6 replies to this topic

[snapseddie]

Hi

 

My rear curtain flash sync seems to be wrong on my 7200.

 

With a speedlight attached the flash fires when the shutter opens and when it closes. It only fires when the shutter closes when using the pop up flash. So is the camera faulty or is it me please

 

Edward 

[Merco_61]

Is the resulting photo correctly exposed? Does the first flash give any ghost effect?

It might be that you notice the metering preflash from the more powerful speedlite but not from the built-in toy.

[snapseddie]

Many thanks for the reply. I will check this out at the weekend to see if that is the case. I just saw the flash and assumed it was a normal one. Thinking on I am a bit lost as to why the flash would want to pre fire in this situation as the subject could well be in a different place at the end of exposure flash couldn't it. Still I will check it out a bit more carefully as I said and post back.

 

Edward

[Merco_61]

The preflash has to be made before raising the mirror as the meter is mounted up in the prism. The OTF metering that worked so well in the late film bodies doesn't work with a digital sensor as it is dependent on having a matte surface to meter from. That is why D-TTL and later iTTL were developed, with their preflashes as the only way to meter.

[snapseddie]

Ok I am a bit behind my schedule but I have the following to report.

 

When set to rear curtain sync the pop up flash does not emit any visible flash at all when the shutter opens and only fires when it closes

 

With a speedlight in the hot shoe the flash fires at opening and closing.

 

I have tried an experiment as follows.

 

Taken a photo at normal settings with the flash firing at opening only

 

Taken the same photo again with rear curtain sync and the flash fires twice and looks identical to the first photo

 

Taken the photo again with the same bulb settings and covering the speedlight before the shutter closes. This picture is not as light as the pictures in the previous two shots.

 

It seems to me that the pop up flash works correctly as with rear curtain surely you don't want any flash at all when the shutter opens only when it closes

 

Edward

[dcbear78]

Try with the flash in manual rather than TTL. I agree with Peter and think you are seeing the TTL pre-flash which is more exaggerated with the long shutter speed.

Flash in manual and you should only see the one flash.

[snapseddie]

Ok first my apologies for the long delay in replying to all of this. (It was called life). I have found out by trial and error that all my different speedlights  and the pop up flash all work with rear sync as suggested here in manual mode on the flashes. At least I can now carry on with my project. It makes sense that way after a lot of thinking as for rear sync to work the flash must not fire at shutter opening as that spoils the effect. I shall have to work out the flash settings etc with some exposures before starting the project and all should be fine. Thanks to everyone who chipped in with their thoughts and suggestions. Helpful to have you all here 

 

Edward