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Thread: Understanding T5 value of flashes.

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    Understanding T5 value of flashes.

    Hi,

    I'm having a little trouble understanding the t0.5 value as it corresponds to studio lighting. Supposedly this will give me the shortest flash duration if I am not mistaken. However, I'd like to know how this setting usually achieved.

    I own an Elinchrom Ranger RX AS Speed, and from my understanding the fastest (Shortest flash duration) is achieved from attaching the A Flash head in to the B socket of the power pack. As usual I can set 0.1 value up to 7.5 for maximum output from the head, however, this socket will only provide about 366Ws of power. Any help from other powerpack owners welcome as I seek to understand my power pack a little better.

    More specifically do I just plug one A Head in to socket B, set it at Maximum or Minimum value and that's it?

    Thanks
    Po
    Last edited by pophoto; 3rd March 2013 at 02:22.
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    Re: Understanding T5 value of flashes.

    I am mistaken in thinking for example a Profoto B4 at t0.5 is the shortest flash duration and can only be reached at the lowest power setting? So this means only shooting in complete darkness can this be achieved?
    Last edited by pophoto; 3rd March 2013 at 02:23.
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    Re: Understanding T5 value of flashes.

    http://www.bron.ch/uploads/tx_bronpr..._1200_L_02.pdf
    Profoto USA | D4 Air 1200 | Air Flash Generators

    Have a look at the data sheets for two fairly new generators designed specifically to have a fast (short) flash duration.

    The shortest flash duration can only be achieved by the generator working at its lowest power setting.

    Use of a bi tube or quad flash tube head will also lessen the flash duration, because you are further reducing the power to each tube that fires simultaneously.

    You need a flash and ambient light meter to measure the ambient level of light to know if it will effect the scene. It's usually not necessary to shoot in the dark, but using a light meter will tell you definitively.

    And WiKi http://en.wikipedia.org/wiki/Flash_%28photography%29
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    Re: Understanding T5 value of flashes.

    Quote Originally Posted by Giorgio View Post
    http://www.bron.ch/uploads/tx_bronpr..._1200_L_02.pdf
    Profoto USA | D4 Air 1200 | Air Flash Generators

    The shortest flash duration can only be achieved by the generator working at its lowest power setting.
    But that's not universally true. Take another product from one of the same manufacturers, Profoto's D1, for example, has it's shortest duration at full power. Which has nothing to do with T.1 vs. T.5 values.

    Po you can't set a T.1 or T.5 on your flash. Changing the power settings on your flash will change it's flash duration. What the manufacturer tells you that duration is may have been measured as a T.1 or T.5 value.

    When a flash reaches T.5 it has dropped to 50% of the energy output when it fired. When a flash reaches T.1 is has dropped to 10% of the energy output when it fired.

    So if 2 different flash (head/pack or monoblock) are rated with a flash duration of 1/1500 sec. but one is a T.5 value and the other a T.1 value there is a significant difference in the light available during that 1/1500 sec..

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    Re: Understanding T5 value of flashes.

    Thank you Georgio!

    Thank you Kirk, yes most online explanations about T.1 and T.5 are confusing at best!

    I believe the Elinchrom ranger RX Speed has shortest flash duration at maximum power as well. I am also triggering with Pocket Wizards now, Mini on the 5D Mark III and ST4 on the Ranger battery. However, I will be experimenting with hypersync, to see whether exceeding the x-sync speed or having a shorter flash duration will be more advantageous where applicable, especially knowing the shortest Flash duration is at Maximum power B-socket but only giving out 366Ws, or Hypersync at faster shutter speeds with 1100Ws possibilities and to what extent on the 5D Mark III.

    I know Tombol has reached 1/8000s with the Nikon D800 with Hypersync.

    Anyways, I really appreciate the help.

    Thank you,
    Po
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    Re: Understanding T5 value of flashes.

    Quote Originally Posted by Kirk Candlish View Post
    But that's not universally true. Take another product from one of the same manufacturers, Profoto's D1, for example, has it's shortest duration at full power. Which has nothing to do with T.1 vs. T.5 values.

    Po you can't set a T.1 or T.5 on your flash. Changing the power settings on your flash will change it's flash duration. What the manufacturer tells you that duration is may have been measured as a T.1 or T.5 value.

    When a flash reaches T.5 it has dropped to 50% of the energy output when it fired. When a flash reaches T.1 is has dropped to 10% of the energy output when it fired.

    So if 2 different flash (head/pack or monoblock) are rated with a flash duration of 1/1500 sec. but one is a T.5 value and the other a T.1 value there is a significant difference in the light available during that 1/1500 sec..
    Kirk,
    For more useful information just get out and use the stuff.
    Bron, Broncolor also has a lot of useful information on there site and whenever I have the option (rental studio) I always opt for Bron flash gear as I have found that it is the most color consistent and fastest (short) flash duration of any system out there. But that is just my opinion.
    Be well, shoot more...
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    Re: Understanding T5 value of flashes.

    Po,

    T.5 is the duration of half the total flash power emitted. Most strobe companies use this number because usually it looks better on paper, but in fact, there's still visible power that can be seen (trails) and not always flattering.
    T.1 is 90% of flash power emitted and more closely represents the true duration of a flash. Also, there's significant color shifts with some strobes at various durations.

    In regards to hypersync, certain strobes at full power (long duration), benefit from HSync by catching the moment with faster shutter speeds when the flash pulse is brightest.
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    Re: Understanding T5 value of flashes.

    Quote Originally Posted by Giorgio View Post
    Kirk,
    For more useful information just get out and use the stuff.
    Bron, Broncolor also has a lot of useful information on there site and whenever I have the option (rental studio) I always opt for Bron flash gear as I have found that it is the most color consistent and fastest (short) flash duration of any system out there. But that is just my opinion.
    Be well, shoot more...
    Huh ?

    I have been 'using the stuff' for 30+ years. I was replying to the original post.

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    Re: Understanding T5 value of flashes.

    Quote Originally Posted by johnnygoesdigital View Post
    Po,

    T.5 is the duration of half the total flash power emitted. Most strobe companies use this number because usually it looks better on paper, but in fact, there's still visible power that can be seen (trails) and not always flattering.
    T.1 is 90% of flash power emitted and more closely represents the true duration of a flash. Also, there's significant color shifts with some strobes at various durations.

    In regards to hypersync, certain strobes at full power (long duration), benefit from HSync by catching the moment with faster shutter speeds when the flash pulse is brightest.
    Go Johnny go.

    Show us what you know.
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    Re: Understanding T5 value of flashes.

    I just thought I'd update here my result after spending some time with Pocket Wizard technical support.

    I can reach 1/8000s with my 5D Mark III and Elinchrom Ranger RX AS Speed with S Head; no clipping at all power levels.

    This was achieved with MiniTT1 on camera and PwerST4 on the Ranger battery. Using latest factory firmware with one exception, I was using the BETA firmware (Canon 6.201) with the MiniTT1.

    Major settings in the HyperSync tab, with the beta firmware, they have increased the limits to which you can slide the slider to the left, originally at -1600, it now goes to -4500 which is where I am for this at initial try. More info in the release notes!

    I will see what limit I will get with the A Head, and to compare the quality of light and power since I am still pretty new to all of this. So far so good!

    Much credit to Chris from Pocket Wizard and their team for getting Canon cameras this far!
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    Re: Understanding T5 value of flashes.

    Quote Originally Posted by pophoto View Post
    I will see what limit I will get with the A Head, and to compare the quality of light and power since I am still pretty new to all of this. So far so good!

    Much credit to Chris from Pocket Wizard and their team for getting Canon cameras this far!
    The 5DII tops out at 1/500 - 1/640 with an S head. The improvement with the 5DIII is due to the new shutter. The slight change in the PW app is a smaller part of the equation.

    An A head is the antithesis of what you need to achieve a high sync speed because it's designed to create a very short duration with it's special flash tube.

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    Re: Understanding T5 value of flashes.

    Hi Kirk,

    It was only up until yesterday that I started talking to PW. On the 5D Mark III and S Head, I could not get past 1/500 without clipping, this was at -1600 value. Yes, I agree the S Head should give better results because of the trail end of longer flash duration.

    However, upon researching all of this I have seen results from the web from blogs with the 5D Mark2 reaching successfully 1/2000 with this setup even a while back!

    I have to say, more and more mid to high end DSLRs are at a good place today, these performances are just the extra icing that's it that much more enjoyable. To be honest I was frustrated not being able to get past 1/500 with the S Head, since I pretty much ordered it and crossed my fingers!

    Over powering the sun should be less of an issue now, but I still need to play with it more. Next will be finding other creative limits with this setup!
    Actually the main reason to see if this all worked out was to add some Ranger Quadra Hybrids to the setup and to see if I stick with the A heads or S Heads all the way!

    Ultimately, from this exercise, if I was limited to 1/200 x sync with the A heads and 366Ws I would be fine with most indoor action shots. However, I wanted to know if the lighting gear had more to offer and outdoors too!

    Po
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    Re: Understanding T5 value of flashes.

    "The flash duration is typically described with two numbers: t.5 is the length of time for which the flash impulse is above 0.5 (50%) of the peak intensity, while t.1 is the length of time for which the impulse is above 0.1 (10%) of the peak"

    Other than the T measurement you should be aware that most radio flash synch devices cannot trigger your flash accurately at shutter speeds of less than 1/500th of a second. For this reason alone I do not use radio synch when I need to stop motion.

    To stop motion use a synch chord, set your highest possible shutter speed (1/800th for my (Leaf Shutter) and try to keep the ambient light low. Use a flash that has a very short flash duration and you will stop motion.

    To Kirk, sorry if you have taken offense. None intended, I thought I was replying to the OP and only wanted to offer an explanation.

    Sometimes too much information can obscure the simple answers.
    Ciao,
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    Re: Understanding T5 value of flashes.

    Quote Originally Posted by pophoto View Post
    However, upon researching all of this I have seen results from the web from blogs with the 5D Mark2 reaching successfully 1/2000 with this setup even a while back!
    I've tried 6 different 5DII bodies and not one of them synced above 1/640 without the frame being clipped. I think anyone who's claiming higher shutter speeds is getting a frame they have to crop. And I seriously doubt that anyone is getting anything useable at 1/2000.

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    Re: Understanding T5 value of flashes.

    Kirk that may be true, I have not tried, I still have the Mark 2 body I can try with the newer beta firmware to see if there are any improvements!
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    Re: Understanding T5 value of flashes.

    Quote Originally Posted by Giorgio View Post
    "The flash duration is typically described with two numbers: t.5 is the length of time for which the flash impulse is above 0.5 (50%) of the peak intensity, while t.1 is the length of time for which the impulse is above 0.1 (10%) of the peak"

    Other than the T measurement you should be aware that most radio flash synch devices cannot trigger your flash accurately at shutter speeds of less than 1/500th of a second. For this reason alone I do not use radio synch when I need to stop motion.

    To stop motion use a synch chord, set your highest possible shutter speed (1/800th for my (Leaf Shutter) and try to keep the ambient light low. Use a flash that has a very short flash duration and you will stop motion.

    To Kirk, sorry if you have taken offense. None intended, I thought I was replying to the OP and only wanted to offer an explanation.

    Sometimes too much information can obscure the simple answers.
    Georgio: Are you able to shed any light on how I may be able to sync at higher speeds with sync cord but with a 5D Mark III?

    Thanks
    Po
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    Re: Understanding T5 value of flashes.

    PocketWizard® - HyperSync

    Best case scenario, for the focal plane shutter.
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    Re: Understanding T5 value of flashes.

    Quote Originally Posted by Giorgio View Post
    PocketWizard® - HyperSync

    Best case scenario, for the focal plane shutter.
    Isn't this what I've been saying? Am I misunderstanding?
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    Re: Understanding T5 value of flashes.

    Hey Guys,

    Any solutions for the gradient I am seeing, darker upper frame in landscape orientation, but no clipping.

    **UPDATE:Okay, it seems like I found the answer to my question! Getting the right exposure removes the gradient. My willy nilly trail and error shots to remove the clippings saw the said gradients. As soon I expose the shot better, clipping and gradients are removed!


    Thanks
    Po
    Last edited by pophoto; 6th March 2013 at 22:30.
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    Re: Understanding T5 value of flashes.

    Here are some t0.1 times I measured for the Ranger Quadra with an A head:

    B socket 132 J (full power) - 1/2010 s
    B socket 100 J - 1/2025 s (fastest, surprise)
    B socket 50 J - 1/1910 s
    B socket 25 J - 1/1795 s
    B socket 8.2 J (lowest power) - 1/1455 s

    A socket 400 J (full power) - 1/930 s
    A socket 200 J - 1/850 s
    A socket 100 J - 1/750 s

    The measurements were made using two Ranger Quadras and two Broncolor FCC meters at a distance of one meter, 5 times for each pairing, then averaged.
    Note that these are t0.1 times, not t0.5, but you could get a rough estimate of the t0.5 times by dividing by 3 since the Quadra uses normal flash tubes and doesn't use IGBT. I was rather surprised that the flash duration did not increase more as the power was lowered - increased rather than decreased because of the way Elinchrom regulates the power in its packs.
    Last edited by gss; 8th March 2013 at 15:28.
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    Re: Understanding T5 value of flashes.

    gss: Thanks for sharing!

    How do you like using your Quadras and A heads?
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