{"id":7255,"date":"2009-06-24T18:08:02","date_gmt":"2009-06-25T02:08:02","guid":{"rendered":"http:\/\/moosepeterson.com\/blog\/?p=7255"},"modified":"2009-06-24T18:08:02","modified_gmt":"2009-06-25T02:08:02","slug":"the-ttl-flash-system","status":"publish","type":"post","link":"https:\/\/www.moosepeterson.com\/blog\/the-ttl-flash-system\/","title":{"rendered":"The TTL Flash System"},"content":{"rendered":"

Flash Basics<\/a> | Ambient Light<\/a> | Manual Flash<\/a> | Here Comes TTL<\/a> | Flash Key<\/a> | Flash Fill<\/a>
\nThe Math of Flash Key and Fill<\/a> | TTL \tAdvantage<\/a> | The Shutter Speed Mystery<\/a>
\nSB Operation<\/a> | Programming<\/a> | Visualizing The \tEffects<\/a> | Compensation<\/a>
\nOff Camera Flash<\/a> | Multiple Flash<\/a><\/p>\n

What follows was written in spring, 2004. While the theory of TTL remains the same, in 2008 we’re in the iTTL world of the D3. For a more up to date explanation of using iTTL, you’ll want to head to the D3 site.<\/p>\n

Flash is still the most difficult aspect of wildlife photography to \tmaster both technically and aesthetically. It doesn’t matter what camera \tyou have, flash still takes plain old personal skill. Though this commentary \tcan apply to any form of photography, I will as always focus in on wildlife \tphotography (there I go with the bad puns). There a lot of theory being \tpresented here, an exercise and basic concepts to aid in your mastering \tthe flash. Remember this one very imprtant bit of advice. You learn \tflash only by doing flash. Reading what I have to say here will assist \tyou in better understanding it, but you can only master it by doing \tit. So, on with the show! (Those shooting with the F5 should head directly \tto F5 Flash )<\/p>\n

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<\/a>Flash Basics<\/h2>\n

It doesn’t matter if you’re using Nikon or any other brand, flash \tbasics are flash basics. The basics of manual flash and manual flash \texposure must be understood even with today’s modern TTL technology! \tWith the introduction of the N8008 and SB-24, it was said that those \tnot knowing flash photography would become good and those knowing flash \tphotography, would become great with its technology. True, the breakthrough \ttechnology of that system improved the mathematical percentage of technically \tcorrect exposed photographs. But the quality and creativity of flash \tphotographs taken by the average photographer have not made the same \tquantum leap. This stems from the fact that basic flash exposure and \ttechnique has never been very well understood. This includes understanding \tall the advantages the Nikon flash system makes available to the photographer!<\/p>\n

Before diving into this topic, one statement needs to be made about \tunderstanding flash photography. It takes time to master flash! Because \tit’s something we can’t see, understanding flash is a very, very difficult \tprocess. Don’t expect to comprehend all the theory and put flash into \tpractice after first reading through this or any other explanation of \tflash. Give yourself and your equipment time to let it sink in. This \tbook will have you up and running with flash, but it will still require \tsome time before you’re using flash as a natural, unconscious photographic \ttool.<\/p>\n

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<\/a>Starting with Ambient Light<\/h2>\n

Understanding flash begins with ambient light. Flash is needed when \tambient light is either too low, contrasty or nonexistent to properly \texpose the subject. Low light can come from shooting in the shade of \ta tree or late evening. Contrast seems to haunt our every exposure as \twe fight the battle between highlights and shadow. And no light for \tphotography can be encountered in our own homes when shooting a birthday \tparty. In any case, understanding these deficiencies is the first step \tin properly using flash.<\/p>\n

The next step is understanding how we properly expose film for ambient \tlight. Ambient light is the light that comes from the sun (99% of the \ttime, artificial lighting such as from household lamps could be considered \tthe other 1%) that bounces everywhere in and out of doors. To properly \texpose for ambient light, we have available to us shutter speeds and \tapertures. We must use the correct combination of shutter speed and \taperture to properly expose film for the existing light based on the \tfilm’s ISO (film’s ISO to light index). A proper exposure in general \tterms is when detail can be seen in the highlights and shadows of a \tphotograph. (If detail is not seen in either the highlight or shadows, \tthen the range of exposure is beyond the ISO of the film.) The shutter \tspeed and aperture each have a separate yet combined roll to play in \tproper exposure.<\/p>\n

The shutter speed determines how long the film sees the light. Shutter \tspeeds are described in terms of time. Current Nikon cameras have shutter \tspeeds with durations of 1\/8000 of a second to a full 30 seconds (this \tdoesn’t include manual speeds\/times fired using the bulb function). \tNo matter how the shutter speed is set, whether manually dialed in or \tautomatically derived via the camera’s computer, the shutter speed determines \tthe length of time the film is exposed to the ambient light. The shutter \tspeed also determines how long the film sees the subject. If the subject \tis not moving, the length of time the shutter is open and the film sees \tthe subject does not matter. But if the subject is moving, long shutter \tspeeds can result in out-of-focus subjects because movement is seen \tby the film.<\/p>\n

The aperture regulates the amount of light that strikes the film. \tThe aperture is a large hole normally at the rear of the lens through \twhich light must travel to reach the film. It has blades that can be \tclosed down, making the hole smaller, or opened up, making the hole \tlarger. The larger the hole, the more light that can strike the film. \tThe smaller the hole, the less amount of light that can strike the film. \tThe size of this hole is described most commonly in f\/stops (though \tnot technically correct, but who cares as long as we all know what we’re \ttalking about). The larger the hole, the smaller the f\/stop number is. \tThe smaller the hole, the larger the f\/stop number is. For example, \ta large hole would have an f\/stop of f\/1.4 and a small hole an f\/stop \tof f\/32. The size of this hole also determines the depth-of-field in \tthe photograph, that is, the depth of focus in front of and behind the \tsubject.<\/p>\n

These are our only two means of regulating the light that strikes \tthe film. In flash work, it’s important to remember that shutter speed \taffects how long the light strikes the film and that aperture affects \thow much light strikes the film.<\/p>\n

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<\/a>Manual Flash Exposure Calculation<\/h2>\n

Understanding the above is relatively simple, but now is when it becomes \tmore difficult! In the old days (less than a decade ago), flash exposure \tcalculation was the cause of divorces. We all have those infamous holiday \tphotographs when dad’s flash either made us white as ghosts or mere \tshadows against a wall. This was and still is, because of the lack of \tbasic understanding of the two exposure regulators of the flash exposure. \tWe have flash-to-subject distance and aperture as our only means of \tregulating manual flash exposure. We’ll start with flash-to-subject \tdistance as it’s normally the hardest concept for folks to understand.<\/p>\n

Flash-to-subject distance is just what it says, the physical distance \tbetween the flash and the subject. Even with TTL technology, this concept \tmust be thoroughly understood! Back in the old days, this distance was \tgenerally determined by first focusing on the subject, and then reading \tthe distance off the distance scale on the lens. Other methods such \tas a measured length of string, pacing off steps and even tape measures \twere used to determine this all important distance. This unit of measure \twas then put into a formula to calculate the needed aperture for proper \texposure.<\/p>\n

Generally, flash units would have a sliding scale on them for making \tthis calculation easier. The table required the film’s ISO and flash-to-subject \tdistance. With this, determining the needed aperture for correct exposure \twas made easy. Ha! And if you were really unlucky, your flash had no \tsuch table and a hand written, mathematical formula had to be used. \tThis often required a piece of scratch paper and pencil, and lots of \ttime. It also required knowing the flashes guide number and having excellent \tmathematical skill. But most importantly, it made flash photography \textremely user unfriendly! It is also what made using flash so unpopular \tand dreaded, a sentiment carried by some still today! Since modern TTL \tflash technology, knowing or reading all these formulas is useless, \tlets cut to the chase and leap ahead to the more currently related flash \tproblems.<\/p>\n

The reason that flash exposure is determined by flash-to-subject distance \tis because of the power of the light emitted by the flash itself. The \tamount of light the flash bursts off is referred to as Guide Number, \tGN for short. The higher the number, the brighter the light emitted \tby the flash. The brighter the light, the further it can travel from \tthe flash. But as the light travels from the flash towards the subject, \tthe power or intensity of the light falls off. In fact, the light falls \toff at a tremendous rate called the inverse square law. This law says \tlight from flash falls off at the rate inverse to the square of the \tdistance the light has traveled. In plain language, flash units have \treally little power.<\/p>\n

To illustrate this point, let’s look at the rate of light fall off \tfor the SB-24\/ 25\/26 (which are all the same). Using film with an ISO \tof 125, a subject at 60 feet can be properly exposed at f\/2.8. At f\/4 \tit drops to 40 feet, f\/5.6 to 30 feet, f\/8 to 20 feet, f\/11 to 15 feet, \tf\/16 to 10 feet and at f\/22 to a mere 7 feet. That’s an incredible drop \toff in power in the space of a few feet. But it’s important and a fact \tof life we must work with. (This assumes the subject is an 18% gray \tand does not take into account whether the subject is white or black \tbecause either case can radically change the needed f\/stop.)<\/p>\n

You should also note from this point the relationship between flash-to-subject \tdistance and aperture. Aperture is our other means of regulating the \texposure. Using the information in the above example, if the subject \tis 30 feet away the proper exposure is f\/5.6. But if our subject is \twhite and at that same distance, we would probably want to open the \taperture up to f\/4 to record the subject as white. And if the subject \tis dark, we would want to probably close up one stop to f\/8. During \tthis whole exercise, the flash-to-subject distance never changed. We \tchanged exposure strictly by changing the f\/stop.<\/p>\n

The limitation with this is, what if we’re shooting a group of people \tat a distance of 30 feet? We should be using an f\/stop of f\/5.6, but \tthat’s not enough depth-of-field to have the whole group in focus. And \twhat if the group is a bunch of actors dressed in black costumes? The \tnightmares are just beginning for someone trying to accomplish this \twith manual flash. Yet thousands of situations like this were successfully \ttaken with “old” flash technology because those photographers understood \tthe basics of manual flash. But what does this have to do with modern \tTTL technology? Hold on, we’re getting there!<\/p>\n

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<\/a>Here Comes TTL<\/h2>\n

Nikon first introduced TTL (Through The Lens) flash technology in \t1980. The basics of TTL operation is rather simple and applies to all \tcamera systems. With TTL flash exposure, when the shutter is tripped, \tthe light from the flash fires off, racing to hit the subject. This \tlight hits the subject then bounces back to the camera. The light traveling \tthe speed of light, travels through the lens (and any filters which \tmay be attached) and strikes the film plane. The light then bounces \tdown off the film to a sensor which reads the light as it builds up \texposure on the film. Once the sensor and the connected computer software \tdetermines the light has massed enough for the correct exposure, the \tcamera’s computer turns off the flash (just like a light switch in a \thouse goes on-off). Keep in mind, this is all happening at the speed \tof light! Why is this technology so important to flash photography today?<\/p>\n

Lets look back at the path of the light once it leaves the flash. \tThe correct exposure for this equation was not determined by using either \tflash-to-subject distance or aperture. The correct exposure was achieved \tby simply turning off the flash! Whatever the size of the aperture, \tthe hole the light must pass through on its way to the film, is dealt \twith by the camera’s computer at the film plane. Does this mean that \tflash-to-subject distance and aperture are not important to flash exposure? \tNot hardly, but it means we can control the flash rather than it controlling \tour photography.<\/p>\n

With TTL technology, the camera’s computer provides the correct exposure \tregardless of the aperture or flash-to-subject distance (as long as \tthey’re within the realm of the flash’s power). TTL technology puts \tthe control of depth-of-field back into the hands of the photographer. \tWe can pick the aperture for the desired depth-of-field and not have \tit preselected by the flash-to-subject distance. We can do this because \tthe camera’s computer delivers the correct exposure for the aperture \twe’ve selected. If I’m going too fast and getting too excited for you \tto follow, let me explain it through an example.<\/p>\n

Photographing nesting birds was, until TTL technology, a major pain. \tLarge, bulky flash units had to be introduced into the home of the bird, \toften causing stress because of their size and presence. These large \tflashes were needed to light the nest sufficiently to obtain the desired \tdepth-of-field. Because of their large size, these units had to be placed \tback from the nest and consequently had to have even more power because \tof the flash-to-subject distance. Then came the TTL flash units.<\/p>\n

I remember this very scenario back in 1981 when I shot a nest with \ttwo SB-12 flash units and another photographer used two Norman 200b \tunits. I stood four feet from the nest, had the two small flash units \tright beside the lens for the light pattern I wanted and most importantly, \tselected whatever f\/stop I wanted for the depth-of-field I desired. \tI did this without any concern for the exposure as the camera’s computer \tdid it all. The other photographer had to carefully place his flash \tunits and use a flash meter to determine the correct f\/stop. And once \tselected, he could not change that f\/stop without moving his lights \tand thereby changing his flash-to-subject distance.<\/p>\n

So TTL has taken all the calculations out of basic flash exposure. \tThis is true for those who only want basic flash photographs. But I \tassume you bought this book because you want to take your flash photography \tbeyond the basics by using flash as a creative tool. For this to happen, \tthe melding of flash and ambient light is required.<\/p>\n

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<\/a>Flash Key vs. Flash Fill<\/h2>\n

Lets understand the terms. Flash key is where the light from the flash \tis the main light. Flash fill is when the light from the flash is filling \tin the deficiencies in the ambient light, in other words, filling in \tthe shadows. The Nikon TTL flash system is more than capable of handling \tboth of these situations without any help from us. But getting more \tthan the standard canned light from the flash takes more from us. The \tspecifics for programming the flash units will be covered under the \tappropriate sections. Here, I just want to discuss the concepts and \ttechniques.
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Flash Key<\/h3>\n

Flash key, like I said, is when the flash is the main light source \tfor the photograph. This is not to say there is no ambient light, but \tthat it’s not the major light source for the exposure. The main point \tto remember when the flash is the key light, it’s creating the light \tpattern for the photograph. This is a very important concept that will \tbe discussed in greater depth later.<\/p>\n

Exposure for flash key is normally a straight line affair (unless \tbouncing the flash). The TTL metering calculates the exposure based \ton what the light does bouncing off the subject. The light from the \tflash fires and shuts off, requiring the photographer only to remember \tto turn on the unit. When operated in this manor, the exposure for the \tambient light will fall wherever it may, possibly influencing the final \tphotograph or not. Generally, the only concern is the exposure of the \tflash.<\/p>\n

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<\/a>Flash Fill<\/h2>\n

Flash fill is used to fill in the shadows found in ambient light. \tThis is a technique compacting the exposure range of the scene to fit \twithin the latitude of the film. Most films can only hold information \tin the shadows and highlights when the range between the two is less \tthan three stops. For example, if the exposure for the highlights is \tf\/11 and the exposure for the shadows is f\/5.6, the film will record \tdetail in both. But if the exposure should be one stop more in either \tdirection, the film will loose detail in the overexposed or underexposed \tarea. The flash helps by pumping light into the shadows, decreasing \tthe range and aiding the film in recording the detail.<\/p>\n

Flash fill is described in terms of ratios. A 1:1 ratio means the \tlight from the flash is equal to the light level of the ambient light. \tThis means there are no shadows because the light from the flash wipes \tthem out. A ratio of 1:2 means the flash is one stop less in exposure \tcompared to that of the ambient light. In this case, there will be a \tshadow that is one stop less in exposure than the ambient light and \twell within the range of a film’s exposure latitude. The ratios keep \tgoing, 1:3, 1:4 and soon on, but after 1:4, the fill light is doing \tvery little for your photograph.<\/p>\n

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<\/a>The Math of Flash Key and Fill<\/h2>\n

Taking flash to a higher level starts here! We must meld two light \tsources to really be successful in communicating photographically with \tflash. This requires understanding the two influencing factors of ambient \tlight and flash.<\/p>\n

Ambient light exposure is regulated by shutter speed and aperture. \tFlash exposure is regulated by flash-to-subject distance and aperture. \tThe only variable in common for properly exposing the two light sources \tis aperture. This means that the aperture is the constant when melding \tthe two light sources. The shutter speed must be changed to match up \twith the constant aperture (for proper flash exposure) to properly expose \tthe ambient light. At the same time, the flash-to-subject distance must \tremain constant to provide the correct exposure for that aperture.<\/p>\n

To further illustrate the point, let’s throw some numbers into the \tdiscussion. Using the SB-28 GN, we know that we must use an f\/stop of \tf\/5.6 when the subject is 30 feet from the flash. Our shutter speed \tmust then match up with f\/5.6 to properly expose the ambient light. \tAs long as the flash stays 30 feet away, our aperture at f\/5.6 and the \tshutter speed is correctly set, we’ll have beautifully exposed ambient \tand flash light. At least until the subject moves, the sun is blocked \tby a cloud or we need more depth-of-field. We are locked in to this \tformula when working with manual flashes if we want to properly expose \tambient light and flash. But TTL gives us another option.<\/p>\n

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<\/a>The TTL Advantage<\/h2>\n

Because flash-to-subject distance doesn’t affect our f\/stop with TTL \t(as along as we’re within the realm of the flash’s power), we can maximize \tand manipulate aperture and shutter speed to our advantage. In the instance \tof flash key, we can manually set the shutter speeds to correctly expose \tfor the ambient light. We can also set the shutter speed to underexpose \tthe ambient light. This can be as little as one stop to make a busy \tbackground disappear. Even in bright daylight, we can make the photograph \thave the appearance of being shot at night by underexposing two or three \tstops by using the shutter speed. This whole time, the flash is providing \tus with the proper exposure for the subject. We can do this only because \tTTL provides us with the proper exposure for the aperture selected regardless \tof the flash-to-subject distance! Wow!!<\/p>\n

There’s a lot more to this than this simple explanation provides. \tBut the specifics of how all this can be put into practice will be saved \tuntil actually talking about the specifics of the particular flash units. \tJust being aware of this and thinking about it though will help prepare \tyou for those sections.<\/p>\n

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<\/a>The Shutter Speed Mystery<\/h2>\n

Many wonder why the shutter speed does not affect flash exposure. \tIt’s simple, the shutter simply isn’t fast enough! The duration of the \tburst of light from the SB-24, 25, 26 and SB-28 ranges between 1\/1000 \tto 1\/23000 of a second. The light from the flash must be able to expose \tthe film in one, solid burst to properly expose the film (this is not \ttrue with the FP feature on the F5, N90s\/F90x). This means the shutter \tblades of the shutter must be completely out of the way when the light \tstrikes the film or there will be a shadow on the film. Currently with \tNikon’s focal plane shutters, a top shutter speed of 1\/250 is available \tto sync with the flash. If a shutter speed of 1\/500 or faster is used, \ta dark ban will be on the final photograph (the shadow of a shutter \tcurtain). So why can’t the shutter control flash exposure, it’s simply \tnot fast enough to freeze that burst of light!<\/p>\n

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Can TTL Metering be Fooled?<\/h2>\n

You bet, even with the new flash matrix technology! The mechanics \tof how the new matrix technology works will be covered later. But be \taware that the camera’s meters are still looking for 18% gray even in \tflash exposure. White or black subjects can throw the metering off and \tcause bad exposures. Size of the subject and placement in the frame \tcan likewise cause exposure problems. The drawbacks with each flash \tunit and camera body when it comes to exposure will be covered under \tthe appropriate sections. Just be aware that you, the photographer, \tstill must be in charge and that all this technology is still only a \ttool and not the final word on exposure perfection!<\/p>\n

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Conclusion<\/h2>\n

There’s a lot of material in this page on the theory of flash. Being \tsuccessful in using flash means no one can see that flash was used in \ta photograph. This requires understanding the nuances of flash and ambient \tlight exposure. There’s a lot more to learn in using the Nikon SB-24\/ \t25 \/ 26 \/ 28 that will aid you in this quest. There are a number of \tspecial effects that with knowledge of flash, can be programmed into \tthe camera’s and flash’s computers that can take dramatic photographs \twithout all the calculations. But to arrive at that point, understanding \tall the points made here is imperative!<\/p>\n

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<\/a>SB-24\/25\/26\/28 Operation<\/h2>\n

Getting past theory and into using Nikon’s TTL flash system is an \teasy step. Nikon’s flagship flashes are the SB-24 (discontinued but \towned by thousands) the SB-25 and current SB-26. These are TTL units \twith standard ISO shoes which fit the F4, N90 and N8008 series cameras. \tUsing the two flash units on the respective bodies in practice is not \tthat different, so the following operation information is generalized \tfor all models.<\/p>\n

The SB-24\/25\/26 can do all, part, or none of the flash exposure calculations \tfor the photographer, depending on how it’s programmed. These flashes \tcan also fill, mix or overpower (with limitations) the ambient light. \tThe LCD panel on the back of the camera is where all settings are programmed \tto achieve this control. It’s where we’ll start to get a handle on the \ttechnological side of flash work.<\/p>\n

The SB-24\/25\/26 are able to sync with the camera’s shutter in two \tways: “NORMAL” and “REAR”. In “NORMAL” sync mode (selected by simply \tsliding the switch to the Normal position) the flash is fired the exact \tmoment the last shutter blade of the first set opens the shutter. In \tthis mode, the flash records the action the instant the shutter opens \tbecause it’s firing at that exact moment (remember the duration of the \tflash is faster than the shutter). When the F4\/N90\/N8008 are in Aperture \tpriority and the flash is set to “NORMAL,” the only available shutter \tsync speeds are 1\/60-1\/250 (these are stepless speeds though). The N90\/N90s \tand F5, this speed goes down to 1\/20.<\/p>\n

If the ambient light requires a shutter speed slower than 1\/20, the \tcamera underexposes the ambient light. In this mode, the camera is unable \tto go to 1\/19 or slower shutter speed to correctly expose the ambient \tlight. When working in dimly lit situations which require such low shutter \tspeeds, switch the camera to manual mode (taking it out of aperture \tpriority) and check the ambient exposure. If a slower shutter speed \tis required to properly expose the ambient light, manually dial in the \tshutter speed and shoot (stepless shutter speeds are lost when in manual \tmode). Or, switch the sync on the back of the flash to “REAR”.<\/p>\n

In “REAR” sync mode, the flash fires the moment the first shutter \tblade starts closing the shutter after the ambient exposure is made \t(opposite of “NORMAL”). With the flash in this mode and the camera in \tAperture priority, the camera can sync using stepless shutter speeds \tranging from 30 seconds to 1\/250. This is a tremendous range of exposure \tflexibility with TTL control!<\/p>\n

Rear Curtain sync is a great feature, but it’s not where the flash \tshould be permanently set. There are a number of reasons for this. Mainly, \tthe photographer needs to be in control of what the flash is doing and \tin this mode, it’s easy to become complacent. There are many instances \twhen a 30 second exposure wouldn’t work (such as nocturnal photography). \tThere are times when the flash should be the key light and the shutter \tspeed needs to be regulated. There will also be times when the fastest \tshutter speed possible is needed. For these and many more reasons, the \tflash should not be permanently set to “REAR” sync.<\/p>\n

Understand these two modes and use them when the special application \tworks the best for a given situation. For the majority of applications, \tthe flash should be left in the “NORMAL” position. Switch it to “REAR” in \tthose instances where it’s required, then switch it back to “NORMAL” when \tdone. And whenever possible, take advantage of stepless shutter speeds \tby staying in Aperture priority.<\/p>\n

The flash isn’t always used for fill-flash. For example, for night \tshooting when the flash is the only light, set it on “NORMAL”. Then \tset the camera on manual mode and set the shutter speed at 1\/250. Since \tthere is no ambient light to be properly exposing, use the fastest shutter \tspeed possible. It speeds up the process, the motordrive goes faster, \tthe shutter goes faster and everything else moves quicker. This gives \tthat slight edge needed to get the photograph. It also insures the sharpest \timage possible when hand holding.<\/p>\n

An obvious but none the less important switch is the Flash Mode Selector. \tThere are four modes of flash operation with the SB-24\/25: “A”, “M”, “Lightning \tBolt” and “TTL”. The “A” makes use of the built-in flash sensor (not \tto be confused with TTL) for exposure. The “M” throws the photographer \tback to the days of manual flash, calculating flash-to-subject distance \tfor proper exposure. The “Lightning Bolt” provides repeating flash operation, \ta strobographic effect which is more fun than practical. The “TTL” is \twhere the flash should be set, taking advantage of its full potential.<\/p>\n

Be aware of the distance scale on the LCD panel whether in “REAR”, “NORMAL” and “TTL” mode. \tWhen a lens with a CPU is in use, the distance scale and f\/stop are \tdisplayed on the panel (this is true only when the flash head is set \tat the ninety degree position). The distance scale shows how close or \tfar the subject can be from the flash with the f\/stop selected (which \tis displayed). This is important information because beyond these distances, \taccurate TTL exposure cannot be made.<\/p>\n

The SB-24\/25\/26 can be set for “Automatic Balanced Fill-Flash” and “Standard \tTTL” flash exposure. With Automatic Balanced Fill-Flash, the camera \tand flash computer are in complete control of fill-flash exposure. These \twill vary the flash exposure to equal the ambient light to underexposing \tthe flash by minus 1 1\/3 stop. The photographer never knows the amount \tof fill-flash used until the exposed film comes back from the lab and \tthen it’s too late to see if the camera’s meter and computer figured \tcorrectly. With Standard TTL, the photographer is in complete control \tof the fill-flash, the way it should be.<\/p>\n

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<\/a>Programming the Flash<\/h2>\n

Photographers want to be in control of the Exposure. Accomplishing \tthis requires programming information into the SB-24\/25\/26’s LCD panel. \tThis can be a little tricky, so I want to go through the steps to clarify \tany holes in the instruction book.<\/p>\n

To program Standard TTL on the SB-24, press the “M” button (not to \tbe confused with “M” mode next to the “TTL”) causing the man\/sun symbol \tto blink. On the SB-25\/26, press the “M” button to make the man\/sun \tsymbol disappear. The flashes are now set to Standard TTL. The flash \twill now automatically expose the fill-flash to equal the exposure of \tthe ambient light. In many instances, this is what’s needed (because \tof the subject’s absorption of light), but more often the flash is only \tneeded to fill in the dead zones giving them more life. A little more \tprogramming is required to accomplish this.<\/p>\n

With both units, press the “SEL” button to call up an analog scale \twhich is where the amount of fill-flash is programmed. On the SB-24, \tpress the up arrow to program minus compensation. On the SB-25\/26, press \tthe down arrow to program minus compensation. On both units, once compensation \tis dialed in, press the “SEL” to register the compensation or press \tnothing and after ten seconds, the compensation is automatically registered. \tInside the camera’s viewfinder, the compensation warning will light \twhen flash compensation has been programmed. The camera\/flash computers \twill deliver the programmed amount every time the flash is fired.<\/p>\n

This brings us to the question of how much fill-flash is the correct \tamount? Generally, I have my flash units programmed with minus 2\/3 stop \tcompensation. This is an amount that will clean up shadows and colors \twhile not overpowering the quantity or quality of the ambient light. \tKeep in mind that dark subjects suck up light and light subjects bounce \tlight back.<\/p>\n

If there’s a doubt concerning just how the flash affects a subject, \tdo a test. Apply the exposure compensation test to flash. Set up the \tteddy bears and shoot a test in various lighting conditions varying \tthe flash compensation. Remember that we’ll all want a different amount \tof compensation according to individual personal taste in photographic \texposure. The only way to find out that amount without the loss of good \timages is to test.<\/p>\n

Ever seen a photograph of wildlife you know are out during the day \tbut the photograph looks like it was taken at night? How about those \timages of wildlife taken during the day but the light is coming from \tdifferent directions? My favorites are the over lit flash photos or \tthose with five catch lights in the eye.<\/p>\n

These are all mistakes in using flash that can be avoided and corrected. \tThe black background comes from incorrectly exposing for the ambient \tlight. The multi directional light comes from misunderstanding ambient \tlight. Over lit derives from a lack of control of the flash exposure \tand multi catch lights are simply evidence of misplaced flash units. \tProvided throughout this book are the techniques to avoid these pitfalls.<\/p>\n

SB-28 The really new thing about the SB-28 is its look. Besides being \tsmaller, trimmer, it has an entirely new back panel, LCD display. The \tbuttons are rubber coated and recessed on the SB-28, there are no longer \tany sliding MODE switches or the like. Even the On\/Off switch is now \ta button so you can no longer accidentally change a function or turn \ton the flash. In fact, you must depress and hold down the On\/Off button \tfor a few seconds in order for the flash to come on. And the SB-28 will \tautomatically go into Standby mode after approximate 80 seconds.<\/p>\n

There are five basic modes possible with the SB-28 depending on the \tcamera in use. There are no real surprises here, the instruction book \tpretty well lays things out. If you want to shoot in “standard” mode, \tyou simply press the MODE button until just the TTL message is displayed \tin the top, left corner of the LCD. This puts you in control of the \tflash fill compensation as previously described.<\/p>\n

There might be two “drawbacks” to the SB-28 depending on how you look \tat it. The first is it does not have Red-Eye reduction capability with \tthe F5. As this is a feature I have never personally used, I don’t find \tthis a drawback. The second drawback and more important to my own photography, \tis the smaller and dimmer AF illuminator. I don’t have a way of measuring \thow much dimmer it is, but it’s enough that I use the SB-25 for nocturnal \tshooting as my main flash, to take advantage of its AF illuminator.<\/p>\n

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<\/a>Special Compensation Technique<\/h2>\n

The unique capabilities of TTL technology can be taken one step further. \tWith a firm grasp of flash compensation, use it in conjunction with \tthe camera’s compensation. In situations where the flash is to be the \tkey light and the background underexposed, the camera and flash computers \tcan do it all, thus avoiding lengthy exposure computations.<\/p>\n

In our example, we’ll assume we want the background (ambient light) \tunderexposed by one full stop. The camera is set to Aperture priority, \tthe metering set on Matrix. Dial in minus one stop via the exposure \tcompensation on the body. This underexposes the ambient light by one \tstop; it also underexposes the flash by one stop. No problem because \twe’ll go to the flash and program it to overexpose by one stop. Now, \tthe flash is the key light with no compensation.<\/p>\n

If the subject is light colored and we want the flash to expose it \tto come out white, dial in no compensation or up to plus one stop. If \tit’s a dark subject, program in more than one stop plus compensation. \tRemember though that ambient light is underexposed and the flash is \tthe key light, don’t make a mistake and underexpose the flash thinking \tits fill-flash. This is an excellent technique for making a distracting \tbackground disappear.<\/p>\n

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<\/a>Visualizing the Effect of Flash<\/h2>\n

It’s often difficult to judge the direction flash illumination will \ttravel and its effect. When is the right time to take the flash off \tthe camera? Previsualize by converting the flash to a flashlight. Point \tthe imaginary flashlight at the subject and visualize the effect it \twill have. Where will the light strike the subject? Does it create a \tshadow and if so, where does the shadow fall around the subject? If \tthere is a shadow on the subject that we want to make disappear using \ta flash, where should the flash be placed? Imagining the flash as a \tflashlight will help assess how the flash will effect the photograph.<\/p>\n

Keep in mind that we want to imitate the sun and its effect when using \tflash. The key word here is imitate, not replace. The sun comes from \tabove us, always. This means that shadows should always fall below subjects \tand not above them. So when using flash, shadows must appear below the \tsubject and not above. There is also just one sun so there should only \tbe one highlight reflected in the eye. With proper technique, multiple \tflash can be used while maintaining just one highlight.<\/p>\n

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<\/a>Off Camera Flash<\/h2>\n

The SB-24\/25 can be taken off camera while maintaining full TTL connections \tvia the SC-17 cord<\/a>. This permits the flash to be placed anywhere around \tthe camera up to three feet away. This provides all of the features \tof TTL flash and allows complete control of the flash’s light. Up to \tthree SC-17 cords can be connected together creating a nine foot off \tcamera cord. More than this creates too much resistance in the cord \tfor all the TTL information to quickly communicate between flash and \tcamera computers.<\/p>\n

When attaching the SC-17, it’s recommended that it be attached to \tthe camera body first, then the flash. The foot on the SC-17 where the \tflash is attached must have a flash attached to complete the cord’s \tcircuit. Plugging an SC-18\/19 cord into the foot of the SC-17 for a \tslaved flash without a “Master” flash attached to the foot will not \twork. The SC-17 has a 1\/4-20 threaded socket on its base to allow attachment \tof the unit to a bracket or stand.<\/p>\n

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<\/a>Multiple TTL Flash<\/h2>\n

Nikon’s flash system is capable of controlling five TTL flash units. \tThese flash units are linked together via the SC-17, SC-18 or SC-19 \tcords and the AS-10. The SC-18 cord is five feet long, the SC-19 is \tten feet long. The AS-10 is required on all slaved units to complete \tthe flash circuits (it attaches to the flash foot). The AS-10 also provides \ta 1\/4-20 thread enabling the flash to be attached to a stand or bracket. \tThe SC-17 foot and AS-10 provide TTL sockets for the SC-18\/19. Use the \tsockets on the side of the flash rather than these.<\/p>\n

Since the SC-18 and SC-19 are only three lead cords (five leads are \trequired for full computer communication), as many as three SC-19s or \tsix SC-18s (a total of 30 feet of extension in either case) can be coupled \ttogether for TTL operation. These cords are connected together via the \tAS-10 which doesn’t require a flash to complete the circuit. The SC-18 \tcan be trimmed down (not recommended by Nikon) to accommodate any special \tbrackets or applications thereby eliminating any excess cord from being \tin the way.<\/p>\n

The SB-24\/25\/26 have two connections on their sides. One is a standard \tPC connection and the other is a TTL connection where the SC-18 and \tSC-19 cords are plugged in. When a TTL flash is used as a second light \t(slaved unit) via an SC-18 or SC-19 cord, all programmable functions \ton the second light are governed by the master flash connected to the \tcamera’s hot shoe (whether on camera or attached via the SC-17 cord). \tThe flash head Zoom function does work on the slaved units and should \tbe manually set to match the master flash.<\/p>\n

The SB-24\/25\/26 power switch has two modes, “STBY” and “ON”. Standby \t(“STBY”) saves on battery power and is a great feature for wildlife \tphotographers. In general applications the flash is used for a period \tof time and then turned off. When the flash is needed over a long period \tbut only sporadically fired, “STBY” is an excellent option. In this \tmode, the flash turns itself off after 60 seconds and comes on immediately \twhen the shutter release button is pressed. (All slaved units must be \tset to “ON” and not “STBY” because they do not receive the impulse from \tthe shutter release when pressed.)<\/p>\n","protected":false},"excerpt":{"rendered":"

Flash Basics | Ambient Light | Manual Flash | Here Comes TTL | Flash Key | Flash Fill The Math of Flash Key and Fill | TTL Advantage | The […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","advanced_seo_description":"","jetpack_seo_html_title":"","jetpack_seo_noindex":false,"jetpack_seo_schema_type":"","sync_status":"","episode_type":"","audio_file":"","podmotor_file_id":"","podmotor_episode_id":"","castos_file_data":"","cover_image":"","cover_image_id":"","duration":"","filesize":"","filesize_raw":"","date_recorded":"","explicit":"","block":"","itunes_episode_number":"","itunes_title":"","itunes_season_number":"","itunes_episode_type":"","_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"{title}\n\n{excerpt}\n\n{url}","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"_wpas_customize_per_network":false,"jetpack_post_was_ever_published":false},"categories":[93],"tags":[],"dipi_cpt_category":[],"series":[],"class_list":["post-7255","post","type-post","status-publish","format-standard","hentry","category-technical-tips"],"episode_featured_image":false,"episode_player_image":"https:\/\/i0.wp.com\/www.moosepeterson.com\/blog\/wp-content\/uploads\/2018\/06\/Podcast.jpg?fit=1500%2C1500&quality=89&ssl=1","download_link":"","player_link":"","audio_player":false,"episode_data":{"playerMode":"dark","subscribeUrls":{"amazon":{"key":"amazon","url":"https:\/\/www.audible.com\/pd\/Podcast\/B08JJQC1GR?ref=a_pd_item-n_c0_bc&pf_rd_p=1da7ab30-c785-4a0e-a160-4a7e7077b353&pf_rd_r=EEDMYHQM3DZ05FPRTHMJ","label":"Amazon","class":"amazon","icon":"amazon.png"},"apple_podcasts":{"key":"apple_podcasts","url":"","label":"Apple Podcasts","class":"apple_podcasts","icon":"apple-podcasts.png"},"rss":{"key":"rss","url":"","label":"RSS","class":"rss","icon":"rss.png"},"spotify":{"key":"spotify","url":"https:\/\/open.spotify.com\/show\/2fRA9VaVfSdQMKf1ipxr0tipxr0t","label":"Spotify","class":"spotify","icon":"spotify.png"},"itunes":{"key":"itunes","url":"https:\/\/podcasts.apple.com\/us\/podcast\/moose-podcast\/id1107405746","label":"iTunes","class":"itunes","icon":"itunes.png"}},"rssFeedUrl":"https:\/\/www.moosepeterson.com\/blog\/feed\/podcast\/moose-podcast","embedCode":"

The TTL Flash System<\/a><\/blockquote>