Flash and shutter speed

[Alex]

Hi, this may be a stupid question, but with a lot of my indoor shots using sb800, I really need more shutter speed than when 'correct' exposure calls for. I shoot normally in aperture control mode and find that even when wide open the shutter speed is way to slow to capture moving object or even slightly moving objects. I remember reading somewhere to only worry about aperture and flash exposure comp, but not the shutter speed? Does shutter speed have little effect when flash is used? So would it be better to shoot in "M" mode and set aperture that you want, let sb800 figure out the correct amount of flash in iTTL mode and just set a 'safe' shutter speed of 1/125 s and not worry about what the camera's meter says?

Thanks for any suggestions
Alex

[johnd]

Alex, what happens when you shoot in shutter priority mode? I think the D70 will synch with the SB800 up to 1/500 sec.
Thanks for asking the question. I'm looking forward to reading the answers. I've got a lot of learning to do with my SB800.

Cheers, John

[Alex]

Alex, what happens when you shoot in shutter priority mode? I think the D70 will synch with the SB800 up to 1/500 sec.
Thanks for asking the question. I'm looking forward to reading the answers. I've got a lot of learning to do with my SB800.

Cheers, John

John,

Never tried shutter priority with sb800. My guess that if I chose something like 1/250 the meter would say "Lo" even at a wide aperature, but I suspect the meter does NOT take flash into account, i.e. only considers available light as far as exposure metering goes. So I suspect when using flash, you should consider:

1. Aperture needed to achieve correct DOF
2. Shutter speed needed in terms of eliminating or adding movement
3. Let SB800s iTTL decide the amount of flash needed based on iTTL data. This will not be affected much by shutter speed you pick.

I may be totally wrong, I need to do a lot of learning with the flash still.

Alex

[johnd]

So I suspect when using flash, you should consider:

1. Aperture needed to achieve correct DOF
2. Shutter speed needed in terms of eliminating or adding movement
3. Let SB800s iTTL decide the amount of flash needed based on iTTL data. This will not be affected much by shutter speed you pick.

I may be totally wrong, I need to do a lot of learning with the flash still.

Alex

That's pretty much my guess as well. So might as well use manual mode. It's all about experimenting for me at the moment. Hopefully we'll get some answers from those with more experience with the SB800.

Cheers
John

[phillipb]

Alex,
I could be wrong on this as well, but if you're getting blurred photos due to subject movement, the last thing you want to do is open the lens up because you are relying more on ambient light and less flash - ie. fill flash. If the flash is the main light sourse, then it should freeze all movement.

[Onyx]

Ambient (light) exposure is based on shutter speed and aperture.
Flash exposure is based on aperture and distance to subject.
Ignoring ISO sensitivity above as it's in common with both.

If you say set your flash manually to a constant output level (eg. 1/32), and take the same composed shot at 1/60s and 1/500s - and you're using flash as your sole source of light, the two images will not differ in exposure. Not one bit. Changing shutter speed as no effect on flash exposures - this may sound strange if you're used to ambient (non-flash) exposures where shutter speed is very much a factor.

If you're in darkness and relying solely on flash to illuminate the scene, don't be afraid to crank up that shutter speed if you need it to freeze the action. BTW, the D70/s camera as is shipped is set up with 1/60s as the minimum shutter speed in aperture/program/auto mode. That means no matter the ambient reading, turning on the flash (SB800 or built-in) your shutter speed will be bumped up to 1/60s. This minimum setting can be changed from 1 second upto 1/125s in the custom functions menu, but any faster and you'll have to manually switch to shutter priority or manual modes and select the appropriate shutter speed.

The D70/s's flash sync speed (maximum shutter speed when flash is used) is 1/500s. To exceed 1/500s - the camera needs to support Auto FP (focal plane) mode. The D200 and D2 series Nikon SLR cameras supports this. To exceed 1/500s on a D70, you will need to use an external speedlight (eg. SB600/SB800) and 'retard' the flash exposure system by half chopping off the camera to flash communications. This can be done by masking the two frontmost contact points on the flash hotshoe connector.

I have tried this with an SB800 on my D70 and it seems to work without much negative effects. ie. still retains full (or close to full) iTTL flash metering capabilities (incl. balanced fill), all the way upto 1/8000s shutter speed, but the flash mode 'defaults' to slow sync (ie. able to drop below the 1/60s or set minimum shutter speed if ambient exposure dictates).

However because this is not an officially documented feature, I suspect it shouldn't be used because of some dramatic ill effect it may have on your images, camera and/or flash unit under certain circumstances and I'll disclaim all responsibilities if you wish to try this - do so at your own risk.

[johnd]

If you say set your flash manually to a constant output level (eg. 1/32), and take the same composed shot at 1/60s and 1/500s - and you're using flash as your sole source of light, the two images will not differ in exposure. Not one bit. Changing shutter speed as no effect on flash exposures - this may sound strange if you're used to ambient (non-flash) exposures where shutter speed is very much a factor.

I assume this is because the time that the flash is emitting light is very short, something less that 1/500 sec I guess. Is this the case

[Slider]

The D70/s's flash sync speed (maximum shutter speed when flash is used) is 1/500s. To exceed 1/500s - the camera needs to support Auto FP (focal plane) mode. The D200 and D2 series Nikon SLR cameras supports this. To exceed 1/500s on a D70, you will need to use an external speedlight (eg. SB600/SB800) and 'retard' the flash exposure system by half chopping off the camera to flash communications. This can be done by masking the two frontmost contact points on the flash hotshoe connector.

I have tried this with an SB800 on my D70 and it seems to work without much negative effects. ie. still retains full (or close to full) iTTL flash metering capabilities (incl. balanced fill), all the way upto 1/8000s shutter speed, but the flash mode 'defaults' to slow sync (ie. able to drop below the 1/60s or set minimum shutter speed if ambient exposure dictates).

However because this is not an officially documented feature, I suspect it shouldn't be used because of some dramatic ill effect it may have on your images, camera and/or flash unit under certain circumstances and I'll disclaim all responsibilities if you wish to try this - do so at your own risk.

Was just about to post a question about Auto FP with the D70s and SB800 when I found this thread already happening (gotta love "Search").

I won't hold you responsible of course but have you heard of any issues using your "trick"? Would love to try it out but I am not brave when it comes to risk of "cooking" something

[Alex]

Onyx,

Thanks very much for clarifying this for me (us). It certainly explains a lot and will allow me more non-blurred in-door shots.

Cheers
Alex

[Onyx]

JohnD, that is correct. The longest flash duration from the SB800 is 1/840s (off the top of my head). For the SB600, it's 1/1200s or so... This is the flash firing at full power. For lessor flash power, it diminished down to 1/128000s (one twenty eight thousandth of a second) which is far more brief than the duration of the shutter opening.

Slider - the tape trick won't cause anything to blow up. The most danger you'll face is stuffed up photos like if the flash doesn't know how strong to fire and does so at full blast; or doesn't correctly sync with the shutter and you get uneven flash exposure within a frame.

The only way the camera and/or flash unit could sustain damage is by physical impact, or if you use an old flash unit from the era of mechanical cameras that has a very high trigger voltage (eg. 300V; the modern ISO standard is 24V, Canon Speedlites are 6V, Nikon Speedlights are 12V). Even so, I've used an old Metz flash with a trigger voltage of ~250V directly on my D70 hotshoe for 2 months with no negative impact*.

* Do as I say, not as I do. Don't try it at home kids...

[shutterbug]

So would it be better to shoot in "M" mode and set aperture that you want, let sb800 figure out the correct amount of flash in iTTL mode and just set a 'safe' shutter speed of 1/125 s and not worry about what the camera's meter says?

Set dslr in M mode and set flash to TTL.

[Slider]

Onyx, Thanks very much for the info. Much appreciated

[Alex]

Thanks Onyx and Shutterbug.

Cheers
Alex

[elffinarts]

I wish I'd read this kind of info before last night - though after some trial and error with a SB800 and SB600 and two very patient models, figured this out anyway. lol

[johnd]

For lessor flash power, it diminished down to 1/128000s (one twenty eight thousandth of a second) which is far more brief than the duration of the shutter opening.

You shouldn't get too much subject blur with that exposure time.

Thanks for the info Onyx and others. Good question Alex. This forum sure is a great aid to learning.



Cheers, John