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Thread: Getting the correct lens settings for a synced strobe?

  1. #1

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    Getting the correct lens settings for a synced strobe?

    Hi all. Super new to large format photography and this is my first post.

    I have been shooting 8x10 and as scary as itís been itís so fun and Iím loving it. So far Iíve shot outside in the daytime so results have been fine and things are working ok, lots to improve on but getting there.

    I have the chance tomorrow to use a strobe light with my photos syncing it with the X socket on my camera. This is all great but I have absolutely no idea what I set my camera lens to settings wise for this. Iíve never done this before with any camera.

    I have a copal no.3 Schneider-Kreuzhnach symmar 1:5.6/300 lens and have no instructions or anything for it but really I wondered what do I need to set the f stop and all that to. I am using 80 iso film but how do I know the setting and how do I calculate them?

    Any help much appreciated.

  2. #2
    Vaughn's Avatar
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    Re: Getting the correct lens settings for a synced strobe?

    Exposure will be a combination of aperture and flash (shutter speed is not a factor). And the aperture will depend on the subject distance. As I said, shutter speed will not be a big factor...unless it is long and starts recording a significant amount of ambient light.

    Most flashes will have a graph showing what aperture to use for what distances.
    "Landscapes exist in the material world yet soar in the realms of the spirit..." Tsung Ping, 5th Century China

  3. #3

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    Re: Getting the correct lens settings for a synced strobe?

    You will need a flash meter... This will give you an f stop to set the lens to...

    You also need to make sure your shutter has X synchronization setting so the shutter is completely open when flash goes off...

    Leaf shutters will synchronize at all speeds, but shutter speeds do not affect the strobe light, just the ambient light...

    Steve K

  4. #4

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    Re: Getting the correct lens settings for a synced strobe?

    Bring a digital camera and put it without lens in to the back of the camera. Take a 1 second picture while tripping the shutter on the lens. Bring up the histogram to see exposure. Fast learning is more fun

    Sent fra min SM-G975F via Tapatalk

  5. #5

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    Re: Getting the correct lens settings for a synced strobe?

    Most flash units have a graph or a guide number. Use the guide number to determine flash-to-subject distance (camera distance is irrelevant) for a specific aperture; or use it to find the right aperture for a specific distance.

    See here: https://en.wikipedia.org/wiki/Guide_number

    Best,

    Doremus

  6. #6

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    Re: Getting the correct lens settings for a synced strobe?

    OK amazing, thanks os much for your help here! Let me try all this, will get back to you!

  7. #7

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    Re: Getting the correct lens settings for a synced strobe?

    Ok thanks so much for your help, apologies for being so dumb about all this but wondered if you wouldn't find helping me with this stuff.

    The strobe is a ProfotoB1X and I cannot find any chart anywhere. I found the user guide but no chart. Any ideas where I could find one or is someone able to help me work this out roughly based on a similar model or type?

    Also to add here is my lens.

    Click image for larger version. 

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    There is a X socket so I presume I link the strobe to that which makes sense. When I use the X socket does this socket end up controlling the shutter so it completly opens or is that only the case in more modern lenses, if it does not should I just ensure the camera is set to fully open?

    I don't have a digital camera to try that idea but that does sound great and should probably try that.

  8. #8

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    Re: Getting the correct lens settings for a synced strobe?

    The PC socket just acts as a switch that closes a circuit.
    X signifies Electronic flash.
    M signifies M-class flash bulbs.
    You want X .
    Your strobe should have a Guide Number somewhere in the instructions....usually measured at 10 feet.
    Say, for example, it says GN 160 at ISO 100. Divide the GN by 10, and you get 16.
    f16 at 10 feet...FLASH to SUBJECT.
    Your shutter syncs at all speeds, so let's say you're inside, and the strobe is your main light...set your shutter at 1/125 @ f16 and you're good to go with the flash to subject at 10 feet with ISO 100 film.
    That'll get you through until you get a flash meter.
    ***This assumes no modifiers, like umbrellas, softboxes, etc.***
    Last edited by Dugan; 22-Sep-2021 at 13:08. Reason: More cowbell

  9. #9

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    Re: Getting the correct lens settings for a synced strobe?

    Ah wonderful thank you! I'm getting a flash meter haha. Ok how about this situation. I have ISO 80 film so what would the math be for the GN then?

    In the user guide I have yet to find the chart or guide for distance etc - Heres the suer guide - https://www.bhphotovideo.com/lit_files/375284.pdf

    Thanks again so much for your help this is making more and more sense haha

  10. #10
    Drew Saunders drew.saunders's Avatar
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    Re: Getting the correct lens settings for a synced strobe?

    Quote Originally Posted by Dugan View Post
    The PC socket just acts as a switch that closes a circuit.

    Your strobe should have a Guide Number somewhere in the instructions....usually measured at 10 feet.
    According to the user guide:

    https://cdn.profoto.com/cdn/0529ab3/...r-guide_en.pdf

    Guide number at 2m, 100ISO with Magnum Reflector is "452/10"

    Not sure I know what the /10 is about.

    This: https://www.search-manual.com/profot...-388539-manual

    Says: Guide Number 291 @6.56' (2.0 m), 100 ISO with Magnum reflector

    So, in short, buy or borrow a flash meter or use a digital camera and do a LOT of testing!
    https://www.flickr.com/photos/drew_saunders/

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