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Thread: Qns regarding fill in flash

  1. #1
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    Default Qns regarding fill in flash

    I understand sometimes u need to have some fill in flash for your subjects...but exactly how do u use one? can use the inbuilt flash or i could also use a external one? do umeter ur scene without flash then shoot 2 stops under with flash or do u use flash exposure compensation and by how much? suppose u're shooting a subject under bright sunlight and that are shadows on her face, what would u do?
    would appreciate it with some expert's comments thanks

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    Experiment and bracket. That's the way to learn. Fill flash can be done using either internal flash or external flash, or diffused external flash, etc. Usually up to -2, depending on situation (from experience, if unsure, bracket the flash compensation).

    Regards
    CK

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    For situation where the person is against a bright background.
    The way I do it is meter the background first.
    Then AE lock.
    Then force flash.

    I think pic shd be correctly exposed.

    Anyone can comment ?

    darkavgr

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    bracket, bracket, bracket....the only sure way of getting a pleasantly exposed frame, especially with slide films.

    I'm on a non-TTL camera body so the only form of automatic flash is that built into the flash. The commonest example of when I'd use a fill-flash is the family snap-shot, especially during travels. For example, you're at the Padang and you want to take a group photo of folks with the CBD skyline, problem is the sun is shining from almost behind the group of people so without fill-flash, the faces will most likely be underexposed. Here I have 2 basic considerations:

    1. exposing the people properly.

    2. exposing the CBD skyline properly.

    Let's consider point 2, exposing the CBD skyline, for this I would let the camera meter for the scene and lock the exposure value. This ensures correct exposure for the skyline.

    Now consider the faces of the people. They will most likely be about 2 or 3 stops underexposed going by the camera's lock exposure value. So I'd use fill-flash to brighten their faces. By how much? Usually I estimate the camera-to-face distance then manually set the flash for that distance. Usually setting the flash for the "correct" exposure will result in a rather harsh rendition of the faces, so then I would instead stop down the aperture on my camera for maybe one or 1.5 stops for the flash power that I had set earlier on. Basically, the idea is for me to deliver a flash power that is about one to 1.5 stops less then recommended. You can use other ways to achieve the end result, like lowering the power of the flash itself. For me, I find that controlling the flash power manually is a good way to start learning about fill-flash, at least I'd know the basic principles first before relying on automatic, TTL, matrix or whatever other sysytems, because essentially these forms of automation strive to achieve the same end result.

    Here're some example:

    in this photo, notice the relatively dark background behind the parrot at JBP around 2pm in the shade. I had set the shuttle speed to maximum sync of 1/125s on my camera because the bird was moving its head around, so I needed to "freeze" the movement, resulting in an exposed parrot but an underexposed background.

    http://www.photo.net/photodb/photo?photo_id=631395

    in the photo, linked below, the guanaco was standing in sunlight coming from the left, the shadow from its ear would thus be across the face (and probably the eye) so I added a little underpowered flash of about minus one and two-third stops while exposing my camera's shuttle speed and aperture for the background thus lifting the shadow and getting a bit of "catch-lights" on its eyes.

    hope these help. if there are any mistakes in my above statements, please do correct me as I myself am not very proficient with using flash.

    andrew

    http://www.photo.net/photodb/photo?photo_id=920580

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    the thing about manual flash that i dun understand is exactly when is it manual? i've the 420ex and being ETTL i heard that everything is pretty much auto. (i've read alot bout flash and the TTL systems but i'm still very much confused)

    In your first example when u metered for the scene first (this is without flash rite?)
    After that for the fill flash, u said to go 1-1.5 stops less with the aperture for the flash exposure. So am i correct to say that
    1. u metered with flash in manual mode, then apply 1-1.5 stops down with the metering....Or
    2. u metered with flash in manual mode, then applied 1-1.5 down in flash exposure compensation?
    i always get confused with these 2 ....are they the same? with ETTL would the flash juz increase the output for 1. thus defeat the purpose?
    any comments on this ckiang? u've mentioned in quite afew threads of ur method in 'stoping down 2 stops with shutter then leaving the rest to flash'...so is that 1.?
    Last edited by Mystix; 28th August 2002 at 04:10 PM.

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    Originally posted by Mystix

    In your first example when u metered for the scene first (this is without flash rite?)
    After that for the fill flash, u said to go 1-1.5 stops less with the aperture for the flash exposure. So am i correct to say that
    1. u metered with flash in manual mode, then apply 1-1.5 stops down with the metering....Or
    2. u metered with flash in manual mode, then applied 1-1.5 down in flash exposure compensation?
    i always get confused with these 2 ....are they the same? with ETTL would the flash juz increase the output for 1. thus defeat the purpose?
    I used a flash without TTL ability. That is, my flash only has aperture auto and manual. Let me explain what this 2 methods are before explaining the rationale behind my first example.

    In aperture auto, I simply set the flash to a particular aperture (let's say f/5.6). Using the flash in this method and within the appropriate camera-subject distance, the flash will fire a certain amount of light until the sensor on the FLASH unit detects that this amount is enough, then the flash will stop firing. Now, with this method, I have to set my LENS aperture to f/5.6 so as to receive the "correct" amount of light. If I want to get 1 or 2 stops less light onto the film, I would then set my LENS aperture to f/8 or f/11. You can do it the other way, that is set the FLASH to f/4 or f/2.8 and keep the LENS aperture fixed to f/5.6.

    The main disadvantage of aperture auto method, to me, is that if the background is very bright (like afternoon sky). The light from the sky will fool the sensor on the FLASH into thinking that enough light has been fired from the flash. Thus, the flash will stop its light output before the appropriate amount has been fired. Resulting in an underexposed subject. The reverse is true when using this method in the dark. The sensor on the FLASH will think that not enough light is fired, so it will fire more light than appropriate, resulting in an over-exposed subject.

    In manual mode, I estimate the distance. Let's say the parrot was 2 metres away from me. Then I will set the power of the flash to a distance of 2 metres for my given LENS aperture (say f/5.6). Using this method the sensor on the FLASH is not working but the flash will always fire an exact amount of light that is appropriate for a subject 2 metres away and for a LENS aperture of f/5.6. So if you shoot with this setting on the FLASH and f/5.6 on your LENS the exposure will be "correct" for anything that is 2 metres away. Now if you want to compensate, you then simply set the LENS aperture to f/8 or f/11 for -1 or -2 stops respectively. The flash compensation (on the FLASH unit) does not work in my case because the light output is fixed and the light sensor is not working.

    Now for the parrot example. My first consideration was that I have to use a shutte speed fast enough so as to freeze the movement of the parrot. And I know that my top flash sync speed is 1/125. So I set my camera at that shutter speed. Now I wanted to blur the background so I opened the LENS aperture to f/4. Remember now, my camera and lens setting is 1/125 at f/4. So at this setting the picture will normally be underexposed in the afternoon shade. I then estimated the camera-subject distance to be 2 metres, so I used the manual method, setting the FLASH to fire an amount of light that is appropriate for 2 metres and at f/4. So now everything that is at 2 metres away from me will be appropriately exposed but anything beyond will be underexposed. Therefore, the parrot was lighted up while the background (which is more than 2 metres away) was dark.

    So remember, when using the FLASH unit in manual mode, the light sensor on the flash unit is not working. TTL is also not in play here. In manual mode, the light fired by the flash is FIXED, you will have to compensate by either changing the aperture on your LENS or by moving further or closer to your subject. The reason I prefer manual mode (and it is strictly a personal preference) over aperture auto or TTL is that the light output is always correct for a subject that is a certain distance away regardless of whether the background is dark or bright. I therefore have one less factor to consider when using flash in manual mode. For me when using flash my personal rule-of-thumb is: use shutter speed to get the appropriate background exposure, use lens aperture to get the appropriate flashed subject exposure. If however the background cannot be appropriately exposed because of limitations in shutter speed (like the parrot example) then bo-chup the background, just whack the subject and compose it in my frame as much as possible.

    andrew

    p/s it's too long to type about TTL system and the principle behind it. suggest you continue reading. if you want, e-mail me privately and i'll try to answer.

  7. #7

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    Originally posted by kh_drew

    p/s it's too long to type about TTL system and the principle behind it. suggest you continue reading. if you want, e-mail me privately and i'll try to answer.
    How about taking portrait pics under the shade in the afternoon while using bounce card. Do you normally overexpose the flash by +1 or +2?

  8. #8
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    Originally posted by scanner


    How about taking portrait pics under the shade in the afternoon while using bounce card. Do you normally overexpose the flash by +1 or +2?
    For bounce flash, it is best to have a low ceiling and if taking colour it's best that the ceiling be white in colour. The principle is essentially the same for me, I would use the shutter speed to get an appropriate exposure for the background. From personal experience I have found that using the aperture auto method works pretty well indoors and there isn't any need to compensate at all. For example, at lens aperture f/5.6, I just set the aperture auto setting on my flash unit to f/5.6 and tilt the head up, pull out the card, then just shoot. The only problem with bouncing may be the slight shadow I get underneath the chin of the model.

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