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Author Topic: mirror-lock-up is made pointless by a t.1 flash duration HOW short?  (Read 1524 times)
markwilliam
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« on: August 05, 2013, 04:25:23 PM »
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If I photograph motionless objects lit only by strobe/flash and use a tripod with a 25 MP "full-frame" sensor and a 100mm lens, then how short must my strobe/flash duration t.1 be in order to make mirror-lock-up pointless? How would that number change if I use a 400mm lens? A 50 mm lens? Thanks!
« Last Edit: August 05, 2013, 08:36:51 PM by markwilliam » Logged
Ellis Vener
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« Reply #1 on: August 05, 2013, 07:09:51 PM »
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That would depend on your tripod and how =you make it vibrate and the frequency and amplitude of the vibration...

But if the room isn't moving, if the camera isn't moving, and if the subject isn't moving,  even at a t0.1 flash duration of 1/80th (Profoto Acute 2 2400  with a single Acute head at 2400 w-s) is going to freeze the non-existant motion.

A lot is going to depend on what you use to support the camera with the 400mm lens.
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Ellis Vener
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markwilliam
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« Reply #2 on: August 05, 2013, 08:35:53 PM »
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Thank you very much for your reply, Ellis Vener. You have been helpful to me before on other forums, and I very much appreciate your expertise. You help me here by revealing to me what I failed to consider--and that there are many variables I have not yet figured out how to quantify (and that might be moot, given my circumstances). So...

I will try to get closer to learning what I need to know by adding some information and then asking a different question:

My t.1 flash durations are always around 1/588 or shorter (faster); two Paul C. Buff Einstein units per exposure synced with Buff CyberSync Transmitter and Tranceivers, usually firing very close to full power.

When I use the 50mm and 100mm lenses, the camera is supported on a Bogen/Manfrotto 410 geared head sitting on a Gitzo Series 3 aluminum tripod with center column extended just a few inches or so; when I use the 400 mm lens, it's attached via lens collar/foot to a Gigapan unit (operating in rigid mode with 3-second pause between position shifts and three-second pause after each mirror-lock-up) sitting atop the aforementioned head and tripod.

Under these circumstances, does using mirror-lock-up make a difference? (I fear that I further reveal my ignorance by hoping that this question is any more answerable than my first one; please don't hesitate to straighten me out!)

Many thanks,

Mark
« Last Edit: August 05, 2013, 08:38:56 PM by markwilliam » Logged
kaelaria
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« Reply #3 on: August 05, 2013, 08:41:22 PM »
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When you use the center column you are no longer on a rigid tripod, you are on a short monopod.  Bad idea.
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Kirk Gittings
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« Reply #4 on: August 05, 2013, 09:11:35 PM »
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When you use the center column you are no longer on a rigid tripod, you are on a short monopod.  Bad idea.

Again it depends on the equipment. I have a couple of tripods that I don't hesitate either using the center column all the way up even on very long exposures http://www.adorama.com/BG3251.html. Or http://www.manfrotto.com/055-mag-fiber-tripod-3-sct half way up. This is with both 4x5 view cameras or FF DSLR.
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Thanks,
Kirk

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kaelaria
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« Reply #5 on: August 05, 2013, 09:16:46 PM »
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That may be the case, but what I said is still true.  It all depends on conditions, what will work.
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Vladimirovich
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« Reply #6 on: August 06, 2013, 01:42:58 AM »
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Under these circumstances, does using mirror-lock-up make a difference?
do a simple test... find 300mm lens, mount it, switch to live view, use max magnification... if you notice evem a slightest vibration on your LCD then you are wasting resolution (even w/ 100mm lens).
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markwilliam
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« Reply #7 on: August 06, 2013, 01:46:52 AM »
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do a simple test... find 300mm lens, mount it, switch to live view, use max magnification... if you notice evem a slightest vibration on your LCD then you are wasting resolution (even w/ 100mm lens).

Excellent idea; unfortunately, my camera does not have Live View. But thank you for your helpfulness.
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Vladimirovich
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« Reply #8 on: August 07, 2013, 07:08:15 PM »
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Excellent idea; unfortunately, my camera does not have Live View. But thank you for your helpfulness.

I am sorry... I  missed the point that it is probably MFDB like P25 (?)...  but then just grab some FF dSLR camera (that has a live view) & lens from a friend... tripod setup will be the same and if you see vibration there w/ that you will also have vibration w/ MF camera/back (even if MF camera/back/lens weight more than dSLR setup used to test).
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