Maxing the flash an unusual way

Discussion in 'Nikon' started by RaymondC, Oct 28, 2017.

  1. Just a thought it's summer here now I don't use my flash often. People are often in direct sun and shadow like from trees.

    Underexpose the ambient light then use the flash full power if need bebto get rid of shadows.

    Aperture and iso controls the flash. Would it help if one shoots wide open and increase the iso and use ND filters to keep the shutter speed so it's not high speed sync.


    Cheers.
     
  2. An ND filter controls the exposure of both flash and ambient, just as the aperture setting. The shutter speed, affects only the ambient. Using an ND filter to lengthen the shutter time or use a wider aperture is a net zero solution. Flash exposure is also affected by distance, which is another parameter you can use to accomplish the desired results.

    Expose for the daylight and use the flash for fill. I would not underexpose the ambient, unless you wish to suppress the background. Plus, flash on camera yields rather unflattering results when it is the dominant source of light. If necessary, stop down until the shutter speed is at or slower than the maximum allowed for flash. Automated flash systems, Nikon and Sony for example, often limit the maximum shutter speed when the flash is attached and turned on. When used for fill, I set the flash compensation to -1 stops, so that shadows are filled without washing out the modeling of natural light.

    Some flash units have an FP mode, which allows the use of higher shutter speeds. The flash is pulsed very rapidly at reduced intensity, emulating a continuous source. Flat LED panels are also a portable source of continuous light, and some are small enough to fit on top of the camera. You must be fairly close to use either FP mode or LED lighting in sunlight.
     
  3. Yes, I was like under 1m from the person, focal length 70mm, direct flash with SB800 manual full power (no diffuser) the person still had shadow on his face. I had to drop the ambient -1EV before it worked, again flash direct full power. Was testing. Is this the best it could had been? I did use F5.6 to bring the flash out of FP. Would F4 or F2.8 with the ND filter helped? Any other way (not including on location studio lights)?

    I also tried bounce card pivoted up a bit with the flash head. At full power also didn't work. Subject was clearly underexposed.
     
  4. You would have to underexpose for ambient light* by three or four stops for the flash to render sun and shadow moot. You would then need to be within the distance specified by the guide number for full power flash at that f/stop. You would, of course, need the shutter speed to be at or below the flash limit. Using the "sunny 16" rule as a sanity check, you may not be able to achieve that combination of ambient settings in sunlight. At ISO 100, the aperture setting at 1/250 second would be f/32 to f/48, not commonly available on a DSLR. If you use a 3 stop ND filter and f/11, you would have to use the flash at a distance of the guide number divided bye 11+3, or f/32. My flash (Sony HVL-F60M) has a guide number of 197 at ISO 100. With a 3 stop ND, the guide number would be 24 (=197/8), and maximum distance at f/11 would be about 2'.

    You could set the flash manually, or rely on auto exposure (not fill), or other methods within the limit imposed by the maximum and minimum power output of the flash. If the camera has a compensation setting, make sure it is not applied to the flash. There are usually options for ambient, flash, and ambient+flash.

    Even with flash 3 or 4 stops over sunlight, you may still see shadows. The solution is to move the subjects out of the shade, into complete shade, or provide artificial shade (a tent or screen, and hope the wind doesn't pick up). It's up to you to control the scene and the light.

    * Sunlight is about 120,000 lux, roughly equivalent to a 400 joule flash with a 50 degree reflector unit at 10'. Your subject(s) would only recognize you by the sound of your voice ;)
     
  5. Thanks for that. There has been times with people and they want to stand there with this nice background also so the background cannot be underexposed and it also happens to be a summer day just after lunch at 1.30PM :-D It is what it is.
     
  6. I understand, but rather than eliminating shadows, try using the flash to open them up, even a little. That gives you a lot more room to work, and IMO, looks better than a flat on flash. See if your camera and flash has a "fill flash" option. If not, then "rear flash" will accomplish the same thing - expose for ambient then add flash just before the shutter closes. If the flash or camera has flash-only compensation, they -1 stops.

    I'd give an example, but I'm currently rebuilding my Lightroom directory, and it's taking a really long time (190,000 images).
     
  7. "Yes, I was like under 1m from the person, focal length 70mm, direct flash with SB800 manual full power (no diffuser) the person still had shadow on his face."

    That doesn't add up. 70mm @ < 1m would be a really tight head shot, and the aperture would be at f/32 for that distance at full power. The background would have been at least 2 stops underexposed.

    Since light is additive, if the face was in full sunlight, then an aperture closer to f/45 would be needed, and not many lenses will stop down that far.

    An exposure @ f/5.6 and 100 ISO would be totally blown out by a full-power SB-800 at a distance of less than a metre!

    I suggest you check the EXIF data to find out what the exposure really was. Or we're not being given the full details of your setup.

    Is it possible the lens was partly or completely blocking the flash? This often happens with bulky lenses and camera-mounted flash at close distance; especially if the lens is fitted with a hood. Try moving the flash off camera, or reversing it into a large reflector.

    Usually a flash fill of minus 2 stops from ambient is all that's needed to lift shadows nicely. Any more fill and you get a very artificial look, with shiny skin from specular flash reflection.
     
    Last edited: Oct 29, 2017
  8. Just the 35-70mm F2.8 with SB800. So prob it wasn't blocked.
    A no. of test shots. One without shadows on face (and that particular time), was a direct flash with no diffuser. ISO 100, 1/2500, F2.8. No flash or exposure compensation. There was so blown highlights on face but at least no shadows.
     
  9. "ISO 100, 1/2500,F2.8."

    - Well, there might be the problem. At speeds above X-synch (1/250th) the flash is effectively a continuous source and control by aperture alone no longer applies. The camera also needs to switch into FP-synch mode.

    Have you set the camera flash menu to 'Auto FP (1/250)' to enable HSS? If not the flash won't register at 1/2500 s.

    When the flash and camera are in FP mode, there is no variation between ambient and flash, because both are affected by aperture and shutter speed.
     
  10. Raymond, a fundamental thing about lighting is - no amount of added light can COMPLETELY remove shadows.

    By way of explanation, imagine a white background with, say, 10 arbitrary units of light on it except in a completely black shadow. Many photographers think more light will remove the shadow. Let's say they put on 10 more units of light on the background - now it has 20 units overall, but only 10 in the shadow, a 2/1 ratio. So they add more light, say 100 units added. Now the BG has 110 units overall, but only 100 in the shadow, an 11/10 ratio. Not too noticeable, but still there. Once you let shadows intrude, the best you can hope for is to make the shadow relatively insignificant, OR exceed the recording limits ("blowout") of your system.

    The rule of thumb I used to work with in studio design was, that if the ambient light was kept below 1 or 2 percent of the total exposure, it was pretty nearly negligible. This is rough a 6 or 7 f-stop difference in ambient vs flash exposure. This is a pretty tall order to fill when you're in sunlight, so probably best to forget about completely overpowering the shadows.

    If you can't get your group out of the shadowed sunlight, I'd say to just bring in a reasonable amount of fill light and then live with it.
     
  11. Yes FP is set to on by default on mine. The FP word is on my SB800.

    There were blinking highlights on the face but there were no dark shadows. The best I could do ...
     
  12. In as much as I have an area of expertise, this isn't it... but it feels as though your problem is more direction of light than power? More diffusion (shooting through a convertible reflector/diffuser, or just off a soft reflector) or using a ring flash (or adaptor) might help?

    I usually rely on dynamic range to dig out the shadows, but I tend to think of reflectors at ground level as being the solution to sunlit shadows, rather than direct flash. It also limits the colour balance issues to some extent. I'm no strobist, though.
     

Share This Page