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Basics of Flash Photography
Four Fundamentals we must know

1. Inverse Square Law - Guide Numbers - Bounce flash - TTL Flash Compensation

2. Continuous vs. Instantaneous light - vs. Shutter Speed   -   Auto FP mode (HSS)

3. Soft Light   -   What Hot Shoe Flashes Do

4. Flash photos are Double Exposures

w     Menu of the other Photo and Flash pages here


What hot shoe flashes do

Here is another look at "what lights do". This time uses a camera hot shoe mounted flash (flat frontal lighting), in various configurations. Note that (speaking generally of basics), here we are discussing:

Now, on-camera frontal light can make harsh shadows behind the subject, but On the subject itself, frontal light is very even (to a fault - flat, excessively even everywhere, no shadows on the subject's face for example), so soft is not really a consideration when flat (no shadows to be soft). Off-camera lights intentionally make shadows On the face (tonal gradients which show shape), but which must be made soft to be pleasing. Bounce flash is one way to get much of the light effectively off-camera, and soft too.

So I think sometimes beginners do not realize at first what they should be looking for in such comparisons. A direct hot shoe light is flat frontal lighting (on lens axis) which does not make shadows "on the subject" (flat - does not show shadow gradient tones which define shape and curves). Any shadows are mostly hidden behind the subject, but it can make a few shadows "under" the subject due to the higher hot shoe angle, normally sharp and dark and objectionable. However, again, frontal light is flat (even), no visible shadows on the subject itself to show its shape. So that is better seen on the previous page because this page is hot shoe flash and mostly frontal light, but nevertheless, we can judge the softness of the light by the shadows, under the shell here, and in the detail on the shell. There are reasons to use either method. Harsh hard light from the side (dark shadows with sharp edges) can show texture detail better, where soft light (dim, vague shadows with fuzzy edges) sort of smooths and covers up surface blemishes (for example, the ridges on the shell - compare the hard and soft light). FWIW, these pictures were with a Nikon D300 at four feet, a 60mm f/2.8 lens, and a SB-800 hot shoe flash.

Above: Direct flash, SB-800 on camera hot shoe, at four feet. Harsh dark sharp shadows, but one advantage is that the flash position directly above the lens puts most shadows directly behind and below the subject, mostly hidden there, out of sight of the lens. We still see the shadows "below" the subject (arms, ears). The downside is that on-camera lighting is a very flat frontal light, illuminating all areas equally. In contrast, the light from off-camera lighting adds shadows which can model the subjects features, pleasing and natural, when we can soften them. Note too that if camera were turned on its end to portrait orientation, then the hot shoe flash is beside the lens, and would make a terrible shadow on the other side of subject. So, rotating flash brackets are designed to flip the flash back to be directly above the lens in that case, for this reason, to always keep the shadow hidden behind the subject. This background is a 30x22 inch white paper from craft store, curved up behind bear, close, with thought of showing intentional shadows here.

Above: Added Nikon SB-800 diffusion dome, still aimed at subject, still same direct flash. Still very flat direct frontal lighting, still dark and sharp and harsh. Again, judge the softness of the light by the shadows under the shell (see the last umbrella picture below for what soft light looks like). The diffusion dome has a just-perceptible slight effect, very slightly softer shadow edges, slight gray fringes around the slightly less dark shadow. This is hardly perceivable up close (this is only four feet), but the light does appear relatively larger up close to the subject than when more distant. It has even less effect at greater distance. If you might imagine your directly aimed dome is actually doing something at 8 or 10 feet, better check it again. The dome does require more flash power, so the flash color will become slightly warmer which you may like, however, we can do that other ways too. The point here is that there is very little effect from the dome with direct flash, the light is simply too small (about 2 inch dimension). Repeat this same test so you can see and believe.

Above: Heavy Duty diffusing - Still using plastic diffusion dome, but also covered it with piece of white bed sheet linen for more diffusion. The shadows do have slightly softer edges (lighter gray fringe around slightly less dark shadow - filled more by scattered light), but not much. The light is still very small, still the same size as the flash head, about two inches. If perhaps this white fabric were larger and hanging a couple feet out in front of the flash, so the light pattern on the cloth would be larger.... like a shoot-through umbrella perhaps. Large is what makes soft.

Above: SB-800 pull-out wide angle adapter. Less effect. It is a diffuser too, but diffusion is not what does the job. Diffusion just scatters the light outward, wider angle, but mostly missing the subject. Large is what makes soft.

Above: Bounce flash, on 10 foot ceiling (7 feet above table), still same hot shoe flash, same as before, but pointing up now, with no accessories. Bounce is a Big Deal, adding much advantage. Notice the shadows of course. Bounce is a very soft light, because the ceiling is large, and now it acts like a very large "light" up there (and large is what makes soft). However this light comes from above now, vague dim shadows below the object. We can barely detect the shadows of the bears arms down on the "floor" beside the legs. We can barely detect the ridges on the top and left side of the shell (absence of shadows to show those ridges). For clinical detail, the hard light shadows may show the ridges on the shell better, but the soft light is aesthetically smoother. The bounce light is very natural for the bear too, but the steep direction down also causes eye socket shadows (camera with bounce should not stand quite this close to subject in practice).

Notice we lost the catchlights in the eyes now, with light from ceiling above instead of direct from camera. I think the bear is frowning now? Catchlights are very important. But a bounce card or dome can restore it, below.

Bounce is also somewhat less affected by the inverse square law - the longer path up and down is more able to "fill" a small room with even light everywhere, instead of being dark behind our subjects. When there is a suitable ceiling, bounce is the best thing you can do for a hot shoe speedlight, but it does need a slight frontal fill (small bounce card). Bounce also requires a lot of flash power. Start at ISO 400 and f/4, which is mostly fail safe in most situations (a small flash likely needs more ISO). With lower ceilings, you can experiment with f/5.6 and/or maybe ISO 200, but watch the Ready LED for insufficient power warning, and for excessive recycle time.

Above: Same bounce flash with SB-800 diffusion dome added. It is aimed up for the bounce, from same position. The difference now is that the spill from its front side adds forward fill. We get the direct shadows back, but this forward spill is why we use it. The frontal fill shows the bear's eyes, and the ribbon in the chin shadow now. We get some of the shell ridges back (direct frontal shadows). One very important aspect is that it adds catch lights in eyes (on humans too, which is necessary sparkle to add "life").

But this forward spill adds the same rear shadows as direct flash (under bear's ears and arms for example), however they are a little less dark here because the bounce light fills them, and the direct spill fills the bounce shadows too. Question: Which does it more? Rhetoric, but it is a question you should be able to answer about your own pictures. In this case, the camera is only at four feet, and the flat frontal fill shadows are the darker shadows, so the direct spill is the major light here, not the bounce. We would prefer the opposite, the forward spill should be fill, not the main light. Excessive direct forward spill in this case. Clear to see if we just look.

We like to pretend the dome's spill light hits all the room's walls and comes back to subject from all directions, but consider that the inverse square law says this is usually not very likely. The dome above is four feet from the bear, and five feet from a wall on camera right of the shell, and there is no evidence of any shadow on the left there. The light is just lost. Five feet to wall, five feet back is ten feet, plus losses at the wall reflection, so any side spill here is at least three stops less than the frontal light (insignificant). Maybe better if the subject were also at ten feet. Or maybe in a small room, but I have tried and tried, and even with closer walls, I never find any evidence of the scattered wall bounce. The forward spill is too great, it wipes out the bounce shadows, and now it is direct flash with bounce fill. But there is the obvious frontal fill, which is why we might use it (but my bet is on the small bounce card).

It is good to know that this forward spill is what domes do, however the bounce ought to be the major effect and main light (my opinion). But the forward spill fill with bounce is what the domes add, and any imagined diffusion is the least of it (the dome is just too tiny). The domes should be judged by how well they do this (and not by how warm their higher power requirement changes flash color - which was balanced later here). IMO, these are some of the things our comparisons should be looking for.

Above: Bounce flash with SB-800 pull-out white bounce card - its forward spill adds the same catch lights and frontal fill as the dome. This is my preference. Less amount, but you can use larger bounce cards, if you have to (for extreme subject distances). The built-in card is a fine size, and it is adjustable, we do not have to pull it all the way out for close distances. My opinion is that the small bounce card is usually better than the dome, and better than a large card, because less is more (and the card does not reduce the overhead bounce power like the dome does). The camera was too close for bounce here (4 feet is too close), so stand back a bit and zoom in if necessary, a little more angle, to have less extreme vertical light. We always want to keep the camera at least six feet from human faces anyway (for the proper perspective, to prevent enlarging noses, etc). For bounce, stay 8 or 10 feet back, to make the angle less steep (regarding eye sockets, etc). Zoom in when necessary, but don't actually stand too close. For the greater distances, perhaps aim the light near the halfway point on the ceiling, but watch your forward spill, you are aiming that too. My flash head is routinely at about the angle shown in the red picture here, so the direct flash lens itself will not spill forward.

In this bounce card picture, we see the direct shadow of the outright arm, and we can also still detect the arms bounce shadow down on floor by leg (compare both shadows to the dome just above - we need to realize what our light is doing). Direct is a darker shadow, we are only four feet away, but both are still present, and we did not totally blow away all effect of the bounce. On the previous diffusion dome picture before, this same lower shadow from the bounce is imaginary - we only have a direct frontally lighted picture there ... the bounce has effect with dome, but as fill light, not as main light. Was that the intended lighting? We need to learn to look at our results. :) If we are going to use bounce, we ought to see some trace of it (and we do some, in darker spots, but we have to hunt for it). The big point here, this stuff is there to see, just look.

But all situations are NOT equal. This is from very close distance, and the direct spill will fall off to become weaker at greater distances (inverse square law), but the bounce light will hold up a little better at distance (in a small room). The point is ... look. And think. This is how we know what the lights are doing. Don't simply just add a huge forward direct spill and think you've done something. Flat frontal light. Direct flash will do that easier.

The size of the bounce card, and its degree of forward spill, is distance dependent. If you use a Large bounce card, probably all you get in small rooms is flat frontal fill, which may overwhelm and cover up all the soft bounce light which you spent flash power to try to get. You can see all of this if you think to look. The trick is each situation is a little different (different subjects), but there are many common situations too (distances). This SB-800 white card effective area above the flash is small, only 2x1.5 inches, and it does a LOT in small rooms. More is often not better, often less is more. But sometimes more is needed. We can watch what happens, and we can know to use different size bounce cards for different situations. But I normally use the small pull out card routinely, except at larger distances. Just watch, and if you don't see soft shadows from the ceiling bounce, you used way too much frontal fill (the bounce is no longer your Main light then). For example, the shadows around the bear's legs are very natural, expected, no problem. The shadows on the rear wall are less natural, less expected, more problem.

Above: Same SB-800 flash is in one white 45 inch reflected umbrella, fabric immediately above internal commander flash, fabric literally touching the top of the camera (same four feet distance), but its size is 40 inches taller. This is not where you would put an umbrella, off camera is a big advantage (see previous example), but I was just trying to match the hot shoe flash pictures here (to show effect of size). The light is very soft. The umbrella is large like the ceiling (large makes soft), and is closer than the ceiling (close makes large, which makes soft). The umbrella is more frontally located than the ceiling, adding good catch lights and no eye socket shadows (umbrella has advantage that you can put it wherever you want to put it). And is almost shadowless behind the bear, without the harsh rear shadow added by bounce card or diffusion dome with bounce flash. The shell, not quite so much, but it is very close to the paper, little room for the fill light to wrap in under it. This is what soft light is. Two umbrellas become a different game of course, and then your ratio can be as shadowless as you wish, if close enough.

The Theory: Both the umbrella and the diffusion dome are "diffusers", scattering the straight flow of light. The dome is only 2 inches wide (tiny, near zero, only 2.4 degrees wide as seen from four feet), so the only direction it can scatter light is outward, so that much of it simply misses the subject all together. The umbrella size is 40 inches (actual) and it is curved to catch and scatter the outer light inwards. It is placed close to the subject, making it be "large" in the face of the subject, 45 degrees large as seen by the subject at four feet. So light is coming from either side of the subject, from their left and from their right, and from top and bottom too. All these multiple paths of light from every which direction fill the shadows from all the other paths, so what we have is self-filling light, which is a very soft light. Large is what makes soft. And close is one factor of what makes large.

This picture of a bear is not important, but looking a minute to understand what the flash is doing is a good skill to polish. It is really not rocket science. It is merely about the size and direction of the light. We can easily see everything that happens. The trick is to look at what you can see. It is like Yogi Berra said, "You can observe a lot just by watching".

bears

These are the same pictures as above, in same order, from Raw, but now all with constant Flash White Balance, and are not individually corrected for color as was done above. The different methods do cause the speedlight flash to operate with differing power levels... close direct flash is minimum power and blue, and ISO 200 f/7 bounce on a ten foot ceiling is maximum power and red (studio flash are often the opposite, a design that becomes red at low power). The various methods and modifiers cause the power difference, but do not cause the color variations directly. The flash power level causes the color. The red pictures simply used more flash power than the blue pictures. Regardless of the modifier, the color will continue to vary with flash power, for example with subject distance and ISO and aperture and ceiling height. The point is, weigh this into your evaluation of these various gadgets. That is, don't confuse color with lighting. Don't attribute the color to the device, because the color will still vary with power level, with the same device.

Note that Auto White Balance does a lot for a hot shoe mounted flash, because the Nikon or Canon system will get relatively accurate color temperature information from the hot shoe mounted flash, and can use that information with Auto White Balance (but not if you specify Flash White Balance, which is a constant).


I wanted to show this one more time. You can do this too, it is a five minute exercise. It is the looking later that takes time. You ought to be able to see the effects of actions that you believe to help, to know why you are doing it. This example is the simplest possible case. Hot shoe flash, just plop the gear out there, and press shutter button.

D300, ISO 400, f/8, 1/200 second. SB-800 hot shoe flash in TTL mode. Subject is at eight feet (80 mm lens DX), and 10 foot ceiling is 7.5 feet above table top. Statue is 14 inches tall, red paper is 22x28 inches, propped up against an empty cardboard box. There is a wall five feet to the right, but I am unable to detect an any effect of the dome "reflecting from all the walls". I do of course see its forward spill.

Bounce requires a lot more power, very near maximum here at f/8. The dome needs even more, and power level changes flash color if not corrected. I used a white card (outside the crop area) to color correct by clicking it. #1 is direct flash, and rather different, but Adobe Raw says it came out 6550K, Tint -4 (blue at low power - 8 feet at f/8 is GN64 at ISO 400, which is GN32 in ISO 100 chart, which at 80mm, shows about 1/32 power level) and its appearance was quite different. The others were bounce, and 4800K, 5050K & 49000K, Tint -12 (reddsh at near full power, before correction). Point is, there are definitely two strong effects here, color and lighting. I did later adjust Raw exposure -0.3 EV on the first one, and +0.6 EV on the last one. Some of that is because TTL metering sees the preflash shadows too.

Direct flash

Bounce flash, alone

Bounce with SB-800 Pullout white bounce card
Fills bounce shadows, adds mild background shadows

Bounce with Nikon diffusion dome
Fills bounce shadows, adds background shadows

To know what we are doing with the flash, we need to learn to look at the shadows, and at the shaded tone gradients we create. I am trying to encourage you to study your pictures, repeatedly (until you are able to see them), to learn what you are doing with the flash. There is no magic, it is all there in front of our face, and we can see it all, if we just look, and see. Since there is more here than many will see, perhaps this animation might help them notice more. Learning to look is the trick of lighting.

1. Direct flash. Black background shadows of course, but it is a flat frontal light. Direct frontal flash uses little power level. Flat frontal does not create shadow tone gradients. It seems hardly recognizable in #1, but that is a small lamb at far right.

2. Bounce flash. Flash head simply aimed up. Softer light from larger ceiling reflection, no black background shadows. But look at tonal range on the subject. Under the man's chin for just one example - shadow tone there shows the shape of the chin. Rest of his face too. Direct flash made it hard to even tell what the little lamb is. Look at the detail, curves and shapes and angles. The shadow tones are what helps to show shape and detail. We try to create those gradient tones (and flat frontal does not).

3. Pullout bounce card added - spills some direct flash forward for fill. Best of all, it adds catch lights to human eyes, to add liveliness, vitality. Card was pulled out about half-way here, and it causes direct flash fill shadows to appear, under mans out-stretched arm, behind lady's head... (but nothing like direct flash alone). Look at how the bounce shadows are filled somewhat, still present, but lighter. Lightening the shadows reduces the contrast, but still tonal gradients remain.

4. Diffusion dome added instead of bounce card - This causes the same effect, the dome just adds forward direct spill, but greater fill level - the bounce shadows we added are almost covered over and gone. The direct background shadows are instead darker, more direct flat fill. Certainly not any softer, that's impossible (soft is NOT anything that tiny domes can do). The dome spills light in all directions, and some notions are that it reflects back from all the room walls, to aid softening. Might happen in very small rooms, but the inverse square law (distance to wall and back to subject, compared to direct subject distance) usually makes this be only wishful thinking. In the pictures above, the dome direct shadow is sharp, darker and not filled by any room walls. What the dome does is shown, direct forward spill. Actually now, the direct light is the main light, and the bounce is filling the dome's shadows. The dome will use more flash power to cause a warmer color cast if not corrected (and we may like that, but there are easier ways we can control better), but any dome is far too tiny to add "softness". Look at your own results, and believe in and plan for what you can actually see happens.

Domes do about the same job, but I like to use the bounce card better. The effect of the card can be adjusted by not pulling it all the way out, or using a different card, and the card obliterates the bounce lighting less, and it does not obstruct the ceiling flash power. A small card is enough, even for photos of a group of people. A large card just becomes brighter flat direct frontal light canceling the bounce effort, but still too small to be soft. The large ceiling bounce light is soft and purposeful, don't obliterate it. You should be able to identify some mild shadow somewhere contributed by the bounce (else what's the point of bounce?).

Copyright © 2009-2016 by Wayne Fulton - All rights are reserved.

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