Large exterior group shot - manual fill-flash setting?

I'm shooting a big group in a couple of days - family thing - about

20 people. I'm planning to use my Rolleicord 6X6 for obvious

reasons.

 

The shot will be taken outside in the late afternoon. I'll be able

to find a shaded area but am still concerned about losing some face

detail in shadow.

 

I'd like to use my Nikon SB-28 as a fill flash. I'm just not sure

how to set it - 1/2? 1/4? 1/1?

 

I'll meter the ambient light for the exposure - do I need to take a

couple of flashmeter readings, too? Will the flash have much effect

outdoors at a distance of 20-25 ft from the subjects?

 

Any advise out there?

I'd use it at full power and calculate the f-stop based on the guide number of 118 (approx f/11)at 10'.

That's a big question Robert. I'd like to take Maury's idea and run a bit with it. I'm going to break down my attempt to explain this in two pieces. In the first piece I'm going to calculate the flashes contribution to the light hitting your subjects. Once you know how to calculate that, you can then regulate the fill to ambient light ratio to best effect. Assuming you are shooting from 25 feet away and that your flash guide number is indeed 118 @ 100 ISO (at the appropriate zoom setting) then your flash output for ISO 100 film at 25 feet would yield a correct f-stop setting of 118/25 = f 4.72 (between f4 and f5.6). If you were using ISO 400 film, the guide number would be 118 X square root of (400/100) or 118 X 2 = 236, which would result in an f-stop of 9.44 (between f8 and f11). So, if there was no other light source and you set the aperture on the Rollei to f4.7 for 100 speed or f9.4 for 400 speed you'd get perfect exposure at 25 feet. If you set that flash to 1/2 power, you will lose one f-stop of light and will have to open up to f2.8-f4.0 for ISO 100 or f5.6-f8 for ISO 400. At one 1/4 you lose yet one stop more of output, so open up another stop. If I have not totally confused you, you can now calculate the flash output manually.

 

Now that you can determine flash output, you will have to decide how much of that flash light you want to add to the existing natural light. If you are just trying to add a tad of sparkle to the skin and eyes, then you will want the light output of the flash to contribute from about one half to one eigth of that contributed by the ambient light. Let us assume you want a gentle, but not too subtle fill result. This will occur with the flash contributing about 1/4 of the total light (not 1/4 power on flash). Let's assume your old Rollei is mounted on a tripod and you've loaded it with 160 speed portrait print film (fuji NPS or Kodak Portra 160NC, which I expose at 100) and you want to shoot around f8.0. Take a meter reading (incident is best) and find your shutter speed . It may be 1/30 of second for instance at f8 in open shade. If we wanted our flash to match the ambient light, we'd have to get an f8 of output. However we want about a 1/4 contribution so that would be two f-stops less or an f4 output. Let's figure how we have to set the 118 guide number flash to accomplish this. It is not necessary to calculate the ISO 160 guide number, but it would be 118 X SQ ROOT(160/100) or 149. Let's use the 100 guide number at 25 feet and we get a full power output measuring 118/25 = f4.7. So Maury is a pretty savvy guy, because this is really close to the f4 output that we desire. If instead of using f8, you used f5.6 on the Rollei. Now to get 1/4 power you might want to drop your flash to 1/2 power where your output would be f 3.3 . In a nutshell, set your flash output to be between 1 and 2 stops lower than the f-stop you have selected on your camera for the ambient light. If you have a flash meter it is even easier to get it right, but that's for another time. I've already blown too much hot air.

Bob

 

I don't disagree with what has been said, but will just say it another way.

 

Anytime you have a situation where you have more than one light, or even with one light, you have a lighting ratio (i.e. highlights to shadows)

 

you want to determine what ratio you wish to use, depending on what type of materials you are using.

 

Generally speaking, for color negative film, a 3 to 1 or 4 to 1 ratio works well. anything more and you will lose detail on either the high or low end as the paper cannot handle more ratio. there are two ways to speak of ratio. one way is to look at ratio where the fill light hits both the highlight and the shadow side. the other way is to look at ratio where the fill light hits only the shadow side and not the highlight side. when I speak of ratio I mean where the flash hits both sides (as is generally the case when you use fill in flash)

 

take your meter and measure the ambient light on the highlight side (for a family group outside, preferably in open shade meaning no direct sun, but direct open sky, and preferably with the light coming in at an angle that doesn't make the people squint) you can tell when you have perfect light by looking under the chin or closely at the eyes. when these areas have very little shadow you have real good lighting and might not even need fill)

 

anyway, measure on the highlight side, and then on the shadow side. see what your ratio is. for example, you may have f8 at 1/125 on one side and f8 at 1/30 on the other side for a difference of 2 stops, which is 4 to 1 and which may be acceptible, depending on how high in the sky the light is coming from. (generally, the higher the incident light, the more fill you will need to get rid of racoon eyes and deep shadows under the chin. you can tell this by looking at a person closely, and then putting something like a large card over the persons head. if the deep shadows in the eyes disappear when you put the card over the head, then you know you have a little bit too much overhead light which is causing bad shadows in the eyes.

 

anyway, the next step is to set up a flash on the shadow side, and meter it until you get the ratio you desire, again probably looking for a stop between the highlite and the shadow side at the subject.

 

Having said all of that, another general rule is that when you are outside, you must expose for what you cannot control and then control what you can control. by that, I mean that if there is direct sunlight anywhere in your photograph, even if your subject is in shade, you will probably have to expose for the sunlight and bring your subject up to that exposure. that is because if you do not and you print for the subject the sunlit portion of the photo will be so washed out as to look very unprofessional.

 

Don't forget, light is additive, meaning that if you put light all over the subject, you are adding to both the highlite and the shadow side. But so long as you don't go over the capabilities of the paper to handle the ratio you will have achieved the goal of less local contrast in the negative and therefore a more pleasing portrait.

 

Kevin

I didn't read all of the of the previous posts. I'll make it simple: You don't have enough flashpower to do an adequate fill job. You're best bet is to position this entire group with their backs to the sun. Use a tripod and expose them for iso 100 film at f5.6 1/30th if the sky is open and blue. The "hairlight" that the sun produces can blow out their hair, but so what; it will make many of them look "angelic". By exposing just for the natural light, you will have a real looking background with soft detail. If you fill flash, you will in practical fact be darkening the background while you are illuminating their faces. This is because your flash does not reach to the 40-100 feet in back of your subjects. If you want to provide just alittle fill, use a white foamcore board which is medium size of about 4x4 feet. This will not do alot to illuminate them, but it will chase away some of the bluishness in their skin as a result of being exposed to blue sky, and illuminate alittle under their eyes.

 

If you use 400 film, then you have alittle speed to play with and you must change your exposure. Rate it at 250 iso or 320 iso. Use an incident meter. You need at least an f5.6 for sharpness, f6.3 preferred. Use a tripod and a plunger release. Extend the tripod to tall. Shade the lens.

 

Again, do not use much fill power. You will only be creating a black background or thereabouts.

 

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