Inconsistency in flash metering

Discussion in 'Canon Accessories' started by JuliaBu10, May 29, 2013.

  1. JuliaBu10

    JuliaBu10 TPF Noob!

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    Hi
    I have been photographing weddings for a while but had a long break, just got back recently, upgraded my flashgun from 430ex to 600rt and I notice that sometimes the photos are underexposed. It is very annoying as I don't understand it at all! I use ETTL (direct flash or 45º or with gary fong lightsphere), I use same exposure usually, 800ISO, 60 5.6. Sometimes it might be because of black or white clothing but I do use spot metering. I don't know how to overcome it, thanks god for lightroom so I go through all the photos, correctng exposure in some. The photographers I work with use Nikon and all their photos are perfectly exposed, they use their flash on Automatic mode and it gives them perfect exposure each time. Anyone had a simillar problem with Canon flashgun or have an idea how to solve this? I tried shooting with flash on Manual, but it is not always possible as when everything is changing quickly and I move from long shot to wide, from close up to group portrait in seconds, I can't adjust the flash too often.
    I attach 2 photos I shot one after the other, one perfectly exposed, the other 7 sec later (enough time for flash to recycle) much too dark.
    Will appreciate any feedback
    Thank you very much!


     

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  2. cgipson1

    cgipson1 TPF Noob!

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    Your meter is going to try to make whatever you meter on 18% gray (or 12% depending on the camera)

    The first shot... reasonably close... I usually meter skin when shooting flash in situations like this, easy to correct for.

    Second shot... that white shirt is pretty close to 18% gray.... looks underexposed about 2 stops or so... depending on how you are metering, this is what I would expect with that much white in the image. Exif shows SPOT (single point metering) what did you meter on? I am assuming you moved the focus / meter point to somewhere other than the middle of the viewfinder?? This is not an edit.. merely showing where the center of the viewfinder / focal point would have been if not moved. (I will delete it if you would like.. let me know)

    $IMG_8327.jpg

    [PhotoME]
    PhotoME version: 0.79R17 (Build 856)

    [Overview]
    URL: http://www.thephotoforum.com/forum/...424-inconsistency-flash-metering-img_8327.jpg
    File type: JPEG
    File size: 80 KB
    Creation date: 5/28/2013 20:01
    Last modification: 5/29/2013 14:40
    Make: Canon (Canon Global)
    Camera: Canon EOS 5D Mark II
    Dimension: 600 x 400 px (0.2 MP, 3:2)
    Focal length: 95 mm
    Aperture: F5.6
    Exposure time: 1/60"
    ISO speed rating: 800/30°
    Program: Manual
    Metering Mode: Spot
    White Balance: Auto
    Flash: Flash fired, compulsory flash mode

    ISO 800 with flash seems excessive also.. I usually shoot flash at 100, seldom more than 400. Also, As I am sure you are aware... TTL is never going to be as accurate as manual flash, it is very prone to inconsistencies!
     
  3. Derrel

    Derrel Mr. Rain Cloud

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    Spot metering with flash...oh my...I think that is very,very inconsistent and risky. Canon has for many years had difficulty getting flash metering consistent. In fact, I think this is one of the areas where Nikon's focus on 3-D, distance-aware, distance-evaluating, color aware, reflectivity-aware analysis makes a Nikon shooting in matrix TTL flash metering mode simply a more reliable camera than anything yet developed for run-n-gun type flash.

    I think Spot metering in flash work is just not the way to go. Spot metering can lead to positively HUGE exposure fluctuations with just minor, tiny movements of the camera, or the subject. I would strongly suggest trying something else.

    BY the way, I have owned and used the Canon 20D and 580 EX-II and the Canon 5D for about seven years total, and yes, I have had a lot of inconsistent flash exposures with those two cameras and that flash. I have a 2-body, 10-lens Canon system, as well as NIkon stuff. I prefer Nikon for flash. "it's better".
     
    Last edited: May 29, 2013
  4. cgipson1

    cgipson1 TPF Noob!

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    I use spot metering with TTL flash a lot.. works very well on my Nikon. Not having used Canon, I can't say much... but I have heard that it is less accurate than Nikons TTL metering.
     
  5. JuliaBu10

    JuliaBu10 TPF Noob!

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    Thanks cgipson1, I did use spot metering, I usually focus/meter on the eyes of the subjects and then recompose.
    I used evaluative metering before with the same problem of inconsistency, spot metering gives me actually better results but still some photos are way under.
    Such a shame Canon has this issue, it really seems Nikon is much better for flash on camera ttl work which is what you need in wedding photography, it's a bit too late for me to move to Nikon... ahrrrrrrrggggggg.....
    I wish there was a better way to overcome this, rather than correcting later?
     
  6. grafxman

    grafxman TPF Supporters Supporting Member

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    Can you still get satisfactory results with your old 430? If so, the solution is obvious.
     
  7. Tony S

    Tony S Been spending a lot of time on here!

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    Do you have the exposure locked in so that when you recompose it does not change? If not it will change when you recompose. Easy test is to lock focus on something, then holding the shutter button halfway down move the camera around to see if the meter in the view finder changes. You need to set exposure lock.
     
  8. cgipson1

    cgipson1 TPF Noob!

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    ^ Good call! I didn't know about the recomposing when I wrote that earlier. Recomposing is one of the most difficult things to do properly... most people mess it up. Why do you recompose when you can move your focus / meter point around in the viewfinder... much more accurate way to shoot! That or make really sure you have the exposure locked in. I never recompose... I just lock the point on what I want sharp, and go for it.
     
  9. Robin_Usagani

    Robin_Usagani TPF Noob!

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    HMMMM.. I dont think it matters what metering ON YOUR CAMERA (unless you are not using manual setting on your camera). The flash has it own metering system. For canon you have Evaluative vs Average. This is separate from your camera metering.

    The reason #1 picture is more bright is because you have less reflective subject. The flash metering thinks it needs a lot of flash power. The second one you have a subject with light shirt. There is a lot of light bounced back to the lens so the flash thinks the scene is bright.
     
  10. cgipson1

    cgipson1 TPF Noob!

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    Robin, why do you think they call it TTL (Through the LENS)? It is measured in the camera via the pre-flash. The only time the flash would use it's own metering system is when it is in Auto Flash mode.
     
  11. Robin_Usagani

    Robin_Usagani TPF Noob!

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    yes.. via preflash through the lens. It doesn matter what metering though. If it is already set at 1/60, ISO800, f/5.6, it does not matter what metering you have. It only matters what is on the frame. The more reflective it is, the lower the power. Your diagram is flaw.
     
  12. KmH

    KmH In memoriam Supporting Member

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    It does?

    The Canon 600rt specs don't list a metering capability, and metering in the flash unit is not mentioned in the 600rt users manual Index

    Could you provide a link or some direction to the information on in-the-flash-unit metering? I would like to learn more about this feature in Canon speedlites.
     

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