Low f stop with flash??

Discussion in 'Beginner Questions' started by jennine_hadfield|1, May 15, 2010.

  1. Hi everyone,
    I have a couple of questions.
    First, I am trying to accomplish taking portraits outside in aperture mode with a low f-stop such as 2.8 to get quite a bit of blur in the background for the shot. At this setting the camera automatically puts me at a shutter speed of 1/1000. When I don't use my SB 600 the picture turns out perfect. Great! However, with these shots I would like to have my SB 600 turned on for fill flash for shadows on their faces but as soon as I do that the shot is way over-exposed, naturally. Is there a way to get this shot at such a low aperture with a flash or is raising the f-stop my only choice with flash or maybe just deal with the shadows and keep the flash turned off? My SB is turned to the lowest exposure and zoom possible.
    Secondly I have tried to do this in manual mode but when I have this aperture at 2.8 the camera only allows me to have the max shutter speed of 200. Why can't I get the shutter speed any higher in manual mode? I have a Nikon D90.
    Any help would be greatly appreciated as I'm really confused after learning that using flash is good for fill flash on faces and that a low aperture is great for portraits.
    Thanks.
     
  2. Many cameras will not synch with flash at speeds greater than 1/200. Check to see if yours has a high-speed synch option. That might buy you a little bit more. Also, turn down the ISO as far as you can. However, once you are down to your minimum ISO and max speed (presumably, 1/200), there is no way to let in less light other than closing down the aperture.
    You can get plenty of blur at apertures somewhat smaller than 2.8 if the background is a bit of a distance behind the people.
     
  3. You could try using a neutral density filters to cut down the amount of light entering the camera 3 stop filter would bring you down to 1/125s and that is within the camera's synch.
     
  4. Kris is korrect.
    ISO to minimum (or slowest film speed).
    Neutral density filter.
    Case closed.
    Jim
     
  5. Consider adjusting your flash output compensation to -2 or -3 stops. This should soften shadows, but not overexpose the scene in aperture priority. Also check the custom functions for high speed synch and turn on this option.
     
  6. Jennine -
    You might want to consider working around the problem - if you can, simply move into a shadier area, and move the subjects away from the background. Also, if you have control over the timing, wait for a nice overcast day - you can make some really nice images using the SB600 & d90 when you aren't fighting the power of the sun.
    Mike
     
  7. Spearhead

    Spearhead Moderator Staff Member

    Doesn't the SB600 have high speed sync? The specs say it does.
     
  8. Both, your camera D90 and the flash SB600 have FP flash mode.
    Just read documentation that came with your equipment.
    You can use any faster shutter speed, with SB600 is camera hot shoe, or as a remote FP CLS automatic exposure flash.
     
  9. Spearhead

    Spearhead Moderator Staff Member

    Exactly. Ignore all answers that don't reference high speed sync (FP mode), they're wrong. You just have to set things right and you can do exactly what you want to do.
     
  10. Stick an ND on
    Turn the output of the flash down as low as you can, bounce it off white paper/card to further reduce output (and get softer light), get the paper closer to the subject to further soften the light (but you'll really need low-power flash for that)
    Make sure you're using the diffuser
    Minimum ISO
    I find it amazing that you have too much light — I usually find myself lacking enough of it.
     
  11. Spearhead

    Spearhead Moderator Staff Member

    There's no need for any filter. The flash can handle the high shutter speed.
     
  12. As Frank and Jeff noted, the FP option with Nikon's CLS compatible dSLRs and flashes will handle subtle flash techniques in bright daylight. I've used this trick many times with my Nikon gear for fill flash in daylight. Even with full automation it often works well enough that I don't need to make any other adjustments or use manual overrides.
    Here's a link to Nikon flash tutorials on the Nikon USA website.
     
  13. It is true high speed sync will allow you to use wider apertures in bright light. However, any discussion of high speed sync should also point out that the power of the flash diminishes in this mode--the higher the speed above the 'normal' sync limit, the more the flash power diminishes. This is very important to know because if you don't stay relatively close to your subjects (or keep the flash close to your subjects) you will not get any fill benefit, and it is worse the brighter it is. It will vary, but for instance, against bright sun, for a subject distance of 10 feet--you aren't going to see any fill benefit.
     
  14. William_W

    William_W Moderator Staff Member

    “taking portraits outside . . . Any help would be greatly appreciated as I'm really confused after learning that using flash is good for fill flash on faces and that a low aperture is great for portraits”
    . . . and also, as well as taking acute notice of the advice to use High Speed Sync and also the fact that you need to stay close – or at least the Flash needs to stay close to the subject - you should also be aware: that using a diffuser or bounce card will even further diminish the amount of Flash Fill you have to fill – so in this circumstance using a Diffuser or Bounce card is a very bad idea – you need to use Direct Flash.
    Think of it this way:
    In Full Sun (with the sun as Backlight, Hairlight or Sidelight) the Flash has to fill the face to somewhere near equivalent of the exposure the sun is making on the subject and also the rest of the scene, (so the Background is not blown-out and so you fill the Shadow area of the face).
    Now that means the Flash is wanting to make an exposure of something to nearly match the F/16 rule – which simple put - is quite a lot of Flash Power from any On Camera Flash.
    ***
    Also, just on the idea of using the ND filter, which I DO NOT recommend for mostly all circumstances, IF the camera and Flash are capable of High Speed Sync:
    The value of ND Filters vs. HSS (High Speed Sync) was discussed at length in the Wedding Forum about a year or so ago – I cannot find the thread.B
    But the bottom line is, before the Flash is at the (Distance) limit of its range, you can get farther away from the Subject using HSS than if you used an ND Filter. What this means is, you have more flexibility if you use HSS.
    Also, using ND filters for this particular purpose likely creates or exacerbates other problems the most dangerous of which is either direct Flare or Veiling Flare.
    This is because when using Flash Fill in Open Sunlight, the Sun is usually the side or back light and in this circumstance one should necessarily NOT use any filter if at all possible: especially if one is using a zoom lens; especially if one is using a kit zoom lens; and especially if one has no lens hood. . .
    WW
     
  15. William_W

    William_W Moderator Staff Member

    “and that a low aperture is great for portraits”
    . . . but there’s more:
    A “low aperture” (I think you mean a Large Aperture, which is represented by a “low number” – e.g. F/2.8 is a larger aperture than F/8)
    A Large Aperture might be very useful for Portraits to allow the Photographer to Blur the Background and create a shallow Depth of Field . . .
    BUT more often than not a nicely blurred background is more dependent upon the physical separation (distance) of the Background, to the Subject.
    Try this quick practical quiz . . .
    If you have a 50mm lens, put it on your D90, or set your zoom to 50mm.
    Stand the Subject in sunlight about 2 ft from a garden wall or hedge behind them . . .
    You stand 10ft away from the Subject, and frame the shot vertically, you should have a nice Half-shot of the Subject.
    Set the aperture to F/5.6 - now that is NOT a large aperture.
    Take a Photo . . .
    you should get a very yucky and minimal background blur...
    Now move the Subject away from the Garden Wall or Hedge so that they are 15 ft from the nearest Background and take another shot – presto - nice Background Blur.
    I chose 10ft for the Shooting Distance because you should be able to use Flash Fill at that distance (see Nadine’s comments) and I chose a 50mm lens because I guessed you would have that FL available to you and also 50mm is a nice, flexible Portrait lens on a D90 when working outside.
     
  16. I agree with William really - I shoot my wife on the beach on vacations - the high speed option is doable and ok in many instances. I doubt you will be able to bounce flash - on a bright sunny day, you have to really punch in that direct flash to fill in those very contrasty shadows (at least in my limited experience). Also, William points out that you can achieve a nice blurred background via simply moving the subject relative to the background and getting your lens as close as possible. I have a 50mm prime 1.8 - I usually would opt to use my kit lens 18-105mm in such an arena (I have the D90 and presume you have this kit lens) - note that using higher focal lengths compresses the background nicely at higher f-stops so you can achieve the same result.....I recall even with my SB900 using auto FP high speed at f2.8 or so, it really is diffuclt to fill in these harsh shadows.
    Also would simply use a reflector if possible as well is another option? Oh, and I am sure this is quite obvious, but I have done it (yeah, I know, I am so an amateur) - MAKE SURE YOUR ISO is at a low setting in this scenario - that would obviously worsen your perdicament :) Finding shade is easier too and generally I prefer this if possible personally, but when I am on the beach or in harsh mid-day light, I punch that flash in there or use a reflector.
    Oh, and just be cautious not to totally cut out your shadows on the face - then it just looks un-natural alltogether.
    Ok, hope you figure it out - take care.
     
  17. I don't know about your flash, but on mine, the distance that the flash (in high speed sync mode) can reach are shown on the flash's LCD when you've plugged in your variables on the camera. Always consult that to see if you have enough reach in that mode, to do your fill.
     
  18. There is an old trick that isn't used much anymore since autofocus became common. It was called "front focusing". You dial in as tight an aperture as you need, then manually focus in front of your subject. So if your subject is 7 feet away, you might focus at 5 or 6 feet. Your tight aperture gives you enough depth of field so your subject is in focus, but the background is a blur.
     
  19. Robert, what a novel concept that is so simple yet applicable here - I will keep that in mind personally :)
     

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