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The Sync / Strobe Aperture conundrum!

JacJac Member
edited February 2016 in flash & lighting
I'm having a hard time getting the right exposure with my flash. 

My problem: I bought a Phottix Indra 500 strobe (500 watts). Tested it at 3 meters/10 feet with only the "cone" light modifier it came with at full power. Light meter read f/11. 

As you all know a Canon 6D maximum sync is 1/180. 

I would like to under expose bright sunny background (f/16) by one stop at least. Don't want to sacrifice light output by using HSS. BUT also dont want to go all the way to f22 and get soft pictures. 

Any pros out there that can help me? Please....I've been working on this problem the whole day. Is an ND filter worth considering? ....It will keep the Fstop low and i'll just push up my ISO to 200? Will it work? 

 Please help me. I have a wedding on the 20th of Feb! And would love to snap my fingers and get a Profoto D1 but that will mean killing myself financially


  • Neil vNNeil vN Administrator
    edited February 2016
    OK ... let me see if I have this summary correct. 
    You want f/22 exposure from the flash which gives you f/11 at that comfortable distance. 
    So you have to gain an extra two stops of light from your flash?  
    (For now, forget about the f/22 diffraction softness you might run into.)

    Before you even think about going to HSS or dealing with diffraction problems - your flash only gives you f/11.
    That's your limitation right now. You can't under-expose the ambient light by two stops (i.e., f/22) if you can only dump f/11 worth of flash. 

    Going to 200 ISO won't gain you anything either in terms of your balance between flash and ambient. 

    Your only way out of here is a more powerful flash (by two stops). 
    When you get there, we can figure out the way to keep you at f/16 instead of f/22
  • dbrunodbruno Member
    edited February 2016
    I might be mistaken, but I think Jac *doesn't* want to go to f/22.

    Not to get too off topic, but why in the world would Canon limit the sync speed to 1/180 on the 6D (I have one)? Even my 600D has 1/200.
  • Neil vNNeil vN Administrator
    Yes, Jac doesn't want to go to f/22 ... but before we get there, we need to figure out if his flash can deliver enough power to give correct exposure, when the camera is set to under-expose the ambient by two stops.

    Once we have that down, we can figure out the combination of camera settings to achieve what he wants, but at f/16 or f/11
  • TrevTrev Moderator
    edited February 2016

    Something is not right here with your readings.

    A 500W light at only 10ft and it gives f11 at full power? Any normal speedlight would give that result.
    It just does not gel to me with those results you posted.

    What's this "cone" you are talking about, size? Reflector, small dish type?

    The reason I ask is I have a  360W Light and when I read your initial post I thought it did not make sense with your results.

    I tested my light, 360Ws, to make absolutely sure as I was certain I got f11 @ 4.5m, and again to be doubly sure.
    (just finished testing it right now, and I went over each measurement 4 times and same result each time).

    Light Meter Settings: ISO 100; Shutter 1/160th (I could not set my meter to 180th, but that would make NO difference whatsoever).

    I set up my light, then I got out a tape measure and laid it out along the floor, just so I was absolutely precise, then I cranked up the 360 to full 1/1 power.

    Results (precisely measured to the millimeter, well to my big toe):

    @ 2.5m - f20
    @ 3 meters (10ft) f18
    @ 3.5m f16
    @ 4m f13
    @ 4.5m f11
    @ 5m f10

    Just on that premise alone your readings for that Indra 500W full power of 3m and only f11 cannot be right, surely.

    You should be pumping out something like f27 or slightly lower with a 500W @ 3m, for sure.

    So I think either you did not measure correctly, or that 'cone' is severely hindering the light output.

    The 360 I used has a 5inch silver reflector dish type on it, totally default accessory it come with.

    Image shows what I am talking about re reflector, I own a Cheetah, which was made by Godox and this shows a Godox 360W



  • TrevTrev Moderator
    edited February 2016


    Another thought just struck me, are you sure you had the light full power in manual, as it's a TTL light, and if you tried to meter it in TTL you will only be getting a pre-flash reading, and at those results, it looks like that may be the case, if not, it's as I described above.

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