Flash Depth of field

Hi

I am using a Conon EOS 33 and a Speedlite 520EX. If I am taking a pic,
for example, at a wedding of a group of people I need a fairly deep
depth of field to get everyone in focus. If I set the camera to manual
and choose say f8 how do I know that setting the speed to 1/60th or
better 1/125th will give well exposed images? The camera at this stage
will say it is too dark for a well exposed photo.

Any input on working out flash dof is greatly appreciated.
Thanks

StephenC

wrote:
Hi

I am using a Conon EOS 33 and a Speedlite 520EX. If I am taking a pic,
for example, at a wedding of a group of people I need a fairly deep
depth of field to get everyone in focus. If I set the camera to manual
and choose say f8 how do I know that setting the speed to 1/60th or
better 1/125th will give well exposed images? The camera at this stage
will say it is too dark for a well exposed photo.

Any input on working out flash dof is greatly appreciated.
Thanks


What's the guide number for your flash? It should have a number in feet or
meters. Divide the guide number by the F/stop. That number will be the range
of the flash at full power. This assumes the flash maker is telling the
truth about the guide number.

So for example. You've got a guide number [GN] of 80 and F/8. You end
up with 10 feet.

That all ignores your shutter speed. If your shutter speed is less or
equal to your sync speed you can ignore it with the flash. Now if you want a
nice balance of room light and flash light you need to take shutter speed
into account. If you meter the room and it tells you that 1/30 at F/8 is
what you need then 1/125 is going to give you a dark room. The closer you
get to 1/30th the better exposed the room will be. The flash taking care of
the group in front.

Nick

wrote in message
oups.com...
Hi

I am using a Conon EOS 33 and a Speedlite 520EX. If I am taking a pic,
for example, at a wedding of a group of people I need a fairly deep
depth of field to get everyone in focus. If I set the camera to manual
and choose say f8 how do I know that setting the speed to 1/60th or
better 1/125th will give well exposed images? The camera at this stage
will say it is too dark for a well exposed photo.

Any input on working out flash dof is greatly appreciated.
Thanks

StephenC


If the DOF is what is important to you, you should use the apperture
priority mode and let the camera choose the shutter speed.

Now the final note. Weddings are no time to be learning about all this.
You need to know well beforehand how to handle these things and what to do
when something goes wrong, which it always will. Broken equipment, lights
that have changed when you thought there would be plenty of ambient light.
Don't do weddings, as the primary photographer, until you know all the
answers and have practiced them many times.

I agree. I didn candid shots for 2 weddings last summer for friends or
family.
Everything happens really fast and you really have to know EXACTLY what
you're doing.

wrote in message
oups.com...
Hi

I am using a Conon EOS 33 and a Speedlite 520EX. If I am taking a pic,
for example, at a wedding of a group of people I need a fairly deep
depth of field to get everyone in focus. If I set the camera to manual
and choose say f8 how do I know that setting the speed to 1/60th or
better 1/125th will give well exposed images? The camera at this stage
will say it is too dark for a well exposed photo.

Any input on working out flash dof is greatly appreciated.
Thanks

StephenC

If your lens has a DOF ring then use that to select an aperture. If not then
you may have to use a DOF chart. Now select an applicable shutter speed for
your aperture that will also sync with your flash. Note that the distance
the flash covers can be dramatically affected by ceiling height and other
reflective surfaces. Guide numbers assume 8' to 10' ceilings and nearby
walls.
Good Luck,
me

writes:

Hi

I am using a Conon EOS 33 and a Speedlite 520EX. If I am taking a pic,
for example, at a wedding of a group of people I need a fairly deep
depth of field to get everyone in focus. If I set the camera to manual
and choose say f8 how do I know that setting the speed to 1/60th or
better 1/125th will give well exposed images? The camera at this stage
will say it is too dark for a well exposed photo.

Any input on working out flash dof is greatly appreciated.
Thanks

Flashes don't have a depth of field in a sharp focus sense, so you're
asking the wrong question.

Here is some information you need to know.

1. If you set your camera to 1/60 and f/8 and it reports that there
isn't enough light then without the flash the picture will be dark
(and this is what the camera meter will report).

The only way to make the picture correctly exposed is to blash the
flash out until there is enough light, which is what the camera
will try to do (assuming TTL flash metering)

2. Flash light intensity decreases very fast[1] with the distance from
the flash. It is likely that if you're taking a picture at f/8
which lets only a small amount of the light into the camera, you
will be limited in the maximum distance. Check your flash manual.

2a. A consequence of this fast falloff is that things in the
foreground will be much brighter than things in the
background. Given this, what did you need an aperture like f/8 for,
anyway?

3. Flash is not your friend, can you get away with faster film and a
wider aperture?


So in short, 'flash dof' isn't a useful concept. You should probably
spend some time doing experiments with flash around f/4 or so to find
out how it works in low light and what causes it to not work. I'm sure
you're not foolish enough to do such experimentation at a wedding.

B

[1] with the square of the distance, but this isn't relevant here.

Many thanks for the contributions - all appreciated.

I also came accross this information in a previous post:
"The solution for your problem is to shoot in manual mode. You
still get fully automatic flash operation, and the camera will quench
the flash when it feels the foreground is correctly exposed. But you
also get full control over shutter speed (keep it under your X sync
speed - 1/125 on the II/IIe - unless you're using FP sync mode) and
aperture.
--
Stephen M. Dunn (SD313), CNE, ACE "

I will test this and the other suggestions to determine what works best
for my situation.

Kind regards

StephenC