Capture ambient light with 580EX II Flash?

[Shaun Hill]

Hello there.

I want to use my Canon Speedlight to fill flash a subject and then capture the ambient light, which can be achieved by using a longer shutter speed. However, I want to keep the speedlight in ETTL so there is less fiddling to do and this needs to be possible whilst using camera handheld rather than static on a tripod.

What is the best way to achieve this? I am guessing ISO is going to play a big part.

 

[Hamish Gill]

Yep, ISO up then assuming the flash isn't a million miles from the Nikon sb900 you should e able to turn the flash power down a bit ... This makes the effect of the flash more subtle and captures more ambient detail

 

[Hamish Gill]

I've changed the name of your thread to be a bit more specific ... Its better for future reference that way

 

[Mark Grant]

This link on the Canon site is useful,

Canon Professional Network - Getting the most from Speedlites (Pt. 1): Controls & modes

Page 6 mentions second curtian sync which is probably what you need.

 

[Hamish Gill]

Longer shutter speeds cause bluring of the background though, especially hand held ...

 

[Shaun Hill]

But when you use a high aperture the background is blurry anyway? Am I being thick?

How will the second curtain advantage me? I do understand the principle of the two shutters inside the camera due to previous experience with an old manual flash which would be exposed on only a portion of the image because the shutter speed was too quick.

 

[Paul Lange]

Does your flash not have a Fill Light mode? If it does you just need to turn it on and everything else is automatic. I think you can still change the flash power (EV), even in ETTL mode.

 

[Hamish Gill]

But when you use a high aperture the background is blurry anyway? Am I being thick?

I different type of blur ...
take flash out of the equation for a second
take a photo at say 1/2 a second and everything is blurred with motion blur
that blur is different to out of focus blur ...

when you fire a flash with a slower shutter speed you get the motion blur but anything that can be lit by the power of the flash will be frozen by that flash of light ... flashes only light up for a very very short period of time so they are very effective at freezing a subject regardless of the amount of time the shutter is open
this is called slow sync flash
there are a bunch of examples here
13 Great Examples of Slow Sync Flash Images

How will the second curtain advantage me?

There are two types of slow sync flash ... "first curtain" on cameras typically called "slow" and "second curtain" on cameras typically called "rear"
simply put, first curtain fires at the first moment the shutter is fully open, second curtain fires at the last moment before the shutter closes ...
so in 1/2 of a second if you want to freeze your subject at the beginning of that period of time use slow. if you want to freeze your subject at the end use rear

to complicate things slightly more depending on flash power you can freeze different things
Flash duration of a Canon 580Ex flashgunPhotosbyKevbut day to day that will not make much odds to you

your flash is also capable of "stroboscopic" flashing ie you can set it to flash many times whilst the shutter is open ... that is how the effect of the knife chopping the apple is achieved in the above link

I do understand the principle of the two shutters inside the camera due to previous experience with an old manual flash which would be exposed on only a portion of the image because the shutter speed was too quick.

technically speaking there is only one shutter, just two elements to it ... this is to provide uniform exposure
although in certain circumstances it can make some fun things happen

Talk:Samples: High-Speed Shutter & Flash-Sync - CHDK Wiki

 

[Hamish Gill]

... if i have any terminology wrong there anyone let me know ... im shatterd and not functioning properly

 

[Dan Cattermole]

That makes perfect sense to me H.

 

[Hamish Gill]

... I should also add...
I have previously got confused when using rear flash with longer shutter speeds as there is often a "pre flash" which makes it seem as though the flash is firing twice ... It is, but the first fires before the shutter opens
This only happens on ttl modes

You should also find with a high end flash that you can achibe sync up to the fastest shutter speeds ... The sb900/d3 combo syncs up to 1/8000th of a second on FP mode ... Although technically speaking this is achived by the flash fireing for the duration that the shutter is open...
This allows the use of flash with fast lenses used wide open ... That way you could get both motion and out of focus blur

I was reading about this the other day ... Can you tell?

 

[Chris Dodkin]

Canon ETTL should do this anyway - you'll get more ambient and less flash as you dial up the ISO, or open up the aperture

Or you could use a longer exposure to get more ambient light in

AND, you can adjust the power of the Canon flash using flash exposure compensation, so effecting the balance between ambient and flash.

 

[Shaun Hill]

Flash exposure compensation doesn't change the output dramatically does it? SO I was right in presuming the main way to achieve this effect is to use a longer shutter speed.

 

[Hamish Gill]

Flash exposure comp does change output ... By the level it says it does...
No, it's one of the three possible ways depending on the effect you are after and on how the camera is set up
The more light that can get into the camera the less the flash needs to and will fire
A longer shutter speed allows more light, as does a larger aperture ... Higher ISO is more sensitive to what light there is

For now though ignore everything that has been previously said for now as I'm now confused ...

Set the camera to aperture priority
Take a photo with the flash
Then set the flash power down by 1 stop and see what happens
Then leaving the flash power as it is now dial in plus 1 stop of exposure compo and see what happens

If you dial in positive exposure compo vs negative flash exposure compo you will change the ratio of ambient to flash light in the way that you want to ... It's just about finding the right amount of both types of compensation

I'm probably not the best person to be answering this ... I do find flash photography a but confusing sometimes ...
I just know what I do when I want more ambient light and that is turn the flash power down and up the iso

 

[Chris Dodkin]

Flash exposure compensation with the 550EX can be set up to ±3 stops in 1/3-stop increments (or 1/2-stop increments with some cameras). You can also use flash exposure compensation in combination with normal exposure compensation (to control the background’s exposure level) in a flash picture.

550EX manual online here: http://gallery.nathue.dk/tingsager/Manualer/speedlite-550-ex-eng.pdf

Exposure comp section starts page 36 - also some good sections on balanced lighting on page 28

 

[Mark Hoy]

Are you shooting in manual mode (the camera)? If you are you can control the subject exposure by changing your aperture and using FEC as needed.

Is the distance to your subject fairly constant or changing a lot?

 

[Shaun Hill]

Hello there, I was playing around Croome on Sunday with my flash fitted to a lightstand with umbrella, using a wireless ETTL trigger.

I put the camera into manual and realised that aperture and iso had a huge impact on the power of the flash (without playing with the flash output). I found it slightly annoying when using 50mm as I had to have aparture around f22 to get the right exposure. I want to make the aperture around f7, but the photos were so over exposed it was rediculous!

I noticed that ETTL did not work when trying to take photos of the rain, the photos were extremely overexposed in that instance too.

I couldn't seem to change the power output on the flash enough (when changed to manual or stroboscopic). I have read through the manual but that doesn't really explain why changing settings as I did didn't have any impact.

Subject distance remains similar, else I make relevant adjustments.

 

[Hamish Gill]

Are you shooting in manual mode (the camera)? If you are you can control the subject exposure by changing your aperture and using FEC as needed.

Is the distance to your subject fairly constant or changing a lot?

Blimey ... Hi Mark ... nice to see you still keeping up with the place ...
I was thinking you would be handy when this thread popped up ... Its too far out of what i do to be that good at describing what i do

 

[Mark Hoy]

Hello Hamish Sorry for the long absence...

@Shaun, if the distance to subject is fairly constant with both the camera and flash in manual mode, set the shutter speed to expose the background correctly and then set the aperture to your desired setting e.g. f6.3 and set the flash to manual mode and 1/8 power.

Take a photo with the flash enabled. Is the subject over-exposed or underexposed? If they're under exposed either turn the flash power up or move the flash closer to the subject. If they're over exposed turn the flash power down or move the flash further away from the subject.

If you're using a light modifier e.g. umbrella or softbox I'd get the flash as close to the subject as possible and adjust the flash power. Other things you can adjust are the flash zoom..

There's the basics of it and you can experiment from there

 

[Hamish Gill]

No problem buddy ... good to have you back ... we are starting to get a bit more busy these days so its a little more interesting than it was when you first joined!

If you ever have the time to come up with any tutorials on this stuff Mark that would be ace ...

Hows life treating you?
(sorry for thread drift Shaun)