On a 580ex High Speed and Second Curtain are set with successive presses of the same button which has three modes:
• Off (normal single burst sync as sensor is fully exposed)
• High speed FP sync
• Second curtain (single burst while shutter is fully exposed, just before end of the exposure).
Thus it is physically impossible to enable high-speed sync and second curtain sync on the flash at the same time. Secondly, second curtain, like normal sync, because it is a single burst mode and is subject to the same sync speed limit as normal flash.
Second curtain is typically used in situations where where the shutter can be dragged for 1-2 sec., giving a subject moving linearly across the frame time to create the blur trail behind the subject against a sharp background before the shutter freezes the foreground action. The problem with second curtain is the opposite of x-sync: getting long enough shutter times in the range of (1-2 sec. needed) to create the blur. Getting the shutter that slow requires a darken room indoors, or the use of ND filters on the lens.
An alternative to second curtain to achieve a similar illusion of motion in a still photo is panning the camera, which can be done without flash. It is a technique used for photographing fast moving objects like race cars. The difference vs second curtain is that the background is blurred, which is an effective way to isolate the foreground from the background clutter.
If shooting a waiter carrying a tray of food across a crowded room where the context of the background is important then second curtain would be the most effective technique. On the other hand if you wanted to convey the waiter as a cool and calm amidst the chaos of the crowded space you might instead choose to pan the camera, with or without second curtain flash, so the waiter is isolated on a blurred background. Start with the goal for the message of the shot, the then apply the technique most effective at creating the underlying perceptual reaction which will convey it.
Zenon:
With regard to your latest set of tests they all look artificial for two reasons: 1) the foreground is brighter than what would be seen by eye in similar lighting, and 2) the direction of the flash fill is flatter (coming form a lower angle) than the natural lighting.
To get results which appear more natural start with an ambient only shot which is exposed for the background. It will make the foreground darker than perceived by eye because the camera sensor can't handle the contrast, but you will be able to see the pattern the natural fill light from the OVERHEAD skylight. What you then need to do is just add enough flash to bring the shaded side up to the level you perceived by eye (i.e. the baseline for normal) while at the same time retaining the direction of the natural fill from the sky. You need to raise the flash on the camera so its angle is more similar to the downward direction of the sky fill to avoid the flash creating a flat looking foreground.
I did the edit below in Photoshop from your last photo (right) to show how would need to be illuminated with the raised frontal flash to make in more natural; like the ambient only shot fill direction, only brighter to overcome the physical limit of the sensor:
The biggest difference in the edit is the darkening of the gap between the posts which by virtue of the flat near axis lighting sends the clues that the lighting is artificially low, not naturally downward.
Its a matter of developing the ability to see past the physical limits of the camera to pre-visualize the final desired result using the natural fill lighting from the sky as the foundation and augmenting it, not overpowering it, with the flash to the point were what the camera records (and what you can do in Photoshop) matches what was perceived by eye. That's straight out of the Ansel Adams playbook, but with a new twist: using flash, not negative development, to match scene to final image.
That does look better much better. I'm familiar with raisning the flash techinque. How will this look when there is a bride there instead of the piers. How would I meter for skins tones when using fill flash?
I have been finding all types of information on this. No need to answer unless you want to. It is very welcomed. This was not covered in detail in my class. I understand the concept metering for ambient, flash for subject and have done it succesfully but with objects which have more latitude. I want to make sure when people are involved I'm getting the ambient and flash exposures correct.
wickerprints wrote:
...I'm not talking about HSS in that paragraph. I'm talking about SCS, and explaining why it cannot be implemented when the shutter speed is faster than x-sync. In such a case, the second curtain has already begun to close before the first curtain is fully open, which means there is no way to fire the flash once without causing uneven exposure.
The same is true in 1st curtain sync. That's why HSS is needed at high shutter speeds.
wickerprints wrote:
...SCS can only occur slower than x-sync, and would result in uneven exposure when faster than x-sync. The two can't be combined in any meaningful way.
I think the opposite is true.
If HSS worked by using 1st curtain sync, which fires the flash when the 1st curtain is fully open, the second curtain would already have travelled most of the way across the frame, resulting in uneven exposure.
Instead, I think it's more accurate to say that HSS always uses 2nd curtain sync, starting the flash as soon as the 2nd curtain starts to move. As such, it is not neccesary to set 2nd curtain sync manually; thus the same button is used to set either.
Another possibility is that HSS used an entirely different trigger, starting the flash just before the shutter fires, for example. But it definitely couldn't be a true first-curtain sync for the reason I have shown.
Thanks guys, I've been going nuts trying to workout why all of a sudden I haven't be able to obtain HSS all of a sudden (doh).
I'd needed 2nd curtain and simply didin't change back. That's why you can only set either HSS or 2nd curtail on the 580, I would of thought you could have both worlds with the camera mastering the lot but NO.
BrianO wrote:
The same is true in 1st curtain sync. That's why HSS is needed at high shutter speeds.
This is correct. But as FCS is the default flash mode, I did not mention it. The question was whether it was possible to enable HSS + SCS simultaneously.
I think the opposite is true.
If HSS worked by using 1st curtain sync, which fires the flash when the 1st curtain is fully open, the second curtain would already have travelled most of the way across the frame, resulting in uneven exposure.
Instead, I think it's more accurate to say that HSS always uses 2nd curtain sync, starting the flash as soon as the 2nd curtain starts to move. As such, it is not neccesary to set 2nd curtain sync manually; thus the same button is used to set either.
No. HSS fires the flash multiple times. To say this is an instance of SCS is misleading, because SCS and FCS share more in common both in terms of the necessary exposure parameters as well as the resultant effect on exposure, than either of them have in common with HSS.
Another possibility is that HSS used an entirely different trigger, starting the flash just before the shutter fires, for example. But it definitely couldn't be a true first-curtain sync for the reason I have shown.
HSS is neither FCS nor SCS. How can it be compared with either, when HSS fires the flash many times whereas the latter fires the flash only once?
rogie wrote:
YES! i understand this now. ok im home now and threw the 580 on the 1dii and turns out when in second curtain sync, it wont go past max sync speed however with H mode it will. during the hss the second curtain will follow the first while the flash is spitting out multiple pulses to even out the exposure where as with scs, the first curtain fully opens, flash fires and second curtan follows after. limiting this operation to shutter speeds only slower than max sync of the camera...correct?
Correct. The x-sync speed is defined as the fastest shutter speed at which point the first curtain can still be fully opened before the second curtain starts to close. It is related to how fast the shutter assembly can move the curtains. It would take a very special camera indeed to have a vertical focal plane shutter with x-sync at 1/8000 sec--this would require the curtains to travel with a minimum velocity of 192 meters/sec, or 429.5 miles/hour. By contrast, if the x-sync speed is 1/200 sec, the curtains are traveling at just over 10.7 miles/hour--that is still pretty fast for such a small and delicate piece of equipment.
wickerprints wrote:
...HSS is neither FCS nor SCS. How can it be compared with either, when HSS fires the flash many times whereas the latter fires the flash only once?
Actually, it's the flash unit that determines how many times it fires, not the shutter; think for example of stroboscopic mode.
FCS and SCS deal only with what triggers the flash to begin firing, and when it begins doing so; they have nothing to do with how many times the flash fires, , for how long, or how powerfully.
As long as everyone is clear on when HSS starts working, though, we're all good; understanding the concept is more important than the exact terminology. It's just that you were implying that HSS begins when the first curtain is all the way open, which clearly would not work.
rogie wrote:
YES! i understand this now. ...during the hss the second curtain will follow the first while the flash is spitting out multiple pulses to even out the exposure...
This is exactly correct.
Here is a video that explains it perfectly. It's an ad for Pocket Wizards, but the first section explains HSS in general.
Second curtain sync is a single burst protocol, timed to fire just before the second curtain closes.
High Speed FP doesn't use "2nd Curtain sync". High Speed FP starts the flash pulsing before the first curtain opens: that's really the only "sync" involved. The flash becomes a continuous source in the same sense as a fluorescent light. Like a continuous source shutter speed will affect exposure in High Speed FP mode. If shooting in ETTL the flash will compensate. If shooting in M mode on the flash with High Speed FP you'll notice the decrease in exposure as shutter speeds get faster.
High speed sync is similar to the sync used for flash bulbs. Flash bulbs took some time to ignite and ramp up to full intensity and so like High Speed FP sync the trigger signal was sent before slightly before the shutter opened. My first SLR, a Nikon F, has F (flash bulb) and X (electronic flash) settings.
Concidentally the fact High Speed FP Flash starts before the shutter opens can be used with a optically triggered studio flash at speeds above x-sync with very short exposure times. The hot shoe flash starts pulsing just before the shutter opens, firing the long duration studio light, which stays illuminated long enough for a 1/8000th sec. exposure.
BrianO wrote:
Instead, I think it's more accurate to say that HSS always uses 2nd curtain sync, starting the flash as soon as the 2nd curtain starts to move. As such, it is not neccesary to set 2nd curtain sync manually; thus the same button is used to set either.
Another possibility is that HSS used an entirely different trigger, starting the flash just before the shutter fires, for example. But it definitely couldn't be a true first-curtain sync for the reason I have shown.
cgardner wrote:
Second curtain sync is a single burst protocol, timed to fire just before the second curtain closes.
That's odd; I could have sworn that I've used multi-stroboscopic mode and 2nd curtain sync together. I thought the sync signal was a simple "go" signal, and that all control of flash mode, E-TTL metering, etc. went through one of the other contacts. Maybe I'm confused.
BrianO wrote:
As long as everyone is clear on when HSS starts working, though, we're all good; understanding the concept is more important than the exact terminology. It's just that you were implying that HSS begins when the first curtain is all the way open, which clearly would not work.
Did I actually imply such a statement? If so, please direct me to the sentence(s) in which I did so, because I do not recall saying such a thing and cannot find it in any of my posts in this thread.
LIke High Speed FP the Multi mode starts the flash pulsing before the shutter opens. lOn the flash in Multi-mode the HS / >> button to turn on second curtain isn't active. Mode trumps the sync, even when second curtain is set for single burst flash shooting.
BrianO wrote:
That's odd; I could have sworn that I've used multi-stroboscopic mode and 2nd curtain sync together. I thought the sync signal was a simple "go" signal, and that all control of flash mode, E-TTL metering, etc. went through one of the other contacts. Maybe I'm confused.
Zenon Char wrote:
That does look better much better. I'm familiar with raisning the flash techinque. How will this look when there is a bride there instead of the piers. How would I meter for skins tones when using fill flash?
The first thing to realize is that the flash is the frontal KEY light, not the fill. For example in the photo below, taken with a flash + small diffuser on a bracket, it is the flash which is creating the "mask" highlight pattern on the face..
The fill light in that backlight scenario comes from the sky the person is facing, which is usually 3 stop below the sunny side. What the raised flash does is overlap that fill and create the highlight pattern over it. Note the highlights on the tops of the cheeks and chin which create the mask pattern our brains recognize as "normal" because faces are usually illuminated from above as I did with the flash. That is why getting the flash above your subjects on a bracket by 12-18" is a critical element in making flash lit faces look normal and real instead of flat-lit like a deer in the headlights.
So in terms of exposure, you'd expose for the highlights in the white dress and face, keeping them about 1/3 stop below clipping. A situation like that doesn't fit the metering algorithms, and will "fool" the metering. I make my exposure decisions based on the over-exposure warning in the highlights, keep both the ambient background and the flash lit highlights below clipping.
Once you grasp the front flash is "key" light in a backlit situation you should see that lighting a face with flash outdoors is actually identical in terms of goals and flash strategies:
Full face pose: Raised-centered key light (i.e. butterfly pattern)
Oblique pose: Key light light placed 45 degrees from nose on far side (i.e. short lighting)
The only difference outdoors (with the sun at the back as hair light) is that the wrap around fill of the sky assists both the key and fill flashes. As with indoor shooting you will get more flattering results by using two flashes outdoors in an overlapping key over even fill pattern.
As noted above the sky fill is 3 stops below the sunny side. If the "key" flash lifts the highlights on the shaded side of ambient on the bride's dress and face to just below the highlights creating on the edges by by the sun, the non-flash lit parts in front (i.e. the shadows filled by the sky alone) will still be middle gray, 3 stops darker. Some detail in dark areas may be lost.
For more complete control of the frontal lighting on the faces and clothing use two flashes:
When using two flashes outdoors in a centered "butterfly" pattern I put the second off camera flash below the camera like this:
The flash on the bracket acts as Key light creating the highlights, just as with the single flash example above with the slave acting as fill to augment the sky fill. In that configuration the shadows in front get [ sky fill + slave flash fill ] and the highlights get [sky fill + flash fill + master key flash ] as in any key / fill flash situation the key light overlaps the fill to create the ratio. The only difference outdoors vs indoors is that the ambient sky lifts both.
For a short lit oblique pose the role of the flashes changes. The slave moves behind the subject 45 degrees from the nose where it will highlight only the front of the face, leaving the broad side in shadow. If only the sky light was used as fill the shadows on the side of the face would look dark and harsh. To prevent that the Master flash on the bracket is used to augment the sky fill as the foundation for the lighting ratio: the shadows in front get [ sky fill + masster flash fill ] and the highlights get [sky fill + flash fill + slave key flash ].
If you try those dual flash scenarios with direct flash you will be amazed how soft the transitions on the face are. That is the result of God's own soft box - the wrap around fill of the sky, being the foundation for the lighting. The flashes in those configurations don't fight the direct sun in front, they simply augment the soft light from the sky.
Compared to the sky even a 60" umbrella is puny and will not have much effect on the shadows. But where you will notice the difference with diffuser size is in the catchlights of the eyes and hot spots on damp or oily skin. Larger modifiers will create larger more attractive catchlights and less specularity in the skin highlights. As with any lighting scenario how big of a diffuser to use is a balance of logistics and results. If you experiment starting with direct flash, noting the highlights and gradually add larger ones you will likely find you can achieve a good balance of convenience and results with modifiers which are smaller than those typically used indoors where there is no key fill to assist. Also if you use the neutral-fill dual flash configurations I suggest you will find the fill light lightens and 'softens' the shadows and its not necessary to use a huge wrapping key light modifier. Less is more on a windy day outdoors
One final note when shooting outdoors: BRING A LADDER
When a person is facing the sun high in the sky the brow shades the eye sockets and they fall below the range the camera can record. The same thing happens with the sky light when the subject is posed facing the sky. The light from the sky will be shaded by the brow, resulting in eyes which are darker than the cheeks. No matter how much flash you add the eyes will always be darker than the cheeks. The solution to the problem is raising the faces of the subjects up into the light so it reaches the eye sockets. Then the camera position needs to be raised by the same amount to keep the lens above the eye line so the nostrils are hidden from view.
cgardner wrote:
The first thing to realize is that the flash is the frontal KEY light, not the fill. For example in the photo below, taken with a flash + small diffuser on a bracket, it is the flash which is creating the "mask" highlight pattern on the face..
The fill light in that backlight scenario comes from the sky the person is facing, which is usually 3 stop below the sunny side. What the raised flash does is overlap that fill and create the highlight pattern over it. Note the highlights on the tops of the cheeks and chin which create the mask pattern our brains recognize as "normal" because faces are usually illuminated from above as I did with the flash. That is why getting the flash above your subjects on a bracket by 12-18" is a critical element in making flash lit faces look normal and real instead of flat-lit like a deer in the headlights.
So in terms of exposure, you'd expose for the highlights in the white dress and face, keeping them about 1/3 stop below clipping. A situation like that doesn't fit the metering algorithms, and will "fool" the metering. I make my exposure decisions based on the over-exposure warning in the highlights, keep both the ambient background and the flash lit highlights below clipping.
Once you grasp the front flash is "key" light in a backlit situation you should see that lighting a face with flash outdoors is actually identical in terms of goals and flash strategies:
Full face pose: Raised-centered key light (i.e. butterfly pattern)
Oblique pose: Key light light placed 45 degrees from nose on far side (i.e. short lighting)
The only difference outdoors (with the sun at the back as hair light) is that the wrap around fill of the sky assists both the key and fill flashes. As with indoor shooting you will get more flattering results by using two flashes outdoors in an overlapping key over even fill pattern.
As noted above the sky fill is 3 stops below the sunny side. If the "key" flash lifts the highlights on the shaded side of ambient on the bride's dress and face to just below the highlights creating on the edges by by the sun, the non-flash lit parts in front (i.e. the shadows filled by the sky alone) will still be middle gray, 3 stops darker. Some detail in dark areas may be lost.
For more complete control of the frontal lighting on the faces and clothing use two flashes:
When using two flashes outdoors in a centered "butterfly" pattern I put the second off camera flash below the camera like this:
The flash on the bracket acts as Key light creating the highlights, just as with the single flash example above with the slave acting as fill to augment the sky fill. In that configuration the shadows in front get [ sky fill + slave flash fill ] and the highlights get [sky fill + flash fill + master key flash ] as in any key / fill flash situation the key light overlaps the fill to create the ratio. The only difference outdoors vs indoors is that the ambient sky lifts both.
For a short lit oblique pose the role of the flashes changes. The slave moves behind the subject 45 degrees from the nose where it will highlight only the front of the face, leaving the broad side in shadow. If only the sky light was used as fill the shadows on the side of the face would look dark and harsh. To prevent that the Master flash on the bracket is used to augment the sky fill as the foundation for the lighting ratio: the shadows in front get [ sky fill + masster flash fill ] and the highlights get [sky fill + flash fill + slave key flash ].
If you try those dual flash scenarios with direct flash you will be amazed how soft the transitions on the face are. That is the result of God's own soft box - the wrap around fill of the sky, being the foundation for the lighting. The flashes in those configurations don't fight the direct sun in front, they simply augment the soft light from the sky.
Compared to the sky even a 60" umbrella is puny and will not have much effect on the shadows. But where you will notice the difference with diffuser size is in the catchlights of the eyes and hot spots on damp or oily skin. Larger modifiers will create larger more attractive catchlights and less specularity in the skin highlights. As with any lighting scenario how big of a diffuser to use is a balance of logistics and results. If you experiment starting with direct flash, noting the highlights and gradually add larger ones you will likely find you can achieve a good balance of convenience and results with modifiers which are smaller than those typically used indoors where there is no key fill to assist. Also if you use the neutral-fill dual flash configurations I suggest you will find the fill light lightens and 'softens' the shadows and its not necessary to use a huge wrapping key light modifier. Less is more on a windy day outdoors
One final note when shooting outdoors: BRING A LADDER
When a person is facing the sun high in the sky the brow shades the eye sockets and they fall below the range the camera can record. The same thing happens with the sky light when the subject is posed facing the sky. The light from the sky will be shaded by the brow, resulting in eyes which are darker than the cheeks. No matter how much flash you add the eyes will always be darker than the cheeks. The solution to the problem is raising the faces of the subjects up into the light so it reaches the eye sockets. Then the camera position needs to be raised by the same amount to keep the lens above the eye line so the nostrils are hidden from view.
I seen this image in another post. You also had a fellow with a white towel to avoid clipping. A great technique. I attended a workshop a few years back and they would expose the full frame with white paper. A few weeks ago I would not take my camera of P mode and now I can use it in full manual. I am comfortable indoors and if I had to I could do a simple 3 light studio portrait. I have had fun in room exposing for the window then using the flash to light the room. I seen that being used in church. A great technique.
There has been a lot to absorb in the last 5 weeks. I'm comfortable with flash placement, how to use them, ratios but I have to admit that I'm still having a little trouble with this outdoor concept. I need like a 6 step process. When everyone is talking metering for ambient I assume it is with the flash off. I'm going to have to think quickly as the situation will changing continually. Short, long focal length, vertical, horizontal. Once I get the ambient tuned in then I work the flash. I know this is simple but sometimes you hit these walls as you learn. If you could just in point form list the steps of this process. I'm off to my cottage for 4 days in a few days in a few minutes. No power, no computers. I'm taking a few recommended books with me. I really appreciate your help. It must get frustrating at times.
Here is the course. The last sentence is the link to the outline.
Outdoors the problem is ambient scene range exceeds sensor range resulting in dark mid-tones and loss of shadow detail if highlights are exposed correctly.
The only solution technically to fit scene to sensor is to put the back of the subject to the sun, keeping the front entirely in shade. The important thing to grasp is that the flash you add to the front must be able to INDEPENDENTLY lift the shadow side of the ambient so the HIGHLIGHTS created by the flash over the sky fill look the same as you would perceive the same lighting scenario by eye. You don't want an exact match of flashed highlights to sunny highlights, because by eye you'd perceive the sunny side of the white clothing to be slightly darker. It's not a number matching exercise, but rather finding a balance which overcomes the range limit of the sensor to create something which looks naturally illuminated by sun and sky.
While always putting the back of the subject to the sun might seem to be a rigid rule, the range of outdoor lighting and the limited range of the sensor require it.
Flash assisted shots are often taken with sun hitting the front of the faces. The flash will lift the shadows but it also makes the highlighted parts brighter. Perceptually we react positively to lighter shadows, and accept the lighter highlights, but only up to the point they start to look washed out.
With the back to the sun you light the face just as you would indoors with the sun providing the hair light, controlling the ratio and mood of the lighting on the face with the flash. If you use two flashes for key and fill you can open the shadows, get light in the eyes and retain nice saturated tones in the highlights: total control. the net effect in the photo is similar to what would require four lights indoors: key, fill, hair and background.
1) Adjust Ambient until sunny highlights from the rim light are under clipping with the OEW
2) Set flashes as you would indoors base on the facial angle and desired pattern. If you only have one flash keeping it centered above the lens will mimic the angle of the light from the sky. Raise the face into the sky light to get it in the eyes, raise the camera position, and create the highlight pattern with the flash.
3) Set flash exposure based on the highlights (i.e. white shirt color, or white object held next to the face)
Assume the lighting in that situation will fool the metering so rely instead on your eyes, a reference object like the white towel, and the camera playback clipping warning.
cgardner wrote:
...On the flash in Multi-mode the HS / >> button to turn on second curtain isn't active. Mode trumps the sync, even when second curtain is set for single burst flash shooting.
That seems reasonable. I'll have to do some experimenting.
cgardner wrote:
LIke High Speed FP the Multi mode starts the flash pulsing before the shutter opens.
That's not correct.
For example, I took a shot of a ball rolling across the floor. I set the shutter speed to 2 seconds, and set the Multi-stroboscopic flash mode for 5 flashes at 5 hertz. I could clearly see five sharp images of the ball, along with the ghost of the ball's track. If it had started pulsing before the shutter opened, I would have seen fewer than five balls.
I have an original 580EX, but I think the 580EXII works the same way.
Looks to me like in your first series of shots your exposure was set for the post ( the sky was over exposed) and the flash just added to the post exposure problem. Had your exposure been on the sky the flash probably would have filled the post nicely.
cgardner wrote:
Outdoors the problem is ambient scene range exceeds sensor range resulting in dark mid-tones and loss of shadow detail if highlights are exposed correctly.
The only solution technically to fit scene to sensor is to put the back of the subject to the sun, keeping the front entirely in shade. The important thing to grasp is that the flash you add to the front must be able to INDEPENDENTLY lift the shadow side of the ambient so the HIGHLIGHTS created by the flash over the sky fill look the same as you would perceive the same lighting scenario by eye. You don't want an exact match of flashed highlights to sunny highlights, because by eye you'd perceive the sunny side of the white clothing to be slightly darker. It's not a number matching exercise, but rather finding a balance which overcomes the range limit of the sensor to create something which looks naturally illuminated by sun and sky.
While always putting the back of the subject to the sun might seem to be a rigid rule, the range of outdoor lighting and the limited range of the sensor require it.
Flash assisted shots are often taken with sun hitting the front of the faces. The flash will lift the shadows but it also makes the highlighted parts brighter. Perceptually we react positively to lighter shadows, and accept the lighter highlights, but only up to the point they start to look washed out.
With the back to the sun you light the face just as you would indoors with the sun providing the hair light, controlling the ratio and mood of the lighting on the face with the flash. If you use two flashes for key and fill you can open the shadows, get light in the eyes and retain nice saturated tones in the highlights: total control. the net effect in the photo is similar to what would require four lights indoors: key, fill, hair and background.
1) Adjust Ambient until sunny highlights from the rim light are under clipping with the OEW
2) Set flashes as you would indoors base on the facial angle and desired pattern. If you only have one flash keeping it centered above the lens will mimic the angle of the light from the sky. Raise the face into the sky light to get it in the eyes, raise the camera position, and create the highlight pattern with the flash.
3) Set flash exposure based on the highlights (i.e. white shirt color, or white object held next to the face)
Assume the lighting in that situation will fool the metering so rely instead on your eyes, a reference object like the white towel, and the camera playback clipping warning. ...Show more →
That was very helpful. I did think adjusting ambient for the rim light.
I just read On-Camera Flash Techniques for Digital Wedding and Portrait Photography but Neil van Niekerk on the weekend. A lot of good information. He will use both methods. He may expose of ambient and adjust flash power for the subject or he will meter of the brides dress and then use the flash.
There is one image in his book where the bride is under a tree but behind her there is quite a bit of white behind her where there are no branches. No direct sunlight so no rim light.. He metered the brides dress and set his exposure +0.7 EV. I read in his book that typically for Nikon to get white, white it is +2 and Canon is +1.7 (and then confirm with histogram). I guess he set it at +0.7 because he new the flash would take care of the rest. He had the TTL at -2. He could have used a flash meter but he also stated to make sure that metering does not hamper the flow.
I am going to read that book again and apply what I have learned here. I want to try that butterfly method and I have light stands for that. We will be doing outside formal shots. The groom is a friend and a photographer so we are going to plan this well ahead of time. We will be on at the location several times before the event. I'll have a bit of breathing room time wise.
What really helped me was taking a basic intro to lighting course so now I understand you have to work with both ambient and flash and have some decent results indoors. We did not cover the outdoor stuff that much. Last class is a workshop and I plan to spend some time with the instructors on this.
You hear about people avoiding professional photographers and approaching family members and friends. If only they knew. To them all you are doing is pressing a button.
