flash meter, how to use it properly?

Discussion in 'Lighting Equipment' started by maxmalossini, Mar 23, 2005.

  1. I am playing around with flash exposure, flash meter etc. for the
    first time. Subject was myself or a stuffy (?) bear. Even my 5yr-old
    daughter refused to pose! I guess I have to prove that I can take
    good pictures before they (family) model for me!
    To make it simple, I have [at least] two questions:
    1. I set the camera at the value given by my flash meter (minolta
    auto meterIII) and I noticed that several shots were overexposed.
    When I was holding the meter for incident light reading I also
    noticed that it made a difference how I held it (the white dome):
    near the subject and towards the camera? pointed upward? pointed
    towards the light source? I think I am not holding it correctly and I
    probably wasn't consistent while experimenting.
    2. next, I used a main light and also a second light (key 45deg right
    of camera, fill opposite key, in the back of the subject), the
    readings were f16 for the key light and f8 for the second light.
    Bracketing showed that the best exposure was f22. Does it make sense?
    and how do I combine two different values into the final correct
    I will hopefully have some pics to post in the next few days. I know
    that would help if I want specific answers.
    Thank you, Max M
  2. Max-- We need more info on what you mean by "overexposed." Was the side of the subj. lit by the key light the only thing that was too hot? In general, what you want to do is think of the half-globe of the flashmeter like the face of the subject. A good starting orientation is to point it directly at the camera. However, if the difference between the light side and dark side of the subject (contrast ratio) is large, the meter might average the two sides and the hot side will get burnt.

    Also, what kind of flash are you using? Is it an autoflash? Monobloc? What brand? What was it set at? Are you using a zoom lens that might have a variable aperture? Are you using an umbrella? How was it triggered? What brand and make of camera and lens? All these can be have major effects on your results.

    Also, if you keep in mind that combining lights increases the amount of light on the subject, the f16 plus f8 equalling f22 is only about a half-stop or 2/3 stop off.

    I have had to calibrate my meter to my various cameras and lenses. Sometimes it's as much as a full stop different than the settings. This is normal, in my experience, and what most pros have to do to achieve the desired perfection. What I require is consistency, and there the meter does OK. This is what you need to test for. If you consistently get readings that are a half- or full-stop off in the same direction with a particular lens, then you know how to compensate.

    Happy shooting. -BC-
  3. My personal experince has shown the Autometer III to not be as accurate as the Miinolta Flashmeter models. That said, even the best meter may need calibration. The rounded "lumisphere" reads too general a direction for critical exposure readings IMO.
    I find a "lumidisc", (the flat, white receptor) to offer more accurate exposure control. It will read only the intended source when aimed at that source. Getting true control of your lighting and exposure requires being able to understand exactly what's going on in this area.
  4. This is probably obvious, but don't forget to set the meter to the correct ISO setting for your film or digital equivalent.
  5. Bill, thank you. You already answered some of my questions.
    To make it simple, forget about the second light. One light, sb26 through a large scrim (may be too close to the scrim?, but this should only affect harshness of light). One reflector opposite the light and slightly low, pointing up to the subject's shadows. Camera n90s, manual mode, flash in manual mode, at various levels of power such as 1/1, 1/2 down to even 1/32. I left the shutter speed at 1/125 through the entire roll. Flash was set as slave, triggered by a small on camera quantaray with a IR filter (a piece of developed-unexposed E6 (right?). OK, what I see from my prints is that the side where the key light is, is overexposed, very light, almost burnt, lost lots of details of sweater or facial features. The other side, where the reflector was, is actually very well exposed, shadows are not too dark, just at the right point. Lens was a sigma 105 f2.8, then I also used nikon 85f2 with not much different results.
    I think I was may be pointing the dome too much towards the camera, thus hiding some of the flash light, or, like you said, this is just how this combination works, and if it's consistent, I can make appropriate adjustments.
    Just thought about this: the background was pitch black, like I wanted it. May be this has something to do with the problem? But the camera and flash were in manual mode.
  6. My advice will agree with some of the others here and disagree with others. First set the camera ISO and make sure that auto ISO isn't on. Try your main light left of the camera about 4 to 6 feet away high enough to point down on your subject at about 45 degree's. Put your fill light over the top of the camera or just to the right of the camera position. To meter, set the camera's ISO in the meter and with the dome held at your subject point it at your main light and take a reading with your fill light off. Say it's F/11. Turn your fill on then shield the fill light from the main and read the fill. Say it's F/8. Try adjusting you lighting to get these f stop readings. You will combine both readings to get your taking aperture because that's the same light you'll be taking the picture with. The reading should be about F/11 3/4. Try to get the lighting set at the same readings I described for practice and you should get a proper exposure.

    Here's a few site's that explain basic lighting setups.


  7. Whether or not others can make all this clear to you, you'll need to do some extensive tests to make it clear to yourself, and feedback, either by polaroid or by digital.

    There's one thing you should start out with considering, in terms of exposure/frontal lighting, pointing an incident meter directly at a lightsource gives you a reading for that lightsouce, however..........if that lightsource is right over the camera hitting your subject from the front, your reading is going to mean something different than if that same lightsource is off to the side and hitting a subject at a 90 degree angle.

    Put a light right over your camera, put your incident meter right in front of the subjects nose, take a reading, say for instance you get F5.6,.........now move the light from behind the camera to the side so it hits the subject illuminating half the subjects face and leaving the opposite side of the face from the light in shadow,...........again point your meter at the light and take a reading,........you'll again get F5.6, both positions give the same reading if you point the meter at the lightsource at each position, but the lighting isn't the same.

    Direct frontal lighting where you have the lightsource fairly close to the lens axis will basically illumate most everything with a minumum of shadow, when you have this kind of lighting set-up, pointing your meter at the lightsource is the same as pointing it at the lens, the meter reading is pretty much going to reflect the way the scene will look.

    Now with lighting from off camera/off to the side, these lightsources are going to leave more of a shadow, what do you wish to do with the shadows? If you get F5.6 pointing a meter directly a lightsource that has the subject matter in sidelight(half the face lit, half the face dark) and you open up from F5.6 for the side of the face that's in shadow to get detail in those shadows, it's going to eventually burn up the illuminated side of the face.

    If you leave the 'sidelight'(half the face lit, half the face in shadow), at F5.6,..............then set up a softer light over the camera pointing directly at the subject and meter this light until you get F4.0, you'll get detail the shadows from this light, and some spill from this light on the area of the face lit by your 'sidelight' but not enough to where things will look 'burned up'.

    That's one way to do it, but remember when you point your meter away from your lightsource and toward the lens because the lightsource and lens are in two DIFFERENT positions, you're NO LONGER getting an accurate meter reading from that lightsource, you're now getting a compromise reading between that lightsource and a shadow, or in the case of pointing an incided meter BETWEEN TWO LIGHTS, you're getting a compomise reading for both lights.

    You've got to mentally switch gears as to what you're actually doing with your light meter, are you pointing your light meter directly at lightsources, to get an accurate meter reading in relation to their illumination, or are you pointing the meter in some OTHER direction, which is giving you a compromise between that light AND an area in shadow.

    The only way to get a feel for this is for you to do some extensive tests.
  8. Max-- By now you've probably gotten so much information that your brain is on overload. That's normal.

    From your description, it sounds like your scrim may be too close to your subject. Subject placement and angle can play a big part, too. If the light source is very close to the subject, then even an inch or two of lean can drastically alter the exposure locally.

    Sometimes light balance is a touchy thing, and as one respondent says, what you have to do is test and experiment. When I shifted studios recently, I found that some white cabinets on the side of the room were giving me specular hot-spots on some subjects, but it would only happen if I was shooting at very low power with the flashes. It turned out to be my trigger flash (which has since been modified to solve the problem). It's tracking down little things like this that can drive you nuts, and even with all elements being kept as consistent as possible, you can still run into differences that seem unaccountable.

    Your problem would seem to be somewhat more basic, and my guess at this point is, if you're getting the shadows where you want them, it's more a problem of light placement. Upload an image or two so we can see better what you're talking about.

    Or, as one of the photographers I assisted for very early in my career said, "Sometimes the only thing you can do is mess around with it until it works."

    Best of luck, and happy shooting. -BC-

Share This Page