets very near the sun. Includes a slender crescent phase, too.

Where to See the Milky Way

Central Nevada, Eastern Utah. Montana. In short, remote areas far from city light pollution afford the best view. But if you know what to look for and when and where to look you can spot the Milky Way from many places throughout the world. Or you can wait for a massive regional blackout. I have seen the Milky Way very clearly from the top of Mission Peak in Fremont, California – an area with over 8 million people in literally every direction. However that glimpse required that the entire Bay Area be blotted out by low, heavy fog. My perch was above the darkness blanket that the fog provided. Yosemite National Park is still mostly dark despite cities like Fresno that are doing their best to ruin the darkness. As Numerous at the Grains of Sand Anywhere along a remote area of the coast far from cities there is a chance to see the Milky Way. For example, I spotted a washed out Milky Way just 8 miles north of Santa Cruz, California.  A long exposure and some photo editing improved the view.  If you get farther away from civilization the results can be much more spectacular as you see here. Finding somewhere in the country where it is truly dark, like the Black Rock Desert in Nevada, or White Mountain in Central, Eastern California the Milky Way reaches its most inspiring awesomeness. If you live outside the United States, do not despair, you have a good chance of seeing the core of the galaxy from anywhere south of 55 degrees northern latitude. Above that latitude the core of the Milky Way will never rise above the horizon.

How do I See the Milky Way

Visor View [C_033780]I know what you’re thinking: don’t I just “look” in the right direction? The answer is no! It takes your eyes 15 to 20 minutes to see their best in the dark.  Any bright light source in the direction you look will diminish the view. Running out of a well-lit house, or jumping out of a car where you’ve spent the last 15 minute driving with the headlights on will make the Milky Way far less awesome.  Avoiding ALL light and shielding your eyes from anything you can’t avoid will help a lot.  Do you see the Milky Way in this photo from the top of Clouds Rest in Yosemite? I promise you it is there. It juts out above the Yosemite Valley near the center of the image. Here is a view from the wilderness in Yosemite.

Lost in Yosemite [C_033706]

Can You Help Me Find the Best Time Where I Live/Work/Travel?

In short, no. Please read through the comments for many such questions and answers. It’s impossible to cover information for everywhere on earth, but our notes here cover all the general concepts. Moreover, the moon phase is different – the moon doesn’t behave like the sun, so even though the Milky Way may be glorious this year on say August 8th, next year the moon may be full and obscure your view. Also, weather conditions may affect your view, so do not neglect that variable!

How Do I Photograph The Milky Way?

Cameras are getting better all the time, and there are some nifty tricks you can use to make a compelling photograph of the Milky Way even if your camera is not the top heavyweight performer in the gear smack down.  We’ll cover cameras and techniques in installment 2 of this series!

Famous III [C_035478]