The point of a light meter?

Discussion in 'Beyond the Basics' started by silversprej, Jul 6, 2008.

  1. silversprej

    silversprej TPF Noob!

    Joined:
    Jun 30, 2008
    Messages:
    33
    Likes Received:
    0
    Location:
    Sweden
    Can others edit my Photos:
    Photos OK to edit
    Hi,

    I recently got a gossen digisix into my posession, and today I tried it out. To my dissapointment it actualy works not nearly as good as the built in meter of my Nikon D200, not even as good as the EOS350D. It seems like it's point-metering, and the overall exposure is just not right. Is there a point using a seperate light meter only if you don't have one built into the camera, or am I doing something wrong?

    I would like to use it with my older analouges, but as it is I don't trust it's result enough.
     
  2. Mike_E

    Mike_E No longer a newbie, moving up!

    Joined:
    Jan 26, 2007
    Messages:
    5,327
    Likes Received:
    264
    Location:
    The Upper West Side of Mississippi (you have no i
    Can others edit my Photos:
    Photos OK to edit
    Have you checked it for calibration?

    Are you pointing it at the sky or have significant portions of the sky in it's view?
     
  3. RyanMillerPhoto

    RyanMillerPhoto TPF Noob!

    Joined:
    Jun 21, 2008
    Messages:
    53
    Likes Received:
    0
    Location:
    Southern California
    Can others edit my Photos:
    Photos OK to edit
    When you click the light meter, are you pointing the dome directly at the camera and the light meter is right at the location of your subject? If you are simply taking taking some wide open shot, a light meter may not help. However, great for a specific subject with constant lighting.
     
  4. silversprej

    silversprej TPF Noob!

    Joined:
    Jun 30, 2008
    Messages:
    33
    Likes Received:
    0
    Location:
    Sweden
    Can others edit my Photos:
    Photos OK to edit
    Thansk for your fast replies!

    @Mike: How am I supposed to calibrate it?

    @Ryan: I was just pointing it at the subject. Am I supposed to point it at the camera? The user manual doesn't say (perhaps they assumed everbody buying it should know :p)

    Still, I wonder abour the metering method that is used. Is it supposed to be better then the built in methods in some way (in what way)?
     
  5. Mike_E

    Mike_E No longer a newbie, moving up!

    Joined:
    Jan 26, 2007
    Messages:
    5,327
    Likes Received:
    264
    Location:
    The Upper West Side of Mississippi (you have no i
    Can others edit my Photos:
    Photos OK to edit
    Grey card just as you would your camera meter.

    For in depth derection you might try google. :)
     
  6. christopher walrath

    christopher walrath No longer a newbie, moving up!

    Joined:
    Mar 19, 2008
    Messages:
    1,265
    Likes Received:
    23
    Location:
    In a darkroom far, far away...
    Can others edit my Photos:
    Photos NOT OK to edit
    It is the same (more or less) as the one in your camera. Just as with any photographic equipment it's a matter of how familiar you are with your gear. I would go to here and see if you can find a manual for this meter and learn how to use it better. Might come in handy someday when you never know when it might come in handy. Yup, no idea where I was going wiht that last one. Anyway, enjoy it.
     
  7. deanimator

    deanimator TPF Noob!

    Joined:
    Jun 1, 2007
    Messages:
    534
    Likes Received:
    0
    Location:
    East Germany
    Can others edit my Photos:
    Photos NOT OK to edit
    If it has a white dome, it is an incident meter ...this means it is measuring light falling on it.
    So, hold the meter directly in front of the thing you want to photograph and point it at your main light source (usually the sun)...NOT at the camera.
     
    Last edited: Jul 6, 2008
  8. Helen B

    Helen B TPF Noob!

    Joined:
    Sep 16, 2007
    Messages:
    3,296
    Likes Received:
    465
    Location:
    Hell's Kitchen, New York
    Can others edit my Photos:
    Photos NOT OK to edit
    The idea of the dome is to measure light from all relevant angles* when the axis of the dome is pointed at the camera and the meter is being used to determine exposure. If the meter is fitted with a flat receptor, or a shrouded dome**, it can be pointed directly at the source to determine the contribution from that source.

    The Digisix has a sliding dome. With the dome slid out of the way it can be used as a wide-area reflective meter - ie you point it at the subject. With the dome in place you position it at the subject and point it at the camera - or use it in an equivalent location and orientation. For example if the subject is in full sun you can place the meter in full sun and point it in the same direction as it would be if it was at the subject pointing at the camera.

    Most scenes have different levels of illumination - for example sun and shade. With slide film and digital cameras it is usually best to expose for the brightest parts of the scene. With an incident meter this means that you use it in the brightest illumination. If you were using negative film you would probably meter in the shade, so that the shadows were correctly exposed. By measuring the difference between the highest and lowest illumination you can estimate the brightness range of the scene - you add five stops to the difference in meter readings.

    That's all a bit condensed, so please ask if you would like anything to be elaborated on.

    *Domes are considered to have a cardioid (heart-shaped) response and they read light arriving from the side and from partly behind - but they have zero response to light from directly behind.

    **Flat receptors and shrouded domes are considered to have a cosine response - they have zero response to light coming from the side and from behind. This is very similar to using a grey card.

    Best,
    Helen
     
  9. tirediron

    tirediron Watch the Birdy! Staff Member Supporting Member

    Joined:
    Jul 8, 2005
    Messages:
    37,345
    Likes Received:
    10,650
    Location:
    Victoria, BC
    Can others edit my Photos:
    Photos OK to edit
    I don't quite understand that. Where and why are you adding five stops?
     
  10. Helen B

    Helen B TPF Noob!

    Joined:
    Sep 16, 2007
    Messages:
    3,296
    Likes Received:
    465
    Location:
    Hell's Kitchen, New York
    Can others edit my Photos:
    Photos NOT OK to edit
    Here's an example from the last architectural shoot I did.

    In full illumination (the sun) I got an incident reading of 1/15 s at f/32 and in the shadiest part of the scene I wanted detail in I got an incident reading of 2 s at the same aperture. That is a five stop difference in illumination level. I add five stops to that to get ten stops, so that suggests that the scene brightness range could be about ten stops. (It wasn't, in this case, for reasons I will explain later)

    Why five stops? That is the maximum likely range of reflectance of the objects in the scene. If everything in the scene was somehow under the same illumination, with no shadows, the scene brightness range would be no more than about five stops.

    What we think of as a bright white object typically has a reflectance of 90%. Very bright objects have a reflectance of around 96%. (These figures disregard specular reflections). Very dark objects have a reflectance of around 3%, though some are darker than that. The difference between 3% and 96% is five stops (3, 6, 12, 24, 48, 96). The scene brightness range (SBR) is created by a combination of different lighting levels (eg sun and shade) and by different reflectance levels (eg black and white).

    Knowing that you are able to make adjustments to the simple 'plus five' method. If something in the scene has specular reflections that you wish to keep detail in (for example an aluminium grain elevator or an aluminium-painted roof) the SBR could be higher. If there is nothing dark-coloured in the shadows the SBR could be lower. That was the case in the example I gave. Nothing in the deepest shade was below about 6% reflectance, and so I estimated the SBR at one stop less than the 'plus five' method - ie nine stops of SBR. I knew that I could place that on the film's characteristic curve (Portra 160NC) while staying well clear of the toe* (the lowest exposure the film will respond to) and the shoulder (the highest exposure the film will respond to) and thus having clean detail everywhere in the scene.

    Best,
    Helen
     
  11. Robin

    Robin TPF Noob!

    Joined:
    Jun 29, 2008
    Messages:
    119
    Likes Received:
    1
    Location:
    Salford Quays, Manchester, UK
    Can others edit my Photos:
    Photos NOT OK to edit
    As others have mentioned, a hand held light meter with a dome is an incident light meter, meaning it reads the light falling on it. The meter in your camera is a reflective light meter which means it reads the light reflecting off your subject. This is why you need to hold the light meter in front of your subject and point it at your camera, not point it at the subject. Pointing it at the subject is how a reflective light meter reads light.
     
  12. Helen B

    Helen B TPF Noob!

    Joined:
    Sep 16, 2007
    Messages:
    3,296
    Likes Received:
    465
    Location:
    Hell's Kitchen, New York
    Can others edit my Photos:
    Photos NOT OK to edit
    As I mentioned above, the Digisix may be used as an incident meter or as a reflective meter.

    Best,
    Helen
     

Share This Page

Search tags for this page

what is the point of a light meter

,
what is the point of a light meter?
,
where to point light meter