On 7D flash synch speed

Hi Geir,

No, if spec given sync speed of 1/160, any shutter speed greater than that will result in incomplete exposure unless HSS is enabled. Nice articule for reading..

X-Sync

http://www.photozone.de/3Technology/flashtec4.htm

HSS

http://www.photozone.de/3Technology/flashtec5.htm

Cheers!

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
--
My album at: http://objective.bitfikler.com/geirove/web/

Sync speed is a limitation of the shutter, expensive shutters are faster. Nikon can achieve 1/500 because the CCD can "simulate" a shutter.

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
--
My album at: http://objective.bitfikler.com/geirove/web/

Desmond Lim wrote:

Hi Geir,

No, if spec given sync speed of 1/160, any shutter speed greater
than that will result in incomplete exposure unless HSS is enabled.

Not necessarily. Sometimes X sync is a conservative number.

Although my E1 has a reported X sync of 1/180, and the dedicated flash unit, when communicating to the camera, will not allow faster than this, unless HSS, I can sync at 1/320 with third party flashes. You just have to try it with a non TTL or non communicating flash to see what the real X xync potential is.

Patrick

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
--
My album at: http://objective.bitfikler.com/geirove/web/

No, I meant slower speeds. Slower ambient light speeds, no flash.

That's why the top speed is only 1/4000. The spring tension has been set lower.

Evidentally this is one of the technical hurdles KM had to overcome. If they put the kind of shutter that was in the film version, shutter vibraton at any speed could interfere with AS. Thus, a lower tension spring was used. A by-product or indirect result of this is the slower sync speed.

Geir Ove wrote:
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
--
My album at: http://objective.bitfikler.com/geirove/web/

Actually, the shutter speed cannot be faster than the speed at which the entire sensor is uncovered for a time. Any faster speeds would involve a moving slit across the image plane. Unless of course if you are using an FP flash mode.

That speed that I refer to above, is evidentally 1/160 of a second. For instance, my 20D gets sync at 1/250. I contend that the springs used in the D7 shutter are not strong enough to produce an uncovered sensor at speeds faster than 1/160. And I believe, from what I've read, is due to a decision on KM's part to not use a stronger shutter spring, because the result is shutter vibration that interferes with the AS.

Geir Ove wrote:

Alex Escada wrote:

Sync speed is a limitation of the shutter, expensive shutters are

This is not entirely correct. As I said in my original post, the
shutter speed cannot be faster than the duration of the flash in
situtations where you want to fully utlize the power of the flash.

Geir Ove

Although the largest duration of the flash (full power) can be very long (1/200s or so), with less power the duration falls drastically. But the idea is to make a flash where the duration of light is the smallest possible.

The need for high-speed syncs is mainly for fill in where the flash power is reduced most of the times.

Expensive shutters normally can sync faster - by the way the fastest focal plane shutter it's in Minolta SLRs (9xi and 9) with 1/300s.

Geir Ove wrote:

Alex Escada wrote:

Sync speed is a limitation of the shutter, expensive shutters are

This is not entirely correct. As I said in my original post, the
shutter speed cannot be faster than the duration of the flash in
situtations where you want to fully utlize the power of the flash.

Geir Ove

I highly doubt the main difference between the shutters on the D70 and the 7D is price. In fact, the shutter on the 7D could very well be more expensive than the one on the D70 because they had to basically start from scratch on it to figure out how to minimize the vibrations. This was most likely not a concern on the D70. In addition, the D70 could easily use the shutter from an earlier film body.

This being said, I salute both companies. 1/500 sec flash sync is quite impressive! Kudos to Nikon. Also, somehow making AS work at the expense of some sync speed must have been quite a feat. Kudos to KM as well!

Alex Escada wrote:
Although the largest duration of the flash (full power) can be very
long (1/200s or so), with less power the duration falls
drastically. But the idea is to make a flash where the duration of
light is the smallest possible.
The need for high-speed syncs is mainly for fill in where the flash
power is reduced most of the times.
Expensive shutters normally can sync faster - by the way the
fastest focal plane shutter it's in Minolta SLRs (9xi and 9) with
1/300s.

Geir Ove wrote:

Alex Escada wrote:

Sync speed is a limitation of the shutter, expensive shutters are

This is not entirely correct. As I said in my original post, the
shutter speed cannot be faster than the duration of the flash in
situtations where you want to fully utlize the power of the flash.

Geir Ove

Hi Patrick,

You may be right, but I don't bet on that since max sync is given manufacturer is the "safety guideline".

I've tried setting shutter speed beyond my film 7 max sync little (can't remember the exact speed anymore) with studio light. As expected, I got back only half the frame.

Cheers!

Patrick H Lockwood wrote:

Desmond Lim wrote:

Hi Geir,

No, if spec given sync speed of 1/160, any shutter speed greater
than that will result in incomplete exposure unless HSS is enabled.

Not necessarily. Sometimes X sync is a conservative number.

Although my E1 has a reported X sync of 1/180, and the dedicated
flash unit, when communicating to the camera, will not allow
faster than this, unless HSS, I can sync at 1/320 with third party
flashes. You just have to try it with a non TTL or non
communicating flash to see what the real X xync potential is.

Patrick

If you are comparing the D70 1/500 flash sync to the D7D you have to remember that the D70's lowest iso is 200 ISO this is one stop higher than the D7D which means in the same lighting situation if you were shooting with the D70 you might have 200 ISO F5.6 1/500 sec where as the D7D would be 100 ISO f6.1 1/160 sec this is only half a stop difference . I can live with that.