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Old Feb 23, 2012, 12:25 PM   #1
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Default Is this safe? Old vivitar + new D5100

I have an old but still working perfectly Vivitar Auto thyristor 3700. Is it safe to use on my brand new Nikon D5100? I have already attached it to the hot shoe and it did fire when I pressed the shutter.

Is this OK?
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Old Feb 23, 2012, 1:34 PM   #2
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If it were my camera, I'd probably use it (but only after checking it's trigger voltage to make sure it tests the same way as someone else found), as it appears to test at less than 10 volts. You'll find it on this page:


Now, that's still a little higher than some of the proprietary flash models, so use it at your own risk. Personally, I wouldn't have a problem if it tested that way (10 volts or less). If it was much higher than that, I'd be more cautious.

But, I'd make sure to measure it, as sometimes you'll see a *huge* difference in trigger voltages with some of the older Vivitar models (where one may test at hundreds of volts, and another at around 5 or 6 volts, even though the model number is the same). ;-)

Just use a high impedance volt meter, turn the flash on and let it's cap charge until you get a ready light on the flash, then measure the voltage between the center pin in the flash foot and the metal conductor part on the outside of the foot.

See more about measuring Trigger Voltage on this page:


Just note that you'll need to use manual exposure with the camera, matching the camera and flash settings for the same aperture and ISO speed. Then, just use a shutter speed that allows the amount of ambient light desired (around 1/100 second is usually good indoors using around ISO 400 and f/5.6 or f/6.3). Just set the camera and flash the same way for aperture and ISO speed (a.k.a., the ASA film speed setting with an older flash) and tweak as needed.

Set the camera's White Balance to Flash or Sunny (since the camera is not going to communicate with an older flash model like that except for triggering, it won't know how to set the White Balance for the light from the flash unless you tell it). Otherwise, you may end up with blue photos indoors (because the camera's auto WB may try to set the White Balance for the temperature of the indoor lighting unless you change it to use a more appropriate White Balance for the Flash light, which is closer to the White Balance you'd use outdoors in Sunny conditions).

Note that you'll need to stick within the camera's x-sync speed for fastest shutter speed allowed (probably around 1/200 second with your model). Otherwise, you'll run into issues with black bands in images because the sensor will never be fully exposed to light from the flash at anything faster than the rated x-sync speed (giving you a traveling slit of light instead due to the way the shutter curtains are moving once you exceed it's rated x-sync speed).

If you want high speed sync ability (HSS/FP mode) so you can use faster shutter speeds, you'll need to go with a more sophisticated flash model (Nikon SB-600, etc.) that pulses the light during the shutter curtain travel.

But, indoors, no big deal, since the flash itself can freeze the action as long as it's providing most of the light (where the exposure is set so that ambient light is a few stops underexposed without the flash). IOW, around f/5.6, ISO 400 and 1/100 second is going to freeze most action indoors using a flash, because the image would be underexposed (too dark) without the flash using those settings, and the flash burst length is usually very fast (usually 1/1000 second or faster). So, the subject is only properly exposed during the very fast flash burst (freezing the action).

But, using one outdoors in bright conditions at wider aperture settings (for example, f/2.8 or wider to blur more of the background) can hinder an older flash model's usability (because you may have too much ambient light to freeze faster movement at the fastest shutter speeds allowed with an older flash without support for FP mode). So, you may need to stick with smaller apertures (higher f/stop settings) outdoors in brighter conditions using an older flash model like that to stay within the x-sync speed limits (probably around 1/200 second with your camera) to avoid overexposing the images from ambient light.
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Old Feb 23, 2012, 2:56 PM   #3
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Thanks! That was a really great answer, thanks for taking the time
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Old Mar 5, 2012, 8:39 PM   #4
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You cam measure the voltage if you have a multimeter through the output end of a pc cord. I am not sure if the 3700 has that feature. I can do with with my Vivitar 283.
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