# What is 'Slow Sync', 'Rear Sync', and 'Flash Compensation'?



## ted_smith (Dec 6, 2006)

[SIZE=-1][FONT=Verdana, Arial, Helvetica, sans-serif]I am trying tograsptheFlash technology of my new Nikon F80 35mm camera. I've read that Nikon use the following features in their flash systems : 

Slow Sync, Rear Sync, and Flash Compensation.

Can anyone explain what these are, or give me a URL where it's explained. 

I understand the Red-Eye Reduction feature.

Thanks

Ted
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## Big Mike (Dec 6, 2006)

I'm not sure what slow sync is...maybe it's just the opposite of high speed sync...which is a feature that allows you to use flash with a fast shutter speed.  Canon's high speed sync...makes the flash act like a strobe light and pulses the light.

The reason for high speed sync, is that the shutter mechanism in most cameras has two curtains.  With faster shutter speeds...both curtains may not be fully open at the same time.  If the flash is fired while one curtain is not fully open...that part of the image will be underexposed.

Rear sync (or 2nd curtain) is when the flash is fired at the end of the exposure, rather than the start.  If you have that...I suggest that you turn it on and leave it.  I can't think of why anyone would want 1st curtain sync.  Rear sync is especially good when photographing a moving subject when there is moderate ambient light.  The movement will cause a blur...and then the flash will give a sharper image.  The result is a subject that has a blur behind it...and gives a great sense of motion.  With 1st curtain sync...the sharp image is at the start...with the blur out in front of the subject...that looks really stupid.

Flash compensation is adjusting the power of the flash...either positive or negative.  It's basically exposure compensation if you don't make any other changes.  If you want your shots to look more natural, and not look like they have been illuminated by flash...then you would dial in negative flash compensation.  This can be tricky...as you have to find a balance between the flashed light and the ambient light.  It takes practice.


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## mysteryscribe (Dec 6, 2006)

According to my son in law... 

What we called shutter dragging is slow sync.  what it does is allow the ambiant light to match your flash so the flash is almost not a factor except to fill in the shadows.  However if that is the case even thought the strobe light stops the action the ambiant light allows the film to continue being marked.  That will make the image appear to not be sharp or to have a movement blur. if it is rally slow.

On a traditional film camera there is a maximum shutter speed to sync the flash but there is no minimum so you can allow the light to fill in with a slower speed.

I always shot fast sync to stop the action and to blow out the room lights.  Remember that was film where you were better safe than sorry.  Controlling the light by over riding orange and green lights was the safe thing to do.  Strobe is a pure whte light.

A lot of people did use the shutter drag to get a more natural light and with digital it isn't nearly as dangerous as it was with film since you can at least see any giant shadows or any really obvious movement on you lcd at least I hope you can,

if that isnt clear I can try again/


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## ted_smith (Dec 6, 2006)

That's great Mike - a clear explanation. Thanks a lot.


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## sigmuh (Dec 7, 2006)

I've wondered this too! Now I know!


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