Joel Leindecker Photography


view:  full / summary

Star Trails Part 2

Posted by Joel on September 15, 2013 at 11:40 AM Comments comments (2)

This tutorial is a follow up to my previous tutorial on shooting star trails.  If you have yet to read that tutorial I suggest doing so now.  This will pick up where that left off, the editing of a star trail photograph.  As I ended the last tutorial I mentioned that most star trail images will have airplanes, and other distracting elements in them.  This tutorial will teach you one trick to removing these objects without diminishing the actual image.  For this tutorial I will be using this shot taken with a Canon Rebel XS, and a kit 18-55mm lens:

The shot settings for this image are:

Shutter: 30 seconds (82 images stacked)

Aperture: f:3.5

ISO: 400

Focal Length: 18mm

Part 1: Loading the images

In the last tutorial I taught you how to load the images into a stack.  This is critical for editing the image as well.  For this tutorial I will not detail the process of loading the files, I will merely show you what this image looked like when I loaded the files into the stack.  Here is what I saw when I first loaded the images to Photoshop:

As you can see, the image has many planes flying through the frame.  Also, the tree is very bright, and it does not look natural.  If you scroll up to the final product you will see that the tree looks much better than it does in this image.  The reason for this is that I triggered an external flash in the first image.  I was hoping to light the tree, and use that as a way of avoiding a silhouette, but a car's head lights gave a much nicer look later in the shoot.  The car lit the image from the side, and the florescent headlights were not the same tone as the flash i used, and that caused the distracting light on the tree.  This image may not be as appealing as I had hoped, but it is imperative that I save a copy of this image to use later.

Part 2: Removing the distractions

The images are loaded into a stack on the right hand side in Photoshop, and next to each image there is an eyeball.  This eyeball tells you that the image is visible in the stack.  For this step you will go through the stack and click the eyeball on each shot with a distraction in it; this will take the distracting shot from the final image.  However, it will also take the stars out of each shot that has a distraction.  This will make the stars look choppy, and create a very distracting sky.  Here is what this shot looked like with the distractions removed:

You can see the missing sections in the stars, but you can also see that the tree looks better, and sky is free of distracting airplanes.  This is what we want to see.  Next you will save a copy of this image.

Part 3: Blending the shots

You now have two saved images.  One with all the distractions, and one with the distractions removed.  The next step is to load these two images into a stack.  You can either use the feature in the file tab, or you can copy and paste the images into a new document in Photoshop.  Either way, you will want to make sure that the first image (the one with all the distractions) is on top.  Next you will apply a layer mask.  To do this in Photoshop click:

Layer:Layer Mask:Reveal All

After making sure that you are editing the layer mask and not the actual image click your brush tool on the left hand side of the screen, and change the foreground color to black.  This will allow you to erase the top image and allow the bottom image to show through.

Now you will simply draw over the distractions allowing the second image without the distractions to show through.  Remember how the stars looked in the second image?  Since we are only allowing the second image to show through where the planes were we keep those stars from showing.  Here is the result:

Part 4: Final Touch Up

This image is looking much better that did when we started, but it still doesn't pop.  For this I just gave a simple adjustment with the Shadows and Highlights tool.  Now the image has a better glow to it, and I am satisfied with calling this a final product:

Photography Basics: Shutter, Aperture, ISO

Posted by Joel on May 31, 2013 at 9:35 AM Comments comments (0)

Part 1: Understanding the camera

Digital SLR cameras are very technical systems, and if a person intends to use one to its full potential he/she must first understand how it works.  The first question to ask is what does SLR mean?  SLR stands for single lens reflex.  This means that there is a single lens inside the camera which reflects the actual view through a camera lens to the viewer’s eyepiece.  In simple terms, you see exactly what will be recorded in the image.  Below I have placed an image which shows the elements of the camera.

 (image from

As you can see from this illustration the blue mirror reflects the image through a penta-prism into the eyepiece.  This camera gives you a look at an image which a standard point and click camera cannot.  With a point and click camera you see a digital copy of the image which may not match the actual shot.

Another common question is how can you see exactly what is being recorded and still take a picture.  When looking through an SLR camera while taking a picture one will note two things:  the loud noise the camera makes, and the fact that the eyepiece goes black until the image is done being recorded.  These two parts work hand in hand; as the camera records the image the mirror lifts up, blocking the eyepiece, and exposing the sensor to the plane of view.  This is called the shutter release. The shutter lifts up allowing the sensor to record the image (this is also what creates the loud noise you hear).  This is the same for a digital camera and a film camera.  However, in new digital cameras there is no film strip; the sensor works as a digital film strip allowing for the picture to be viewed as soon as the memory card records it.

In the upcoming sessions I will detail the technical aspects of the camera, and how they can be manipulated to create intentional tricks and effects.  The elements which differentiate a photographer from a picture taker are distinct.  In this tutorial I intend to point out some methods which can be implemented in digital photography, to help you take more than just simple snap shots.  A picture taker will just point their camera at the subject and take a “snap shot” of the scene; a photographer will set up and capture a photograph of the same scene using distinct techniques.  This tutorial will enhance your skills and help you become a true photographer.

Part 2: Shutter Release

As I mentioned in the previous section, the shutter is the part of the camera which exposes the sensor to the scene you are trying to shoot.  If you were to think of human vision as a camera the shutter would be your eyelids.  When your eyes are open you are exposing the sensor (your brain) to the scene (the world around you).  However, our brain records images more like a video camera than a photographic camera.  Our mind is constantly processing what we see, and this creates the moving picture we see every time we open our eyes.  If you would like to simulate a photographic camera through vision try this:  close your eyes for a little while, and then open them for a fraction of a second before closing them again.  The scene which lingers in your mind is a still photographic picture.

Freezing Action
Why does this matter?  The answer lies in the effects generated through recording with a fixed sensor over time.  This effect is called a timed exposure.  The human mind records images at 60 frames per second, which means that with still images the human’s shutter triggers at 1/60 of a second.  When using a camera you can record “superhuman” results by using the shutter at a higher speed.  For example, if you look at a fan spinning it appears to be one solid ring, but you know that the ring you see is in fact separate blades.  They appear to be solid because of the speed at which you see them spinning.  By setting a camera’s shutter at 1/2000 of a second we can record motion which the human eye could never record.  Here is an example picture shoot at 1/500 of a second:

1/500 of a second is significantly faster than the human eye can record, but you can see that it still wasn’t fast enough to freeze the racket.  We see a blur where the racket and ball are, and this tells us that the racket was swung at a rate faster than 1/500 of a second.  If I were hoping to completely freeze the action I would have to retry the shot at a faster shutter speed.  Here is an example of action which has been completely frozen:

I was fortunate enough to have the opportunity to shoot a Michigan football game, and this image shows Fitzgerald Toussaint frozen in action as he breaks through the line against Minnesota.  This shot was taken with a shutter speed of 1/6400, which was fast enough to freeze the action.

Timed Exposure

We have discussed how to freeze fast action with a camera, and now we are going to look in the other direction.  The cool thing about having a fixed sensor is that it allows you to record a given scene over a longer timeframe than human eyes are able to see.  Have you ever taken a picture in low light just to find out that everything is blurry?  This blur isn’t because the shot was out of focus, it was because the shutter was triggering at a slower rate than you were able to hold your camera.  The subtle shaking of your hands altered the scene enough to make the shot blurry.   Fortunately, with the aid of a tripod and a shutter timer we are able to snap these slow shutters without moving the camera.  This can allow us to blur moving objects while keeping still objects in place.  

How can we use this in photography?  By showing motion in objects which appear to be still by the naked eye.  One common way this is used is by giving flowing water a silky look.  When we see water flow it looks choppy and rough.  As I mentioned before, our eyes see things at about 1/60 of a second.  At this speed we are able to see the little bubbles formed when water flows, and we are able to see the water droplets when they jump up from hitting objects.  More or less, this is what a waterfall looks like when we view it.  This shot was taken at 1/15 of a second, a little slower than human vision:

As you can see the water looks clumpy as it falls.  We can see bubbles along the bottom of the waterfall, and the water underneath looks rough.  Imagine if you were to view this waterfall over the length of a few seconds.  How would it change?  You would be able to see the flowing of the water, and the lines would be much smoother.  Let’s take a look at this same scene with a two second shutter:

In this shot the water has a nice silky look to it.  Also, because we were able to mount the camera on a tripod which remained still through the entire shot we were able to keep the background still by not moving the camera while the shot was being taken.

Part 3: Aperture
Now that we understand how a shutter works let’s look at the camera’s aperture.  An aperture is a part built into the lens of the camera which opens wide or small in order to allow either more or less light into the sensor of the camera.  If you were to think of the camera as a human eye the aperture would be the pupil.  If you are standing in a dark area your pupils get bigger to let more light in, and if you are looking at the sun your pupils will shrink to keep the access light out of your eyes.  Here is an example of what an aperture looks like:

This image shows how the aperture makes the normally large opening much smaller.  This particular aperture consists of five plastic pieces which create a pentagonal shape in the center.  When the image is actually taken the pentagram will appear to be a circle.  The tricky thing to remember about an aperture is that it also controls the focal plane for the shot.  What is the focal plane?  It is the area in the shot which is in focus.  The bigger the hole in the aperture the less you have in focus.  The smaller your aperture the more you have in focus.  Here are two shots which will help show what I mean.  Both shots focus on the crack in the center of the frame; the first shot uses a large aperture, and the second shot uses a small aperture.

Large Aperture:

Small Aperture:

You can see that the first image has significantly less area in focus than the second shot.  However, in order to compensate for less light getting in to the camera the shutter used on the second shot was open for far longer.  The first shot used a one second shutter, and the second shot used a 22 second shutter.

In an SLR camera the shutter is recorded in what is called an “F-stop.”  This refers to the ratio of focal length to the aperture diameter.  What does this mean?  It means that the further your subject is from the lens, the more you will see in focus.  The ratio between how much is in focus and the distance changed determines the number on the “F-stop.”  The easy way to think of this is the smaller your F-stop, the bigger your aperture hole.  The aperture range is dependent on the lens you have attached, but most lenses have apertures between f/2.8 and f/22.  You express the “F-stop” value by the letter “f” followed by a “/,” than you state the number of the aperture.

If I have a camera set to f/2.8 this is a large whole.  This will allow a lot of light in, which means I will be able to use a faster shutter speed.  Also, it will give me a shallow depth of field; this means I will have a small area in focus with a blurred background.

Photographers often use this with sports photography.  The goal there is to use the fastest shutter speed you can.  By using a large hole you allow a lot of light in, and this allows for faster shutter speeds.  Notice the photograph I have of the football game in the shutter speed section, the background is out of focus because I was shooting with a large aperture (f/4.5).

However, if I have a camera set to f/22 this is a tiny hole.  This means I will need to use a slow shutter speed to compensate for the lack of light; it will allow for a large area to be in focus though.  This is often used in landscape photography.  The goal with landscape photography is to have as much as possible in focus, and to get as clear of a picture as possible.  Most landscape photographers use tripods, and this allows them to open the shutter for as long as they need without worrying about the subject moving on them.  Notice the waterfall shot I have in the shutter speed section, the whole image is in focus because I used a small aperture (f/22).  This also helped prolong my shutter to allow for more water flow in the shot.

Part 4: ISO
Next I will talk about a tricky element of SLR photography called the ISO.  The ISO will determine how quickly your camera processes an image, and this will control how much light the camera absorbs in a given shot.  However, the quicker the camera processes the image the more noise (or digital pixilation) the camera allows in.  I look at this like reading a book.  You can skim through and just get the main ideas, or you can read through for content, and learn the subtleties in the writing.  The lower the number on your ISO the more details the camera processes, but this requires a slower shutter speed.  If you have the camera process the image fast you will get more noise, but you will be able to use a much faster shutter speed.  Most cameras have ISO ranges between 100-3200; if your ISO is set to 100 there will be little noise in the shot, but if your camera is set to ISO 3200 there will be far more noise.

If you are shooting in the daylight you will most likely be able to use a lower ISO.  Also, if you are shooting with a tripod you are able to use these lower ISOs.  Generally, landscape photographers use these lower ISO settings because clarity is their number one goal.  They use tripods, so it is not a problem to use slower shutter speeds.  Here is an example of a shot taken with a low ISO.  My camera offers ISO 50, and at this setting there is practically no noise whatsoever.  This shot was taken with a shutter speed of 1/125, an aperture setting of f/8, and an ISO setting of 50.

Some situations make you more limited on what shot settings you are able to use.  Often times if one is trying to photograph moving objects in low light settings they will need to increase the ISO to accommodate for the lighting.  If you do not have a tripod you will need to handhold the camera for the shot.  The slowest shutter speeds a person can hand hold are about 1/50th of a second, depending on the person.  If the lighting does not allow for speeds above 1/50th of a second you will need to increase the ISO until this speed can be reached.  

This is commonly needed when doing action photography.  If you need to freeze action the shutter speed needs to be quicker than the action you wish to freeze.  If you have the aperture as open as you can, the only way to adjust your shutter speed and still have the proper exposure is by adjusting the ISO.  Here is a shot I took with limited light.  This shot was taken in near pitch black, and it successfully froze the action of the bass player.  I used a shutter of 1/40th of a second, the aperture was set to f/3.5, and I adjusted the ISO up to 6400.  You will notice that there is far more noise than the previous image, but this is necessary if you wish to shoot in low light.


Part 5: Combining the Elements
Every shot is a unique photographic opportunity, and no two shots are the same.  By learning how to use the shutter, aperture, and ISO settings on an SLR camera one becomes able to capture any scene they encounter in a unique way.  As you approach a scene it is important to note which element is most important to you.  In this section I will pose three possible situations and explain how the three elements we have discussed can help capture the image desired.

Situation 1: Shutter Priority
Imagine you are visiting a nice picturesque park.  This park many wonderful hiking trails, and many people go there in the fall to view the leaves changing colors.  The scenic park also contains many beautiful waterfalls.  You decide to take some scenic pictures of waterfalls, and you grab your camera and tripod.  You reach a waterfall and you notice leaves circling in the water below.  It creates an opportunity for you to capture the motion of the water along with the waterfall.  If the shot were handheld you would freeze the water in the air and the leaves circling the water below would be frozen as well.  However, if you delay the shutter you will be able to catch the motion of the water.  By making the aperture as small as you can and dropping the ISO as low as possible you are able to extend the shutter longer.  With the camera and lens you are using you have the aperture set to f/22, and the ISO is set to 50.  This allows for a shutter speed of four seconds; enough time to show the motion of the water.  Here is the shot you create:

Situation 2: Aperture Priority
Imagine you are out for a hike with a nice telescopic lens on your camera.  You approach a clearing and hear a rustling off in the distance.  You look over and see a young buck deer standing off in the distance.  You bring the camera up as the deer approaches, and look through the viewfinder.  The deer is standing in a clearing with flowers and grass standing tall behind him.  You realize your camera is set to f/8, and with where the deer is standing this will make him blend with the background at that aperture.  With your current aperture setting your shutter is set at 1/15th of a second, which will not freeze the deer, and the ISO is set to 250.  You can either adjust the aperture or the ISO to get a better shot.  You decide to adjust the aperture to the lowest number you can.  With the lens attached you can drop the aperture to f/2.8.  This changes your shutter speed to 1/160th of a second.  This aperture and shutter speed combination will help freeze the deer's movements, and give you a nice blurred background.  You press the shutter release and snap the picture:

Situation 3: ISO Priority
It is night time, and you decide to take an image of the stars.  The stars are small and far away, and if you intend to correctly expose them you will need to use a high ISO.  You set the ISO nice and high to ISO 6400.  The stars are slowly moving through the sky, but if you want to capture as many as possible you need a fairly fast shutter speed.  However, it is still night, so you will need to set the shutter slower than you can hand hold.  You choose to set the shutter to six seconds, this is slow enough to allow light in, but fast enough to keep the stars from overlapping.  In order to get a correct exposure you set the aperture to f/3.5.  This is a large aperture, but the stars are so far away that you know the stars will be in focus.  Remember, the focal field grows the further away you get from the camera.  Here is the shot you take:


Part 6: Conclusion
Photography can be a fun hobby, and by understanding a few basic concepts one is able to fully explore the abilities of an SLR camera.  This tutorial has detailed the functions of a camera’s shutter release; teaching how to capture images which the human eye cannot view.  Also, this tutorial shows how to control the aperture; allowing a photographer to use depth of field to their advantage.  Finally, we have covered the basics behind a camera’s ISO settings.  We have learned how to control the ISO based off the available light in a given scene.

Now that you better understand how to use an SLR camera feel free to take this knowledge and create your own artistic images.  With these basic concepts one can create all sorts of artistic images.  Here are a few more shots I have taken, enjoy viewing them, and enjoy taking your own artistic images! 

Star Trails

Posted by Joel on September 25, 2012 at 8:10 PM Comments comments (0)

This is a tutorial which is near and dear to my heart. Whenever I do a shoot at night I will shoot a star trail shot. There are a few different strategies which I will discuss, and I will detail the method which I use. Also, I will discuss basic knowledge of astrology, and how this can add an extra element to a star trail shoot.  This tutorial is in no way a full explination of how star trail shots can be done, it is merely a quick look into the concepts I use.  If you would like to know more please email me and I will be glad to explain further. To start this tutorial off I will answer some frequently asked questions about the stars, and shooting star trails.


Why do star trails show up?

The first answer most people have for the existence of star trails is that the stars are moving throughout the night. Although it is true that the stars are moving, they do not move at a fast enough rate to capture with a camera. It is the earth that is in motion, and this is what causes the star trails. Imagine throwing a camera while taking a picture. You wouldn’t say the shot blurred because the subject was moving, it is the motion of the camera that creates the blur. The same is true with star trails, the motion you catch is not created by the stars, it is created by the earth moving.

So we are moving, why does this matter?

If we were documenting the stars moving they would all be in motion, and they would all move at the same speed. However, because the earth is moving there is a point which is always stationary; and this point is the north star. The stars seem to circle around this point, and the further away from this point you get the more the stars move in a given timeframe. Also, when you look to the south you will notice the stars seem to come away from each other. This is because once you pass the 180 degree point you begin to see the stars curve the opposite way. I have set an example of a North Star shot and a southward looking shot to show the differences below.

Looking North

Looking South

How can I use this in a photo shoot?

There are many ways to use this to your benefit. If you don’t have much time you can aim south and capture longer star trails in less time. You can also set the north star in a designated spot in a photo, and cause the stars to spin around that spot. I have included an example below.

How do I find the North Star?

As the old spiritual says, follow the drinking gourd; the big dipper points toward the north star. If you imagine the big dipper as a cooking pot imagine pouring water out of the pot. The water would fall on top of the North Star. Here is an image of the big dipper and the north star. I have highlighted the stars in red to make identifying them easier.

Where did it go? Why isn’t the north star in the same spot all year?

Again, back to an old spiritual; the reason that sweet chariot isn’t visible in the winter is because it has swung low. Swing low sweet chariot was sung to tell slaves looking to run north to wait until winter. They did this for a few reasons; water levels along rivers were lower, and night lasted longer, and as they got north they were able to walk along the ice on the river. Be sure to take the season into consideration when trying to find the North Star.

Any other questions?

If you have any other questions please let me know, I am glad to answer anything for you!

Tutorial Time

For this tutorial I will be expecting that all readers have read my Milky Way tutorial. Some information is the same, and because of this I have shortened a few steps significantly. Plus the other tutorial is just as good as this one, so If you haven't read it yet go do that now and come back to this one!

Step 1: Know the weather

NEVER try a star trail shot without looking the weather up. If there is going to be fog wrap your camera, and if there will be clouds stay in. If you don’t have an hour of clear sky it isn’t worth it.

Step 2: Scouting a location

This is the same as my Milky Way tutorial with a few twists. Always note the direction you are looking. North will capture the spinning of the stars, and south will show the lines moving horizontally. Always note where the North Star is, and set the frame accordingly. If the spin is set in an awkward spot the whole shot can be ruined.

Step 3: Shot settings

There are two ways you can go about star trail shots. You can set the camera on the bulb setting, trigger the shutter with a remote, and leave the filter exposed for the whole shot. The second option is the one I will detail. You can take bracketed exposures and blend them into a single shot in post-production.

How it works:

Set the camera to shoot multiple shots and attach a shutter remote. Set the camera to manual and put the shutter on 30 seconds. Set the ISO high, I would suggest a minimum of ISO 1600. The cool thing about bracketing exposures is the fact that the grain in the shots will be removed by stacking the images. Every time you stack an image you remove some grain from the original image.  This means that the more images you stack the clearer the output image will be.  I use a floating aperture, which means I change the aperture to wherever I need in order to get a properly exposed shot. Now you just need to point the camera and trigger the remote.  When I do these shots I just let the camera keep on shooting until the memory card is full.  The longer you leave the camera shooting the better the trails will look.  Also, there will be less grain in the final shot because more images will be stacked together.

Step 4: Post production

In Photoshop select:

File: Scripts: Load Files into Stack

From here open all images from your photo shoot, you will have to wait a while for all the images to load in the stack. You will see the images load under the “layers” tab on the right hand side of the screen. Next you will click on the top image in the layer stack. You will see a drop box which says “normal” next to the word layers. Click it and scroll down to the word “lighten.” It will be subtle, but if you look closely you will see the stars start to trail. Continue this last step with all the images in the stack. You will most likely have airplanes in the shot. There is a fun trick to removing these, but if you want to know it you will have to wait for my next tutorial. Until then have fun shooting, and enjoy these sample shots!


Capturing the Milky Way

Posted by Joel on September 23, 2012 at 10:55 PM Comments comments (0)

This tutorial is designed to teach the reader how to capture the Milky Way Galaxy in still shot images with a digital SLR camera.  This tutorial will advise on what lenses and shot settings work best for achieving stunning still shots, and I will incorporate images I have taken to give examples of what can be achieved with these tips.  Also, I will detail how to set up a shot for maximum results.

Capturing the Milky Way Galaxy

Step 1: Preparation

Any time you plan on shooting at night you need to know what you are getting yourself into, this includes a few things:

1. Check the weather.  There is nothing worse than planning a solar shoot just to have a blanket of clouds cover the sky in the middle of the shoot.  This becomes an even bigger issue if you are shooting star trails, which I will detail in my next tutorial.  Also, you never want to be stuck in the rain in the middle of the night.  It is also important to note the lunar cycle.  During a full moon the landscape will be better lit, but the moon fills the sky with light, and this will take away from the number of stars you will see.

2. Scout out your location in the daylight.  At night it is hard to find your way around, and if you are like me you won't be taking these pictures in your backyard.  Walking around blindly with a flashlight will draw the attention of onlookers, and this could lead to a visit from the police.  If you just do the scouting ahead of time you can save others from worrying about you, and ultimately get better results.  Also, it always hurts when you think you have a great shot just to pull it up on your computer to see brush in the way of the subject, or a telephone line crossing the sky.

3. Double check your equipment.  I will detail what equipment you should use in the next step, but it is important to bring what you will need.  It is the worst feeling ever to walk to your location just to learn that you forgot the clip to your tripod, or a memory card.


Step 2: What you'll need

Great photos can be captured with all sorts of equipment, and this list merely constitutes what I would suggest bringing.  I specialize in night time photography, and in my experience these tools have come in handy.

1. SLR Camera: At the very minimum a point and click camera with manual settings, but the quality achieved with an SLR is far better.

2. Tripod: If the camera were a car the tripod would be the keys; without this you would really have to work to get where you are going.  Any time you are shooting in low light you should have the tripod with you.

3. Laser pointer: This might seem like an odd tool to carry with you, but you will never leave home without one once you use it.  By setting a focus point in the camera on a spot lit up by the laser you can catch instant focus every time, no matter how dark it is outside.

4. Wide angle lens: The wider the angle the more stars you can capture.

5. Shutter remote: This is more important with star trails, but it comes in handy with any night shooting.

6. External flash or flashlight: The external flash will help to freeze the foreground in a set location, and the flashlight will release less light over a longer time period.  This allows you to paint a selected area, and you can use it to show motion with a moving subject in the foreground.

Step 3: Setting up the Shot

Every beginning photographer is taught the rule of thirds (dividing the frame into nine sections; three horizontally and three vertically).  This can work with star shots, but I think it works better to stay away from it.  The more sky you can include in the frame the better.  I like to hug the foreground along the very bottom of the shot, and leave the main area for the stars.  When selecting a subject for the foreground I try to stick with either natural things like a field or an old tree stump, or something celestial like a telescope.  Here is an example of a foreground I would use:



Step 4: Shot Settings

There are a few things to keep in mind for this.  First and foremost, you should always shoot these shots on full manual. Shutter priority, aperture priority, and full automatic are designed to capture images in daylight; they will not help you out with these shots at all.  The most important thing to control is the ISO.  This will determine how quickly your camera processes the image, and this will control how much light the camera absorbs in a given shot.  However, the quicker the camera processes the image the more noise the camera allows in.  I look at this like reading a book.  You can skim through and just get the main ideas, or you can read through for content, and learn the subtleties in the writing.  The lower the number on your ISO the more details the camera processes.  With Star shots you want the sensor to process quickly, so you want to use a high number ISO. This will vary by camera, but with my 5D Mark ii I use ISO 6400.

Why do we do this?  At night the stars provide most of the light, and you want to capture as many as possible.  Also, higher ISO means higher shutter speeds.  The earth is constantly spinning, and this means the stars aren't stationary in the sky when we view them.  If you want to capture all the tiny stars in the sky you will need to use a shutter speed quicker than 15 seconds.  Even by 30 seconds some stars will have blurred together.

When I set up my shots I use a floating aperture.  By this I mean that I will set my ISO and my shutter, and I will adjust the aperture accordingly in order to get the correct exposure.  I try to keep the shutter less than 15 seconds, and I set the ISO at 6400.  This allows in a large amount of grain into the shot, but the number stars offset this in my mind.  In perfect lighting conditions I will set the camera ISO to 6400, Shutter to 10 seconds, and Aperture to f/8.

I hope this tutorial has served you well, if you have any questions please either comment below or email me.  Please browse my portfolio to see other shots I have taken, and I have posted a few more shots below.  Thanks for reading and happy shooting.