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Part 2 Your First Picture

Part 2 Your First Picture

 

 

Time for your first image.  Initially you can set your camera to record images in JPEG format if you wish. However I would recommend you get into the habit of shooting in the RAW format. This will permit much greater freedom to edit and refine images later on.

 

1) You need to put your camera on a tripod. You will be taking pictures lasting many seconds so the camera must be kept still. Make sure its a sturdy tripod. You don't want it wobbling about in a breeze.

 

2) Set the ISO of your camera to a reasonable level. I would suggest starting at ISO800, then move to 1250 and perhaps even 1600. Don't go higher than this at this stage as you will introduce a lot of noise into the image. Also if you are shooting from a City location, the glow from street lights (light pollution) will wipe out your image if it is set to a very high ISO. In fact you may have reduce it to ISO400 if your location is very bad.

 

3) You need to be aware that because of the Earth's rotation, the Stars appear to move across the Sky. Therefore the longer you keep the cameras shutter open, the more chance that you will get a star trail. (see below). However, the effect of star trails are minimised when using wide angle lenses. Below are approximate times before star trailing becomes visible for different lenses. I suggest you experiment and review your first images using your cameras LCD screen. Zoom in to see how much the star has moved. If its a streak and not a point of light, reduce the exposure time. You will soon get an idea of what length shutter speed you can get away with.

 

24mm - 20-25 secs

35mm - 12-18 secs

50mm - 6-8 secs

 

Star Trail Fault

This is 20 second exposure taken with a 50mm lens on a Nikon D7000 (75mm Crop). Note that stars are no longer points of light but streaks

 

I would recommend starting with a 50mm (35mm DX format) lens and setting the shutter speed to about 6 seconds. Use ISO 800 or 1250 to begin with.

 

4) Now you need to focus your camera. By far the best way to focus is to use the Live View function of your camera. Pick a bright star and zoom in on it using the Live View feature. Adjust the focus of your lens manually. Make sure the AF function of your camera is off and focusing is set to Manual. If you are using manual focus lenses you will probably find you have focused to the infinity mark on the lens. However with an autofocus lens you will focus past  this mark. This is due to the way an AF lens works. Don't assume therefore, that setting an AF lens to infinity sets the focus correclty. It won't, you must check it visually.

 

5) Now set the aperture on the lens. As you are trying to gather as much light as possible you may be tempted to set the aperture on your lens to its widest. If so you will be disappointed with the results. Starfields are very demanding of optical quality and camera lenses are not very good at dealing with them. As a start try the lens on its widest aperture, take a picture then look at the result by zooming in to your cameras screen. You will probably find that the stars are a little fuzzy. Now stop the lens down a couple of stops (i.e. from F2 to F5.6). Take another picture and check it again. You should see a marked improvement.

 

Wide Open Aperture Bloom

This is an 8 second exposure using a 50mm lens at its maximum f1.8 aperture. Although we have captured much more light, the stars have become bloated and surrounded by halos. This is caused by the poor optical quality of a lens when used at maximum aperture. Note the Aircraft Contrail that has also been picked up across Orion's belt. Something else you have to watch for!

 

Reduced Aperture no Bloom

 

This is the same 8 second exposure but this time the lens is stopped down to f4. Note how the stars have become sharp again. A camera lens tends to perform at its best around f8 however that would capture significantley less light.


Now you have focused and set the aperture you need a subject. To start with try a Constellation. During the Winter months Orion is a great target. So frame it up and shoot.

 

Light Pollution Auto WB

 

Oh Dear! It's all orange?? Why doesn't it look like the one before??This is a 50mm lens, 6 second exposure, f4, ISO 1250

 

Look at your picture on the cameras LCD. If you have taken it from a City location, it will probably have an Orange cast to it. If you are fortunate enough to be shooting from a remote 'Dark' location, the colour of your image may still not look quite right.

 

You've taken your first image. Now lets fix the colour cast in the next section.

 

Note: The quality of images shown here is not optimum. None of the images displayed are subject to any processing.