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On 7D flash synch speed

Started Nov 7, 2004 | Discussions thread
OP Geir Ove Veteran Member • Posts: 3,115
Re: On 7D flash synch speed

I gather you meant:

interfere with AS at FASTER shutter speeds.

Then I understand and agree

Geir Ove

JackRiley wrote:
I think it because KM had to use weaker springs in the shutter
mechanism in order to avoid vibration, vibration that would
interfere with AS at slower shutter speeds.

Geir Ove wrote:

Hello,

There was a thread covering this subject some time back. I have
been contemplating the subject for a while, and thought I would
share my insights:

The 7D has a synch speed of 1/160 sec if I am not wrong. From the
tables in the Minolta 5600 HS(D) manual, we can read (indirectly)
on page 76 that the max flash duration of the 5600 must be less
than (or equal) to 1/250 sec.

A flash will deliver its power (guide number) through its
brightness and flash duration. For a camera to fully utuilize this
light its shutter speed must NOT be faster than that flash
duration. So for the 7D, we could have had a flash synch speed of
1/250 sec. to fully utilize the power of the 5600.

( The HSS mode allows us to use faster shutter speeds, but at the
cost of reduced guide number. The effective guide number will be
G / Sqrt(S/250) where S the selected shutter speed larger than 250.)

So why doesn't the 7D synch at 1/250 sec? That one I am not sure
of, but I see 2 possibiities:

a) Technical limitations in the cameras design
b) Maybe KM wanted us to be able to utilize Flashes that are slower
than 1/250 sec at their max Guide Number: Studio flashes or 3.
party flashes?

Geir Ove
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