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Thread: Exposure Metering

  1. #1

    Question Exposure Metering

    If I do not have a light meter, can I use the dslr to do the metering? I'm using canon 550D. The only metering I came across the dslr menu is about evaluative, spot, partial metering.

    Reason I ask this is I saw a photography tutorial on youtube and this guy mentioned "the camera tells me I'm 2 stops underexposed". Is this translated from the histogram?

    He also mentioned "let's see what is the aperture value required" after doing some setting on his camera for night shots.
    Is it similar as using shutter priority, auto ISO, then the camera will show the required Aperture value?

  2. #2

    Default Re: Exposure Metering

    here's how I use camera metering, set mode to Manual,

    determine if I wish to fix shutter or aperture,apply first pressure on shutter button, peep at that scale thing, the objective usually is to center the needle in the middle of the scale (correct exposure), by tuning the variable factor.

    eg1 fixed factor: shutter at 1/2000, variable factor: aperture. hence I will tune the aperture until the needle centered. of course if the aperture cannot open wide enough, to center needle, then need more shutter time to capture more light.

    eg2 fixed factor: aperture at F/22, variable factor: shutter time. use the main dial to increase or decrease the shutter time until needle centered.

    of cource for longer shutter times you may need steady support eg tripod,etc

  3. #3

    Default Re: Exposure Metering

    dSLRs are very much capable of through-the-lens metering (TTL). Evaluative, spot and partial metering is how you want your camera to do the metering.

    eg. spot metering will meter the amount of light at a particular spot about 2% in the viewfinder (you might want to read your manual for more details)

    if you are on shutter speed priority, the camera will decide a suitable aperture value required to get the correct exposure
    if you are on aperture priority, the camera will decide a suitable shutter speed for required to get the correct exposure

  4. #4
    Moderator catchlights's Avatar
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    Default Re: Exposure Metering

    If you are asking can use the DSLR to take metering? Yes you can, you need a standard 18% gray card, fill the frame with gray card and place next to the subject facing the camera, take a shot, when the peak of the histogram is right in the center, this is the correct exposure setting of the lighting falls on the subject.

    btw, judging histogram from a normal scene where has a lot of mid tone is very straight forward, but it needs a lots of experience to interpret the histogram of high key or low key scenes.

    hope this help.
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  5. #5
    Senior Member ZerocoolAstra's Avatar
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    Default Re: Exposure Metering

    Quote Originally Posted by canon550d View Post
    If I do not have a light meter, can I use the dslr to do the metering? I'm using canon 550D. The only metering I came across the dslr menu is about evaluative, spot, partial metering.

    Reason I ask this is I saw a photography tutorial on youtube and this guy mentioned "the camera tells me I'm 2 stops underexposed". Is this translated from the histogram?

    He also mentioned "let's see what is the aperture value required" after doing some setting on his camera for night shots.
    Is it similar as using shutter priority, auto ISO, then the camera will show the required Aperture value?
    To explain metering would be pretty lengthy, so your best bet is some self-reading of photography books, coupled with experimentation on how it works in actual shooting situations.
    The camera meter display would likely be active only when you're in manual exposure (M) mode. It should look something like this:
    http://www.melissamccrottyblog.com/wp-content/uploads/2011/02/camera-light-meter.jpg


    As you adjust your shutter speed, aperture and ISO speed, you should be able to see the 'needle' move up or down the scale, representing over- or under-exposure.
    The statement "the camera tells me I'm 2 stops underexposed" implies that the needle is at the '-2' position.
    Last edited by ZerocoolAstra; 18th April 2012 at 11:18 AM.
    Exploring! :)

  6. #6
    Moderator ed9119's Avatar
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    Default Re: Exposure Metering

    thank you for rendering assistance to the TS guys
    shaddap and just shoot .... up close
    Walkeast

  7. #7

    Default Re: Exposure Metering

    Quote Originally Posted by ZerocoolAstra View Post
    To explain metering would be pretty lengthy, so your best bet is some self-reading of photography books, coupled with experimentation on how it works in actual shooting situations.
    The camera meter display would likely be active only when you're in manual exposure (M) mode. It should look something like this:
    http://www.melissamccrottyblog.com/wp-content/uploads/2011/02/camera-light-meter.jpg


    As you adjust your shutter speed, aperture and ISO speed, you should be able to see the 'needle' move up or down the scale, representing over- or under-exposure.
    The statement "the camera tells me I'm 2 stops underexposed" implies that the needle is at the '-2' position.
    as a newbie and with google from what i read...am i correct to say that the correct explosure ia where the 0 is ? by with a iso fixed, by adjusting the apperture ot shutter speed, once it reach 0 will be the correct ? thanks

  8. #8

    Default Re: Exposure Metering

    Thanks all for the replies. Really lights the bulb in my head.

    Shizuma: Your explanation is really easy for me to understand.
    ZerocoolAstra: Your diagram just visualised Shizuma's reply.

    I have just another question.
    If I'm using manual mode, eg: shutter 1/60, f4, iso200 and the "needle" points to the center of the scale, this should mean that I should have the correct exposure. Can I still "force"the camera to under or over exposure but still maintain all the settings?

    Btw, I just want to share this youtube tutorial which I think is really useful to me. Just type in "Digital photography 1 on 1", the "tutor" is Mark Wallace (not advertising here, just want to share info)

  9. #9
    Moderator Octarine's Avatar
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    Default Re: Exposure Metering

    Quote Originally Posted by buzzmario View Post
    as a newbie and with google from what i read...am i correct to say that the correct explosure ia where the 0 is ? by with a iso fixed, by adjusting the apperture ot shutter speed, once it reach 0 will be the correct ? thanks
    Correct explosure? Don't get caught for that
    Once the needle is at '0' means: the metering system reads the resulting exposure under consideration of the metering mode (evaluative, center-weighted, spot..) to be correct. Exposure is defined by Aperture, ISO and Shutter speed. however, this is only the technical answer. The camera does not see a dress, a face, a flower or the mountain. It can only see shades of grey. Which means: in many cases a technically correct exposure might not necessarily be the best exposure for the subject. Here you need to evaluate the entire picture / scene, the metering mode used and your overall intention. Use then the respective tools for exposure compensation. In Av and Tv you will simply use the EV function, in Manual mode just change one or more parameters for exposure.
    But first of all suggest a good reading of your manual and the newbie guide here. Get the basics right.
    A histogram will not tell you the stops of exposure (ok, you might be able to gauge it after some time), it only tells you the distribution of light and dark pixels across the image and whether there are areas of serious under and over exposure ('blown out').
    EOS

  10. #10
    Moderator Octarine's Avatar
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    Default Re: Exposure Metering

    Quote Originally Posted by canon550d View Post
    I have just another question.
    If I'm using manual mode, eg: shutter 1/60, f4, iso200 and the "needle" points to the center of the scale, this should mean that I should have the correct exposure. Can I still "force"the camera to under or over exposure but still maintain all the settings?
    If you must maintain all three parameters then use Neutral Density filters. It cuts down the light by defined stops.
    EOS

  11. #11
    Senior Member ZerocoolAstra's Avatar
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    Default Re: Exposure Metering

    Quote Originally Posted by buzzmario View Post
    as a newbie and with google from what i read...am i correct to say that the correct explosure ia where the 0 is ? by with a iso fixed, by adjusting the apperture ot shutter speed, once it reach 0 will be the correct ? thanks
    It depends on what you define as correct
    The camera will define (based on its pre-determined set of parameters) what is 'correct' exposure, indicated by the '0' reading on the exposure meter. This is no guarantee that you will like the outcome though. If you decide that it is too dark (under-exposed), then adjust one of the 3 parameters to get the required outcome.

    You will also need to know a bit about how the different metering modes can affect the metered exposure readout. This will require lengthy explanation, best served by reading photography books.
    Exploring! :)

  12. #12

    Default Re: Exposure Metering

    Quote Originally Posted by Octarine View Post
    If you must maintain all three parameters then use Neutral Density filters. It cuts down the light by defined stops.
    Use ND filters to cut down light. Then the opposite is by using speedlite?

  13. #13

    Default Re: Exposure Metering

    Metering is not an easy concept to grasp. Shoot around with Manual after reading up on metering. See the fluctuations in the gauge and try to position it to the centre by tweaking the variables. then u look at ur photo if its correctly exposed.
    D7000 + 50mm

  14. #14
    Moderator Octarine's Avatar
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    Default Re: Exposure Metering

    Quote Originally Posted by canon550d View Post
    Use ND filters to cut down light. Then the opposite is by using speedlite?
    Not necessarily. Reflectors can also be used to get more light to the subject. But the easier way would be to increase ISO. From ISO200 in your example all recent cameras have space to go to ISO800 without loss of image quality. That's 2 stops.
    For the usage of speedlite (or any other flash) you need to keep an eye on shutter speed. If it goes faster than 1/200 (check specs before) you will need High Speed Sync feature. Not all flash models can do this.
    EOS

  15. #15

    Default Re: Exposure Metering

    That is why I love manual mode!

  16. #16

    Default Re: Exposure Metering

    Great advice.
    Thanks to all sifus

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