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Photo Forum / Digital Photography / DSLR Cameras / December 2006Nikon D70, SB-600, and Sto-Fen Omni-Bounce
Here's my (recent) experience 1. Macro shots Using the Nikon D70, any macro lens, the Nikon SB-600, and Sto-Fen Omni-Bounce for macro shots is producing consistently underexposed images. Removing the Omni-Bounce and using the strobe alone, either with or without the built-in diffuser, produces perfectly exposed images at every aperture (at lest for the range I've tried, f/5.6 - f/45). The problem appears with at least two different lenses, the Tamron 90mm f/2.8 and the Nikon 24-85mm f/2.4-8D. The underexposure is on the order of (a minimum of) 2-4 stops depending on magnification (subject range) and aperture setting (I almost always use the A-mode for macros). 2. Moderate range (portraits and party shots) Using the Nikon N70, the SB-800, and the Sto-Fen Omni-Bounce produces consistently underexposed shots with a variety of lenses. The Nikon 18-35mm F3.5-4.5D, the above-mentioned lenses, and the Nikon 70-300mm f/4-5.5D are the most recent ones I've used. Here the underexposure ranges from 1-3 stops depending on a large variety of factors. Okay, I'm guessing that something in either the camera or the strobe is simply using the film-subject distance to calculate the required exposure and not doing the more-sophisticated pre-flash to gauge subject reflectivity and other factors. A, Is my guess (more-or-less) correct? B. Is there some camera or strobe setting that forces it to do the right thing even with the diffuser in place? TIA Norm > B. Is there some camera or strobe setting that forces it to do the right > thing even with the diffuser in place? On the flash, check that the display says TTL in the upper-left corner. If not, press the mode button on the flash. Cheers, Richard | > B. Is there some camera or strobe setting that forces it to do the right | > thing even with the diffuser in place? [quoted text clipped - 4 lines] | Cheers, | Richard It clearly says TTL on the flash. On the camera it shows a single lightening icon which AFAIK indicates normal flash operation. Is there any other, menu-based setting that might affect this? Norm > It clearly says TTL on the flash. On the camera it shows a single > lightening icon which AFAIK indicates normal flash operation. > > Is there any other, menu-based setting that might affect this? Hmmm. The diffuser would cause a light drop, but not that severe and metering should compensate for it (at least at short ranges). It does smell like something's using a calculated power (contrary to the TTL setting). It would seem: a) Light from the diffuser is somehow directly entering the meter. This is plausible if the flash is in auto-flash (self-metered) mode, because of the sensor's placement; it shouldn't be possible in TTL mode except with very short prime lenses. This could be tested by taping a piece of cardboard to the bottom of the flash head to block any direct light from the meters. b) Mere presence of the diffuser is changing behavior. There is a sensor on the SB-800 (and presumably the SB-600) that will zoom the flash head out to 14mm when a diffuser is installed. On the SB-800 version of the Sto-Fen, there are ribs on one side to prevent triggering the switch. (The sensor switch is on the bottom of the flash face.) I'd bet on this one, though it doesn't explain what you're seeing with close-range macro work. c) The diffuser is lighting the scene differently, and matrix metering is keying off unexpected areas (e.g., more illuminated foreground). Spot-metering would be a way to test for this. Other thoughts... * If you have Auto-ISO enabled, turn it off and test with ISO 200. (So tests are really apples-to-apples.) * Try with the head head tilted up at 45 degrees. * There is an EV adjustment set on both the camera and the flash, and they're additive. * If exposure bracketing is on, turn it off. * Confirm the Flash Mode in the D70 menu is set to TTL (option 19). * Are you using a second flash here, or just the SB-600 on the camera? It's probably something so simple we're not seeing the forest for the trees... HTH, Richard [BIG CLIP] | Other thoughts... | [quoted text clipped - 17 lines] | HTH, | Richard Auto-ISO is never on. It's almost always set to 200. Bracketing is off. Flash mode is definitely TTL. No second flash, most of the time an off-camera SB-600 connected with a Nikon SC-17 cord, though I've experienced this with the flash screwed onto the camera as well. A brief test confirms that tilting the flash head up 45 deg, does indeed help and there's a very vague recollection in the back of my fading memory that Sto-Fen in fact suggests doing the same thing. It's been suggested that with the flash set flat and the diffuser on there's too much light entering the flash's sensor directly. I'll try this for a while and see if it really does cure the problem. Norm > No second flash, most of the time an off-camera SB-600 connected with a > Nikon SC-17 cord, though I've experienced this with the flash screwed onto [quoted text clipped - 6 lines] > entering the flash's sensor directly. I'll try this for a while and see if > it really does cure the problem. Yes, StoFen does recommend pointing the head up 45 degrees. But in TTL mode the flash's on-board sensor shouldn't be influencing the exposure - it should only come into play in non-TTL auto-exposure mode. I suppose a quick test would be to tape a piece of cardboard to the bottom side of the StoFen with it pointed straight forward, to see if blocking it from the lens / on-board sensor has an effect. FWIW, I've had good results with this larger soft box: http://www.bhphotovideo.com/bnh/controller/home?O=3750&A=details&Q=&sku=32690&is=REG Regards, Richard > [BIG CLIP] > | Other thoughts... [quoted text clipped - 34 lines] > > Norm I would just confirm using a SB-800 the clip on diffuser will lock the flash head at 14mm and if you use the slide-out diffuser it will lock at 17 mm. Any diffuser use will defeat TTL function. For general flash use, vary different angles of bounce and indirect placement. Using either the SB-800 or SB-600 in slave mode and appropriate placement will give you great creative flexibility. Good luck, Leonard >Here's my (recent) experience >1. Macro shots [quoted text clipped - 14 lines] >the most recent ones I've used. Here the underexposure ranges from 1-3 >stops depending on a large variety of factors. Try tilting the flash up 45 degrees, maybe light diffused from the Sto-Fen is hitting the flash sensor and causing the underexposure.  SignatureCharlie... http://www.chocphoto.com >>Here's my (recent) experience >>1. Macro shots [quoted text clipped - 17 lines] >Try tilting the flash up 45 degrees, maybe light diffused from the Sto-Fen is >hitting the flash sensor and causing the underexposure. I often shot with the diffuser on and the flash pointing at the subject. No problem with underexposure.. Jack That happens if the reflected light enters from the eyepiece. In that case he needs to cover the eyepiece. Nikon provides a cover with the camera for that reason. Otherwise, in iTTL, the flash sensor of the flash should not be used. SignatureDimitris M > Try tilting the flash up 45 degrees, maybe light diffused from the Sto-Fen > is > hitting the flash sensor and causing the underexposure. Please Disregard > Please Disregard General education mode = ON alt.test misc.test rec.test comp.test There are many more... General education mode = OFF Austin |
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