loosing exposure with V-Grip at 1/1600s

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loosing exposure with V-Grip at 1/1600s

Postby NN634712364275741699UL » Sat Feb 02, 2013 11:12 am

Hi,

I own the Mamiya DM33, the body 645DF, the 80mm LSD lens and the V-Grip. I sync the camera with a Profoto Pro-7b or D1 500Ws through the profoto air sync receiver or the build in air remote of the D1. The Air sync receivers are powered by non-recharcheable batteries.

All pictures are taken with the V-Grip as the transmitter:
Up to 1/250s the exposure is correct, means even if I select a exposure time of 1/125s - or even longer - the exposure of the picture remains the same.
As soon as I shorten the exposre time to 1/500s or 1/1600s the picture will losse 1/3f-stop or even 2/3f-stops.

According to the Profoto manuals of the pro-7b and the D1, the flash duration time should be short enough if not used at full power. I have tried different ISO/aperture/exposure time combinations but it's always the same phenomenon: I loose expose as soon as the sync time is shorten up the 1/1600s

Does anybody else face the same problem with the V-Grip?

Thank's in advance for the replies!
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Re: loosing exposure with V-Grip at 1/1600s

Postby Digital Transitions, Doug » Wed Feb 06, 2013 6:24 pm

Do you have the Fast/Normal switch set to Fast or Normal?
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Re: loosing exposure with V-Grip at 1/1600s

Postby NN634712364275741699UL » Thu Feb 07, 2013 11:56 am

Switch is set to FAST.
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Re: loosing exposure with V-Grip at 1/1600s

Postby Jon » Thu Feb 07, 2013 7:22 pm

As long as the air transmitter is in Fast mode we can basically pin the loss of light on flash duration. The flash duration times listed by Profoto are in T 0.5 terms so they really only describe the duration above 50% of total flash output when you pop the strobe. This means you can still be cutting light with the shutter. The full illumination time even when the T0.5 duration is 1/3000 will be longer.

That said, you could lose some syncing if your firmware is out of date on the camera body. It needs to be at least 1.21, however the current firmware 1.55 is recommended.
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Re: loosing exposure with V-Grip at 1/1600s

Postby NN634712364275741699UL » Thu Feb 07, 2013 11:39 pm

I have checked the DB Firmware and Interface versions and I have the latest ones 5.041 and 3.050. The body firmware (displayed at the wheel dial position CF and selecting C99) is 1.25.

I understand the t0.5 issue but then the complete Profoto D1 series and Pro-7b is not completely compatible with the V-Grip! According to the manuals you can only use the battery packs AcuteB2, Pro-B2, -B3 and -B4 at lower power level or the generators Pro-7 or 8a (approx 1/8th power or even less). The Acute, D4, D1, battery pack pro-7b or AcuteB won't work flawless even if used at minimum power levels.

I don't want to overstate the issue of noticable f-stop losses with some Profoto products when syncing at 1/1600s. Both brands work great and the option to sync up to 1/1600s is fantastic. You just have to overexpose a little bit to compensate the loss of exposure and hope that you do not dial the power up to much otherwise the slower flash duration will neutralise the effect again.

People should be aware of the fact that the conditions under which the syncing at 1/1600s works flawless are so limited that you cannot use any generator or battery pack at mid or high power levels because a flash duration of 1/3000s at t0.5 won't be fast enough!

However I will reach out to my MamiyaLeaf representative to get the latest firmware 1.55 for the body. I keep you in the loop if any improvement show up!
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Re: loosing exposure with V-Grip at 1/1600s

Postby Digital Transitions, Doug » Fri Feb 08, 2013 4:03 pm

Profotos current pro pack (pro 8 ), studio pack (d4), and battery pack (pro B4) can all go much faster than needed.

The Pro B4 can get to a 1/25,000th of a second in fast mode, and has a display of flash duration (in t0.5) on the pack that updates in real time.

As you've discovered, you do need to know what the flash duration of your pack is at the settings you'll use them at. Phase One has provided a tool to sync with any type of flash at 1/1600th; making sure that your flash is fast enough (if not losing light is important - which is usually, but not always, is) is your responsibility.
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Re: loosing exposure with V-Grip at 1/1600s

Postby NN634712364275741699UL » Sat Feb 09, 2013 4:04 pm

Just updated the 645DF body from firmware version 1.25 to 1.55 and did some test shots. No improvements regarding the fast sync at 1/1600s, still loosing about 1/3 f-stop to 1/1 f-stop depending on the output level of the flash.

Of course Profotos top line can handle the ultra fast sync speed of 1/1600s better than the compact line like the D1 but the markup hurts!!

By the way 1/25000s won't help you much if you can only reach that flash speed at output level 4.7 which is about 30Ws! 30Ws may be enough if you use DSLRs with let's say ISO 200 or 400, some soft boxes and f4 - 5,6 from 2m distance but if you shoot MF with ISO 50 and f5,6 or better f8 because of the shallow Depth Of Field you may be in trouble if you need to fight the ambient light at noon...

However: To have such a tool like the V-Grip enabling photographers to sync up to 1/1600s is one of the best invention of the last years! Thumps up!!
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Re: loosing exposure with V-Grip at 1/1600s

Postby NN634712364275741699UL » Thu Feb 21, 2013 11:12 pm

I have tested the Profoto Pro-B4 (at a mamiyaleaf Credo meeting) and Nikon sB-900 with a sync speed of 1/1600s with my Mamiya DM33!

Pro-B4: Even at the shortest regular flash duration of t0,5 = 1/5.500s you will lose 1/3 of a stop. So it doesn't matter if your t0,5 flash duration is 1/2.600s (Profoto D1) or 1/3.000s (Pro-7b) the result is the same! In the second step I set the B4 to freeze mode with a flash duration of 1/25.000s! Finally there was no difference in exposure - but at the cost a strong blue colour shift! At Freeze mode you sacrifice colour consistency with the B4.

Nikon SB-900: at 1/4 power there was no lost in exposure but with 1/2 power you could measure a loss of about 1/3 of a stop again.

conclusion: you better buy a bunch of SB-900s and couple them together instead of buying a 7.000 EUR Profoto Pro-B4 if you need the max. sync speed to overpower the sun!

P.S. The new Leaf Credo 40 showed the same results as my Mamiya DM33. I guess I don't have a defect MF camera...
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