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Thread: external flash underexposing problem

  1. #1

    Default external flash underexposing problem

    my current set up is a panasonic fz20 coupled with a metz 32 z1 flash.

    when using it together with a hoya +4 close up filter for macro, i would use a bounce card and the exposure would be accurate, at least to me, its adequate.

    when using the flash in a low ceiling place, like my room, the metz exposure would be spot on too...

    my problem is when using it during concert hall environment, or ballroom environment with inadequate lighting if without using flash (ceiling not low enough to bounce).
    the metz would cut off the flash a little too early...at first i tried to bounce it like i would for macro, overexposing on the cam by 1 stop. the shot turn out too be way underexposed. so i assume it would be the bounce card.

    off goes the card and i tried to bounce off the ceiling...no good too, cos ceiling, though low, but not low enough for the flash to be bounced off it.

    then instead of a 45 - 60 deg upward tilt, i tried direct this time, ie, 90deg straight ahead...the first shot turn out fine. subsequent shots, way underexposed.

    if i block the sensor of the flash, it gets way overexposed...

    settings on the metz: 100 iso, f8
    settings on cam: 80 iso, f4, 1/60

    any idea how i can take better shots in concert/ballroom environment?
    thanks...
    too many shots...

  2. #2

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    How about showing some sample photographs?

  3. #3
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    how far are you from the subjects and is the ceiling light-coloured? coloured ceilings would result in colour cast and dark ones would absorb most of the light.

    also note that recycle times for the flash is (significantly) longer when the batteries are weak.

  4. #4

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    i m most probably about 10m perhaps?
    i took some shots and i was about 6m max to the subjects. it was a group photo and it was underexposed too...

    i think i ll upload some pics to show...

    Ah pao, mpenza, thanks for replying though...
    too many shots...

  5. #5

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    Firstly, about how high is the ceiling and what kind of ceiling is it? I've shot in high ceiling dimly lit ballrooms. Using bounce, sometimes the ISO needs to be pushed to ISO1000 and f2.8 to get good lighting. May even help if the flash exposure is increased by 1 stop.

  6. #6

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    Quote Originally Posted by snowspeeder
    Firstly, about how high is the ceiling and what kind of ceiling is it? I've shot in high ceiling dimly lit ballrooms. Using bounce, sometimes the ISO needs to be pushed to ISO1000 and f2.8 to get good lighting. May even help if the flash exposure is increased by 1 stop.
    i ve pushed it to high iso before and f2.8, result is still the same if i m using Auto modes. it'll only make a difference if i use full manual mode on the metz.

    erm, what you mean by "flash exposure" increased by 1 stop?
    if metz f2.8, cam f4; would that be considered?
    too many shots...

  7. #7
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    nope, the other way round. metz f4, cam f2.8 is increasing flash exposure by 1 stop (assuming ISO is set to be the same for both).

  8. #8

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    Try to use manual flash and adjust its power to the max.

  9. #9

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    Quote Originally Posted by mpenza
    nope, the other way round. metz f4, cam f2.8 is increasing flash exposure by 1 stop (assuming ISO is set to be the same for both).
    oh ya...sorry...suddenly become sotong...
    ok, so thats called FE...
    would zooming the flash helps?
    too many shots...

  10. #10
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    that might help a bit. it's better to attach a bounce card though, which will help to direct more light to the front.

  11. #11

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    but for longer distances, the bounce card wont be that effective when compared to using direct/omnibounce?
    too many shots...

  12. #12
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    Quote Originally Posted by codling
    ...i would use a bounce card and the exposure would be accurate, at least to me, its adequate.

    when using the flash in a low ceiling place, like my room, the metz exposure would be spot on too...

    ...

    then instead of a 45 - 60 deg upward tilt, i tried direct this time, ie, 90deg straight ahead...the first shot turn out fine. subsequent shots, way underexposed.
    I think I have encountered similar case with my brief experience with a Sigma flash. Bounced flash (with card or ceiling) turned out dead on, but direct flash will be about one stop under. I did a comparison with a Canon flash and found that it works better direct, and a little under when bounced. I guess that is just the property of the flash, though TTL flash metering should work in the camera body instead, so I don't have a good explaination for it. This is where FEC comes to good use.

  13. #13

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    i guess sometimes the ambient lighting fools the sensor...if ambient lighting is poor, and flash reach not sufficient, i would assume the sensor would make the flash send out its full available power set by the aperture and iso value of the flash...but sometimes, doesnt work...
    so i m still second guessing what i did wrong, or right whenever the pic turns out ok...
    too many shots...

  14. #14

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    If your flash behaves erratically (unpredictable) under the same scene and lighting conditions, it may be the flash's electronics failing, since its not working consistently.

    Otherwise, it may be the batteries weakening. I once too had such a mistake thought that the metering when way off (using TTL metering)...I tried setting FEC +1EV, bump up the ISO, doing direct flash etc. to no avail. Then I realised that the batteries are weak.

    Another possibility is the output limitation of the flash. There is only so much light a flash unit can produce, and what's more most of the light would have been diffused by a high ceiling during bounce.

    I hope you are not using the P/Auto mode of your digicam in a dimly-lit ballroom? Your subject will be correctly exposed but the rest of the scene (background) will be way underexposed. Switch to Slow-sync/Night mode (Aperture-priority) or Manual and see how.

  15. #15
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    my problem is when using it during concert hall environment, or ballroom environment with inadequate lighting if without using flash (ceiling not low enough to bounce).
    the metz would cut off the flash a little too early...at first i tried to bounce it like i would for macro, overexposing on the cam by 1 stop. the shot turn out too be way underexposed. so i assume it would be the bounce card.
    I am not sure about FZ20, but with the 10, if you are able to set exposure on the cam, then you have removed the flash auto detect function. NB:changing the shutter speed when using flash does not change the flash output. It only helps to increase ambient light.


    off goes the card and i tried to bounce off the ceiling...no good too, cos ceiling, though low, but not low enough for the flash to be bounced off it.

    then instead of a 45 - 60 deg upward tilt, i tried direct this time, ie, 90deg straight ahead...the first shot turn out fine. subsequent shots, way underexposed.
    when using bounce, your guide number is greatly reduced. ie since you set the flash to F8, you would already reduce the effective distance to 32/8 = 4m. with bounce card, probably max 3m.

    if i block the sensor of the flash, it gets way overexposed...
    This just means that your thyristor is working as it should.
    settings on the metz: 100 iso, f8
    settings on cam: 80 iso, f4, 1/60

    any idea how i can take better shots in concert/ballroom environment?
    thanks

    Final word:
    1.when taking wide angle shots, take note of the max distance of your flash. max it out by setting to the widest F stop. If you leave the cam to auto detect external flash, the setting is auto set to F2.8 @1/160.
    2.When using zoom, zoom your flash as well to increase flash reach as well as to conserve battery. For increase reach, you can always add a fresnel lens in front of the flash (the map reading kind you get in book stores)
    3. To reduce confusion, always match your flash settings to the cam and then compensate the flash output by changing the flash ev setting.
    4. Use direct flash unless you have a really powerful head.
    Hope this helps.

  16. #16
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    Quote Originally Posted by codling
    i guess sometimes the ambient lighting fools the sensor...if ambient lighting is poor, and flash reach not sufficient, i would assume the sensor would make the flash send out its full available power set by the aperture and iso value of the flash...but sometimes, doesnt work...
    so i m still second guessing what i did wrong, or right whenever the pic turns out ok...
    usually ambient light does not full the flash. But if there happens to be a very shiny object eg. mirror, brass plaque etc. infront of the flash (you may not notice it in your pic especially if you are zooming in close) it could be fooled to underexpose.

  17. #17

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    Quote Originally Posted by Ah Pao
    If your flash behaves erratically (unpredictable) under the same scene and lighting conditions, it may be the flash's electronics failing, since its not working consistently.
    hmm...when close ups...no problem in being consistent....

    Quote Originally Posted by Ah Pao
    Otherwise, it may be the batteries weakening. I once too had such a mistake thought that the metering when way off (using TTL metering)...I tried setting FEC +1EV, bump up the ISO, doing direct flash etc. to no avail. Then I realised that the batteries are weak.
    not too sure on that...whenever i plan to use the flash for an outing, i ll always recharge the 2100mAh the night before and i ll bring a spare set of alkalines...
    usually, the first shot would be ok...then subsequent ones would be underexposed...


    Quote Originally Posted by Ah Pao
    I hope you are not using the P/Auto mode of your digicam in a dimly-lit ballroom? Your subject will be correctly exposed but the rest of the scene (background) will be way underexposed. Switch to Slow-sync/Night mode (Aperture-priority) or Manual and see how.
    no, i use manual if possible...but mostly, i find myself using aperture priority for concerts...so the cam auto sets the x sync to 1/60 shutter speed...
    too many shots...

  18. #18

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    Quote Originally Posted by MDZ2
    I am not sure about FZ20, but with the 10, if you are able to set exposure on the cam, then you have removed the flash auto detect function. NB:changing the shutter speed when using flash does not change the flash output. It only helps to increase ambient light.
    i understand the above pointer...but what do you mean by "flash auto detect function"
    do you mean if i set the exposure, eg, aperture to f4, the shutter selected would be like 1sec or so (assume that the ambient lighting is poorly lit) due to the fact that the cam assumes no flash would be fired?


    Quote Originally Posted by MDZ2
    Final word:
    1.when taking wide angle shots, take note of the max distance of your flash. max it out by setting to the widest F stop. If you leave the cam to auto detect external flash, the setting is auto set to F2.8 @1/160.
    2.When using zoom, zoom your flash as well to increase flash reach as well as to conserve battery. For increase reach, you can always add a fresnel lens in front of the flash (the map reading kind you get in book stores)
    3. To reduce confusion, always match your flash settings to the cam and then compensate the flash output by changing the flash ev setting.
    4. Use direct flash unless you have a really powerful head.
    Hope this helps.
    for pointer 3, you mean to say to change the settings on the cam itself rather than the flash?

    thanks for the idea increasing flash reach...i ll look into it...

    appreciate all your replies...it has been most enlightening...
    now all i have to do is to try it out and hopefully, i can get it to work...i think its user problem...
    too many shots...

  19. #19
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    Sorry to confuse you. I remembered incorrectly that the sync speed of the cam is 1/160 with ext flash on. So disregard the flash autodetect statement. What I meant by that was that if you allow the camera to automatically detect the flash, it will set the shutter and aperture automatically. To override this setting, you have to switch detection off.

    For point 3, I meant to set the flash settings to match the camera. ie. if camera is auto set to F2.8 @ iso 100, then set the flash to that same setting as well. So if the pic still under or over exposes, you can set the flash ev setting to over or under compensate accordingly. This removes the confusion of what aperture setting to use for the cam or flash, each time you take a pic.
    Hope this clears up that little bit of confusion.

  20. #20
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    hmm... how do you set the flash EV setting? If it's on the camera, it won't work at all. And not all flash have settings for flash exposure compensation.

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