Wednesday, July 20, 2011

Technique: Capturing a Splash

The photo technique for capturing a high speed splash is not difficult once you understand the basic setup.  When taking pictures of water, or glass for that matter, you need to begin by lighting the subject from behind.  Since transparent liquids and glass allow you to see the background, this is the surface you need to light first.  If your subject is highly transparent, like water, the background may be all you need to light.  Otherwise you can add two more lights, one pointing directly at the subject from behind, and the other aimed at the subject from the front.
Blue gels were put over the lights to add some color to this scene.  The background lights were aimed low so there would be a fall off of light causing a gradual shadow towards the top.  Note the black lines in the water.  These are caused by reflections from the black tub placed beneath the water to catch it.  The lines help sharply outline the water shape against the light background

The key to freezing high speed action is having a light that gives off a very short duration of flash.  Most flash units made for SLR cameras fall into this category.  The flash duration is even shorter when the flash unit is used at a lower power rating, such as 1/16th or 1/8th power.  The trade off here is in depth of field.  In order to keep the splash in full focus you will need to stop the lens down to a low aperture, such as f/11 or f/16.  

A light meter that can measure light from a flash is helpful, but not absolutely necessary.  You can probably come close enough to the correct exposure with some trial and error tests.

This setup uses four Nikon SB-900 flash units.  Two are aimed at the background.  The other two are aimed at the subject, one from behind right, the other from the front left.  Two units are used on the background to keep the flash power on a low setting that will allow for even shorter duration of flash.  The black tub does double duty.  It catches the water from the splash, but also caused black reflections in the liquid and glass to help define its outline. 
Setting up the camera:

Your camera may have trouble focusing on the splash so set it to manual focus and, with the camera on a tripod, take a manual focus reading of an object placed in the spot where the splash will occur.  Put the camera in its manual exposure setting and choose the highest shutter speed you can for your camera/flash combination.  This is usually in the range of 1/250th of a second.  A lens of medium focal length is a good choice.  The ISO setting should be set low to maximize quality. 

An assistant dropped one ice cube into the soda from about a foot above the glass.  Timing has to be perfect to capture the splash at the right moment.  Try keeping both eyes open so you have a peripheral view of the hand dropping the ice cube and can be prepared to snap the shutter at the right moment.
The exposure on the background should be approximately 1-2 stops brighter than the light falling on the subject from the front.  With the camera set to the correct exposure for the subject, the background will now be pure white.

A shot like this requires pinpoint timing and very good hand-eye coordination.  An assistant threw a dart at the water balloon, and the shutter had to be pressed just as the dart entered the frame.  Keeping the shutter button half-pressed will shorten the length the finger has to travel to complete the exposure.
This is a combination of two water splashes similar to the one that began this article.  They were put together and twisted with post-processing software.  The exposure setting for all the images in this article were done at 1/250th second, ISO 200, and f/14.

Thursday, July 14, 2011

How to Photograph Manhattanhenge

Twice a year, approximately  three weeks both before and after the summer solstice, the sunset lines up with the street grid of Manhattan.  The term for this, Manhattanhenge, was coined in 2002 by astrophysicist, Neil deGrasse Tyson of the American Museum of Natural History as a reference to Stonehenge in England.  It only applies to those streets beginning with 14th and going to upper Manhattan that were laid out in 1811.

The edges were allowed to go dark to enhance the effect of New York as a canyon of buildings framing the setting sun. See the photo at the end of this blog for a different interpretation of this same image.
Although the exact date for Manhattanhenge is when the sun is a full ball centered on the street as it sets on the horizon, it is possible to obtain great photos for at least five days before and after the main event.  

Be sure to allow plenty of time in advance of actual sunset.  You will have approximately ten minutes from when the sun peaks around the corner of the southern building until it finally sets.  So get to your shooting site at least a half hour before the time listed for actual sunset.

Photographing the sunset event is not too difficult, if you don't count taking your life in your hands to dodge street traffic.  The three things you will have to deal with are:  finding the right location, selecting the proper lens for what you want to capture, and setting the proper exposure when shooting directly into the sun.


While any cross street on the grid above 14th Street will provide the proper vista, a good choice is usually one of the wider streets, such as 14th, 23rd, 34th, 42nd, etc.  Two streets that make particularly good vistas are 34th and 42nd Street.  That is because they contain two important New York buildings that look distinctive in silhouette.  The Empire State Building is on 34th Street at Fifth Avenue.  The best place to record its silhouette and the sunset is from the East side of Park Avenue.    

A similarly dramatic view can be had of the Chrysler Building, which is located on 42nd Street at Lexington Avenue.  The best place to include it in your photograph is from an overhang that crosses 42nd Street near First Avenue.  Unfortunately, this is one of the most popular views and is very crowded with people, some of whom show up in the early afternoon to reserve a spot.  Another view of 42nd Street including the Chrysler Building is from street level where 42nd crosses Second Avenue.

The shooting spot happens to be right in the middle of the Street.  People wait for the "walk" signal and then quickly take a few photos before scurrying back to the safety of the sidewalk when the light changes to give the traffic the right of way.  Large groups also gather on the 42nd Street overhand that goes up Park Avenue to Grand Central Terminal.  The problem with this view is that the Chrysler Building is not in the shot so you have to be content with a simpler shot.

Whatever location you choose, it is best to scout it out ahead of time.  The Sunset event happens quickly in less than ten minutes.  When you couple that with all the traffic and crowds, you really do not have much time to prepare on the spot.  

Lens choice:

There are basically two types of shots to this event: One is a wide view that includes some of the story-telling detail of the city.  The other is a tight, telephoto shot of the ball of the sun, perhaps combined with some to the city traffic to add interest.
In this case a moderate wide angle focal length of 35mm includes a full view of the city with the Chrysler Building on the right framing the setting sun.

Here a long telephoto lens of 400mm compress the space.  This enhances the congestion of traffic and provides a solid circular shape to the sun.  The refracted blurs over the traffic were caused by shooting directly into such a powerful light.
For a vertical wide angle view you will need the equivalent of a 24-50mm lens.  (All focal lengths here are expressed for full-frame format cameras.  On a camera with an APS format divide the focal length numbers by 1.5.  For instance a 24-50mm in APS size would be approximately 16-33mm).  To obtain a horizontal shot like the first one on this blog entry you will need a lens between 16-28mm.

To capture the ball of the sun takes something between 200-600mm, with 300-400 providing a good combination of full sun and some compressed areas of the city traffic and buildings.


Shooting directly into the sun, especially with a telephoto lens will usually fool the camera light meter into under-exposing the image, resulting in a very dark silhouette with no detail.  It is best to put your camera on manual exposure mode and take a light reading.  Do not read the light with the camera pointed directly into the sun.  This will result in an under-exposed image.  Instead, point your camera to an area of the sky where the sun is just a tiny bit out of the frame, and take a light reading of this area.  Use that as the basis of your starting exposure.  To play it safe, bracket your exposure by shooting one full stop lighter and one darker than the correct exposure.

You probably do not need a tripod because you will be shooting directly into the sun.  This will provide an exposure with plenty of motion-stopping shutter speed.  An ISO setting of 200-400 should work fine for this, and should be sufficient to allow a fast enough shutter speed to hand-hold the camera at a lens opening of f/4-5.6.  

Special effects:
The exact same six-sided star filter was used to create these two photos.  The lens on the left was set to 24mm, while the one on the right was set to 44mmm.  This resulted in a much more exaggerated star effect.
A star filter can enhance the effect of the sun with a wide angle lens.  On a lens of normal to telephoto length it can become a bit over-powering.  


In a situation like Manhattanhenge where you include a very bright light object and dark areas of shadow, it is best to take the photograph in RAW format.  This will give you a wider color and exposure latitude to make corrections and adjustments afterward.  All of the photos used above were done in RAW and enhanced later in Photoshop to bring out the color and details where desired.  

This is the same photo as the one at top that opened this blog entry, but it shows far more detail in the shadow areas and a different tint to the sunset.  Bringing out an image like this was only possible because it was shot in RAW, providing plenty of color and detail with which to work in Photoshop.

Saturday, July 9, 2011

Filters: Using a polarizer

The ability to alter images in post-processing of digital photography has eliminated the need for most of the enhancement filters that had been so popular in film photography.  In fact, the digital sensor is so much more sensitive to optical quality that placing any filter -- especially one of poor optical quality -- in the optical path will most likely be detrimental to the quality of the final image.  One filter effect that does not lend itself to complete obsolescence in the digital age is the polarizer -- although one of the more common uses of the polarizer, darkening blue skies, can usually be done with simple post-processing.

A popular use of a polarizing filter is to darken a blue sky.  With modern digital photography and post-processing this is not as important a use as it once was.  In the photo above a polarizer was not necessary.  The sky was simply darkened and contrast added afterwards in Photoshop.

What to look for:

Polarizing filters come in two varieties: linear and circular.  On a camera incorporating either AF (auto-focus) or built-in metering -- which is to say all modern DSLR cameras -- use a circular polarizer.  A linear polarizer will disrupt the AF ability of the camera and give false readings to the built-in light meter. 

A polarizing filter must turn to produce its result.  This necessitates a filter mount that may be thicker than an ordinary filter, and can cause vignetting with wide angle lenses.  Better quality polarizing filters are specially made with thinner mounts.  As with any filter used in digital photography, it is best to spend a little extra for a higher grade filter mount, optical glass, and coating of the glass.  This will have the least negative impact on the optical system of the camera.

Darkening blue skies:

A polarizing filter can be used to add punch to a landscape or travel shot by intensifying a blue sky, particularly if there are interesting cloud formations present.  The clouds will stand out more dramatically against the deeper blue.
The photo of the Empire State Building on the left is without a polarizer; that on the right is with.  Notice how the sky is darkened, plus additional color and contrast are added to the building in the polarized image.
 As already mentioned, much of this darkening can also be done in post-processing of the image.  Nonetheless, when you combine the ability of the filter to also add deeper color to other reflective surfaces in your shot, using the polarizer may be a better solution that post-processing.  Keep in mind that a polarizer will only work on a blue sky.  It does nothing for a cloudy sky. The ability of a polarizing filter to darken a sky depends on the type of sky and your shooting angle in relation to the sun.
A polarizing filter has its greatest darkening impact on a sky when the section of the sky being photographed is at a 90 degree to the sun, as in the illustration above.  At sunset, with the sun directly behind you at 180 degrees a polarizer will have no effect whatsoever
The polarizer works best when it is used closest to a right angle (90 degrees) from the sun.  With the sun behind you or overhead, turn the polarizer in its mount until you see the darkening effect in the camera viewfinder.  A polarizer can darken the exposure by as much as 2-stops.  Be aware of this and make any necessary exposure adjustments in your cameras, if you are in manual exposure mode.  Your camera meter should be able to compensate for this adjustment automatically.  

This image illustrates two potential problems with adding a polarizer to a wide angle lens.  First, the filter mount was too thick for the 28mm wide angle lens on this full-frame camera.  This resulted in dark, vignetted corners in the image.  Second, the sky varies in darkness from left to right resulting in uneven exposure.    This is amplified more through use of the polarizer.  Here is an instance where no polarizer would have been better.

Using the polarizer in conjunction with a wide angle lens may cause other problems.  The blue sky changes intensity as it moves from the 90 degree angle in relation to the sun.  A polarizer can negatively emphasize this exposure contrast when using very wide angle lenses.  

A second thing to look for with a polarizer on a wide angle lens is vignetting, which is the darkening corners in the image.  This is caused by the lens actually seeing part of the filter mount and recording it as a dark out-of-focus area.  Be aware of these problems.  You may not actually be able to see them occurring through the viewfinder.  When using an extreme wide angle lens, it is best to also take a backup shot without the filter in place.

Restoring color to foliage and other reflective surfaces:

One of the most useful implementations of a polarizing filter is in landscape photography for bringing out the saturated color of foliage.  A polarizer also cuts down the exposure, sometimes by as much as one or two stops.  This can be an aid to photographing moving water where you want to create a blur of the water by using a slow shutter speed.
Without a polarizer to cut the reflections the leaves in the top photo are completely washed out through over-exposure.  In the bottom image the full color and saturation of the leaves is restored by turning the filter to eliminate the unwanted reflections.
A typical example of where a polarizing filter is important.  It was used in conjunction with a neutral density filter to lower the exposure to 1/2 second which added a blur motion to the moving water.  At the same time the polarizer cut out the reflections on the foreground leaves and rock surfaces to result in a deeply saturated photo with plenty of color and detail.
One of the most important reasons to use a polarizer is so you can restore color to reflective surfaces.  This is particularly prevalent when photographing landscapes with foliage.  The surface of leaves are pointed skyward.  Since the leaf surface is glossy, it will reflect the pure light falling on it from the sky.  This will result in loss of color and actual over-exposure of the bright, reflective surface on the leaf.  A polarizer can eliminate this reflection and restore the natural color beneath it.  

This is a dramatic example of how a polarizing filter can eliminate the sky reflections in foliage and bring out the true colors of the leaves and flowers.
Here the polarizer is doing double duty by darkening the blue sky and also bringing out the colors in the autumn leaves.

Eliminating unwanted reflections:

The ability to remove unwanted reflections can be beneficial when photographing any reflective surface, such as glass, metal, water surfaces, or even shiny skin. 
The polarizer works best at a 90 degree angle to what is being reflected.  The photo on the left of a store window reflects the street scene to such a degree that the sign in the window is almost illegible.  On the right the polarizer almost completely eliminates the distracting reflection and now the sign behind the window is clear
Use of the polarizer on the right image eliminated the white sky reflections in the statue and brought out more color in the metal.
The only difference between these two images is that the polarizer was used for the photo on the right.  Color saturation is restored, glare is eliminated.
 The polarizing effect can sometimes be overdone.  It is not always necessary to turn the polarizer to its full effectiveness.  This may eliminate reflections that are integral to the final photo.
In this instance, the polarizing filter totally eliminated the reflection of the sailboat in the water.  Including some degree of the reflection would have made the shot more interesting.
Here the polarizing filter was only partially turned -- just enough to deepen the colors in the water and the shiny skin of the model, but not so much that it eliminated the important reflection of the girl in the sand.
As always, proper use of an aid to photography should enhance the creative outcome of the image, not detract from it.  Know the limitations and abilities of your equipment and accessories.  Sometimes knowing when not to use a piece of equipment is as important as knowing when to use it.

All content copyright 2011, Tom Grill Images, LLC