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 p.4 #4 · Fill Flash for Outdoors. Why? It looks bad. | |
Peter Figen wrote:
Just to prove that you can actually shoot in direct sun with no flash and no reflectors, I'm posting this shot of Lyle from 1994, shot on the roof of Westwood Music in L.A. T-Max100 in a Nikon with a 25A Red filter, developed in T-Max developer and drum scanned on a Howtek. No high priced model. Just another real life person.
The DR of the camera is the limiting factor requiring flash. The B&W film you used for that shot had (potentially) twice the range of a digital sensor.
The "magic" of photographic process is that takes no great effort technically to produce a realistic tonal range in a photograph. All you need to do is get both ends exposed with detail and everything in the middle winds up looking "normal" as perceived by eye automatically because the response of the recording medium (it's gamma) is engineered to be similar to that of exponential response of the human eye.
The cones sense color and are located in the center 2° of our visual field. The don't sense RGB they sense yellow/blue and green/magenta. Lab color space coordinates and how RAW files are encoded are base on how the cones see color. The rod cells only react to greenish light. They cover the other 130° or so of the FOV of the eye. They are about 3000x more sensitive than the cone cells (3 x 10^3). That explains both why we can see a transmitted density range of about 3.0 in a transparency and why the Bayer sensor has two green pixels for every blue-red pair: to mimic the eye's greater sensitivity to green.
Why does any of that matter? Because it help to understand why digital sensors can't record things as we see them and why we sometimes need to "fake it" with the assistance of flash to make the photographic rendering look more like the seen by eye impression which in most situations is a full range of detail.
By a happy coincidence (discovered after a few centuries of alchemy and by trail and error) the silver salts used in B&W photographic emulsions happen to have a dynamic range, DlogE and color response characteristics nearly identical to human vision and the combined response of the cone and rod cells of the eye.
Color film and digital sensors can be engineered to match the color response and contrast, but not the dynamic range which is about 1/2 of what the eye can see under average conditions.
http://super.nova.org/MP/EyeSensorContrast.jpg
Where the technical and creative arguments start about flash is when the camera can't handle the scene range in the ambient light. On a clear day the lighting ratio on a sunlit face is about 8:1 because the direct sun is 3 stops brighter than the skylight hitting the shadows. B&W film can handle that 8:1 contrast without flash but color film and digital can't.
Could Peter take that same shot today with a digital camera, and exposed for the same tone on the face in the highlights and get the same results? No. The tone in the highlights would be the same because that was the criteria for exposure, but there would be no detail in the eyes and sky would be much lighter. Why? The camera has a shorter range that would result in loss of detail on both ends of the tonal range.
It's also worth noting that direct sun as "key" lighting on the face also worked in Peter's shot because the goal for the look in the photo wasn't "in your face" eye contact with the viewer, but a more detached reflective mood — the impression of the subject you'd get in person. It's more a what I'd call a "character study" study than a conventional, light up the eyes, portrait.
It would also work OK if he had been shooting Stevie Wonder or Roy Orbison with head raised into the sun. Sun doesn't work well as key light when light is desired in the eyes, not because of the technical issues but because we can't stand and look at the sun without squinting.
Photographers in the 60s who switched from B&W to color had to adapt their shooting techniques to the shorter contrast range of the color negative and print. They adapted to the shorter range the same way the OP suggests here: expose for normal faces and don't worry about anything else.
There's nothing "wrong" with the approach of shooting without flash and exposing for the faces to keep them "normal" looking in any light. Both work well in terms of rendering the face when it facing mostly into sunlight or entirely in shade because sun and skylight both come form overhead and model the 3D shape of the face in a way we recognize. It's comparison from that "baseline" perception of natural lighting that makes flash applied from a lower angle seem fake.
When shooting in sunlight becomes problematical, technically in terms of recording detail, is in cross lighting where a face is partially in sun as "key" light and only the skylight, three stops less bright, is acting as fill. In person we will see about twice as much shadow detail as the camera can record in the shaded eyes so we don't usually notice they are shaded in person. Because the color sensing cones of the eyes only see a FOV this wide
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And the rods on the edges are reacting 3000x more our brains evolved to mentally tune out the periphery of our visual field. It does what your camera in Tv mode does to your camera exposure if you zoom from wide to tight on a backlit face: change the aperture wider to normalize the tone of the face, blowing out the background. We see it but the brain ignores it.
The camera can't selectively filter content like that. We or the auto metering must choose between exposing the face or background correctly. If in Tv mode you were to adjust FEC to correctly expose the highlights in cross lit scene, then zoomed the camera onto a face mostly in the shadows the metering would change the exposure by about 2 stops, making the face normal and blowing the background. The difference? The brain of the viewer will not tune out the overexposed background when it's seen in the photo to the same degree.
The degree to which they will notice it will depend on whether there is important information missing. There's really not problem blowing small highlights or the rendering a plain background like the sky much lighter than normal, but that doesn't work for shots like a bride where viewers expect to see detail in the dress.
If scene range fits sensor range you don't need to worry about things like "will the dress have detail?" when shooting and factor that in to the creative aspects of the shot. In the case of a kid or couple in shade under a tree you don't really give much thought to blowing out the background if there's nothing interesting in it. Faced with that lighting situation without flash my thought process is: I need to expose the faces normally. Where can I find a location where it will not be blown out, blowing in out will not be noticed, or even better blowing it out can be used creatively?
For example with digital if I want a white seamless look outdoors I find a vantage point where the clear cloudless sky surround them knowing exposing for the backlit face without flash will overexpose it by 2-3 stops and make the sky white in the photo. If I wanted a dark sky as in Peter's shot I'd need to expose for detail in the sky then lift the foreground with flash.
How much flash?
Without any flash fill natural lighting on a face has about an 8:1 incident lighting ratio because the sun is 8x brighter (3 stops) than the sky fill. In lighting ratio notation where fill = 1 the sun would be 8 units:
H:S
8:1
What happens if you add flat flash 1/4 the strength of the 8 units of sun?
H:S
8:1
2:2
===
10:3 = 3.3:1 reflected
What happens if you add flat flash half the strength of the 8 units of sun?
H:S
8:1
4:4
===
12:5 = 2.4:1 reflected
What happens if you add flat flash just slightly below the strength of the 8 units of sun?
H:S
8:1
6:6
===
14:7 = 2:1 reflected
What happens when flash equals sun in incident strength?
H:S
8:1
8:8
===
16:9 = 1.7:1 reflected
So technically there's no real problem using the sun as key light and filling with flat even flash just as you would with two flashes indoors. You can, by adjusting fill from 0 to equal to the create lighting ratios from 8:1 to nearly flat, even flatter than in a studio where 2:1 is the lowest possible ratio with two equal sources..
H:S
1:1 Even Fill
1:0 Equal key light
===
2:1 reflected
The difference aesthetically outdoors in terms of how the light models the face is that natural skylight is never "flat" 0° to face fill. It always comes from above and has both a modeling and fill dynamic — the modeling you see on the face in open shade. Seeing a shadow under the chin is natural because it occurs in natural light because the fill comes from above stronger than it does from the sides, unless light colored ground like a sidewalk or beach, or light clothing is reflecting it upwards.
What many don't realize about 0° "neutral" flat fill is that when it does it's job perfectly there's no evidence in the photo it was used. When does it do its job perfectly? When you don't notice any highlights or shadows is creates. It will create shadows but they will fall back and mostly out of sight. The will create highlights, but you will no notice them if they aren't specular and in places you don't normally see them on faces and objects.
To process that idea, that might challenge your assumptions, think about your reaction upon seeing a shot where on-camera flash was used. What clues in the photo told your brain consciously that flash was added? I don't know about you, but for me sharp, hot, specular highlights low on the cheekbones are the "tell tale" clue for me. The problem with 0° flash occur when it creates specular highlights that are noticed.
That's a the small source problem Peter referred to. Small sources create more specularity than large ones. What does the larger source do? Make the reflections less specular and noticed less.
There's an assumption by many that any artificial source near the lens is somehow "bad". But flat fill is only flat on flat objects. On 3D face it creates front > back 3D modeling via inverse-square fall off not sideways shadow pattern typically associated with "good" lighting technique.
What creates the gradient over the cheek towards the ear in an oblique view in a studio lit flash portrait where a fill light is used under the lens isn't just the "wrap" of the key light but rather the fact flash from the fill source falls of 2 stops as the distance is doubled. If you take a face and put a single flash at chin level and move it progressively further away, adjusting exposure for consistent tone on the cheekbones, you will see the ears get progressively lighter in tone because of the inverse-square effect
How does that apply to outdoor shooting with flash? Outdoors the natural light has no inverse-square fall off. An object in sun or open shade is just as bright a 20 feet as is is at 2ft.
Put a face in open shade facing north. Raise the face to get light into the eyes. You'll see 3D modeling, highlights and shadows. It will be very indistinct because there's not much difference between the downward "key" vectors modeling the face and the sideways "fill" vectors providing the fill.
Next add flash on a stand from directly above the camera so it hits he face at a 45° angle. Adjust exposure so the highlights are the same as before flash was added. What will you see? Darker ears. Why? Because the light added with the flash being closer than the atmosphere the skylight is bouncing off falls off faster.
Open shade isn't ideal for portraits an some situations because it is too flat. Adding flash at the same angle it models the face won't change the pattern, it will just change the fall off front > back and make the sides of the face darker than in just the ambient.
After doing that move the flash progressively lower relative to the eyes, from the 45° or so relative to the upturned face that matches the "key" angle of the skylight hitting it until it is just below the lens. You see in cancels out the modeling of the natural light.
Why? Again the ratio math helps to explain the cause and effect. Unlike when adding 0° neutral fill to a sunny 8:1 ratio on the face in open shade the ratio is lower, more on the order of 2:1 before any flash is added. What happens when 1 or 2 units of fill is added over that pattern?
H:S
2:1 natural ratio in open shade
1:1 flash fill added at chin level
===
3:2 = 1.5:1
H:S
2:1 natural ratio in open shade
2:2 flash fill added at chin level
===
4:3 = 1.3:1
The light gets even flatter. What was the difference with the same flash was raised at 45° matching the natural "key" vector?
H:S
2:1 natural ratio in open shade
1:0 flash hitting at 45° downward acts as secondary key light
==
3:1 = 3:1 a very "normal" looking ratio on faces.
The take away from all that technical information you can use creatively?
1) When adding light with flash adding it at 0° will lower the lighting ratio without changing the shape clues the key light is creating if the fill source doesn't create any tell-tale specular reflections. . Flat even fill will change the ratio on a sunny cross lit face from 8:1 to less than 2:1, but it will not make the eye sockets as bright as the cheeks unless the face is looking up and the "sun" key light reached them. Due to the effect of shaded eyes on the emotional reaction of the viewer it's a more effective strategy for action shots where bright light in the eyes isn't important to the message of the photo.
2) Raising the flash off axis vertically will raise the lighting ratio. It will also affect the modeling so the best strategy is to place it at same angle relative to the face as the natural light is hitting creating a double large/small key light effect which is similar to the brighter more collimated center of an umbrella used as key light. This raised single flash strategy works well to overcome the very flat lighting seen in natural open shade and backlight. Even when using a reflector vs. flash in those situations you would want to position it above the head rather than down at eye level so it will act as key and increase the ratio and shadow tone rather than lighten and flatten the lighting ratio.
3) Regardless of were you put the flash a larger source will reduce specular reflections from it that are "tell tales" that it has been used.
If logistical considerations or sloth prevent using large modifiers to eliminate specular reflections on stands a good "Plan B" is to hide them where they will not be noticed by raising the flash, keeping in mind that raising the flash will also increase the lighting ratio.
So if planning to shoot with the sun as key light you'll want to plan to bring along a big SB and keep the fill eye evel and neutral to lower the ratio without any "flashed" clues in the highlights.
If you can't bring along a huge SB or could but don't want to be bothered, then a better strategy all things considered would be to keep the face out of the sun and then use the raised flash strategy to add a bit more "pop" and contrast to the modeling on the face than open shade or backlighting by itself will produce. In that situation the fact the flash created highlights are more specular can work in a positive way to add needed contrast, but they must also fall up on the tops of the cheeks, chin, etc to seem natural.
The shadow clues on a face are directional and if you match the angle of the flash and its shadows to the direction of the shadow the natural light is creating shadows on the face the two will blend seamlessly. You will find that when the flash is raised to put the highlights it creates higher and more similar to natural highlights the shadow also wind up looking more natural also.
It's just a case where the same tool, used different produces a different result. Craftsmanship and technical competence is knowing when and how to use the tool in those different ways when needed to meet goals.
It's not necessary to know how something works to use it effectively and creatively. Sooner or later most photographers will get to the same level of technical competence by trial and error and rejecting techniques what didn't work. I usually understand what I'm doing every step of the way because I try to understand the cause and effects of how the tools I use work before I used them. That's why I do systematic tests with targets. The targets let me see more objectively how each change in technique, such as using a single flash at eye level or 45°, or with a no modifier or a big one affects the outcome.
What actually got me started thinking about the cause and effect of lighting, how it triggers emotion responses and writing tutorials to explain it was looking at shots with on camera flash and thinking, "Why does this look fake?" I never had the problem because from the first day I used a flash it was on a bracket. I've used flash without brackets since and by comparison saw the problems it created, which is way now my speedlight are still on a bracket.
Once you figure out what makes near axis flash look fake on a cause and effect level and know how to prevent it and your use of flash, when needed, will wind up looking "unfake", which is another way of saying natural. When sensor range can't handle scene and you need to know how to fake it with flash so it winds up looking natural and part of that is recording a full range of detail — if that matters to you.
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However - and this isn't a criticism - there just looks to be something 'missing' - after considering it a while the only thing I think that 'missing' thing might be, isn't to add 'fill' which would reduce contrast, (or even give that over flashed look) but quite the opposite, ironically, in view of the situation, I think it needs contrast adding with maybe the addition of a light from where the child is looking towards? An introduction of shadows might be an easier explanation.. and in this case it wouldn't want to be from directly on camera or anywhere near it, or classed as 'fill' as any sort.
did the use of the Red filter work in this instance. It goes back to the mixed light that is in play with respect to the warm vs. cool @ front vs. back of subject.
