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omd:manual_exposure

using manual exposure with the Olympus OM-D cameras

why shoot in manual exposure mode?

  • if your lighting conditions are not changing quickly, you can generally get better and much more consistent exposure results by using manual exposure
  • this is particularly the case when using flash as you can set the manual exposure to control the ambient scene exposure and then choose either manual flash exposure (best for static scenes where flash to subject distance is not changing and you are not changing your aperture between shots), or TTL flash auto exposure +/- flash exposure compensation if you really don't have the time for manual flash exposure

  • in an ideal world we would be using an incident light meter, but these require putting a meter at the position of the subject and facing it into the light
  • all cameras by necessity use the much less reliable reflection light metering technology which tries to make your subject mid-gray in tone even though it may be light or dark, and furthermore, it can be tricked by a light or dark background.
  • furthermore the camera does not know what YOU want your image to look like - you may want an “under-exposed” dark, moody image or an overexposed bright, airy, happy image perhaps with some lens flare
  • while you can get use the exposure compensation dial to address this in the non-manual modes, if you recompose your scene, you may have to keep adjusting your exposure compensation
  • the beauty of mirrorless camera systems such as the Olympus OM-D cameras is that they use an electronic viewfinder (EVF) which can be set to display a reasonably accurate rendition of how your photo will appear before you take the shot (within limits - extreme underexposure or overexposure may not appear as total black or total white in the EVF).
  • we can thus use this WYSIWYG viewfinder image to great advantage when using manual exposure metering as not only do we get to see what the image looks like but Olympus cameras have a few extra tools such as meter reading, shadow-highlight display and live histogram in Olympus cameras which can be used to great effect in assisting us in determining the best exposure.
  • the Olympus OM-D cameras also allow us to choose some interesting metering options
    • evaluative metering - this is the most sophisticated mechanism and mostly is reasonably reliable given the above caveats
    • spot metering - this allows us to meter a person's face, and set the manual exposure accordingly (although we may still need to adjust it for the type of skin)
    • spot metering HI - this allows us to aim the spot on a piece of white paper and the camera will adjust the metering to ensure it stays white and not mid-gray as would normally happen
    • spot metering LO - this allows us to aim the spot on a darker area (but not black) and the camera will adjust the metering to ensure it stays dark and not mid-gray as would normally happen

setting up the camera for manual exposure

  • unless you are doing astrophotography, studio flash with gross under-exposure of ambience, or other photography where the in-camera metering is very unlikely to be useful, make sure you set Olympus Live Boost viewing feature to OFF otherwise your EVF will not show you the effects of your exposure settings

  • the Olympus OM-D cameras are extremely versatile cameras which can be set up in a multitude of manners to suit nearly everyone and every photographic scenario - but this versatility can make it bewildering!
  • my preference for adjusting settings within the EVF or on the rear panel is to use the Super Control Panel (SCP)
    • this is not available by default, so you need to go into the camera menu, go to custom menu (cogs icon), right arrow to options, then arrow down to Disp/../PC, right arrow to drill down, arrow down to Control Settings, then right arrow, then down arrow to select P/A/S/M then right arrow, then down arrow to Live SCP and ensure it is ON.
  • ensure you also enable live histogram and highlight/shadow by choosing Info Settings (which is below the Control Settings in the above menu process), right arrow and select LV-info then right arrow to turn these features on - they will now be accessible in the live view by toggling through using the INFO button.

shooting in manual exposure mode

  • set PASM dial on the top of the camera to M (manual exposure)
  • the two dials on the camera top right will then control aperture and shutter speed (there is no exposure compensation in M mode except for TTL flash exposure compensation)
  • you adjust these dials until you have the correct exposure
    • often you will want to start with a certain aperture to give you the depth of field (DOF) you need then adjust the shutter speed
    • other times you will want to set the shutter speed first (eg. for action shots, flowing water shots, perhaps flash, etc), then adjust the aperture
    • don't forget the 3rd component of exposure you can adjust - ISO
      • optionally can use AutoISO to still give auto exposure:
        • current Olympus cameras allow you to set ISO to autoISO in manual exposure mode but this then acts as an auto exposure mode but without any option for exposure compensation so it is usually best to avoid autoISO in manual mode
        • Set “ISO” to Auto this allows you to set shutter speed and aperture as fixed but still have auto-exposure
        • Set “ISO Step” to 1/3EV to ensure you have enough exposure precision
        • Set “ISO-Auto Set” to the maximum ISO to 1600-3200 depending on how much grain you will accept and the “Default” to 200

options for determining the correct manual exposure

spot metering

  • spot metering is very useful if you have an area in the scene which is lit by the main light and you can know you can set the exposure to it, for example:
    • photographic gray card, primary colours or dark tanned Caucasian skin:
      • just use normal spot metering mode and aim for reading of 0.0
    • lighter gray card of a WhiBAL card
      • use spot metering mode and aim for reading of +1.3
    • darker gray card of a WhiBAL card
      • use spot metering mode and aim for reading of +1.0
    • white paper
      • use spot metering HI mode, and aim for reading of 0.0, or
      • use normal spot meter and aim for reading of +2.3
    • average Caucasian skin
      • normal spot meter and aim for a reading of approx. +0.7-1.0
    • black paper or iPhone screen turned off:
      • use spot meter LO and aim for reading of 0.0, or
      • use normal spot meter and aim for reading of -3.0
  • don't forget you can walk closer to the scene, take your reading, adjust your settings then go back and recompose knowing your camera is not going to change your setting on you - that is one of the beauties of manual mode and you don't have to run into issues with AEL changing your exposure when you half-press the shutter to lock focus.

  • if you regularly take a white cardboard or piece of foam with you it can act in 5 roles:
    • as your spot metering HI target (or +2.3EV in normal spot meter mode)
    • as a custom white balance target, or at least take a photo of it so you can use it in post-processing to determine white balance
    • as a reflector to bounce sunlight back into a subject's face
    • as a flash bounce reflector
    • to block light hitting your lens or your subject

live histogram

  • the metering, including the live histogram is dependent upon jpeg settings and white balance
  • it is an AVERAGE of the 3 colour channels
    • do not use this for colors of only red, green or blue or when using an IR filter as it will be misleading and risk blown highlights UNLESS you have set Picture Mode to Monotone and applied a filter so it is only reading one colour channel - eg. for IR choose the Red filter in the Picture Mode so only the red channel will be metered.
  • the width of the histogram represents ~8EV
  • the green area represents the subject in the centre spot of the scene
    • gives a defacto spot meter even in ESP mode!
    • if aim at white paper, the green area should be near the right end but there should still be a gap
    • if aim at average Caucasian skin the green areas should be just a little to the right of middle of the histogram

shadow highlight indicator mode

  • this can be used as a final check to see if and where parts of the image will loose detail due to extreme underexposure or over-exposure - if these parts are important, you may wish to make further adjustment to the exposure
  • remember, it is generally best in digital photography to have important parts of the image to the right of the middle of the histogram as that is where you get the best tonality
    • avoid under-exposing skin as increasing exposure in post-processing can make it look sub-optimal
    • female skin often renders best if it is a touch over-exposed
    • try to avoid blowing out highlights unless they can't be retained or are not important

trial and error

  • one of the great things about digital photography is that you can do test shots and see the images with their histograms on all 3 colour channels immediately
  • it is a good idea to check the 3 channel playback histogram at least while you are getting your exposure correct.

use an incident light meter

  • the most accurate exposure metering is usually by using an incident light meter as it will not be fooled by your subject's tonality
  • this requires carrying an extra tool and being able to place this tool at the subject
  • furthermore it assumes your lighting will not change between taking the reading and taking the shot
  • you will need to factor in:
    • use of filters on your lens - especially polarising or ND filters
    • calibration of your camera's ISO values - do they reflect standard ISO measurements?
    • may not be so useful for infrared photography
omd/manual_exposure.txt · Last modified: 2016/08/15 00:46 by gary1