Handheld Flash and Exposure with Manual Cameras
I recently got an off-shoe cable for my flash (thanks Paul) and I'm curious to discuss elements of exposure when using a set up like this.
I plan on holding it in left hand, which allows me to focus manually even though the flash is in my hand, and of course exposing with the right hand. I'll be using a pretty basic Canon 155A speedlite on my Canon EF (FD body). It can be set on manual for a GN of 28 ft, or on 2 different AUTO settings with 2 aperture choices, determined by DOF preference and subject distance. Aperture will be manual, and let's assume dark interiors (that is, not fill flash outdoors... yet).
What I'm wondering is the best modus operandi for this kind of shooting. Should I set it on manual and try to think in "GN mode", and can I rely on the auto-exposure eye of the flash anymore?
Furthermore, what are some good exposure guidelines for bounce flash and the positioning of the flash within my reach.
I've always fancied this kind of flash usage, and I think it holds the most promise for getting really unique and striking (re: good) lighting from a flash, and not that deer in the headlights look; more studio.
Also, known work of shooters that use this technique would be cool to share. Bruce Gilden of course pops to mind.
For me, I'm going to be in situations where careful determination of flash exposure is not an option. I want to be able to have a a mental understanding of how best to get in the ballpark of exposure.
Good Evening, Holmburgers,
A lot of light is lost when using bounce-flash. A small flash with a GN of only 28 would be extremely limited in bounce-flash mode; it might be usable if the reflecting surface is white or shiny and very close to the flash.
The eye on the flash reads from whatever it's pointed at and is generally useless for bounce-flash. Some auto-flash units have auxiliary sensors which can be camera-mounted, but I doubt if something as tiny and basic as the 155A allows that option.
I don't know if I understand the first question. When you set the flash on manual, your flash will always flash at full power, i.e. 28. So you entirely rely on the relation:
Originally Posted by holmburgers
GN / distance = aperture
and you have to change aperture "any time" the distance of the main subject changes. There is no automatism working on the flash any more.
The GN works within walls. If you are in the open, you must calculate with a smaller GN (have no idea how smaller). That's because normally the GN is determined by producers by taking into account light bounced by ceiling and walls (by far the most common situation).
If you use the automatic exposure, you can leave the aperture "fixed" so that you can concentrate on focus (and composition etc.) only.
You should obtain the correct exposure provided that:
- Subject distance does not goes out of the distance operating range for that aperture;
- There is nothing in the foreground which is not your subject but that it is conspicuous enough to fool your flash;
- Your subject is big enough (or the flash will expose for the background);
- Your subject is not very dark or very bright (automatism will overexpose the former and underexpose the latter, as usual).
As far as the second par is concerned, I would keep in mind that bounce flash (on ceilings and/or wall you mean?) works well if said ceiling or walls are white, if they are not you are going to have a badly coloured light hitting the subject;
When using bounce flash I would only use autoexposure because GN method would become totally unreliable, unless you can do some test in advance (not very practical especially while using film). But that's me, I use slides. As usual, with negatives one has a certain error margin on the overexposure side so it is possible to be a bit more daring.
Konical is certainly right on that. I don't know your flash. Certain flashes, like mine, have a head (the "torch" proper) that can be tilted upward or sideways while the rest of the flash remains normally vertical and looks toward the subject. With those automatic flashes, you can use autoexposure when using bounced light.
Originally Posted by Konical
If the head cannot be tilted upward or to the side, and you turn the entire flash toward the ceiling or the wall, the cell will meter for the ceiling or floor.
If you keep your flash in your left hand, the cell of the flash must point toward your subject, regardless of how you oriented the torch in order to bounce the light.
For off camera flash, it is important to remember that if you plan on using manual guide numbers to calculate exposure, it is the distance between the flash (not the camera) and the subject that matters.
The 155A doesn't offer tilt or swivel, so if you want to use the auto exposure function, the flash need to point directly at the subject. Bounce isn't really available in auto, although you could use a small amount of diffusion.
I'm assuming that your off camera cord is the special Canon one designed for the flash. If so, IIRC all it really adds to the equation is the fact that setting auto functions on the flash will result in the camera being set to match (or is it vice versa?).
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If the flash head does not have any movement, one could make an upward reflector with some aluminium foil, that you fix with some adhesive tape to the flash. The foil will divert the light toward the ceiling. You should find some illustrations on the internet.
It is important, as said, that the aluminium foil does not cover the cell, so that you can use your flash with automatic exposure. You should choose the wider aperture available in automatic mode, as bouncing is going to absorb a lot of power.
GN 28 in feet = f2.8 @ 10 feet. To use bounce, your distance is 1)flash to ceiling 2)ceiling to subject. With that flash, it's not very far. For manual use it's easiest to test and determine the aperture for a given distance. Make a reference card if you like.
In the auto mode(s) if the subject isn't filling the frame or sensor. and the surrounding area is darkened, the flash will try to illuminate the darkened area. Your subject will be massively overexposed.
If you're using the flash off-camera, but not bounced, using a predetermined exposure will give more consistant results than the auto exposure.
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Are you sure of your guide number?? I think your Canon 155A is a guide number 17 in METERS in manual mode. That would mean about 50 in feet.
Develop, stop, fix.... wait.... where's my film?
Exposure is more simple with flash than it is with ambient light. With ambient light, you are stuck with what is there, and you have to tailor shutter speed and f stop to match what you are given, while still trying to get what you want in terms of D of F and motion stopping. With flash, you have more control. Shutter speed's effect on exposure is negated for the most part, and the flash will always "freeze" your subject by virtue of its short burst of light. On the most basic level, you pick a film, pick an f stop appropriate for the subject's distance and any modifications you have made to the light, and you are done. Add a variable power flash, and you can manipulate your depth of field a bit more; turning down the flash allows you to open up the aperture more.
As for bouncing, I would use a flash meter for some initial experiments, so you can see what effect the bounce has, and then incorporate those changes caused by the bounce into your GN/distance scale calculations.
If you want generally-acceptable results, you can use a TTL flash metering system or an on-flash metering system. But these systems suffer the same inherent flaws as any reflected light meter that is used to measure a broad area to determine exposure. If you want the best possible exposures for each shot, you'll use an incident flash meter and/or distance scales, combined with a knowledge of how certain types of modification effectively cut your flash power.
If you bring a flash meter with you, take a few initial readings in different areas of the location, and simply remember what camera settings to use for which parts of the location, you'll do better than using auto flash IMHO. This is the same thing I do with or without flash at any location, so I do not have the need to meter when shooting. In any location, I will measure the light in three or four likely shooting areas, and just keep the settings in my head. I know if I am in the sun with the subject directly lit, I use such and such setting. I know if I am shooting something that is in the shade, I open up so much. I know if I am shooting something in indirect sun, such as a backlit person, I am going to open up a certain amount from the direct sun setting. I know if I walk indoors and shoot near a window, I use another setting, and if I walk to the middle of the room, I will open up more. Etc.
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Even if not specified, I suppose the GN 28 is indicated in metres. If we exclude in-camera flashes, it is very difficult to find a flash which has a GN less than 14 in metres, that would be around 52 in feet.