Flash pictures in total darkness

[BetterSense]

Assume it's completely dark, and you want to use off-board flash (Nikon SB-28) to light a scene up to take a night picture. You have no way of remote-triggering the flash with the camera except the 'flash' button on the flash. Your camera does not have auto-exposure, but you know your film speed. You intend to lock the shutter of the camera open and use the entire flash output to expose the film.

Is there some way to quantify the total output of a flash, so that you can get a grip on what flash settings, even how many flashes may be required to expose the film properly?

 

[MattKing]

Determine the Guide Number of the flash, for the film you are using.

Measure the distance between the flash and your subject.

Divide the distance into the guide number - that will get the f/stop to set on your camera.

Bracket a bit. If you are working outside or in a very large room with high ceilings, you wont have the benefi of much reflected light, so a bit more exposure may be necessary.

If you need a smaller aperture, you can use multiple flashes.

If your flash has an onboard sensor, you may be able to do this with the flash's automatic function. You can, however end up with too much exposure, if your subject only fills part of the scene.

Matt

 

[Ian Cooper]

As Matt posted, use of the flash's guide number is the only 'paper' way of going about it. Unfortunately some manufacturers seem to allocate their flash guide numbers on the basis of the flash being used inside a small white matchbox. If you try using the flash in an environment where there isn't any bounced light (eg. outside) then the guide number can work out quite a bit less - you may get away with it using negative film, but reversal isn't as accomodating! :rolleyes:

Personally I tend to use a flash meter to check what the actually output of my flash is. Firing the flash multiple times at the same spot can be used to give extra exposure, but soon gets tiring: Firing twice to gain a stop is no problem, but firing four times to gain two stops starts to get beyond a joke if you're lighting a large area!

I've got numerous examples of the technique hiding on Dead Link Removed:

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Both on the surface, such as the examples above...

...or underground such as the examples below:

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...and yes, my apperance in the far distance was intentional! This photo required firing the flash about 45 times. On each occasion the flash was illuminating a slightly different section of the photo - you can see why trying to gain 2 stops exposure by firing x4 times at the same area soon gets impractical with a flash recycle time of about 8 seconds!

In both of these examples I've been standing actually in the frame to fire the flash - but with a little care I don't appear on the final photo:

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If I might make a suggestion, it can be a good idea to place a lit night-light type candle on the ground just behind your tripod - it might be embarassing to walk into the camera whilst returning to it to close the shutter in total darkness! The small spot of light by the camera can also be of use when you're 'in the frame' and need to check exactly where the camera is located.


Regards,
Ian.

 

[Steve Roberts]

Great pictures Ian. I think I recognise Snailbeach Mine but not sure about the others - Box, Wilts perhaps?
I can't add anything to what's already been said with the exception that I guess I'd go equipped with armfulls of batteries for the flash, as in the dark/cold I suspect the recycling time would soon get to be rather long.
Steve

 

[Ian Cooper]

Hi Steve,

10/10 on Dead Link Removed:

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The other photos were taken up in Cumbria, the lead mines around Dead Link Removed

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You're right about needing plenty of battery power. I use a Metz 45, but rather than constantly feeding Metz NiCad packs into it or AA Alk. cells, I've made myself a waist mounted high capacity battery pack using 'F' type cells. This gives a 7Ah capacity and will run the flash most of the day before the recycle time starts to slow down.

I started off using Portra 400 negative film, the latitude of that is so wide you can get prints without worrying about getting the exposure spot on. I now use Provia 400 reversal so I can project the results - getting the exposure right is a bit more important these days! :rolleyes:

 

[David A. Goldfarb]

Determine the Guide Number of the flash, for the film you are using.

This is the key thing. You actually need to test it in advance with film. I did this once for every flash head and reflector/diffuser combination I had with my studio strobes before I could afford a flash meter, and I would diagram portrait shoots in advance and determine the exposure, and it was 100% accurate. I still had flexibility in the shoot to move the lights around as long as I kept the flash-to-subject distances the same.

 

[removed-user-1]

Using the guide number is a workable solution, but the name says it all: "guide" number. It's certainly not a direct measurement of watt-seconds. Therefore, getting a flash meter is not a bad idea if you expect to do a lot of this type of work. I have used a Sekonic L-308 for many years. It reads ambient and flash, by reflected or incident measurement, and cost is under US$200 new; you may also find a used one at KEH.

Those pictures of the mines are amazing! There is an old gold mine near Charlotte, NC - Reed Gold Mine, the place where gold was first discovered in North America in 1799. I'm going to have to give this technique a try there if I can get the permission to bring in my RB67 and some lights...

 

[BetterSense]

Wow that's some amazing photagraphing. I didn't know there was such a thing as a flash meter. That's really what I think I need. Besides 35mm I have a pinhole camera and you know how slow those are...I would like to be able to take pictures indoors or when it is dark but I wouldn't begin to know how to get a grips on exposure.

 

[Stephen Frizza]

wow ian you have mastered that! i loved seeing these pics.

 

[Ian Cooper]

Don't be surprised when taking photos outdoors at night if you get local residents wondering what on earth all the bright flashes are - they tend to think you're mad taking photos in the dark!

Even using the flash meter I'll still tend to take two shots with perhaps 3/4 stop exposure difference between them, just in case. Not only does this give a choice of exposure values, it can also allow for messing up by having the flash actually visible in the photo (a danger if you're not using hidden flash locations), ghostly silhouettes (if you stand in the wrong place) or any number of other problems.

Although he doesn't use flash photography, the work of Berthold Steinhilber is certainly impressive. He uses a spot light powered from a car battery to 'paint with light'. His "lightworks" photos around the mining ghost towns of the US are amazing. Although I have had reasonable success using the techniques he's perfected, I generally find using a flash gun easier. If you want to capture the dark blue skies of evening then you only get one opportunity per day to take a photo!

One final thought, depending how trustworthy you are it might be worth taking a 'helper' along to sit by the camera - you can potentially be walking off and leaving it unattended in the dark for a reasonable period of time. Not only would it be a shame to return to find some low life has walked off with the camera , having a helper on hand also means when you've finished you can shout to them to close the shutter or put a lens cap on, thus saving you walking back to the camera without shining a torch towards it!

Best of luck!

 

[keithwms]

Yeah a flash meter is pretty useful, I use a gossen digipro.

 

[archphoto]

Ian, absolutely great photo's !!

 

[pgomena]

A flash meter is handy, but photographing outdoors in the dark requires testing. Establishing the guide number for you flash is as important as establishing a personal exposure index for any film used in daylight.

It is very easy to do. You will need an assistant and a 10-foot tape measure.

Set up outdoors in full darkness, well away from reflective surfaces. Think large parking lot or ball field.

1. Set up camera, use ISO 100 transparency film.
2. Set up flash directly over camera lens axis. You want on-axis light for the test, even if you will not be shooting on-axis later.
3. Set flash for full "manual" power.
4. Measure exactly 10 feet from flash and have assistant stand there, facing camera. Nice bonus to have him/her hold an 18% gray card. Assistant should not be wearing dark clothes or anything that is highly reflective (i.e. safety vest or jogging clothes with reflective strips)
5. Run a wide bracket of exposures changing only aperture. Write down aperture setting for each frame.
6. Process film normally.
7. Choose best exposure. Note aperture for that exposure.
8. Multiply aperture number by 10. This gives you the guide number for your flash. (Best exposure f/8 = guide number 80.)

To use the guide number, divide guide number by distance to subject.(Example: guide number 110, distance from flash to subject 15 feet, aperture setting approximately f/7 or about halfway between f/5.6 and f/8.

This becomes intuitive in no time at all. Testing with transparency film is best because processing is standardized and film latitude is fairly narrow. It's easy to pick the best exposure. Never trust a manufacturer's guide number. You have no idea of their testing standards, and it likely is overly optimistic.

Peter Gomena (Vivitar 283 flash, G.N. 80)

 

[Nick Zentena]

I didn't see it mentioned. Does your flash have a manual mode? If it's auto only that will bring it's own problems.

 

[MattKing]

Assumptions are funny.

When I made my initial post, I just assumed that you didn't have access to a flash meter.

If you have one, a flash meter is definitely the most straightforward approach.

Matt

 

[Ian Cooper]

I would just clarify that although I use a flash meter, not all the positions are metered.

I'll sort out the position of the main light and take a couple of meter readings of the light falling on the subject. I'll then pace out the distance from the flash to the subject and thereafter ensure I'm roughly that distance away from whatever I'm pointing the flash at.

If I'm aiming the flash up at the top of trees or buildings then I might fire the flash two or three times to throw a bit more light at the further subjects, if I'm in a restricted place and can't get far enough away, then I might dial down the power on the flash (in which case I'll have probably metered that position in advance to check how far the power needs reducing).

Before opening the shutter I'll have worked out in my mind all the places I'll stand to fire the flash. Much of it is instinct and practice after I've taken the first couple of meter readings as a guide.


If I'm in total darkness then a handful of night-light candles hidden about the place throw just enough light to be able to see where to walk without showing up in the photo (unless you're a really long time, in which case an orange glow starts to form near where the candle is hidden!). It is possible to use a torch to see where you're going, but you have to ensure it only ever points away from the camera! (and look out for anything which might reflect the light straight back to the lens! - mirrors, glass, shiny metal/paint) Likewise, when returning to the camera it is possible to shine a torch in the opposite direction behind you - the dim light generated in the direction you're wanting to walk can be enough to ensure you don't trip over things. It can take 10 minutes or so before your eyes fully adjust to seeing in darkness, but when they do it's amazing just how much light one candle or one LED can actually produce!


Also watch out for any 'ready' lights on the back of the flashgun! A bit of 'duck' tape over them will still let you see a dim glow when they're 'on', but will prevent the camera generating light-trails! A bit of card can also be useful to shield the flash from the camera if you're not using hidden locations - this will block any chinks of light from the side of the flash when you're holding it at an angle (best made the card dull and dark toned - light toned card can act as a reflector and give a faint ghost of your face/hand etc. )

 

[tac]

somewhat off topic; sorry

I like the candle idea, but I always used an assistant with a flashlight- I didn't like being miles down in a mine by myself!

I always thought that learning to shape and use light was much more important than learning the workings of a particular camera.

If you get a flash meter, you don't really *need* a guide number; useful to know, but not absolutely necessary.
If you do use a guide number, be aware that you will get different exposures shooting outside and in an enclosed space; white walls in a small room will bounce light all over the place, whereas black walls (as in an undusted section of a coal mine- we got lots of those here in the wv! or outside at night) will make a lot of that flash output go bye-bye.

Like I said; a flash meter avoids this situation.

You can make lovely "glowing" portraits of people by sitting them in the middle of a small, white-walled room, and firing the flash at the L or R wall, metering from the subject. Try this with just a regular tungsten bulb in one of those shop reflectors, and vary it around a bit to see what kinds of 'looks' you can achieve with different placements of the bulb, further, closer, up, etc.

Good Luck and Have Fun!