sb-800; ev on camera and flash?

Discussion in 'General Discussion' started by marc, May 20, 2005.

  1. marc

    marc Guest



    this is the question or the observation; any help appreciated

    using sb-800 on d2h or d2x, makes no difference

    when you + ev on camera the shooting distance of flash reduces, when you -ev, shooting distance of flash increases.

    when you dial in +,- ev on flash same thing happens.

    can someone explain, what is happening and how to effectively use these settings?

    one more thing, if you use +ev on camera and -ev on flash are you just cancelling out the settings?

    all the help i can get, thanks
     
  2. Q #1: Yes

    All other questions relative to EV compensation can best be answered by saying "don't mix camera and flash EV adjustments." Decide to use one or the other but not both. Thom Hogan suggests using the flash adjustment. When you mix them they fight against each other and you never know or learn what you will get. Flash is complicated enough without entering that problem into the mix. When using the program mode with iTTL, things are pretty automatic and it does a credible job. For consistent repeatable results in controlling the background I suggest you use manual or aperature on the camera and TTL on the flash. Then practice, practice, practice.
     
  3. gho

    gho

    Feb 7, 2005
    California
    I mix them all the time...

    Exposure compensation (camera): controls the background light. add +EV to brighten it up, -EV to darken it.

    Flash Compensation: controls the falsh output (foreground subject). Add +EV to increase the light output, increasing the subject lighting. Add -EV to decrease - for fill flash you'd want -1 EV to -2 EV depending on how much fill you want.

    Normally, when shooting with a flash, I shoot manual mode. But on occasion, I'll shoot with a program mode, and that's when I use both compensations together).
     
  4. Just quoting Thom Hogan's D2H Ebook Gregory. I too use EV compensation when in manual by increasing or decreasing the shutter speed and/or aperature. I do not use the +/- compensation setting on my camera but instead use it on the flash. Thom is trying to point out how to achieve consistant results. :)
     
  5. gho

    gho

    Feb 7, 2005
    California
    Oh, I'm not saying you're wrong or anything, obviously your source is expert. I'm just pointing out an alternative method.

    Flash compensation and Exposure compensation are two different things - they just happen to have the same value (EV).

    I like to control the lighting ratios of both the flash and background, and hence why I apply exposure compensation (via camera).
     
  6. marc

    marc Guest

    gregory

    you are not helping, please read my post

    why do the shooting distances change as you + or - ev in opposing directions

    i understand the ev, i just do not understand why , the useful exposure distance changes as you + or - ev, in opposite direction
    can you explain?
     
  7. gho

    gho

    Feb 7, 2005
    California
    Sorry for confusing you Marc, maybe it was a bad idea to bring it up.

    Basically the way it works is there's two places you can apply an EV compensation.

    #1: Exposure compensation - "camera" EV setting, where you can adjust the exposure that the camera decides is correct - this is what you would change if you were not using a flash at all.

    #2: Flash compensation - This changes the output of the flash (assuming that the flash is the main source of light) so that the flash exposure is where you want it.

    Suppose you are outside and taking a photo without flash. You snap the pic and notice that the entire image is too bright.

    So now you apply -EV exposure compensation, and get a pefectly exposed image.

    Now suppose you're taking a pic of your girlfriend (even if you're married ;)) and your girlfriend's face is partially shadowed and too dark.

    So you pop on your flash and take another shot. Now you notice her face is still too much in the shadows. Apply some +EV flash compensation (for the flash, not the camera) and you get a nice balanced photo with the ambient light exposing the background, and the flash exposing the foreground - typical fill flash situation.

    If you're not worried about the background or don't care if it's too bright or too dark, then the best bet would be to use just the flash compensation, as Patrick said.

    Yes, it does get tricky and complicated, but I try not to dumb things down just to simplify things. Lemme know if I can clear it up any.

    As far as reducing the distance, applying -EV compensation reduces the flash output. So say you shoot a particular scene, at 0 EV compensation. The camera decides it needs full power to properly expose the subject. If you reduce apply -EV, you're effectively telling the flash that it doesn't need quite as much power as it thinks to properly expose the subject, thus you can get more "reach."

    For example, say you shoot a subject and the camera decides it needs full power, yet the results show that it is overexposed. So you dial in -1 EV and you get the perfect exposure. Now you move your subject back, and take another pic. The camera now has 1 stop of extra light that it can work with and can properly illuminate the subject assuming it is still within range.

    If you don't apply any -EV compensation, the camera would have fired at full power on both shots. The first one would have been overexposed as before, and the second one would be a little closer to the correct exposure, depending on how far you moved the subject back

    Hope that's kinda clear and makes a little bit of sense. Lemme know if you have any questions, and I'll try and explain better.
     
  8. marc

    marc Guest

    i understand. most of that

    let me explain again

    on my sb800 if the effective shooting distance is 2-15ft, on flash lcd and i use a - ev setting the gn of 15 will change to 16,17,19, etc.

    if i +ev on flash, or camera then GN is reduced from 15 to 14 or 12 etc.

    this is just the opposite of what i thought would happen, and what i think you explained?

    ok, am i understanding the ev settings, incorrectly or do they work differently when using the flash?
     
  9. JeffKohn

    JeffKohn

    Apr 21, 2005
    Houston, TX
    greyflash, the quote from Thom's book is actually referring to the fact that you can set the Flash EV compensation in two places: on-camera by pressing the flash button and spinning the front command dial, or on the Speedlight using the +/- buttons on the D-pad. These two controls both affect the same affect the same setting even though they're independent and don't reflect each other. So doing +1 on one and -1 on the other would effectively cancel each other out. I think what Thom's saying is that it doesn't make much sense to use both since it's just likely to cause confusion because you'll have to check two places to figure out the actual flash compensation in effect. Best to just leave the on-camera one alone and use the speedlight's setting (since it allows for greater range of adjustment anyway).

    Exposure compensation on the other hand affects ambient exposure via the shutter/aperture and is independent from flash compensation (which affect the power the flash fires at). As Gregory mentioned there are plenty of reasons why you might want to use both exposure compensation and flash compensation particularly in fill-flash scenarios.

    EDIT: on reflection, the above is really only true when using balanced fill-flash or manual exposure mode. If you're using maxtrix TTL flash metering, then things get a little muddy. Maybe that's what Thom is referring to, I don't know. I do know that Thom disliked the balanced-fill mode (TTL-BL) and prefers to always use regular TTL mode, but I disagree with him on that I think TTL-BL works very well for fill-flash.
     
  10. JeffKohn

    JeffKohn

    Apr 21, 2005
    Houston, TX
    Well for instance, with a +1 Flash EV you're telling the flash "for any given metering scenario, fire with one extra EV of power than you normally would." So if it previously fired full power at 10 feet, now it might be firing full-power at 8 feet (just making those numbers up but you get the idea). So by adding the +1 EV flash compensation you've reduced the maximum distance at which the flash can fire and still meet your exposure requirements.
     
  11. gho

    gho

    Feb 7, 2005
    California
    Ah, yes... That's true - I wasn't thinking along those lines. I always set flash exposure compensation via the camera (spining dial thingy).

    precisely. I couldn't have explained it better myself.
     
  12. marc

    marc Guest

    ok, this is what confuses me, if i am telling the flash to add power, why am i reducing the available, shooting distance? more power means more range?

    explain please
     
  13. JeffKohn

    JeffKohn

    Apr 21, 2005
    Houston, TX
    Because the maximum power is a fixed quantity. If you tell the flash that it needs to fire +1 EV, then to achieve that the maximum distance will be decreased.

    Look at it this way: if the flash is firing at full power and can reach 10 meters at 0EV, how far is it going to be able to reach at +1EV? The distance is going to be shorter, not longer.
     
  14. Hi Jeff,

    Here is Thom's exact quote (under balanced fill flash): "Indeed, the classic beginner mistake is to try to use exposure compensation and flash exposure compensation to override the camera's automatic decisions. The more EV change you ask for, the more the camera will fight you. Solution: Put the camera in Standard TTL mode if you want to set the exposure and flash exposure compensations yourself."

    That is the reason I use TTL and set the way I want the background to look by using less or more EV. When I am in a hurry, I use program mode and let iTTL BL do its thing.
     
  15. gho

    gho

    Feb 7, 2005
    California
     
  16. gho

    gho

    Feb 7, 2005
    California
    That's very interesting, Gordon. Never thought it as the camera "fighting" me. I've typically gotten pretty good results using iTTL where you use standard TTL mode. How do you even put the flash in standard TTL mode?

    Welp, I'm guessing I usually don't have a problem anyways, cuz most of the time, I'm shooting in manual mode.
     
  17. JeffKohn

    JeffKohn

    Apr 21, 2005
    Houston, TX
    Well, Thom's a bit more old-school when it comes to flash, that's why he prefers to use iTTL instead of iTTL-BL. He's probably been doing it that way for a long time and knows how to get predictable results. But I'm not sure his advice is the best for somebody starting out with the latest generation of equipment; by all accounts Nikon's latest flash technology in iTTL/CLS is a really big improvement over previous iterations and works quite well.

    I also wonder if that particular advice is for using on-camera flash or a speedlight. I'm pretty sure that if you set flash compensation on the SB-800/600, the camera is NOT aware of said compensation so I don't think the camera's meter would "fight" it. So using exposure compensation on camera and flash compensation on the speedlight will work well. At least, that's been my experience. I've found that using TTL-BL mode with -1EV or so flash compensation gives extremely natural fill-flash when working outdoors.

    In the case of indoor flash or any other situation where the flash is your "main" light then I agree that exposure compensation wouldn't make sense. When using flash as the main light I use Manual exposure mode, setting aperture for required depth of field and shutter speed fast enough to stop motion (or alternately, setting aperture/shutter/ISO to control the amount of ambient light in the eposure), letting the iTTL flash system take care of exposure.
     
  18. marc

    marc Guest

    hey jeff,

    those are the final conclusions, i have come to also
    manual is easy, just put camera i p and see what camera likes, then change to m and duplicate settings or play around a little

    m mode also cancels any pre flashes. this keeps camera and flash exposing
    subject and background to your liking.

    how dumb i was, not to see how really simple using the sb 800 is.

    bl mode is really more for fill, and usually is not recommended for indoor.
    i like i-ttl fp almost all the time
    not sure how AA works, that will be my next objective

    thanks for your considerable help

    marc
     
  19. JeffKohn

    JeffKohn

    Apr 21, 2005
    Houston, TX
    Well, when I mentioned Manual mode I was talking about the camera's exposure mode, not the flash's. So Manual exposure with iTTL flash still gives you a pre-flash unless you use FV-Lock.

    I almost never use Manual flash mode unless I'm using an umbrella/softbox setup and determine the flash exposure using a hand-held flashmeter (which I haven't done a whole lot of yet). For everything else I stick to iTTL or iTTL-BL; I don't really see any reason to use AA mode with an iTTL-compatible camera especially since you still have a preflash.
     
  20. If your D2H is in spot metering, it automatically puts the flash in TTL or your can select it using mode on the flash. If you are in manual with your camera none of this applies anyway and you are totally in control.
     
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