Why Combining Two Images to Make One is Sometimes Better Than Simply Shooting One Image

Sometimes I over-think things. I tend to get caught up in details of how and why something is the way it is. I've even been told, subtly mind you, that I over-complicate things and sometimes create a cluttered view of what I am talking about as a result. I know this to be true and do take it to heart, no really I do, but I just can't help myself when it comes to something where there is a revelation of sorts that seems to jump out at me. Take for instance the subject of this article. Based on the title you might be thinking, well, there he goes again. You'd probably be right, but hear me out, because I do believe this actually makes sense.

So, why is combining two images to make one, sometimes better than simply shooting one image to start with? Well, let me explain. First of all, this idea does not always apply to every situation.  In most cases a single, well-lit photo of a subject is more than adequate to create an appealing image. However there are circumstances where capturing two or more images, then combining them into one will create a more powerful looking image.

Let's take the picture above of an F-4 Phantom aircraft as an example. In recent weeks I have been concentrating on this particular shoot for several reasons and have included commentary in several blog posts about it. The more I began to study the outcome of this image, the more I began to realize  the final result could not have been made without the combining of two separate images. Had I used lets say six or seven flash units all at once, I potentially could have captured this image in a single shot. However, it would never have looked the same and might have even been inferior to the final image created using four speedlights and two combined images.

The reason is this. Had I used six or seven flash units at the same time, they would have been working against each other. Part of the appeal of this image is the dramatic use of light (red light in this case) bounced off the tarmac and then reflected back into the underside of the aircraft. Two other lights were used to illuminate the outside edges. This combination created the first image. Take notice how the light and shadows along with the reflections created a strong dramatic appearance.

After re-positioning the lights, a second image was created by pointing two lights toward the canopy and filling the front, top, and underside of the aircraft with ordinary white light. This flood of white light bouncing off the tarmac is what would create the problem if they were used at the same time as the wing positioned red lights.

In the final results, the second image was layered on top of the first image. The dramatic red light was then revealed by erasing portions of the top layer and leaving the  top half of the layer alone. Had I used six flash units at the same time, the additional two units pointing toward the canopy would have diluted and washed out the red light and shadows coming from behind the wings. The dramatic red light would no longer have been there, at least not at the same intensity levels. Also, most if not all of the Vanishing Point depth and dimension created by the shadows would have been lost.

By combining two separate exposures, the lighting effects of each individual exposure were fully realized without interfering with each other.

The image above is a sample of a similar aircraft that was captured in a single shot using seven flash units at the same time. Notice how the white lights seem to have washed out the power and strength of the red gelled lights. It's a nice photo, but without the drama that could have been, had we used two separate shots. Not every situation lends itself well to this technique, but, sometimes thinking through a problem and observing the results, however unexpected, can often reveal an exciting outcome.

So...maybe I do over-think problems a bit too much. I suppose it is a bi-product of 30 years of mainframe computer programming where that is what you do...everyday. Building a final image from multiple shots is not a new idea, but combining multiple images with creative lighting just might offer a way to experience the power and versatility of speedlights in a unique way. It sort of occurred to me just how much merit this concept really does warrant.

Shaping Light to Fit Your Subject

Dusk was upon me before I was ready and the bright display lights at the Aviation Heritage Park in Bowling Green kicked on as the daylight faded. The lights were much brighter than I remembered and I was concerned they would interfere with my planned shooting for that evening. Turned out my apprehension was premature because in fact they actually helped out because they provided enough illumination so the camera could easily focus, but not so much to drown out the lighting I was planning to use. About the only issue with them was they created a florescent glow the camera wanted to interpret as a greenish cast. A simple tweak of the White Balance eliminated the threat, and I was confident the speedlights would provide enough horsepower to overcome any adverse affect they might have.

As part of the Adventure Photography series, my project for the previous two weeks was to capture the historical aircraft on display at the park. There were five beautifully restored ones all having a connection to Bowling Green and Kentucky. Capturing vintage aircraft such as these in such a way as to avoid reproducing the standard cliche images requires a bit of thought. I had to ask, then answer one question; How do I shape my light to fit my subject?

I could have taken the normal approach and simply pointed my lights at the aircraft and flooded them with light. I knew this would never fulfill my creative desire to capture them in a unique way. I also ran into the problem of having only four speedlights to work with when I actually needed six or even eight to do the job effectively. As I walked around the F-4 Phantom, a huge aircraft even though it was an air superiority fighter, I realized there was no way I was going to capture this magnificent piece of history without taking a multiple image approach, then combining two images into a new single image. The idea was to first illuminate the underside of the aircraft, then photograph the topside. These two images then would be combined to create the final photograph.

My first decision was to decide from which angle to shoot. The F-4 carries itself well from most all angles, but the most striking appeared to be from straight on. Using this angle allowed for a dramatic use of what is known in the art world as a Vanishing Point, where all straight lines tend to point toward a single converging point thus creating an illusion of three dimensions. This also created a sense of movement and speed.

The next problem to solve was how to light this enormous aircraft using just four speedlights. It was much too large to capture in a single photograph. Dramatic lighting was a requirement and to create this drama I was going to use a set of homemade red gels to cover two of the lights. The gels were made from a document protector cut to fit the dimensions of the flash units. Two other units would remain uncovered and provide a basic white light. The idea then was to indirectly light the underside of the aircraft by bouncing the light off the tarmac. Two lights each were clamped to the back edges of both wings with the lights pointing down with a slight angle forward. This lighting setup effectively illuminated the underside of the F-4, but the top part of the airframe remained relatively dark. The lights of course were fired remotely from the camera.

I placed the camera on a tripod and aligned the composition. After some test shots I settled in on an exposure of f/5.6 at 28 mm with a shutter of 1/15 and an ISO of 800, using a remote cable release. Part of the problem was to also eliminate or kill off most if not all of the ambient light spilling over from the background. Once that was confirmed as the best exposure to accomplish this, I locked the camera in place on the tripod and left it alone. The first image was captured.

I now had to capture the second image. With the underside of the airframe captured, I needed to position the lights in such a way as to throw some light across the front and top portion. To do this I used two tall light stands one each positioned just outside the wingtips and somewhat in front of the airframe angled toward the canopy. Leaving the camera setting alone effectively prevented any movement of the camera that could throw off the critical alignment of the two images when blending the final two shots into one.

Again it required several test shots and power setting adjustments to get the desired results, but once I had that accomplished, I was pretty well done for the night. All that was required from that point on was to blend the two images into a single new image and do some tweaking in Photoshop to clean up the image.

The idea of this entire exercise was to avoid simply using light to illuminate the F-4 but to use light to shape the subject. The tarmac in essence became part of the main sources of light. Drama was demanded for this aircraft, to do justice to its classic lines, its history, and to its legacy. Using speedlights to shape light so it fits the subject requires not only an understanding of composition, but of the versatility of using off camera flash. It also required stepping away from the ordinary and looking at the problem in an extraordinary way.

When the normal way of doing something falls short of your expectations, don't be afraid to shake up your approach, try something new, something unique, because only then will you be able to truly gain a comprehensive command of the photographic process. Always doing the same ole thing the same ole way can result in ordinary pictures of things. To create the extraordinary, to capture drama, requires a  unique and extraordinary approach. Shaping light to fit your subject, how better way to use the power and versatility of speedlights.

Speed Light Magic: Creating Your Own Quality Light

Light in all of its magical colors is what transforms the ordinary photograph into an extraordinary photograph. Without quality light your images will most likely become just a simple photograph of an object, but toss in a light source that enhances the moment with its flavor and strength of character, then what might otherwise turnout ordinary suddenly is transformed into something that captures the imagination. Quality Light then, is the driving force behind all great photographs. Photographers crave it, they seek it out, they live for those events when time, place, moment, and light blend to become something extraordinary. Nature and circumstance, however, do not always cooperate. Sometimes they fail completely to provide the kind of light required to create those special moments. When light failure happens, you can with a little help create your own quality light. You do so by employing the power and creative edge Speed Lights provide.

Not so long ago I avoided using speed lights. My excuse was "I prefer to shoot in natural light." The truth was, I was afraid of using them because I didn't understand how they worked. My understanding of using 'A Flash' had roots going back to the old flash cube days where those little portable pocket cameras used one of those cubes to flood the area with light. Their range was limited to about 8 or 10 feet, and their light was harsh and direct often creating not only washed out features and strong shadows, but unwanted red eyes. Unfortunately, most peoples indoctrination into using 'flash' was similar to mine and as a result we developed incorrect mindsets of how flash photography was suppose to work.

In more recent years I found myself becoming more intrigued by their use because through the magic of the internet the real professionals, who know how to use artificial light, share their knowledge. The more I watched them work, the more I realized just how wrong I had been about speed lights. Used properly they can open up a whole new realm of photographic opportunity. Even so, I still struggled to understand the basic principles of their use. I was stuck, again, with a mindset developed through years of using the exposure triangle: f/stop, shutter speed, ISO believing that all exposures were strictly influenced by these axioms no matter who, what, or where you were shooting. Being trapped inside this exposure bubble mindset stymied my progress to understanding how to use speed lights. Then one day, after watching a Joe Brady video on the basics of using off camera flash, that bubble exploded and it all, for the first time, made sense. Even so, putting this understanding into practice took time along with trial and error, lot's of error. The journey has been extraordinary and I'd like to hopefully burst the exposure bubbles of those who also find themselves trapped inside. Let's take a closer look at the basics of this fascinating form of photography.

A single OCF 

First let's take a quick look at how a flash works with your camera. Simply stated, the flash must fire in sync with the shutter operation. The shutter opens, the flash fires, the shutter closes. In the old days, flash/shutter sync was limited to 1/60th or possibly 1/125th of a second depending on the camera. If you tried to fire the flash using a shutter speed higher or lower than this the flash would most likely not fire at the right time and create a dark line usually along the bottom or top of the image. This is because the flash would fire either before the shutter was fully open, or after it was already partially closed. Fortunately, today's digital cameras are much more versatile and the flash will sync with a variety of shutter speeds usually up to 1/200th or possibly 1/250th of a second. You can even shoot them in what is called a high speed sync flash mode, like 1/1000th of a second or faster, but that is a bit more advanced than we need to cover right now.

You can set your shutter speed just about anywhere up to the maximum flash sync speed and the flash will fire properly. But, that brings up the question of exposure. Now most name brand camera's and flash units will fire in what is known as TTL mode, or Thru The Lens exposure. This varies a great deal depending on the camera and the flash unit being used, but fundamentally this means the camera and the flash talk to each other to the point the flash knows how much light to output to create a correct exposure based on the camera settings and ambient light. We won't go into how they do that, just remember TTL is a flash exposure method that talks to the camera usually by using the popup flash on the camera as the trigger.

Let's talk briefly about the flash power settings. Depending on the unit, the output from the flash can be controlled to allow for full power settings with increments down by factors of two...like 1/2, 1/4, 1/8, 1/16....1/128, you get the idea. What this really means is this. The brightness of the light coming off the flash is exactly the same for all power settings, the difference is the length of time the light is allowed to fire. A setting of 1/4 will have a light pulse 4 times faster than a full power setting.

We briefly discussed TTL, so now we will look at shooting the flash in a manual mode. Shooting manually is actually my preferred method of using off camera flash. This gives me full control of the light and exposure. This is where you need to adjust your understanding of the exposure triangle.

When shooting a typical landscape you are setting an exposure based on a single zone of light. The light on the landscape comes from one source, the sun either directly or filtered through clouds or something like that. You use the exposure triangle to achieve the desired exposure, shutter speed, aperture, ISO. Shooting with an Off Camera Flash (OCF) is different and this is an important difference to understand. When using an OCF you are controlling two zones of light at the same time. What this means is your overall exposure is based on the background light or ambient light and the exposure on your main subject is based on the light coming off the flash unit. So...in essence you are setting your exposure to capture different sources of light at the same time.

Controlling two zones of light

The OCF can be a single flash or multiple flashes from different angles and power settings. The ambient light is the light that naturally exists around you. It can be light from nature or from other sources such as indoor lighting, or street lights, a large window, or anything that is not coming from the flash. Call it background light if you like, it is simply the light that is already there that influences the exposure setting.

Now, this is important to understand and is the crux of most of the confusion of how to shoot with OCF. When shooting with an OCF you control the background ambient light exposure using the Shutter speed. You control the light off the flash using the Aperture. To simplify the concept just think of the OCF light as fill light used to illuminate your main subject and the ambient light is what illuminates the area around and/or behind your subject. To control both the easiest way is to set your background exposure based on the ambient light, then adjust your OCF power settings to provide the proper amount of fill light. By doing this, you are then controlling both zones of light at the same time. Let's say your background exposure is 1/125th at f/8.0 and ISO 200. In order to use an OCF to illuminate you main subject, it needs to be set to provide a light pulse that is equivalent to f/8.0. This may require some guess work, or you can use a light meter to see exactly how much light is coming off the flash.

If you change your shutter speed, lets say to 1/200th after making your OCF lighting adjustments, it will not affect the light and exposure coming off the flash. The background ambient light will be darker, but your subject will still receive the same amount of light off the flash. Think about that for a moment. Why is that? Well, the reason is this. When the flash fires, it generates a given amount of light for a specified amount of time based on the power setting. Generally speaking, the duration of the flash is usually very short, something like 1/2000th of a second or faster depending on the power setting. If you change the shutter speed say from 1/125th to 1/200th and retain the same aperture setting, the flash duration is still considerably faster than either of the shutter speeds and the same amount of light will be captured from the flash unit regardless of which shutter setting you select. The faster shutter speed will affect the ambient light making it appear to be darker or more underexposed, but does not affect the OCF light, so your subject will still remain properly lit. In fact, you could in theory eliminate all of the ambient light to create a total black background with the proper settings. However, should you adjust the aperture say from f/8.0 to f/11, then you will affect the OCF light exposure because now your flash is still outputting light at f/8.0, but your aperture is set to allow a full stop less light into the camera. To keep the same OCF exposure, you would need to increase the power output from the flash unit to equal the f/11 setting.

Picture taken outdoors before dusk
All Ambient Light removed by exposure
settings so background is black.
Used two OCF Strip Lights and one
Octobox light overhead

So, the next question is, how do you trigger a OCF? Well, there are multiple ways to do so. Actually, your flash unit will most likely have three basic settings; Wireless TTL, Manual, and Slave. Some flash units can have variations on these settings, but those are the fundamental three. Wireless TTL is most easily triggered by the popup flash on your camera. Once the camera and flash unit are set in wireless mode, the camera and flash talk to each other through a series of light pulses just before the main exposure flash fires. It all looks like a single pulse to the unaided eye, but in reality several short bursts of light fire off before the final exposure is made. A separate Commander flash unit sitting on top of your camera will accomplish the same thing. Another way to trigger your OCF is to use an electronic transmitter/receiver setup. The transmitter sits on top of your camera on the flash boot. The OCF flash is connected to a receiver unit that receives the signal from the transmitter. When the shutter release is fired, the transmitter fires sending a signal to the receiver to fire the flash. Depending on the kind of transmitter/receiver unit used, you can also make adjustments to the flash from the transmitter, things like changing the power settings. Some simply act as a trigger. The Slave mode is a flash setting that allows the flash unit to be triggered by any other flash. When any flash fires, the sensor in the Slave units detect the change in light and causes it to fire at the same time. This can be useful when combining different brand name flash units, or when only one transmitter/receiver is available. The Slave mode will ensure all flash units work together.

Using Multiple flash units

Okay, I know it sounds confusing...but it really is not all that complicated once you begin to apply those principles to your photography. It does take some practice to learn how to shoot with OCF and make it more instinctive, but once you begin to experience the results, you will begin to grasp what is happening. More importantly, you will also begin to see how you can use this knowledge to your advantage and start applying it to different situations. All we've done in this article is to introduce the basics and encourage you to give it a try. The best way to learn how to use OCF is to do it, so don't be afraid to give it a try. Even with a single OCF flash unit, you will open up a whole new world of photographic opportunity. The key is to use it creatively and in such a way it appears to look natural.


p.s.

There are numerous third party speed lights (flash units) available at very reasonable prices that work very well. With a little shopping around, you can get started for well under $200.