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Trouble determining correct flash distance to subject using Pocketwizards.

SpinFxtcSpinFxtc Member
edited June 2013 in flash & lighting
So i set up my camera to expose a scene say it goes something like this:

1/160
f4.5
ISO 800

I want to remotely position my flash at around 3 metres away from my subject (Side light) and zoom the head to 105mm which my flash when on camera tells me it should be set to a manual setting of:

1/128 power
Zoom: 105mm

Which supposedly gives me a correct flash-to-subject exposure distance of 2.7m (close enough to 3m).

My question is: Why is it that when i put my flash onto my pocketwizard, the flash-to-subject distance now changes to .8m?
Why does this happen? It seems so much easier to just have my flash already on my pocketwizard, set the flash correctly according to what distance it will be away from my subject and start shooting away... But doing it that way gives me an incorrect flash-to-subject distance...

by the way i have a Nikon D3s and 2x SB900 with a mini TT1 and 2x TT5

Comments

  • What mode do you have the SB900 in? It sounds like you might using the GN "distance priority" manual flash mode, which I would not expect that to work off camera because it needs to communicate to it (eg. for ISO and aperture). Another thought is if you angle the head upwards, I think the distance priority mode switches off (because it won't know how high you are bouncing). Anyway, I'm more of a TTL flash user, so disregard if what I wrote is nonsensical...
  • Yeah im not angling the flash because i can see the difference in the distance scale in M Manual mode when i move it to off camera. i can see that aperture affects the flash output in manual mode but changing the ISO doesnt affect it?? Why doesn't ISO changes work when off camera? I thought that would be important seeing its a factor in flash output when in Manual mode?? I use ttl for quick shots but like to use manual when staging a shot. Just thought that if I could go by flash-to-subject distance in M manual mode I could cut down my flash chimping.
  • MikeZMikeZ Member
    I presume you are using ttl since you are not mentioning using a flash as a commander or an ac3?
  • Not using ttl. Using a flash set to M on a flex tt5 remotely connecting to a mini tt1 on my camera. I would like to be able to see the correct flash-to-subject distance scale on the back of my flash which is set to M but it gives me an incorrect reading so then I'm left to shoot-adjust-shoot-adjust until I have it right. I just want to eliminate the guess work and see that if the flash is telling me that I need to stand 3m away from my subject then that would be correct flash exposure. But it's not...
  • This makes it easier to understand what im asking here:

    This is in regards to using pocketwizards with flashes: This intelligent system (Pocketwizards) takes note of any changes that you make to your ISO, shutter speed or aperture and makes any necessary changes to ensure perfect exposures...


    Now try this scenario with a remote flash on a pocketwizard (mini tt1 with a flex tt5) and let me know why the distance doesn't work correctly:

    1) Set both your camera and shoe flash in manual mode

    2) Adjust your camera exposure to your ambient light. For argument sake let's say it's F/5.6, 1/60th, at ISO 200

    3) You should see F/5.6 on the LCD screen of your flash unit along with a distance scale in feet or meters

    4) Now you want to judge your distance to your subject… let's say you are six feet away from your subject

    5) Now, dial up or down your flash power with the controller on the back of your flash while looking at it's LCD screen so that the flash output power lines up with your calculated distance to your subject (6 feet in this example)...it may say 1/4 power, or 1/32 power, or some other number. That will give you the proper amount of flash at that distance to your subject and will be pretty balanced with your ambient light.

    cheers
  • As soon as you take the flash off the camera and put it on the Flex TT5 it doesn't know the camera settings anymore. I believe the communications between the camera and PW is only at the actual time of activating the shutter button. It's not constantly talking to the flash.

    For example, if you zoom your lens does the flash head zoom like it would if it were on your camera? The FlexTT5/MiniTT1's claim to fame is being used to handle TTL flash, not as a manual dumb trigger.
  • Awesome thanks for clearing that up Mr Nikonguy. So i guess with flash on Manual, its left to guess work with the distance of flash-to-subject. Do you have any tips on nailing Manual exposure from a remote flash with minimal test shots?
  • You could use a flashmeter. You could also do a few test shots and check the histogram / blinking highlights display.
  • You know the ISO, aperture and the flash distance to subject, manually set the flash power while it is on the camera. Remove the flash from the camera and set it the correct distance to the subject. If you need to make miner adjustments to the flash power, just adjust your flash to subject distance.

    Quin
  • yeah that's what i have been doing and its bang on with the exposure every time. Just thought there may be a trick where you could avoid having to do it on camera and then put it on pocketwizards but its all good. ill continue doing it this way :)
  • TrevTrev Moderator
    If you wanted to be fairly accurate from the get go in manual mode without putting on camera then removing you could in some spare time make a cheat sheet.

    Put the flash on camera in manual mode, choose an aperture of f11, then write down what 1/1 will give you in distance; 1/2 power; 1/4 power; etc.

    then change aperture to f8, do the same and so on with as many aperture settings you commonly work with.

    so it would look something like this:

    f11 - 1/1 6m; 1/2 3m; 1/4 1.5m; etc.
    f8 - 1/1 8m; 1/2 5m; or whatever you get.
    f5.6 - and so on.

    That way, you just have a laminated printed small business size card in pocket and pull it out and set flash power/distance to suit.

    this will get you into the ball park very quickly.

    However, I personally, do not bother, since with experience comes a very rough idea of what to set and it will only take a few seconds to take some tests and get it right.
  • Cheers Trev that sounds logical enough. I am managing to get what i'm after in a few test shots but i was just seeing if there is an easier/quicker way.
  • MikeZMikeZ Member
    Pocketwizard confirmed that the flash will not measure off the camera.


    Distance information isn't communicated to a remote flash. GN and Manual distance scale operation is not the same as it would be on the camera without any radio.

    Best regards, Dan Cirillo
  • DaBearsDaBears Member
    edited July 2013
    If you're using the PW Mini and Flex system, the off-camera flash has to be in TTL mode on the Flex, even if you're going to be using it in "manual". You then use your 2nd flash on top of the Mini in commander mode to manually adjust the output of the remote flash, just as with CLS. Alternatively, you can also use an AC3 controller on top of the Mini switched to manual control. This way you can set the light approximately where you want and simply adjust the output to taste remotely without having to fiddle with the exact distance. If you have to have the distance scale showing, you can use any "dumb" triggers with the flash in Manual mode. But you'd be losing some of the benefits of having TTL triggers' greater control.

    Actually, now that I think about it, you can also reprogram the Flex to be a "dumb" trigger through the configuration tool. Then trigger your flash in Manual mode to your heart's content.
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