About Slow Synch

[thomas goseberg]

I still don't fully understand how it works. Somehow it allows to mix available light and flash.

1 - So what is the difference to fill-flash?

2 - How can this work? Does it regulate the flash power based on the available light? I thought with slow synch you would use rather rear curtain, but I just tried and my 5D uses always first curtain, like it doesn't care about available light, when I press the shutter the flash fires (even if set to rear curtain).

--
KM 5 D, kit lens, fifty 1.7, beercan, 35-7 0/3.5-4. 5, TC 1.4&2.0

 

[tom55604]

I still don't fully understand how it works. Somehow it allows to
mix available light and flash.

1 - So what is the difference to fill-flash?

2 - How can this work? Does it regulate the flash power based on
the available light? I thought with slow synch you would use rather
rear curtain, but I just tried and my 5D uses always first curtain,
like it doesn't care about available light, when I press the
shutter the flash fires (even if set to rear curtain).

--
KM 5 D, kit lens, fifty 1.7, beercan, 35-7 0/3.5-4. 5, TC 1.4&2.0

Slow sync works by using a shutter speed slow enough to capture enough of the ambient light so that the background doesn't black out. In the old manual flash days, we would meter the ambient light, set the exposure 1/2 to 1 stop less than the metered value, and use flash settings (either flash power if variable or lens aperture) to light the subject. The actual settings would be based on the effect we were trying to get and the amount of ambient light on the subject/background.

Rear curtain flash is only used to capture moving subjects so that the blur speed image trails the subject. With front curtain flash the ghost image of a slow shutter speed shot on a moving subject would be in front of the sharp subject. If the shutter speed is 1/60 or faster, second curtain doesn't operate.

Tom

 

[thomas goseberg]

Thanks Tom. I noted on my 5D when I use slow synch, the exposure with flash is the same as without (i.e. it doesn't go to 1/60). But I still don't understand the difference to fill-flash - doesn't the latter do the same, i.e. use available light as much as possible + flash to highlight the closer subjects?
--
KM 5 D, kit lens, fifty 1.7, beercan, 35-7 0/3.5-4. 5, TC 1.4&2.0

 

[Gregory King]

Tom,

I think the difference is which gets priority. Slow sync gives "priority" to ambient exposure and lets the flash add some light to near subjects. Fill-flash gives priority to flash exposure, and lets ambient light fill in the background.

Shades of grey, I'd say.

Greg

 

[Michael Fritzen]

Hi Thomas,

fill flash maintains sync speed (the shortest standard exposure time possible ) and adds only the flash power needed to achieve a correct "mixed lighting" from ambient light and flash light. Fill flash is usually used in ambients plenty of light, but with a little lack of light (due to hard shadows, for example) on your main subject. Thus the use of the flash to lighten a little bit the shadows

Shooting with slow sync means using exposure times longer than the shortest possible sync speed, i.e. 1/100, 1/60, 1/30... when sync speed is 1/125. So slow sync flash is used in darker ambients in order to capture / use more of the ambient light. Think about this: using the standard sync speed of 1/125 (7D) your WHOLE photo will have exposure of 1/125. Shooting with 1/125 without flash everything would be heavily underexposed (black). But if you increase exposure time to 1/60 or 1/30 eventually your sensor will be able to capture light for the double (or 4x) the time so your photo will get less underexposed or almost right exposed. Now add the flash which will fire in this situation with the same power as it would with standard sync speed: it will provide the main subject (closer to the camera) with the necessary (additional) light to correct exposure AND the background will be exposed (due to the longer exposure time) closer to correct.

It´s worth to say that slow sync shots in some circumstances may lead to "strange" results in a way that subjects may show a "motion path" in according to the longer exposure time used PLUS a freezed moment in this motion when the flash fires. If one would use a strobe flash or a real long exposure time of some seconds a fire the flash manually several times during exposure, motion can be captured in sequence in one frame only (used in sports for motions analyses, for example).

Hope this helps.

Cheers,
Michael Fritzen

 

[thomas goseberg]

Thanks a lot, I think I am getting there. I am not that experienced with flash fotography but I'll give it a more serious try.
--

KM 5 D, kit lens, fifty 1.7, 28-7 5/2. 8 ordered, beercan, 35-7 0/3.5-4. 5, TC 1.4&2.0

 

[TPeter]

Can I add a question onto this thread:

does anyone know how to set rear curtain mode with the HS5600 flash ??

 

[Gregory King]

I think you set it in the camera flash menu

Greg

 

[sbolden]

http://forums.dpreview.com/forums/read.asp?forum=1035&message=16347786

 

[tom55604]

Thomas,

Part of the confusion is probably because of the way Minolta used the term "fill Flash" compared with how many others use the term.

Back when I learned on a manual camera, Fill Flash ment that I was trying to capture the ambient lighting (another poster discribed it as 'giving priority to the ambient lighting') and just put a tweak of flash light on the subject usally to fill in shadows.

Minolta used the term Fill Flash to mean that the photographer is forcing the flash to fire even though the ambient lighting is bright enough, usually to put a bit of fill on the subject. The other mode was called 'auto flash', because the camera decided that flash was needed because ambient lighting was too low.

The amount of flash vs ambient lighting doesn't that the Minolta AF cameras select doesn't depend on the "Fill" vs "Auto" setting (in fact most of their later cameras used auto flash only in unmodified green P mode. The lighting selected depends on how the camera interprets the subject and background ambient lighting (for example a person in shade with a bright sunlit background or a person in sun with shadows with the background almost the same brightness.)

The one thing that the Minolta cameras do with flash turned on in either P or A modes is allow a shutter speed no slower than 1/60sec. They also tend to favor large apertures (to maximize flash range) except in bright ambient light where the aperture has to stop down. Slow Sync is the way that you force the camera to set a shutter speed based on ambient.

Other cameras such as Canons (not sure about the newest ones) will automatically select slow sync when the camera is set to aperture priority, I assume that's because the designers assumed that if you Ap, you know what you are doing. I have read a number of posts from novices, however, who when using Ap ended up handholding shots at 1 sec because they didn't understand how that camera worked.

There are some Minolta users who hate how slow sync is implemented and would prefer the Canon approach. Personaly, it doesn't bother me, but I can understand their point.

Tom

Thanks Tom. I noted on my 5D when I use slow synch, the exposure
with flash is the same as without (i.e. it doesn't go to 1/60). But
I still don't understand the difference to fill-flash - doesn't the
latter do the same, i.e. use available light as much as possible +
flash to highlight the closer subjects?
--
KM 5 D, kit lens, fifty 1.7, beercan, 35-7 0/3.5-4. 5, TC 1.4&2.0