Why face camera in incident metering?

Discussion in '35mm Cameras' started by Guest, Mar 24, 2005.

  1. Guest

    Guest Guest

    Why do you have to face the camera from the position of the subject in
    incident metering? you are measuring the light falling on the subject,
    not the light projecting to the camera, no? I can understant why you
    wouldn't have your back to the camera, because then you'd be measuring
    light that is blocked by the subject. Is that the idea then? To
    eliminate light blocked by the subject?
     
    Guest, Mar 24, 2005
    #1
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  2. Guest

    Roger Guest

    With an incident meter the meter reading is taken of the light falling
    on the subject (e.g. the light incident on the subject). Ideally the
    meter reading is taken at the subject position, metering the light
    coming from near or about the camera position. The back of the meter
    faces the subject (face) and the white dome is collecting the incident
    light from all sides (three dimensionally). The person taking the
    reading stands so as not to shadow the white dome of the meter from
    the incident light.

    However you accomplish that, twisting, reaching out away from your
    body, etc. is how you take the reading. Most incident meters have the
    equivalent of a needle lock because for a proper reading the meter is
    often held away from your body. Locking the reading as you reach out
    and then bringing the meter to a position where you can easily read
    the recorded exposure (value).

    I hope that's clear. It's been a long day.

    Regards,
    Roger
     
    Roger, Mar 24, 2005
    #2
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  3. Guest

    Alan Browne Guest

    Incident light readings mean you're measuring the light falling on the
    subject, not the reflection from a subject. Point the dome at the lens
    from that position (or along that axis in the same light) results in a
    setting that always results in a "correct" exposure. (Not counting what
    you want to do specifically to highlights or shaddows).

    The problem with reflected light metering (using the meer in the camera)
    is that the reflected light is always affected by the color of the
    subject. Hence white objects result in underexposure, black in over
    exposure. With an incident reading the exposure is "correct" as it does
    not care about reflectivity of the subject.

    Point your slr at a white, grey and black subject and watch the meter
    readings. They will vary overa 4 or 5 stop range. What's correct?

    In the same light, put a clean, dry styrofoam coffee cup over the lens;
    go to the subject position and point back where the camera will shoot
    from. Take the reading with the cup over the lens. It is the same
    reading as a light meter will give (+/- 1/3 stop).

    Cheers,
    Alan.
     
    Alan Browne, Mar 24, 2005
    #3
  4. Guest

    Matt Clara Guest

    With the dome, stand near your subject and point the dome at the lens to get
    an averaged reading (3d, as you said) of all the light sources emitting
    light which is falling on your subject. With the dome retracted, stand near
    your subject and point the now retracted dome at individual light sources,
    and then average them in your head, or, if you have an nice enough light
    meter, you can use it to store each reading and then average them for you.
    It's not unusual to do this to check individual light sources in studio so
    you can really _think_ about what the light is doing in individual areas on
    your subject instead of just accepting an average of the lights as
    pronounced by your light meter. Of course, the light meter averaged shots
    will be exposed "properly", it's just that individual taste may dictate a
    little more or less exposure depending on the mood/message you're trying to
    convey.

    And yeah, don't block the light you're trying to measure--that's a bad
    idea... ;-)
     
    Matt Clara, Mar 24, 2005
    #4
  5. You've gotten some good answers, but I'd like to offer other information.

    To clear up a possible confusion, _you_ don't face the camera; the dome of
    the meter does. (You may already know this, but other readers of this
    newsgroup may have no clue. Hi, rpd'ers.)

    Generally, with an incident meter, there's a white hemispherical dome over
    the sensor. This dome simulates the subject of the photo. This is fine if,
    say, the subject is the head and shoulders of a person (your model,
    say). The dome then represents all the light falling on your model, in
    three dimensions (well, all the light that your camera will be able to
    see).

    If you have set up lighting on your model, or just posed your model to take
    advantage of existing lighting, putting your meter in the position of the
    model, with the dome pointing to the camera, as is the face of the model,
    gives you an average reading of the light falling on the model's face from
    whatever sources are being considered. This light falling on your model is
    what the camera will "see" and record.

    There is some discussion about pointing the dome at the brightest light if
    using slide film so that highlights are not blown out, but pointing the
    dome at the camera if using print film because of greater latitude. People
    disagree on this; try some exposures yourself and see what works for you --
    remember that the meter is dumb, and you are not. You take a reading and
    then use your judgment whether to make any adjustments to exposure based on
    your experience with the film and the meter. Using your meter reading
    without reflection :-> is tantamount to putting your camera in point-and-
    shoot mode and just clicking away. So take the reading, then think about
    what you're trying to do with this exposure and adjust accordingly.
     
    Phil Stripling, Mar 25, 2005
    #5
  6. Guest

    McLeod Guest

    Or, if you are outdoors and in exactly the same light as your subject,
    you can save yourself some steps and just aim the dome in the
    subject/camera axis to take a reading.
     
    McLeod, Mar 25, 2005
    #6
  7. Guest

    Owamanga Guest

    Having read some of the comments, and not owning a light meter (except
    a prehistoric one that works by magic - no batteries - is missing a
    diffuser dome and has no memory capability), I have some further
    questions:

    Is this method of metering significantly better than a TTL spot meter
    of a properly angled grey-card ? (or is that the point, there is no
    proper angle for the grey-card).

    ...and I guess TTL spot metering a flash-lit subject may get tricky.

    I presume there is some danger of a metering miscalculation with
    incident metering if you have any filters which significantly cut down
    light, something that TTL methods wouldn't suffer.
     
    Owamanga, Mar 25, 2005
    #7
  8. Guest

    Alan Browne Guest

    With a grey card you can angle it to deepen it's shaddows (resulting in
    more exposure) or open it up to the light to cause less exposure.
    Experiment is the word. The dome on the incident meter is an
    (imperfect) analog to a 3D subject but gives a reasonable average. You
    can still meter the light in the shaddows to get some idea of what will
    be on the film.

    In light from behind the camera, regardless of high or low, I just set
    the card perpendicular to the lens axis. One could set it half way
    'tween the light source and the lens axis as well for less exposure.

    In difuse light, card perpendicular to the lens axis is fine.
    It's wholly unreliable as it takes place during the exposure and unless
    you dial in the correct flash-comp according to the color/tone under the
    spot, it will expose according to the subject. Some matrix meters,
    notably the Nikon F5, manage TTL flash exremely well without
    compensation. Distance integrated flash metering (a la Maxxum 5, 7, 7D
    ...) do very well in this regard as well.
    Yes. I measure my filters with my incident meter (remove the dome and
    measure with and without the filter; write the difference in EV on the
    filter box) rather than trust the manufacturer rating. Then I dial in a
    correspondingly lower ISO on the meter when I use the filter. Eg, for
    ISO 100 film, I set ISO 50 on the meter for a 1 EV filter.

    This technique is useless with circ pols however, so if I need to I TTL
    spot off the grey card which is always in my bag when I go out. (It's
    beginning to look a little ratty, actually.

    See my other comments regardign a styrofoam coffee cup over the lens for
    incident metering. It works very well for available light portraits.

    Cheers,
    Alan
     
    Alan Browne, Mar 25, 2005
    #8
  9. Guest

    Bob Hickey Guest

    beauty of a hand held meter is that it forces you to use your head a little.
    There are a million reasons why just about everything won't work, but mostly
    after a while they do. Even something as fool proof as a grey card or a
    white plastic dome, will reflect differently. Sometimes, alkaline batteries
    work, and sometimes only silver. I find that the old Pentaxes have very
    usable meters; so I bought a new one. That thing was all over the road, so
    I just use my antique hand helds again. Every TTL has at least one pattern
    which may or may not change depending on whether you change the shot. Trying
    to figure those patterns out will lead to nothing but a lot of bracketing
    and aggravation. Add a filter or two and maddness is creeping closer. With a
    spot meter, it's so much easier to point it at a picture and decide what you
    want black or white or grey.
    Bob Hickey
     
    Bob Hickey, Mar 26, 2005
    #9
  10. Guest

    Guest Guest

    I think I have been unclear. I'm confused as to why it makes a
    difference that its pointed torwards the camera. If its pointed away
    from the camera, isn't it still measuring the light falling on the
    subject, generally?

    If I'm taking a photo of a friend who is standing in a short distance
    from, say, a wall, and I point my domed meter torwards them, then I get
    the same reading as if they had a meter and were pointing it torwards
    me right? And wouldn't it be the same if they turned around and
    metered with the dome off the wall, short of being in a shadow created
    by the wall no?


    Similarly, given, say, generally undifferentiated lighting, say
    outdoors on a cloudy day in a field, the light falling on me is going
    to be pretty much the same as the light falling on, say, a person at a
    short distance no? So then I can just meter pointing anywhere from my
    own position and get my apetures and speeds from that.
     
    Guest, Mar 27, 2005
    #10
  11. [grinning..] Aww Bob. Now there you go again. Trying to inject a small
    bit of human input into what everyone *knows* is far too complex a task for
    anything other than the latest, greatest, computerized high-tech gadgets.

    When I was younger I played some basketball. Back then I would dribble a
    ball with me everywhere I went. After a while I stopped having to think
    about doing it. It just happened, instinctively and correctly.

    When I was a little older I purchased an apparently now-prehistoric Sekonic
    L-398 Studio Deluxe incident meter. No batteries required. I carried it
    with me everywhere I went. After a while I stopped having to consult it.
    Using my own memory capabilities, I just knew what the ambient light level
    was, instinctively and correctly.

    I still own and use that Paleozoic era meter. And even after these last 230
    million years I can still take it outside on a sunny day, press the button
    and the Sun itself still tells me to expose my ASA 400 film at 1/400 sec at
    f/16. But then, I guess I already knew that...

    Ken
     
    Ken Nadvornick, Mar 27, 2005
    #11
  12. Guest

    Steve Davies Guest

    or ISO 100 at 1/100 ( f16 )
    ISO 200 at 1/200 ( f16 )


    Steve
     
    Steve Davies, Mar 27, 2005
    #12
  13. Guest

    That_Rich Guest

    One vote for the paragraph preceding 'or not'.

    All those other things are great provided one has a concept of
    "composition". Too often lately I see more emphasis on technical crap.

    I remain,

    Full of shrimp stuffed with scallops and parmesan in a paprika
    sauce on a bed of romaine with a *excellent* Pinot Noir.
    Neapolitan pizza to boot.

    Not to mention the beer....
    never forget the beer...

    RP©
     
    That_Rich, Mar 27, 2005
    #13
  14. Guest

    That_Rich Guest


    Yeah but what about the important stuff like in camera sharpening and
    what file format to use, remember to turn on the anti-shake and set
    your auto focus point, pick your exposure sensor, should I use
    matrix.... don't forget the white balance settings... how about
    saturation...

    Geez... I'm becoming Bob Hickey!!

    ;)

    I remain,

    an apprentice curmudgeon,

    RP©
     
    That_Rich, Mar 27, 2005
    #14
  15. Hmm... yeah. I feel your pain... <g>

    Or...

    One could sling a simple manual camera over one's shoulder and just go for a
    walk, spending the time otherwise wasted futzing with the above by simply
    looking at the things one passes...

    Or not...
    We could all do a *lot* worse...

    Ken
     
    Ken Nadvornick, Mar 27, 2005
    #15
  16. Guest

    Bob Hickey Guest

    That's the one I should have gotten, but instead, I got the
    much advanced Seconic Multi-Lumi L-248. Had a battery. Now I'm forced to
    travel in the shadows for fear of being apprehended by the mercury police,
    furtively searching for grey stuff.. Mostly I eyeball the shadows, and use
    the Seconic to check the meters in my ever changing cameras, which I don't
    use anyway. Come to think of it, the only useful advance I can think of is
    multi grade paper. Bob Hickey
     
    Bob Hickey, Mar 27, 2005
    #16
  17. But my cameras meter broke a few years ago about 1986.
    I still get great pictures out of the thing no need to update that thing.
     
    Korbin Dallas, Mar 27, 2005
    #17
  18. Guest

    Owamanga Guest

    The light falling onto the subject coming from all sources in a 180
    degree arc (of both directions, proper mathematical term escapes me at
    the moment) that is centered on the camera (eg, the front of the
    subject as apposed to light coming from the rear or the subject).

    That is, all the light that the subject will be capable of bouncing
    back towards the camera.
    Er, I guess in rare situations it might give the same reading. But
    generally, no. If the light source is behind you for example, then
    expect two entirely different readings.
    If you can guarantee the light is coming equally from all angles, I
    guess this wold work. Rare in most photography - the sun is usually
    one side or other in the sky - even if cloud diffuses it, it won't be
    perfect.

    So, it would seem prudent to face the camera with the meter.
     
    Owamanga, Mar 27, 2005
    #18
  19. Guest

    Andrew Price Guest

    His *real* name is TP ...
     
    Andrew Price, Mar 27, 2005
    #19
  20. Guest

    McLeod Guest

    Not at all. Let's say in your hypothetical situation the sun is
    behind your camera shining on your friend standing in front of the
    wall. If he's holding the meter pointing towards the camera the light
    from the sun is directly striking the dome of the incident meter. If
    he turns around and meters the wall, the dome of the incident meter is
    ionly recieving the light bouncing off the wall. There is going to be
    a big difference between those two readings, since one reading is
    direct light and the other is reading the light that is being diffused
    off the wall.
    If there was a grey card taped to the wall and you took a reflected
    reading off the grey card it should read about the same as an incident
    meter reading with the dome pointed towards the camera.
    If you, at the camera position, are in exactly the same light as your
    subject you should not point the dome at your subject but turn 180
    degrees to the subject/camera axis and take your reading that way.
    "Incident light" is light shining on the scene. "Reflected light" is
    light being reflected off the scene. They are metered two different
    ways. The meter inside your camera is a reflected light meter
    (whether set on spot, centerweighted, matrix, etc.) An incident meter
    usually has a dome that transmits 18 percent of the light. (According
    to Gossen and several other sources...I don't want to argue this point
    again) Most incident meters can be changed to reflected light meters
    by removing the dome.
     
    McLeod, Mar 27, 2005
    #20
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