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  1. #1

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    Do I get this? Flash/Ambient balancing

    Hi all, I am planning on using off camera flash with my Pentax 67 and buying a meter that can meter for flash.

    Before I commit I want to check that I understand how to balance ambient and flash light to get a nicely exposed shot...

    So say for example the shot is a person on a background outside.

    I measure the ambient light and it is EV7 so at (for arguments sake) F4 the exposure for zone 5 (average) is 1/60

    I then measure the flash on the subject. Say it measures EV9 so (again for arguments sake) at F4 the exposure for zone 5 (average) is 1/250 (2 stops brighter)

    So to balance I would set my camera to 1/60 then set the aperture to F8 (2 stops less light than F4) to balance the flash. Or Shoot at 1/60, F5.6 to give me 1 stop of separation on my subject.

    Is this correct!??

    Thanks in advance wise men!

    Paul

    Also if you can recommend a cheap meter that will do this then fantastic!
    Speed Graphic, Fuji GX680,Pentax 67, Mamiya RZ67, Mamiya 645 1000s, Nikon F5, Nikon Fm2

  2. #2
    Steve Smith's Avatar
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    Quote Originally Posted by 10speeduk View Post
    I measure the ambient light and it is EV7 so at (for arguments sake) F4 the exposure for zone 5 (average) is 1/60
    As you haven't stated an ISO value, you should use LV rather than EV. EV is purely a function of shutter speed and aperture whereas LV is an actual light level reading. At ISO 100 they are the same numbers.

    I personally do this by setting the camera for the correct ambient exposure then I will us a flash with a built in light sensor such as a Vivitar 285 or 283. The flash will then be put on a setting to give one or two stops less light than needed.

    There are two ways to do this. Either set the ISO on the dial one or two stops lower than the actual film being used or use a setting for an aperture one or two stops more open than actually set on the camera. The Vivitar flash has multiple coloured settings on the dial which make this an easy option. Not all flashes are this versatile.

    Another advantage of the Vivitar is that you can unplug the sensor from the front and connect it with an extension cable so the flash can be away from the camera with the sensor at the camera.

    Quote Originally Posted by 10speeduk View Post
    Thanks in advance wise men!
    The wise men can answer properly now.


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  3. #3

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    You should keep in mind that flash exposure has nothing to do with shutter speed and everything to do with aperture. In complete darkness and a manually set flash, f/4 and 1/2 sec will look the same as f/4 and 1/125 sec. As long as you are at or below your camera's flash sync speed, you can ignore shutter speed for flash. Or to look at it another way, use aperture to control overall exposure, and shutter to control the ambient portion.

    I do a lot of on location strobe work, and I'm mixing strobe and ambient all the time. So here's how I go about it:

    First is conceptual...how do I want my subject to appear against the background? If its at the beach near sunset, I'm probably backlighting them with the ambient and then making up the difference with strobe. If it is at a park or perhaps a leafy background, I'm not trying to fight the ambient on the subject, but just change the direction of the light so that it's more pressing.

    So if I'm at the beach, I put the sun to my subjects back and then ask myself: do I want a bright, overexposed background? And do I want a natural look on my subjects faces? Then I'll want my ambient light *on my subjects* to be either +0 or -1. I'll take an incident meter reading at subject position, pointing back to the camera. Let's say it is ISO 400, f/8 at 1/125. If I want barely noticeable flash and super bright background, I'll set my camera exposure to that. If I want a little less background and a little more drama on the faces, I'll set exposure to -1 using the shutter speed (f/8 and 1/250). Then I'll measure the flash component, and adjust the flash power until it reads f/8.

    If I want total drama, I'll set the ambient on the subjects to be -2 and then set a main light and fill lit. Otherwise IMO the shadows on faces can b a bit severe.

    So it's measure ambient first, decide how you want your subjects represented by the ambient, and then adjust flash to create proper exposure. You have to balance things like your camera sync speed: many SLRs can only sync to 1/250 or less, while leaf shutters can sync at any speed (but are limited to 1/500 or so).

    I suggest checking out the strobist.com site for learning off camera lighting. Having a way of seeing your results instantly is a great way to learn. I will often bring a dslr to check my lighting positions before shooting portraits with flash. I don't use it to meter...that's what meters are for. I use it to make sure the face shadows look right before shooting.

    I use a Minolta flash meter. The "IV" I think. It's cheaper that sekonic, which is the de facto standard..

  4. #4
    RalphLambrecht's Avatar
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    i usually measure the scene and pick an aperture,the flash by itself would dictate. The shutter speed is irrelevant, aperture priority in a way.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  5. #5
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    For the flash measurement, 1/250 is not relevant. A flash meter tells you ONLY the aperture because the flash duration is (much) shorter than your shutter speed; the only constraint being that if your camera has a focal plane shutter you need to stay under the X-sync speed.

    Like Ralph says, you pick an aperture that's "suitable" for your flash, i.e. places the flash exposure at normal, -1 or whatever, and after that, you select the shutter speed to get the lighting ratio you want. Or you pick a shutter speed due to some other constraint (moving subject, whatever), that tells you the aperture and from there you adjust the flash power.

    A common configuration is sun for "normal" exposure and flash at -1 for fill. Say you're shooting ISO100, a likely combination would be f/11 1/200s exposure (sunny-16 light) and the flash with enough power to illuminate f/8, i.e. one stop less than what your aperture is actually set to. If you wanted the flash and sun to be equal, obviously you'd set the flash power to f/11 but it's going to look bright & flat and if you're shooting chromes then you'll actually be a stop overexposed on any part of the scene that is lit by both sun and flash. If you want more DOF (smaller aperture) with the same lighting balance, you need both a longer exposure and more flash power.

    Aperture affects both flash and ambient, shutter affects only ambient. Flash/subject distance also affects flash power via the inverse square law, so a little bit of moving stuff around can go a long way.

  6. #6

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    Quote Originally Posted by 10speeduk View Post
    Hi all, I am planning on using off camera flash with my Pentax 67 and buying a meter that can meter for flash.

    Before I commit I want to check that I understand how to balance ambient and flash light to get a nicely exposed shot...

    So say for example the shot is a person on a background outside.

    I measure the ambient light and it is EV7 so at (for arguments sake) F4 the exposure for zone 5 (average) is 1/60

    I then measure the flash on the subject. Say it measures EV9 so (again for arguments sake) at F4 the exposure for zone 5 (average) is 1/250 (2 stops brighter)

    So to balance I would set my camera to 1/60 then set the aperture to F8 (2 stops less light than F4) to balance the flash. Or Shoot at 1/60, F5.6 to give me 1 stop of separation on my subject.

    Is this correct!??

    Thanks in advance wise men!

    Paul

    Also if you can recommend a cheap meter that will do this then fantastic!
    You are getting some good answers above.
    I just want to point out that the sync speed of a Pentax 67 is 1/30 so it's not the best camera design for mixing flash and ambient, unless you have one of the leaf shutter lenses.

  7. #7

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    When you said the flash meter display EV9 there is some problem with that. I don't know if other meters like the Sekonic would take into account of the shutter speed when it displays
    the EV number or not. I use only Minolta meter and with the flashmeter III when set to EV display mode it display the EV number from f/1.0. So if it displays EV9 it means f/22 regardless of the shutter speed. On the flashmeter VI it switches back to aperture display even if you set the meter on EV display mode when you measure flash.

  8. #8
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    What the meter tells you is what you get on film.

    In your example, EV7 background vs EV9 subject, the subject will be two stops brighter than the background regardless of the camera settings. (I'm going to assume it is an incident style flash meter.)

    If you want the subject and background lighting to be balanced, the meter needs to read the same EV for both. It really is that simple.

    (This is true of all photography regardless of the lighting source or sources; it is the root fact of the Zone System, BTZS, ...)

    Typically in outdoor photography it is impractical to change the lighting on the background. From your example I'll use EV7 and assume that it is fixed there by mother nature. Also from your example I'll assume that f/4 is the aperture you have chosen to get DOF where you want it and that that means 1/60 is the right time to set the camera to expose the background as you specified you want it pegged to Zone V.

    At this point you are done adjusting the camera, end of story.

    The lighting on your subjects face though may meter at EV5, so too dark.

    To get the subject meter reading up to EV7 (the balanced lighting you want), the flash output needs to be adjusted, not the camera settings.

    If the flash on the first try gives you EV9 on your subject, you need to adjust the flash output or move the flash farthur away from the subject and try again.
    Last edited by markbarendt; 09-02-2012 at 09:50 AM. Click to view previous post history.
    Mark Barendt, Beaverton, OR

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  9. #9
    Maris's Avatar
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    Instead of thinking deeply about the problem here's a rote formula I use to get basic 50% fill-flash that works all times all places:

    Incident light flash-meter the subject.
    Note the f-stop reading and set one stop smaller; say for example the flash-meter reading is f8 then set f11 on the lens.
    Then set the shutter speed for correct over-all exposure of the scene at that aperture; for f11 in this example.
    Shoot!

    The result is a correctly exposed over-all scene but the shadows where you originally placed the flash meter are opened nicely from about Zone IV to Zone V, the mid tones move from Zone V to Zone V+1/2, and the higher values scarcely move at all. Most casual viewers accept this photograph as a beautifully lit clear and detailed picture and don't even notice the flash effect.
    Photography, the word itself, invented and defined by its author Sir John.F.W.Herschel, 14 March 1839 at the Royal Society, Somerset House, London. Quote "...Photography or the application of the Chemical rays of light to the purpose of pictorial representation,..". unquote.

  10. #10
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    Quote Originally Posted by 10speeduk View Post
    Hi all, I am planning on using off camera flash with my Pentax 67 and buying a meter that can meter for flash.

    Before I commit I want to check that I understand how to balance ambient and flash light to get a nicely exposed shot...

    So say for example the shot is a person on a background outside.

    I measure the ambient light and it is EV7 so at (for arguments sake) F4 the exposure for zone 5 (average) is 1/60

    I then measure the flash on the subject. Say it measures EV9 so (again for arguments sake) at F4 the exposure for zone 5 (average) is 1/250 (2 stops brighter)

    So to balance I would set my camera to 1/60 then set the aperture to F8 (2 stops less light than F4) to balance the flash. Or Shoot at 1/60, F5.6 to give me 1 stop of separation on my subject.

    Is this correct!??

    Thanks in advance wise men!

    Paul

    Also if you can recommend a cheap meter that will do this then fantastic!
    To 'balance' set your shutter and f/stop to the ambient light reading, and dial down the flash power -2EV, and then both sources of light would be same intensity.

    Or you could use f/8 but select 1/15 for shutter speed on ambient, then the ambient intensity equals the flash with no adjustment of flash output at all.

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