Welcome to the forum!

As an adjunct to the Tangents blog, the intention with this forum is to answer any questions, and allow a diverse discussion of topics related photography. With that, see it as an open invitation to just climb in and start threads and to respond to any threads.

How to set flash for fill light only

LoriclappLoriclapp Member
edited October 2013 in flash & lighting
I'm trying to make sense of page 48 of Neil's book. It says...
"if we decided to use manual flash, we'd meter for our manual flash to give us an exposure 2 or 3 stops below what we have set our cameras to for our background. For example, if we had settled on f/4 at 100 ISO, then we'd set our flash so that our flash meter tells us we need an aperture of f/2 (or thereabouts) for a correct exposure."

I just cannot get what he means by setting our flash so the flash meters tells us we need f/2. Can someone explain that to me?

Comments

  • ZenonZenon Member
    edited October 2013
    For example if I want to shoot in the studio at f/8 but the flash meter is telling me f/11, I decrease the flash power, fire the flash, check the meter and repeat until I get f/8. Just do the opposite if you what a shallower DOF.

  • ZenonZenon Member
    edited October 2013
    I guess I should add to that. Flash meters work by inputing ISO and shutter speed that you set on your camera. When your fire the flash it tells you the appropriate aperture. In your case the ambient is f/4 but you want less flash. By "decreasing" flash power the flash meter is telling you to open the aperture to f/2 because there is not enough flash exposure to match the f/4 you selected for a balanced ambient and flash exposure. But you are going to ignore what the flash meter is telling you. By doing that you decrease the flash power in measurable stops so you are not guessing for fill flash exposure.
  • ZenonZenon Member
    edited October 2013
    I keep reading this and I hope it makes sense to you. One last bit. Basically when working in an environment where both ambient and flash are both part of the exposure typically you want to balance them.

    Camera = f/4, 1/160, 400

    Flash meter = 1/160, 400

    You adjust the flash power until it shows f/4 on the flash meter and you have a balanced exposure.

    Next you reduce flash power until the meter shows f/2 but you leave the aperture alone. Now you have less flash power or fill.
  • Here si a good video on balancing ambient and flash.

  • Neil vNNeil vN Administrator
    edited October 2013
    Lori ... you want your flash to be fill-flash. In other words LESS light than proper exposure ... and just enough to lift the shadow details.

    So if f/5.6 is the correct exposure, you'd meter for the flash as if it would be correct at f/2.8
    and that would give you flash at 2 stops under .. which is perfect for fill-flash.

    Follow this article as well:
    http://neilvn.com/tangents/flash-photography-essentials/
  • I think I get it. So I would first meter for ambient. Then I would turn on the flash, and meter with flash, then I adjust the flash until it is 2 stops under ambient? It sounds so simple until I am with a client, and then it all goes right out the window! Lol. Thanks so much for all the help. I have read the book about 4 times, trying to get it all to sink in! I'm not usually this slow, but OCF is just NOT my thing!!
  • Neil vNNeil vN Administrator
    ... or just use TTL flash set to -2 FEC. It should get you there faster, even if less consistent at times (which isn't much of a factor with fill-flash, really.)
  • ZenonZenon Member
    edited October 2013
    Hey people get hung up. It took me a bit of time to piece together the flash and the camera had separate jobs. Went to bed with a few headaches and still stared at the ceiling trying to figure it out.

    Also thinking on your feet is not easy some times. The show is on. You just can't walk away from it for 20 minutes like when you are alone to give the brain a break. It is just experience and one day you will be able to it all while multi tasking.

    ETTL works great and is a good option which I use a lot. I find if I have the time manual flash and my meter is just more consistent.
  • Zenon - that's exactly what I do - lay in bed not sleeping and going through scenarios in my head! Thanks for the encouragement.

    I am really trying to learn to use manual flash. I have always used TTL, and I am not happy with the inconsistencies with it. However, when I'm rushed and can't figure out what I'm doing, I usually go back to TTL!

    Thank you so much for the help!
  • I prefer the non headache way, ttl and -2 fec ha. trying to use manual flash at a wedding would be a complete nightmare for me and probably wouldn't have time and miss the shot(s)
  • Neil... you wrote: So if f/5.6 is the correct exposure, you'd meter for the flash as if it would be correct at f/2
    and that would give you flash at 2 stops under .. which is perfect for fill-flash.

    Did you mean to write f/2.8 is 2 stops under? I thought full stops went from f/5.6 to 4 to 2.8 to 2. Am I getting that right or am I misunderstanding?
  • To remember all the full stop figures you only have to remember 2 numbers PDH7981, (1 and 1.4), all the full f stops are multiples of these numbers.

    1 2 4 8 16 32 65
    1.4 2.8 5.6 11 22 45 90 .........

    f stop = Focal length / diameter of the lens iris.

    e.g. A lens with a focal length of 100mm, with an internal lens iris diameter of of 10mm will produce an aperture of f10.

    Because apertures relate to the area of circle then, (Area = ∏rxr), some of the numbers are rounded off, hence the 2.8, 5.6, 45 & 65 etc.

    You are right though the difference between f2 and f5.6 is 3 stops - a small slip up on Neil's behalf.
    I can forgive him :)
  • Neil vNNeil vN Administrator
    PDH7981 said: Neil... you wrote: So if f/5.6 is the correct exposure, you'd meter for the flash as if it would be correct at f/2
    and that would give you flash at 2 stops under .. which is perfect for fill-flash.

    Did you mean to write f/2.8 is 2 stops under? I thought full stops went from f/5.6 to 4 to 2.8 to 2. Am I getting that right or am I misunderstanding?
    You have it correct. I made a typo which I've corrected now for clarity. Thanks for picking that up!
Sign In or Register to comment.