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Basics of Flash Photography
Four Fundamentals we must know

B&H Photo - Video - Pro Audio

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 (and diffusion domes?)   -   What Hot Shoe Flashes Do

4. Flash photos are Double Exposures

    Menu of the other photo pages here

3.   Soft light

Soft light is created by a relatively large and close light source, like an umbrella or softbox. It is soft because it is large and close. Implementation is easy, just open an umbrella, and place it close.

hard light

Hard Light (small light)

hard light
soft light

Soft Light (large light)

soft light

What is soft light?

On camera frontal light is even (to a fault), and is flat and featureless, uninteresting. Therefore off camera lights are used to cause intentional shadows and shading seen by the lens angle, to show depth and shape on the subject.

The top picture is direct flash, and is a small light, but it is off camera, so its hard shadows still show shape of the subject. Hard light (from the small direct flash, about where the top of the umbrella would be, same angle) causes dark sharp shadows, is more contrasty (note the reflection of "Nikon" on the egg). Hard side light emphasizes details of texture (seeing detail is not always a plus, in skin complexions or wrinkles for example), but soft light has no dark shadows to emphasize surface texture.

The second picture is large soft light, from a large close 45 inch umbrella at about 4.5 feet (shaft is 30 inches long, top of stand is 24 inches from egg). Large and close is the idea (often "close as possible" is the idea). The large wide light still has a direction casting shadows, but its large size is throwing light from many directions to the egg shell, coming from the left of it, and from the right of it, and from above it. All these many light paths fill the shadows caused by all the other light paths. This self filling of shadows makes the shadows dim and indistinct and soft, more just gradient tonal shading than actual shadows (the opposite of dark and sharp-edged and harsh). This is speaking of the shadow ON the subjects surface (we try to prevent shadows behind the subject, greater background separation for example). This automatic fill greatly minimizes the shadows, but the remaining tonal gradient shading is still important to show the shape of the nose and cheeks and chin. The soft light is more smooth and even, vague dim shadows, and like magic, the width of the light tends to wrap around the object(s) instead of causing a sharp terminator edge (like on the moon).

The gradient tonal shading shows the shape of the object (not flat). The first light's harsh dark shadows show shape too (and fill light can help its appearance), so off camera light is better than on camera (flat). We need the gradient shading caused by shadows from off camera lights, but soft is smoother than harsh. One downside of an umbrella - notice the wider stray spill into the room. Two lights in two umbrellas could totally eliminate all trace of shadow (flat again), but we need and seek a little shadow gradient to show sculpted curves of subject. All you have to do to get the soft light is to open the umbrella, and set it near.

What is soft light?   It is light that diffuses the shadows, and wraps around the subject. We like that.

How does it do this?   It does it by the light being LARGE and CLOSE. (this is really the only way)

How does Large and Close do this?   Say it is a four foot light (like a softbox or umbrella) that is say four feet from subject. The subject sees it big and in-their-face, it being around (trig: 2 arc tan(2/4) = ) 53 degrees wide at the subject. This means some light is coming to the subject from 26 degrees on the subjects right, and some light from 26 degrees on their left (and top and bottom too)... because the light is that large and close. There are many paths of light to the subject, from all areas of this large light. All these light paths from the Large source fill the shadows made by all the other paths... resulting very vague soft diffused shadows, actually more just tonal gradients now than shadows, but these tonal gradients show the shape of the curves of the subject (interesting appealing light). Lighting is all about the smooth tonal gradients (which we call soft, obviously softer than harsh hard dark shadows). Learning to look and see this is the difficult part at first, but seeing is what lighting is about, and it is always there to be seen. Beginners just have to learn to look.

All this assumes the light is OFF CAMERA, from an angle, normally maybe 45 degrees wide and high. This side angle intentionally makes shadows which the lens can see from its angle, to add interest and depth. This is the full opposite of flat. However, large and soft makes those shadows very diffuse, gradient tonal shading, pleasing instead of harsh. We like that.

A light ON CAMERA is direct frontal light, making no shadows. It lights everything evenly, no shadows. There may be shadows BEHIND the subject (which we try to prevent), but there is NONE ON THE SUBJECT from flat frontal light. It lights everything the lens can see, from the same angle. There are no shadows to be filled, none which could have made gradient tonal shading, none which could have shown shapes. It is not that it is not soft - frontal flat light is soft by definition, since there are no shadows, and no contrast. But the subject is lighted abysmally flatly (dull, too evenly, 2D, no dimension to it, uninteresting). Whereas, we instead dearly love soft gradient tones ON THE SUBJECT, which shows shapes. Flat light might be a preference for a few things, it is a style, it evenly illuminates things, but there are other choices too, usually considered better.

Diffusion of any small light ON CAMERA (like diffusion domes) can only scatter it, which only makes the light go outward, to now totally MISS the subject (wasted, no longer of any interest to us). It has no width dimension to deflect it inwards, that has no possibility, no meaning. From a small light, the scattered diffused light can only go outward, away from the subject. The more distant the flash, the smaller it is.

Any LARGE light (if close enough) has relatively extreme width (and height, ie, size), enough width to be able to deflect light inwards, to hit the subject from many different angles, mentioned above, filling the shadows from all the other paths. This light is NOT wasted, it is softly lighting the subject. And Close makes it appear larger. The usual rule of thumb for "large enough to be definitely soft" is a size dimension about the same as its distance to the subject (like a four foot light four feet from subject). This is a good goal, but the world will not stop if the distance is a little more (it's always better than if no umbrella). For a reflected umbrella and stand, some cases might be worded "as close as possible", just keeping them out of the camera view.

A Main light ought to be off camera (to intentionally make shadows from a different angle than the frontal lens, so the lens can see those shadows, which adds interest and shows shapes (specifically, to NOT be flat). Maybe it is the sun, but the direct sun is small, only 1/2 degree in size, so it helps to diffuse it through a large white cloth screen, which can then be relatively large and close. Same idea as putting a speedlight in an umbrella, makes it much larger. "Soft" is about "large", and "close" helps it be large.

Diffused main or not, Fill light ought to be frontal, to fill all the same shadows that the lens sees, without making its own shadows. Frontal is flat, and flat is soft, but fill is at very reduced level, a stop or so down, to keep the main light as the primary light with major effect. Fill is not lighting it, the Main is doing that. Fill is just enough to reduce the shadows somewhat (reducing the contrast of this image). We plan to leave tonal gradient evidence of those shadows, that is what lighting is about.

A bare speedlight on camera can be wonderful fill for harsh sunlight main light (see Part 4). It should be reduced level, a stop or two down (a common rule of thumb is around -1.7 stops less than the main light). It should NOT be obvious in the photo that a fill light was used (it should just leave a better result, without making shadows itself), but its dimmer result is extremely helpful (to make the dark shadows lighter, more acceptable contrast).

Bounce flash indoors... the flash may be On Camera, but it is not flat frontal light (see Bounce section). The ceiling is like a large umbrella up there (soft diffused tonal light). Maybe not the most ideal place for it, but the light is portable, and it is natural from above, and is a soft light, and it beats flat direct flash by a mile (bounce also tends to light up the rest of a normal size room). A small bounce card on the flash can provide direct frontal fill (and adds important catch lights in the eyes). However, it should NOT be a big bounce card. It should NOT obliterate all the soft gradient tones of the bounce, with instead only its flat frontal light. What is the point of the bounce then? Bounce should be the main light, should be making shadows still visible, just reduced (tonal gradients). The pullout bounce cards are NOT too small - and then we don't have to pull them all the way out.

Learning to see this gradient tonal shading is what lighting is about. For awhile, beginners may think they look at their lighting, but they do not see, and don't know what they do not see, until they realize what they are looking for (this is classic, we all started there). It is all there to see, and when you learn to look (and think) and see what you are creating, then you know what to do about it.

A large close light source creates soft light, by virtue of appearing large to the subject. Conversely, diffusion domes and bounce cards are tiny devices, too small to be "soft". All they can do is to provide some direct frontal fill when the flash is bounced from the ceiling. The ceiling reflection is large, but both devices are small, direct frontal fill. There is no magic, but it helps to understand what these actually do. The evidence is in the pictures below.

Note one big factor here.... The pictures on this page below are all with the flash off camera, NOT on the hot shoe. One disadvantage of the hot shoe flash is that it is a flat frontal light, with shadows hidden directly behind subject, but often not the best place for the light. With the light off camera (at an angle), it creates visible shadows, for example the shading gradient across the egg below. This shadow shading "shows" the shape of the object, and looks natural, looks good. Whereas a direct flash would just show a flat white oval. However, the off camera flash can cause severe shadows "behind" the subject. One advantage of the hot shoe direct flash 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. The lights on this page are all off camera, specifically to show that shadow. There is a second section on the hot shoe, linked following these red pictures.

SB-800 speedlight flash in one white 45 inch umbrella, shoot-through, fabric 10 inches from the shell (shoot-through this time).

This is a soft light. Very vague dim shadows with indistinct soft edges, very nearly shadowless. The umbrella is a very large "wall of light" seen from only 10 inches away. The light is coming from all directions to the shell, from the left and from the right and from above (see picture at end below), which simply wraps around the subject to fill its own shadows, to create "soft". The idea is Large and Close. Farther away would create darker and more distinct shadows, because the umbrella appears smaller there, with less filling effect. However this shoot-through at ten inches is really too close for many purposes, the Inverse Square Law causes the noticeable light falloff from our right to left (background). The light is large, and a couple of feet is still quite close. A distance approaching the diameter will be acceptable softness, so 40 inches is ideal for sitting portraits, with a 40 inch reflecting umbrella. For a reflective umbrella, this is often about "as close as possible".

A reflective umbrella at a distance roughly same as its diameter (perhaps main light fabric at four feet) is still "close" and will still be "large" and suitably soft for portraits. The standard goal for most portraits is for reflected umbrellas to be "close as possible", to be "large as possible", to be "soft as possible".

Direct flash, at 3 feet from shell (exactly the same flash position, the umbrella was simply removed).

This is NOT a soft light. Sharp-edged distinct dark shadows. Instead of a 45 inch umbrella, this light is a two inch flash head. No large light, no light coming from left or right or all around, no self-filling of shadows. A direct flash is often fine, sometimes ideal, but it is just not soft. Contrasty shadows are good for showing surface detail, whereas soft smooths things over and minimizes blemishes. There are times and places for each method of course. But this case was not one, and closeups of human faces like it softer too.

Any light more distant is relatively smaller, and to the degree possible, even more harsh, less soft. The point being, the speedlight flash head is only about two inches in size, a tiny point source relative to its distance.

Notice how the light in picture 1 wraps around the left end of the egg, and does not in picture 2. And the shell too. Human faces too. This is what soft light is. Here are 100% crops of the egg from these first two pictures, soft and hard eggs. :)

Same direct flash through a plastic Nikon SB-800 diffusion dome (SW-10H), not bounce, flash head still pointed at shell.

The "diffused" light is ever so slightly softer than nothing at this same 3 feet, but certainly not by much. The light is simply not large enough. There will be even less effect when the flash head is farther away than 3 feet, the light source simply appears smaller when farther. Still a sharp-edged distinct hard dark shadow. Perhaps perceptibly different (here at only 3 feet), but pretty much no actual effect. Softening is NOT what domes do. What domes do is to scatter the light, elsewhere in room, not on the subject. Marketing leads us to imagine it bounces on all the walls and comes back, but the Inverse Square Law says this is unlikely, it would be weak compared to the direct forward spill.

Diffusion domes simply don't do much when pointed direct... still only two inches in size. This size is only 6% of the subject distance, here in this very close 3 foot case. Whereas 100% size is a good goal for close work, like a four foot umbrella at four feet.

Choosing a larger dome of 4 or 5 inches size does not change much. We want more like 4 or 5 feet. One rule of thumb is that the light's size and distance should compare to the size of the area in the picture. Which obviously is not always possible, we often must settle for much less, like for groups of people. But ideally, if we are wishing, a great goal is a six foot light six feet away for a six foot tall standing full length portrait. A 45 inch umbrella works fine too, especially with fabric at four feet for a waist up half portrait.

Ceiling bounce plus plastic Nikon SB-800 diffusion dome. This flash was not moved (same shadow), just aimed up to ceiling at about 75 degrees (the upright dome position is an inch or two higher than its light before). The ceiling is large, and it compares to a large umbrella up there. The ceiling is very soft light. The shadow we see here is the SAME, it is the direct forward spill from the dome.

Note that at this close distance, the flat direct flash frontal spill is too much, it has totally obliterated any shadow from the bounce. But the direct shadow is lighter, filled by the bounce.

The only purpose of the diffusion dome or the bounce card is simply to add a direct frontal fill to aid the bounce from the ceiling. The bounce obviously wraps around the shell and the egg well, but the bounce is the fill light for the direct light here. In this case, the frontal fill (at 3 feet) is considerably brighter with darker shadow than the bounce going about 5 feet up and 7 feet back down. These are the factors you need to consider, what the dome does, the tools you work with.

However (tricky point here), the light here is off camera, so the fill is not "frontal" to us this time (next page is a similar comparison for a hot shoe frontal light). This picture is not to take a picture of a shell, but is trying to show the shadow as evidence of what the dome does. The dome on a bounced camera hot shoe flash does provide a direct frontal spill, which is fill. If the flash is directly above the lens, the shadow is directly behind the subject, harder to see, but it is there (sometimes visible, maybe under outstretched arms). But the frontal fill is the effect we seek. This shadow simply shows it exists. You can see it here. This is what domes do. This fill is what we hope they achieve. Diffusion domes do require more flash power for the bounce however.
 
Ceiling bounce plus Nikon SB-800 pullout white bounce card. Same bounce angle to ceiling. The card also aims at subject to add direct frontal fill and highlight (catchlight in human subject's eyes, but on the egg here). We see the same direct shadow as with the dome, they do the same thing (add some direct frontal fill). The dome is a bit more direct forward spill (darker shadow) than the card.

This subject is unusually close for bounce, and both dome and card are excessive forward spill here. Both make the same shadow as direct flash, just not as dark (bounce is filling it), but this close, both still overwhelm the bounce shadows... the dome more than the card. The card still leaves a hint of the bounce shadows. The card could be pushed partially in to be made not as large.

A white 2x3 inch card or paper and a rubber band generally works well as a bounce card, and is the same size as the built-in pull-out card. The "working" or effective area (above the flash head) of this Nikon card is about 1.75 x 1.5 inches WxH. Just don't overdo the size. A larger card may throw a greater distance, but which will cause a darker direct shadow at same distance. A Large card (trying to mimic umbrella size) is only used when bounce is not a factor, maybe outdoors. Indoors, sometimes less is more. We don't want the fill light to obliterate the bounce, and to substitute its own direct shadow. When using hot shoe bounce flash, I usually use this little card for people, even at group distances, believing it helps better than the dome.

These dome or bounce card devices have no magic properties. The photons are still just regular photons. Diffusion just scatters the light, meaning much of it misses the subject now. The only property that can have any effect on the subject is direction, due to the size of the light source, as just described. The ceiling is large, and the ceiling bounce does most of the work. The dome or bounce card simply aims some direct forward spill for fill. Which is a very good thing, but we should not believe in magic photons.

Same ceiling bounce, but no dome and no bounce card (and no fill shadow and no highlight, which they would have added). This background is darkened because it curves up vertical (see bottom setup picture) so the bounce misses it, and there is no fill light to fill it this time. We can see the shadow from the ceiling bounce here, from above, under the shell and egg, and pretty soft, but this is a ten foot ceiling, probably five feet up and seven feet back down, so it is not very close, not like an umbrella could be. Not much of this bounce shadow is left from the close card above, and virtually none of it left from the dome two above. I would not use the card for this, but bounced portraits of humans at seven or eight feet need it, for slight fill in eye sockets and ESPECIALLY for catch lights in the eyes.

In general (for a hot shoe speedlight), the ceiling bounce is what does the work. Bounce is very hard to beat. It is usually as soft as an umbrella, but the shadow comes from above. Umbrellas are easier to aim, and umbrellas are normally closer (giving more effective flash power). But sometimes we must take what we can get. Bounce is free and easy, just point the flash up to a white ceiling. The flash TTL exposure automation still handles it automatically (adjusts flash power level for your aperture setting). Bounce requires a lot of power however, ISO 400 and f/4 is usually a safe starting point for TTL flash.

Bounce creates soft light, but human faces do benefit from slight frontal fill and a catchlight in the eyes. The frontal fill is a good thing in moderation. Did I mention that the catchlight in human eyes is good too? It adds a sparkle, vitality which seems to make the picture more alive.

Two close shoot-through umbrellas, which fill each others shadows. Two umbrellas are much larger than even one umbrella. Same light used as in first picture, with a similar second one now on left side. Of course, this fill is from the left, not from above. This try is very flat even lighting (no shadows) because the two lights are set to be equal intensity at the subject.

Frankly, I dislike this one. Flat and dull, the egg is more two dimensional than round. We need some hint of shadows to sculpt the shapes there. We would normally use some degree of lighting ratio, often with the fill light set one stop weaker, to fill less completely, creating very soft shadows for modeling of the shapes on the subjects face.

I prefer reflected white umbrellas with black covers at every opportunity, but close subjects like this sometimes needs shoot-through to fit into the space available. Here is useful information about mounting hardware to put your speedlights into umbrellas. This is very easy, and umbrellas are very inexpensive, and very satisfying. Umbrellas are Good Stuff.

One point here is that we can see these shadows we are making. We can associate those shadows with the lights we are using. We can think about the shadows we see, and decide if that is the way we want to see it. If we use some special procedure or gadget, we ought to be able to see the actual result of that procedure, to know if it actually does anything or not. Wishful thinking does not always get it done. :)

Make no mistake, the domes and bounce cards do NOT add diffusion. They are far too small to be able to that. Size adds diffusion, and these are only 2 inches in size, and there are no miracles. What they do is to add direct forward fill for bounce. You can see that direct shadow, simply just look at the results. For a hot shoe mounted flash directly above the lens, this direct shadow is behind and below the subject, not often observable. The tiny devices are simply too small to be "soft". The ceiling bounce is large and soft, and is aided by the frontal fill. If overdone, the fill is just a flat direct flash picture, but slight fill for bounce is the goal, and is the way the results should be evaluated.

Do try this at home, to satisfy yourself. The results are easy to judge when you know what effect you are looking for. Everything that counts is all there in our pictures for us to judge, the hard part is that we first have to learn to see it. The idea is to think about what you see actually happening, to understand that the dome or bounce card simply adds direct frontal fill to aid bounce (and adds the catchlight in the eyes). This concept should be conscious in your mind at the time. setup

The setup picture is for the first picture above. The subject is about what the lighting does, and the shell orientation was chosen to be as difficult as possible (that dark rear projection placed in the direct shadow). The light stand was not moved or adjusted for any picture. The flash was pointed up at times, for bounce.

All of the pictures above are manual 1/250 second f/10 ISO 200 with Nikon D300, with the SB-800 flash in CLS Commander/Remote wireless TTL mode. Pretty much point&shoot. This is a 10 foot ceiling 7 feet above the shell. The ten foot ceiling is rather high for f/10, but it worked with a long recycle (f/11 failed very marginally, and fussed about insufficient flash power). I usually shoot bounce at f/5.6 ISO 200 on low ceilings, and f/4 ISO 400 on high ceilings, for lower flash power and faster recycle time.

NOTE: There was some white balance adjustment done on the pictures above, because speedlights are blue at low power and red at full power, and the range here is from minimum to maximum power (3 feet direct to f/10 bounce on 10 foot ceiling). The speedlight flash is necessarily a different color at different power levels, often causing people to confuse this result as a better or worse lighting effect, assuming it is about the little attachment, without realizing it is only about the greater flash power level requirement of the little device. Before correction, the top row below (direct, and direct dome) are close range and low power and cool, and the bottom row (bounce dome, and bounce card) are bounce and high power and warm. We would be wrong to attribute the color to either the dome or the card. The color is due to high power required for the bounce.

More words:

The umbrella is "large" and the bare direct flash is tiny. Placing the light (the umbrella) close to the subject makes it appear even larger to the subject. This is the meaning of "large". A silly picture, but the red and blue lines approximate the angular "size" of the lights as seen by the subject, and indicates the multiple angles at which light is arriving at the subject. Apparent size also depends on distance, and a close light emphasizes the "large" effect. Softness is created by being large. We always want to use umbrellas and softboxes "as close as possible". "Possible" has different meanings for head/shoulder portraits, or full length shots, or group shots, as we must always keep it out of the camera view, but the idea is always "as close as possible". Close creates a "larger" light, and it requires less flash power too. But both large and close are THE very desirable properties which create "soft". This is simply how things work.

The umbrella does require placing the light off camera of course, but which is a very good thing in itself. The light in the hot shoe (near the lens) causes a flat light coming back to the lens, everything is the same. But the subject needs a degree of side lighting to cause shadow variations to show its curves and shape (this effect is called "modeling"). If the flash is on the hot shoe, then the best thing you can do (when possible) is to bounce the light off of the white ceiling (when possible). The reflected light from the ceiling is "off the camera", and the ceiling makes it also be a "large" soft light there. This does require more flash power, as much as ISO 400 and/or f/4 sometimes.

The little plastic diffuser domes or bounce cards for speedlights are NOT large. Their light is not "soft". A two inch flash head is just a tiny point source (one degree at ten feet, two degrees at five feet, larger than the sun, but still very tiny). So regardless if you cover it with plastic or not, the shadows from it will necessarily be dark and harsh. These domes are very marketable, because we imagine them to have magic properties - and for $50, you'd think we ought to get something. :) I'm just saying, don't let your wishful thinking fool the evaluation of your results. Actually look at what you can see happens.

However, they do serve a good advantage when used properly. The way these diffusion dome and bounce card tools actually work is that they are combined with bounce by pointing the flash head towards the ceiling. The light bounced down from that large ceiling is large and therefore is quite soft, if close enough. All the diffuser domes and the white bounce card actually do is to spill a little direct light forward to the subject, providing a bit of fill (like in the eye sockets, etc). This direct forward spill from these also creates a highlight in the eyes, to create sparkle which really helps the picture. These are very good properties, and if you judge your pictures by examining those properties, it will all become much more clear what is happening.

The diffusion dome and bounce card are great tools on the hot shoe (when an umbrella is not possible), but they don't make the light soft. They add a bit of frontal fill. What does most of that work is the ceiling, or a wall, or other large bounce surface. Plan on being very conscious of the ceiling and its effect. Depending on your flashes power, ISO 200 and f/5.6 may or may not work easily on ten foot ceilings and standing subjects. Don't hesitate to use ISO 400 and/or f/4 when needed to be more comfortable, regarding maximum flash power and recycle time. Ceilings in some buildings are simply too high to allow bounce to be useful, and maybe try a wall then, or maybe a panel of white reflective board of some kind. Bounce is a very major tool for flash. Bounce is the very most you can do for a hot shoe mounted flash.

If you think about this little diffusion dome, the most the diffusion can do is to scatter the light into going different directions, meaning much of our flash power entirely misses the subject then. Outdoors, this divergent light would go astray and simply be lost forever. There is no help in that, we simply must use more flash power then. The dome or card is simply too tiny to have a softening effect at any working distance. Indoors, the dome marketing says it bounces from "all the walls", but we ought to consider the inverse square law before we believe that is possible. Indoors in a small room, perhaps the stray light bounces from the near wall, and hopefully a little of that might randomly come back to hit and soften the subject, if the geometry is workable. But it is usually much more dependable to rely on the ceiling. The ceiling is usually white, usually close, usually works. Point your speedlight at the ceiling with the diffusion dome or bounce card, as that ceiling bounce is almost the entire effect (and a very desirable effect). There are larger homemade bounce cards which block all of the overhead light, and attempt to reflect 100% of the flash forward. This reflector can be slightly larger than the flash head, but when the ceiling is available, it really loses out. When we want an umbrella, just use an umbrella. When the flash must be on the hot shoe, I prefer the small regular bounce card myself, less wasted light, and it does essentially the same thing as the plastic dome (direct forward fill plus the catchlight in the eyes). The pictures above show why I usually use the pull-out white card on the Nikon SB-800 flash for hot shoe operation, otherwise umbrellas whenever possible.

The next page shows a second similar photo series, with frontal lighting from the camera hot shoe, which is more how the bounce card or diffusion dome would be used.

Continued

Copyright © 2008-2013 by Wayne Fulton - All rights are reserved.

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