Tag Archives: tricks

Intervalometer Tricks

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Red Rockin' Spiffed Up

Scratching your head and wondering what an Intervalometer is?  We’ve covered that in this article, and talked about some super fancy Intervalometers in this article.

Before we launch into the tricks, let’s first get some terminology straight.

  • Long Exposure – in my vernacular this is an exposure over 30 seconds – the limit of most DSLR cameras.
  • TimeLapse – a series of photos taken over time that compresses (or expands) the actual time when made into a movie. Usually all the exposures use the same settings.  An event that takes 3 hours can be distilled into a 30 second video.  An event that takes fractional seconds – like a balloon popping – can be shot at high speed and expanded into a movie that lasts much longer.  Usually expanding the time is called “Slow Motion”.
  • StarTrail – like its timelapse brethren, implies a series of shots taken over time and combined into one exposure to show the star motion OR a StarTrail can be created from a SINGLE very Long Exposure.
  • Bramping (aka Bulb Ramping) – a timelapse techinque in which the length of the exposure is changed over time to accommodate the setting sun, rising moon – anything that involves a gradual change in the ambient light.

How is a Timelapse different from a Star Trail?

The two are not different, except that by intention a Star Trail created from multiple exposures requires a minimal interval between one shot and the next or gaps result. For a timelapse – which can be taken at night or day – the key is having a regular interval between each shot.  Changing the interval between shots has the effect of warping time.

Ok, Got it. Tell Us About the Tricks

Sub-Second Intervals

Why would you want sub-second intervals?  For one, to catch as many meteors as possible. The second or so that the camera spends with it’s shutter closed is a second you might miss that brilliant fireball. Another reason to keep the interval REALLY short is to reduce or eliminate gaps in star trails.  But sub second intervals are the hardest trick of all.  There are almost no intervalometers that allow setting an interval shorter than one second, and even if it’s possible many cameras can not handle sub-second intervals. However, there are a few devices that can do sub-second intervals: Trigger Trap for one.  The best way to find the shortest possible interval is to set up the camera and try! Set the interval to say 700 ms and see if your camera can run off a sequence of 15 to twenty 30-second shots without missing a beat. If that works, set the interval to say 500ms.  Note that the minimum interval will depend on the camera, as well as the size of the image, and speed of the memory card. Once you find the minimum, leave a little extra time and use that. My Canon 5D Mk II was happy with 450 ms intervals between shots. That’s HALF of the waiting time of one-second intervals.

Shake Reduction – Mirror Lock Up

Many people worry about mirror slap. Mirror slap occurs when the little mass of the mirror “wiggles” the camera enough to blur long-ish exposure shots. Mirror slap is particularly pernicious in the 1/4 to 2 second exposure length. It may also be a problem if you have your camera attached to a delicately balanced telescope at high magnification.  How do you solve the problem?  It depends on your camera, but there are several approaches to try:

  1. Leave live-view on (which will eat batteries and may result in excessive warming of the sensor)
  2. Use the camera self-timer in mirror lock-up shooting mode. Most cameras will behave properly if your exposure length is not bulb. That is, they will move the shutter, wait for the delay to expire and then take the shot. Remember to allow a delay that is at least one second longer than the shot length plus the self timer delay. For example, let’s say you want to take as many 24 second exposures as possible but you need at least 8 seconds for mirror slap to stabilize. Set the camera to 24 second exposures with a 10 second self-timer.  Then set the intervalometer to take a 1 second(!) exposure every 36 seconds. The reason for the 1 second exposure is to allow enough time for the shutter release to be recognized while the 36 second delay allows for 10 seconds of timer, 24 seconds of shot and a 2 second safety buffer.
  3. See the Maximum Shots, minimum interval trick. But instead of 1 second delays, change the length of the exposure to the amount of time you need for camera stability + 1 second.
  4. Want to do shake reduction in BULB mode and without a self-timer?  Set the exposure length to the desired amount of time and use a short interval. With mirror lock-up on, you’ll get every-other exposure at the desired length. Note: this is the most “iffy”mode as it depends on your camera behavior.
  5. Finally for shake reduction in BULB mode WITH a selftimer, set the intervalometer as normal, but set the length of exposure longer and include the self-timer interval. For example to take 60 second exposures with a 10-second self timer, set the exposure length on the intervalometer to 70 seconds.

Variable Length Shots

While this technique seldom works well, you can allow the camera to determine the exposure length via metering.  All you have to do to make this work is to have the camera take 1 second exposures (as before) no more frequently than the longest exposure you expect to take. Some fancier devices, like the Trigger Trap and the CamRanger can even be configured to change the exposure length over time. This feature is called “Bulb Ramping”.

Extended Self Timer

Got a big group shot and no wireless remote. Not a problem. Set the camera to a short (e.g. 2 second) self-timer delay, and set the shot delay to say 20 seconds – or as long as you need to safely climb on top of the human pyramid to get that perfect shot.  Since you can allow multiple shots, you’ve all got plenty of time to change your poses, or re-architect your human pyramid.  We use this trick all the time when we’re conducting workshops. It allows us to set up our camera and walk away while we instruct. We leave enough time to set up for the shot.  Most cameras will blink or flash to let you know they are about to take a picture so everyone can time that cheesy fake smile.  Note: If using a Flash, you can lengthen the interval between shots to give the flash extra time to recycle.

Maximum Shots, Minimum Interval

When not in Bulb mode, it can be maddening to not have the Intervalometer and the camera in sync. Set the camera to 20 seconds and the intervalometer to 19 and you’ll miss about every other shot. Bummer.  Here is a trick to maximize the number of shots and not care much about the actual exposure time.  Set the intervalometer to take one second shots with one-second intervals between each.  The maximum shot-to-shot delay will be two seconds that way and it doesn’t matter what your exposure length is on the camera if it’s NOT bulb.

What if you want BULB mode? How do you configure that?

Answer: (Select the text below to reveal)
That’s the normal intervalometer configuration mode. Camera is bulb, length of exposure is whatever you need and the interval should either be 1 second, or exposure length PLUS one second depending on the intervalometer.

Hunting Comets and other faint objects in not-dark skies

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AirGlow Comet [5_070386]

It turns out the much hyped PanSTARRS C/2011L4 Comet is not living up to the hype. Unfortunately failure to meet the over exhuberant expectations  is common since predicting brightness and visibility of an object like a comet is a difficult science. In fact, it’s part science, part black art and part good guessing – mostly the latter.

The photo above was taken on March 12 when the moon and PanSTARRS nestled closely together. The close quarters made finding the comet much easier despite the bands of clouds passing by.  The strategy for finding the comet in that case was simple: use a telephoto lens, put the moon at the right edge of the photo and take different exposures periodically and at different settings (e.g. +2, 0, and -2 stops). Then hunt for smudges.

The IDEAL telephoto lens would be one that was a few angular degrees wider than the difference between the moon’s position and the comet’s position. How to determine the position of each is discussed in the last section below. Figuring out the angular view of your lens is easy using online tools like this one from Tawbaware, makers of Image Stacker (like that program!). If you know the field of view at your minimum and maximum zoom, you can use that information to your advantage.

Finding the Comet with a Nearby Moon

The point at the moon strategy made finding the comet easy because:

  1. There is no way you’d be able to see the comet if you were not able to find the much brighter moon nearby.
  2. On that one night, the comet and the moon were within 4 degrees of one another.  That’s quite close.

I know some people tried to find the comet using wide angle lenses. That strategy might work, but the comet is such a tiny thing and it’s visibility is so tenuous based on the atmosphere, light pollution, and sky brightness that you may only realize – as many did – that you captured the comet after carefully inspecting your photos at home.

Contrails and Comet Tails [B_050938]

The truth is you are unlikely to see PanSTARRS by eye or in your camera’s view finder unless your conditions are nearly ideal.  Hopefully ISON which is coming in December will be brighter and better.

Finding the Comet when the Moon is Farther Away

The following night, both the comet and the moon had moved relative to the sky. On March 13, the moon was 12.5 degrees above the comet and about 4 degrees farther west (again, how I knew this is coming in just a minute).  So one simple strategy for finding the comet would be to zoom your telephoto lens so that it has a field of view of about 14 to 15 degrees in the long direction which for me, is 80 millimeters focal length on a 1.6 crop factor camera.

On a tripod with the camera in portrait orientation adjust the view so that the the moon is in the upper left of the frame. Shoot bracketed shots. Check the lower right corner of each one for the tell-tale comet smudge.  Keep readjusting the view so the moon remains in the upper left for each shot. Zoom out a little bit too, in case your geometry is a little off. Eventually as it gets dark enough or the sky clear enough you should find it.

In fact the way I found the comet last night without using my camera but by using my telescope. The program Clinometer (on my iPhone) measures angles. I sighted the moon with my 8″ Dobsonian telescope and measured the angle along the telescope barrel using the inclinometer program. I then lowered the altitude (elevation angle) of the telescope by 12 degrees to match the altitude of the comet. Then I slowly rotated the telescope northward until I found the comet.  It wasn’t easy from my urban location, but it wasn’t impossible either.  By the time I was able to find the comet it was only about 6 degrees high in the sky – that’s way too low if you have trees, hills, and houses nearby to deal with.  In theory, this strategy would work with a telephoto lens or with binoculars, however, binoculars need to be steady and where I spied from last night had streetlights in the distance and the flare and glare from those streetlights made finding the faint comet nigh impossible.

What if there is no Moon to Find the Comet With?

Unfortunately starting on March 14th, the moon will be quite far from the comet, so the opposite strategy is required:  Use a landmark in a known direction as the starting point and look “upward” from the horizon.  In other words, zoom your telephoto lens so that the field of view covers the angle from the horizon to the comets altitude (angle) above the horizon.  Don’t forget that as the earth spins this angle changes every minute! Orient you camera in landscape mode and point it as close as you can to the correct direction (azimuth). Look along the top of the frame to see if you’ve captured the comet.

IMG_1622.PNG

SpyGlass’s view shows the direction the camera is facing (Azimuth) and the elevation angle (Altitude)

But what direction should you point your lens or telescope? Use a compass application or actual compass. BEWARE however as the compass applications have lots of gotchas and are only accurate to about 5-10 degrees.  And if you aren’t sure how to use a real compass your local magnetic declination might bite you. Better would be a GPS with a built-in calibrate-able compass.  And perhaps even better still would be to use an application like TPE (which I discuss in my Catching the Moon Webinars) to calculate the correct azimuth from the location you plan to stand.  An application that might help a lot is “SpyGlass”
however don’t forget that I found the directional accuracy of my iPhone and iPad to be pretty poor.  Being off by 5 degrees may mean looking in the wrong place.

How Do I Know the Altitude and Azimuth for the Comet?

Stellarium_MoonMarch14

Unfortunately, that’s a tough one.  I use the free program Stellarium. I then added the comet to the “Solar System Data Base” (search around on the web and you’ll find instructions). I selected my viewing location, dialed in the time, did a search for good ‘ol C/2011 L4 and let it tell me the azimuth and altitude.

PanStarrs_March14

Above I’ve dialed up the time and clicked the moon. The highlighted line shows me the azimuth (direction) and altitude (angle above the horizon) for the moon which at that time are 264 degrees or just a little south of west, and 30.5 degrees high.  Clicking on the comet shows 272 degrees – a tiny bit north of west and 9.5 degrees.  So now we know that the comet will be 8 degrees north and 21 degrees south of the moon – and that won’t change significantly for the rest of the night.

Since we also know the direction for the comet is about due west at this time, we can apply the telephoto-lens horizon trick I described earlier.

Another way you can find the azimuth and altitude is by checking my animation HERE – note that the animation is correct for San Francisco  (and most places nearby).  There is also a table of the azimuth and elevation in the text of the Flickr post.

 

By the way, one way to find the right spot on the horizon is to use the sunset location as a guide.

CometIllustration

My Camera Can Not Focus in the Dark – And Neither Can I!

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Original Publish Date: Sep 20, 2010
Updated: November 15, 2017

A common and vexing question is “how do I focus when it is too dark for the camera to auto-focus, and too dark to manually focus?”

There are five strategies that I commonly employ, but before I describe those strategies, it is important to understand a little bit about what focus is and is not. There is no such thing as perfect focus. How to achieve focus will depend on several factors especially the focal length of the lens, the lens speed, the clarity of your viewfinder, the accuracy of the markings on the lens (if any), whether your camera has live view, and whether there is any bright object that can be used to focus.

It might sound silly, but you should start by thinking about what you WANT to be in focus. Usually for a star shots everything should be in focus from the foreground to the stars in the sky.  The stars do NOT have to be perfectly focused, however – more on that in a moment.

Why does focal length matter?

More than anything else the focal length of the lens dictates the depth of field. A long focal length (200 mm for example) results in less depth of field while a short focal length allows a greater depth of field. The depth of field matters quite a lot if you are trying to get a foreground object against a background of stars. The longer the focal length the farther away your foreground must be to keep both the foreground and the sky in focus. The ideal point to work with is your “hyperfocal distance”. Keep your foreground at or beyond your hyperfocal distance and all will appear as sharp as the lens and conditions will allow.

Hyperfocal Distance

Hyperfocal distance decreases as you stop down and increases as you open up the aperture. Shorter focal length lenses have shorter hyperfocal distances. Indeed a 17mm lens at f/5.6 has a hyperfocal distance of about 15 feet (2.8 meters) while a 200 mm lens at f/5.6 has a hyperfocal distance of 1,250 feet (381 meters). That is quite a difference! These numbers assume you are working with a 1.6 crop factor. When using a full-frame (35mm) sensor the distances drop to  1.72 and 238 meters respectively.

But… How DO I Focus?

Ok, with those details out of the way the question remains: how do I get good focus when it is too dark to see to focus.  Here are the methods I recommend. Start by turning OFF auto focus. I am embarrassed to say how many times I have carefully focused only to discover that I did not turn off autofocus!

  1. Do not wait until dark to focus. Focus on your foreground when there is still enough twilight to see clearly. Put gaffers tape, or a lens band across the rings so that focus does not change accidentally.
  2. Use “Live View” and zoom-in to sharpen focus if your camera allows it and there is sufficient light.
  3. If not enough light, find a bright light source in the area and focus on that. The moon, is a good choice (though a closer focal point may work a little better). Try  a nearby streetlamp, sign or other bright object.
  4. Bring your own BRIGHT light source and use it to focus on something at or beyond your hyperfocal distance.
  5. Take high ISO images to confirm your focus and then make minor tweaks to the focus. The High ISO image will be grainy but it will also help you verify what is within the frame of your photo. Tweak the focus and shoot again.

Before you invest a tremendous amount of energy getting the sky in focus consider that the stars are point sources of light anyway. Perfect focus at infinity will improve the contrast of the stars against the night sky, but sharp foreground against a slightly out of focus sky is preferable to a sharp sky and out of focus foreground… at least in my opinion.

One last comment about focusing at night.  You will find more success focusing most manual lens and high-end lenses than autofocus lenses – especially the less expensive ones. Why? Autofocus lenses are cheaper and easier to make if the lens does not stop at the infinity setting and if focus can be achieved with less movement of the lens elements. Autofocus lenses, after all are designed to focus quickly. A manual (or higher end) lens might allow a half or full turn for the focus adjustment range while an autofocus lens may have a mere 1/16th of a turn to tweak with. Curious what other characteristics make for a good night photography lens? We have an article on that.

Topics such as this are covered hands on and in more detail with our students in our Star Circle Academy Workshops.

Are there any other focusing tips, techniques or apparatus?

Why of course!  See here, and here.