How to do fill flash with manual flash and manual camera

Discussion in 'Classic Manual Cameras' started by brian_m.|1, Dec 28, 2010.

  1. Say you have a manual film camera(perhaps with internal meter) and a manual non-dedicated thyristor flash. How would you set them up for fill flash? The camera sets itself up for proper ambient exposure but the flash knows nothing about the camera or ambient lighting. How would the thyristor know when to shut the flash off?
  2. The thyristor flash cuts off when its sensor detects enough reflected light from the subject to satisfy the settings on the flash. If you have it set for f/8 and iso 100 it will shut off when the reflected light satisfies that exposure. If the ambient requires f/11 the flash will add a bit of light to the exposure. If the ambient requires f/4 the flash will add LOTS of light to the exposure. Assuming that you are using the correct flash sync speed of course. So, if you set the flash for 1 stop less light than ambient requires you get fill.
  3. Wo,wo,wo..what do you mean by manual camera? Manual focus or manual exposure? Because you're going to have to know the F stop & shutter speed for this work. Second,we need to know more about the flash. Is it's output adjustable (perhaps color coded?) if not you may be at the mercy of distance. You say,"the camera sets itself up for ambient exposure" so I assume you mean manual focus when you refer to a 'manual' camera. At it's most simple,if you're going to use a manual focus camera in it's 'auto' mode with a simple electronic flash (non adjustable output) you're going to need to know the F stop & shutter speed the camera has chosen to make sure that:1.The Shutter speed is at or below the flash sync speed & 2. the F stop chosen by the camera is about 1 stop above (higher number) than F stop listed on the flash at a given distance. Tell us more about your particular equipment foe a better answer.
  4. The non-auto flash doesn't "know" anything, but it does have a guide number. With your camera set at sync shutter speed, all you have to do is to focus to get the distance to subject, apply the guide number to get the needed aperture based on that distance. Now meter the overall scene with the camera's meter to get the exposure you want (forget about the flash for a minute), and set the shutter speed accordingly. If the scene is such that you need a shutter speed which is faster than your camera's sync speed, you can't do fill flash for that scene.
    This is basically all there is to it. The exposure settings will take care of the background, and the flash will fire to take care of the foreground (the subject you set the distance for). This all works because in any overall scene where you would need fill flash, the flash exposure itself is so short that it is almost insignificant compared to the ambient light.
    Of course, just like there is no one exposure for anything, you can vary the power of the flash if you want less, or you can vary the aperture from the guide number requirement if the flash has no way to cut down the power output. A manual flash or an auto flash used in manual mode does not shut the flash off. It just fires at the power that it is. It's all up to aperture and distance.
  5. Dante Stella has written a good tutorial of the subject here:
  6. Pierre, my flash is a Vivitar 550FD. On the flash I have set the film speed to 200. There is a selector which gives me a range of speeds and an f-number. For ISO 200 it is showing f/5.6 for distances between 3-20 ft. I set the camera to shutter priority and set it at 1/60sec. The ambient light is asking for f/11 according to the camera meter. As you can see I am not doing guide numbers as selectors and thyristor are doing it for me, I think. So how do you reconcile the f/5.6 that the flash is asking for and f11 that the camera wants to use?
  7. So how do you reconcile the f/5.6 that the flash is asking for and f11 that the camera wants to use?​
    If the flash thinks the aperture is f5.6 but in reality it is f11 then it will put out a level of light two stops lower than that needed if the flash was the only light source. As there is ambient light as well, the shutter speed is chosen to give full exposure for f11 and the flash provides fill two stops below.
  8. Which camera are you using? More directly, is 1/60 the fastest shutter speed at which your camera is able to sync with the flash?
  9. 1) Find out the Guide number of your flash for ISO 100. Let's say the guide number is 30 (in metres). Make sure your flash has full manual power selected.
    2) Look at the distance to the subject in metres. Divide the guide number by that distance, and set the resulting number as your aperture. Let's say the subject is 4 metres away. Set your aperture to f8 (because it's roughly 30 divided by four).
    3) if you're using an ISO different from ISO 100, adjust your aperture the appropriate number of stops. eg. if you're using ISO 400, then close the aperture down two stops to f16.
    4) since you only want your flash as fill flash not a full exposure, close the aperture down another stop to make the flash underexpose by a stop.
    5) set your shutter speed to correctly expose the ambient light for the aperture you selected above. Err on the side of underexposing very slightly.
    6) if your shutter speed is faster than the fastest sync speed of the camera/flash, then you're in bright sunlight and the subject is too far away for your flash to illuminate in those conditions. Get closer to your subject.
    In practise, once you've got the hang of it, you can shortcut all the above. If you use ISO 100 in bright sunlight and your flash has guide number 30 (in metres) then you know you will always need to use f8 (full exposure) or f 11 (fill flash) for a subject 4 metres away. If your subject comes closer to 2 metres, you will always need to stop down to f16 (full exposure) or f22 (fill flash). A distance in between will be an aperture in between. Once you know that you can forget about doing maths. You can adjust your aperture between these settings quickly and get much more accurate and consistent flash exposures than you'll get with auto flash, and it's very quick. You can set your camera to aperture priority so that the shutter speed looks after itself, just make sure it doesn't wander above the fastest sync speed.
    If you're being forced below the minimum aperture of the lens, then reduce the power of the flash a stop or two and increase the aperture a stop or two.
  10. As far as I know, it's always going to be inconvenient to use any semi-automatic camera mode like shutter or aperture priority when you are using a flash manually. Set the camera to manual exposure if you can. If you use shutter priority, you have to pay attention to the resulting aperture, and vice versa.
    As you described your situation (or as I understand it), your flash is just giving you the aperture you need for the distance with that flash, no different than if you had an older flash with a simple scale kind of thing on the back. In fact, this is exactly the same as using the guide number calculation. It does NOT mean that it's going to shut the flash pulse off at some point.
    Your camera's meter is giving you what it thinks you need for the composition, but it doesn't know anything about what your flash is telling you, or that you are even intending to fire a flash. If you use the meter's f/11 rather than the guide number's f/5.6, it will be the same as dialing in negative flash exposure on an automatic flash, so you may not get enough flash to the subject. How this will affect the flash-filled parts of the picture depends. Presumably, if the subject is in as bright a lighting as the background is, you wouldn't need to use fill flash to begin with. But if it's not as bright, then using f/11 may not brighten it enough. On the other hand, if you use the f/5.6 your flash and distance require, your background may turn out too bright.
    As you can see, this is exactly one of those situations where you can't do what you want at that ISO with your cameras's maximum sync speed. Why? Because you need to get the camera's exposure to f/5.6, which would require a faster shutter speed than what your camera can do -- f/11 is a smaller aperture than 5.6, and so you would need a correspondingly faster shutter speed to maintain the same overall exposure.
    Fill flash outdoors with classic flashes and cameras often required a faster shutter sync speed than is available on the camera. A sync speed of 1/60 is relatively slow as far as fill flash goes, such that you end up needing either a flash with a higher guide number, or a faster film (so you can use a larger aperture). You can think of aperture as being the same thing as flash power.
  11. Pierre, my flash is a Vivitar 550FD. On the flash I have set the film speed to 200. There is a selector which gives me a range of speeds and an f-number. For ISO 200 it is showing f/5.6 for distances between 3-20 ft. I set the camera to shutter priority and set it at 1/60sec. The ambient light is asking for f/11 according to the camera meter. As you can see I am not doing guide numbers as selectors and thyristor are doing it for me, I think. So how do you reconcile the f/5.6 that the flash is asking for and f11 that the camera wants to use?​
    Sorry I hadn't noticed this further info post by the OP. The Vivitar 550FD's guide number is 24 (metres) at ISO 100.
    That means that with flash at full power, at ISO 200, f5.6 would be an appopriate aperture to use for a subject 6 metres away (pretty much the same as the 20 feet that you mentioned). For anything closer than that, it sounds like the auto setting is just reducing the power of the flash. If you had the flash on manual, then you could leave it at full power and reduce the aperture of the lens instead of trusting the camera to reduce the power of the flash. And reducing the aperture of the lens instead of the power of the flash means you can bring your shutter within the maximum sync speed of the camera.
    If your fastest sync speed on your camera is 1/60th of a second, and your camera meter dictates f11 with that in the lighting conditions you had, that means with your flash set to full power you can only photograph subjects a maximum of 3 metres away in those lighting conditions with ISO 200 and the flash set to maximum power. Any further than that and you have to open your aperture to an extent that will bring your shutter speed above the max sync speed, which is no good.
    So, assuming you've left your flash on manual full power, for 3 metres, set your aperture to f11. For a subject 2 metres away, f16. For 1 metre, f32 (or if your lens won't do this, leave the lens at f16 and reduce the power of your flash two stops instead).
    If you had film that was ISO 100, you need to open all those apertures up a stop. If you want to underexpose a stop eg. to get fill flash, close all those apertures down a stop. The shutter speed should just follow the aperture, according to your camera meter. Easiest thing is aperture priority, then you don't have to think about it, except to make sure it doesn't go above the maximum.
  12. Thanks all. Tremendously valuable information. I am using a Yashica FX-103 SLR. The X-sync is 1/100sec. Maybe I should just whip out my EOS 650 with the 430EZ and let them figure it all. Nah!
  13. By the way, I was just answering the basic question without complicating it too much. Of course, with fill flash, you may want to get a stop or so less light from the flash. For both fill flash and bounce flash, it was always a bit of a guessing game with the manual systems -- and of course, unless you were prepared to do some test shots with Polaroid, you might not know how it turned out for days or even weeks.
  14. By "fill flash", I assume you mean what's done in daylight. Here's a quick guide:
  15. Yashica FX-103 SLR. The X-sync is 1/100sec.​
    So, if ISO 200 is your favourite ISO setting, you need to get the following settings in your head (forget shutter speeds just for a moment and leave your flash at full power also for the moment):-
    1 metre = f32
    2 metres = f16
    4 metres = f8
    8 metres = f5.6
    Write them down on a bit of card. Those will be the apertures that give you a full flash exposure for a subject at those distances for ISO 200. If you want a weaker flash effect (eg. a gentle fill flash), close the aperture down a stop from each of those settings.
    Once you've done that, set the corresponding shutter speed that your internal camera meter recommends for that aperture. If you like, just use aperture priority mode on the camera so that the camera takes care of the shutter. Maybe slightly underexpose ever so slightly (half a stop).
    If the corresponding shutter speed for that aperture is above 1/100th of a second in those light conditions, then [your flash is not powerful enough/the subject is too far away] for those ambient light conditions. For example, in bright sunlight, according to the "sunny sixteen rule", in bright sunshine you will have f16 at 1/200th for ISO 200. That means f22 at sync speed of 1/100th, which means your flash will unfortunately reach no further than 1.5 metres (see the table above) before the necessary aperture forces you above the max sync speed. That's the big disadvantage of having a slow max sync speed on that camera.
  16. p.s. I should have said: since you probably don't have f32 on your lens as listed in the table above, the easiest thing to do for a subject at 1 metre is make an exception to using flash at full power and reduce the power of your flash eg. two stops so that you can open up the aperture two stops to f16 instead.
  17. Everybody seems to have their own way of understanding or dealing with fill in flash, as the previous posts show. Here is what I do:
    I have a simple flashgun with a guide number of 28 (100ASA). There is no thyristor control so it's always full output. I know from experience that at 4 paces (3 metres) the correct fill in aperture is f8 so I set the camera at f8. I then set the shutter speed for the background. Hand held, with my SLR I only have a 60th, 30th or maybe 15th to play with (the limits being the synchronisation speed and camera shake). With my leaf shutter camera I can go all the way up to a 500th because it synchronises flash at all shutter speeds.
    Basically the aperture deals with the flash and the shutter speed (for the given aperture) deals with the background.
    If I step in, I decrease the aperture by one stop (and increase the shutter speed by one stop). If I step out 2 steps I increase the aperture by one stop (and decrease the shutter by one stop)...and so on. In this way I maintain the flash/ambient balance.
    It seems laborious but I find it works well. It's best in the evening just before dusk where I take the ambient reading off the clouds or sky. For shutter speeds longer than a 15th I use a tripod. The subject stands out slightly (like they are illuminated from a window) and the clouds/sky are well exposed. There are usually enough shadows around to give the impression that it is evening. I attach a holiday snap taken in this way. My son and I were having a BBQ on my narrowboat. I remember I used a tripod so the exposure must have been slow. While I was fiddling about the seagull swooped and pinched my sausage! How we suffer for out art!
  18. Here is the snap

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