Newbie to *FLASH* has a quick question..

Discussion in 'Lighting' started by Ambar, Aug 2, 2013.

  1. Ambar

    Ambar Member

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    Just got myself this cheap new flash to start off into flash photography..!
    I have a FM2n and a GF670 so TTL was a no go.. Also, I wanted to understand what the hell is going on before I have some auto-calculator figure things out for me.

    The graph on the backside seems straightforward enough: If I use asa 100 to photograph something at 3.6m/12ft use aperture f/5.6. Things closer become overexposed, things farther become underexposed. Fair enough.
    But that's considering that there is no light in the environment? Does this work during daytime fill as well as nighttime no light?
    The flashes front side has what seems to be a little lens.. does that have any influence?

    I'm gonna play around with it this weekend but I just wanted to know if I'm about to muck everything up.. Am I on the right track?
     

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  2. MattKing

    MattKing Subscriber

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    I would guess that the little lens in front might be part of a built in optical slave trigger.

    And as for daytime use, you determine the aperture to use with the flash from the table at the back and then adjust the shutter speed to give appropriate exposure with the ambient light - remembering that with most focal plane shutter cameras you are severely restricted in which shutter speeds may be used with flash.

    Your GF670 will most likely synch at all shutter speeds, but the FM2n won't.

    You can adjust to taste the ratio of ambient light exposure to flash exposure. I tend to prefer normal exposure from the ambient light, supplemented by flash that is one stop under-exposed.
     
  3. Ambar

    Ambar Member

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    Thanks MattKing!

    Just to be clear, you mean that natural ambient light exposure be one stop underexposed and flash light on subject be normal exposure correct?

    I might be over complicating things a little, but I'm try to get the concept right in my head.

    Does the natural light and flash light have an additive function? Meaning if I do a normal exposure on a subject with ambient light and during this exposure add a normal flash exposure. My subject would then be a Full stop overexposed right (ambient + flash).

    So underexposing by one stop and flashing normal would equal a half stop over exposure of the subject correct? Subject would get half the light it needs from ambient light and all the light it needs from the flash.
    I know the half stop over exposure is tolerable. I just want to know if my rationale pans out..
     
  4. John Koehrer

    John Koehrer Subscriber

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    The first paragraph above is correct re over/under exposure.
    Your second sentence is also correct. In daylight if you can use a suitable speed/aperture combination, you can get fill lighting that will slightly open up the shadows and not be apparent.
    At night, you can get a properly exposed subject(within limitations of equipment) and very dark background. anything in front of the subject will be overexposed. How much depends on distance between flash etc.

    The lens looks like a sensor, but there's no obvious way to turn the auto exposure on or off.
     
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  5. MattKing

    MattKing Subscriber

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    The thing to remember when you are considering the use of fill flash is that one usually uses it when there are shadows that need filling.

    If the ambient light is such that your subject is nicely, evenly lit, you need not bother with fill.

    If, however, your ambient light leaves shadows that are too dark, you can use fill flash to fill them.

    In most cases, those dark shadows occur because the main light source is either behind or beside or above your subject. You fill in the shadows with flash that originates closer to the camera.

    Usually you don't have to worry much about the fill flash and the ambient light adding together, resulting in over-exposure, because the direction of the two light sources is so different. If the direction is similar, you can consider adjusting your settings to take the additive nature of the light into account.

    So normally you set things opposite from what you said in your post - your ambient light exposure is normal, and the fill flash is less, because it is okay that the shadows appear as shadows, as long as they are sufficiently light as to record the detail and texture you want. Some like darker shadows, others like lighter shadows. I tend to prefer shadows that are illuminated by one stop of light less than "normal" (or underexposed by one stop).

    This is all oriented toward fill flash. There is nothing stopping you from making the flash the main light, and letting the portions of the subject lit by ambient light be underexposed by one stop.
     
  6. Ambar

    Ambar Member

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    Thanks MattKing! This has been really helpful!

    If the lens is a sensor, what is it doing? Would it be backing off the flash power when it senses ambient light?
    I believe this CY-20 is equivalent (read identical) to this Metz: http://www.bhphotovideo.com/c/product/483159-REG/Metz_MZ_20220.html
    There's no manual with this and there's something weird about an "Auto Flash" not doing anything automatically..

    Ps: Only buttons on this is On/OFF and TEST. All of which carry their obvious functions. :D
     
  7. MattKing

    MattKing Subscriber

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    The CY-20 isn't at all similar to that Metz flash - it clearly doesn't have any auto functions.

    I expect that it shares a body with another model, which does have auto functions.

    By the way, I've never encountered a flash that sensed ambient light. The auto flashes measure light from the flash bouncing back from the subject, and "quench" the flash at the appropriate amount.
     
  8. Chan Tran

    Chan Tran Member

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  9. markbarendt

    markbarendt Subscriber

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    It looks like the light has one setting. Much like a flash bulb it is all or nothing.

    So if per the chart you set your camera at say F8 with a film EI of 100 to place the subject properly when 8' from the camera, then you would them adjust shutter time to place the background properly per your meter.

    It really is that simple in theory. In reality it takes practice.
     
  10. Ambar

    Ambar Member

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    Thanks everybody for the input! I think I got the idea..

    And have every intention to start getting some practice right away!
     
  11. markbarendt

    markbarendt Subscriber

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    Enjoy.

    One of the things you will find out pretty quickly if you stick with it is that "by the chart" is just a starting point.

    There is one thing that really helped me "get" flash exposure; printing the main subject (the one lit by the flash unit) to look normal while completely ignoring the background.

    This does three things;
    1- it allows you to see that the subject can look normal when the flash is done well,
    2- it allows you to see which way you need to adjust the chart, if the background is too dark the flash is too strong, and
    3- it allows you to see how the direction of the light affects your subject. Get an extension cord for your flash and you can then move it off center and that will make a huge difference in how "normal" or "right" your subject looks, in the real world the light rarely comes from the camera's viewpoint and done well this eliminates the goofy outlining shadow on the wall.
     
  12. John Koehrer

    John Koehrer Subscriber

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    Keep in mind the limitation of synch speed with the FM2n is 1/250 or below. Above that you will have partially exposed frames. For experience, I'd shoot a frame at each higher speed to see this effect.

    Not that anyone here has EVER used the wrong synch speed.
     
  13. LunoLuno

    LunoLuno Member

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    Ambar, why don't you think this way?

    Privided that the subject you are going to shoot is evenly lit. There's no shadow nor highlight in this case. It's like you are going to shoot a wall that is lit by the sun in daytime using flashlight fill. In this case, you will get a picture which is about 1/2 stops overexposed. However, it can be still reasonablly tolerable even if you shoot with a slide film. That is because in this case there's no highlight in your picture. 1/2 stops of overexposure is safely within the film's latitude, which is usually around +2.3~-2.5 stops with the slide films. So, the overexposure only matters if there exists some highlight areas in the field.

    Now you are going to shoot a more realistic subject that has both highlight and shodow areas with it next. However, everyting is still at the same distance for simplicity in this case. You determine the camera's exposure setting according to the ambient light. The meter reads around +0 stop on the main area you are going to shoot, the meter also reads +2.5 stops on the highlight area and -3 on the shadow area in this case. And you use fill flash with -1 stop setting. Do you think the highlight area will become +3.5 stops overexposed by the flashlight fill? - It is not likely, the highlight area remains almost unchanged at +2.5 stops overexposure.

    The thing is, you just can't add the stops when culculating exposure. You need to add them by their percentage figures.

    +3.0 stops -> 800%
    +2.5 stops -> 560%
    +2.0 stops -> 400%
    +1.5 stops -> 280%
    +1.0 stops -> 200%
    +0.5 stops -> 140%
    +0 stop -> 100%
    -0.5 stops -> 70%
    -1.0 stops -> 50%
    -1.5 stops -> 35%
    -2.0 stops -> 25%
    -2.5 stops -> 17.5%
    -3.0 stops -> 12.5%

    So in the case of "highlight+2.5 / main subject+0 / shadow-3.0", the outcome will be...,

    highlight : ambient light 560%(+2.5 stops) + flash fill 50%(-1.0 stop)
    => outcome 610% (less than +2.7stops; almost unchanged)

    main area : ambient light 100%(+0 stop) + flash fill 50%(-1.0 stop)
    => outcome 150 % (about +0.5 stops)

    shadow: ambient light 12.5%(-3 stops) + flash fill 50%(-1.0 stop)
    => 62.5% (about -2/3 stops)

    You can see that the fill affects more on the shadow than on the highlight. This is why people say "Flash fill is for controlling the shadow (contrast of the picture)".


    Sorry for my bad English,:pinch:

    Luno
     
  14. GarageBoy

    GarageBoy Member

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    Can you spend $20 on an ebay Sunpak 422/433 or even a 222? Actual auto and more reliable manual
     
  15. adelorenzo

    adelorenzo Subscriber

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