Flash technique - Dark background..pls help


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peterlimyk

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Jul 14, 2008
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#1
I was shooting an event indoor using external flash and found that the background was dark although the subject is correctly exposed. I used diffuser too

The ceiling was high and not white in color. No hope to bounce the light.

Please advise. Thanks
 

spheredome

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Jul 5, 2007
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#2
Hope this works although I don't do flash photography.

Pre-configure your camera larger f-stop, iso, lower shutter speed (but within flash sync) to capture the background ambient light, then tune the flash power to cover the front. The reason is bec, when the f-stop is high, the lens cannot receive the back ambient light and the diffused flash fall off at a short distance.

Avoid using powerful flash and lightsphere that floods the room with light, it is annoying and uncool.
 

#3
Hope this works although I don't do flash photography.

Pre-configure your camera larger f-stop, iso, lower shutter speed (but within flash sync) to capture the background ambient light, then tune the flash power to cover the front. The reason is bec, when the f-stop is high, the lens cannot receive the back ambient light and the diffused flash fall off at a short distance.

Avoid using powerful flash and lightsphere that floods the room with light, it is annoying and uncool.
The advice above is correct. The flash is not going to be powerful enough to light up the entire room, so areas that the flash did not light up are going to turn black if your camera meter is underexposed. The purpose of the flash is to help you expose your foreground subject correctly. Before you shoot, you should use your camera's exposure meter to correctly expose for the scene, so that you can capture the background even for areas where the flash cannot reach.
 

pokiemon

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Mar 5, 2005
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#4
it will be good to let us know what your camera setting was i.e the mode, shutter speed, aperture setting, ISO
 

peterlimyk

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Jul 14, 2008
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#5
Thanks for the replies

I guess I'd need f2.8 lens instead of kit lens.:)
 

spheredome

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#6
Try not to think as static items. Beside lens alone, iso and speed can detect more light. Too slow a flash shutter (<1/60) may create ghosting with good ambient light.

If you don't tune the flash, the camera algorithm will compensate with more speed, lower iso and higher f-stop to prevent overexposure, that will negate the the lens. All serious company events will have sufficient hall light unless it is year end celebration in pubs where lighting may be low.

Zoom end will reduce light intake than wide end. FYI

Thanks for the replies

I guess I'd need f2.8 lens instead of kit lens.:)
 

daredevil123

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Oct 25, 2005
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lil red dot
#7
Thanks for the replies

I guess I'd need f2.8 lens instead of kit lens.:)
Actually kit lens can still work. I do not use f2.8 even when I have a 2.8 lens because I want DoF to be deeper so I can capture more people at the table in focus. I will use 5.6 or larger. So the key is your shutter speed and ISO and your flash compensation.

Method 1

What you need to do is to use M mode, a little trail and error (that is why photographer have to be at the even early). I start off with 1/20s in exposure, aperture 5.6, ISO 800 if it is quite dark. I will set the flash to bounce (even if ceiling is not white) with a bounce card (I use demb) to send some white light forward. I will also set flash compensation to -0.3. I will test shoot and adjust till I get a favorable lighting effect.

Method 2

I will use A mode. Same testing SOP. Start from F5.6 S will default Shutter speed to 1/60s in low light (in D90). Adjust ISO and Flash compensation till get desired effect.


This is an example of my test shoot. This one is at F2.8 though.


A mode, 1/60s, F2.8, ISO 800, Flash compensation -0.7

After that, when doing the actual shooting, I will be able to adjust my aperture to get DoF I need for specific effect.

One of the result. Don't have permission to post the rest.


A mode, 1/60s, F5, ISO 800, Flash compensation -0.3
 

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peterlimyk

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Jul 14, 2008
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#8
Actually kit lens can still work. I do not use f2.8 even when I have a 2.8 lens because I want DoF to be deeper so I can capture more people at the table in focus. I will use 5.6 or larger. So the key is your shutter speed and ISO and your flash compensation.

Method 1

What you need to do is to use M mode, a little trail and error (that is why photographer have to be at the even early). I start off with 1/20s in exposure, aperture 5.6, ISO 800 if it is quite dark. I will set the flash to bounce (even if ceiling is not white) with a bounce card (I use demb) to send some white light forward. I will also set flash compensation to -0.3. I will test shoot and adjust till I get a favorable lighting effect.

Method 2

I will use A mode. Same testing SOP. Start from F5.6 S will default Shutter speed to 1/60s in low light (in D90). Adjust ISO and Flash compensation till get desired effect.


This is an example of my test shoot. This one is at F2.8 though.


A mode, 1/60s, F2.8, ISO 800, Flash compensation -0.7

After that, when doing the actual shooting, I will be able to adjust my aperture to get DoF I need for specific effect.

One of the result. Don't have permission to post the rest.


A mode, 1/60s, F5, ISO 800, Flash compensation -0.3
Wow! Thanks for your detailed explanation! I didn't even think about boosting ISO to 800 to properly expose the background. Now I know what I have to do. Set ISO to 400/800, flash comp e.g. -.3/.7, fixed the shutter speed & aperture depending on the situation.

By the way, both photos above are very very nicely captured and exposed :)

Is the exposure compensation different from flash exposure comp?
 

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scorpioh

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Jul 17, 2007
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#9
You need to drag the shutter. basically reduce the shutter to 1/30s to allow more background light to come in.
 

daredevil123

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lil red dot
#10
Wow! Thanks for your detailed explanation! I didn't even think about boosting ISO to 800 to properly expose the background. Now I know what I have to do. Set ISO to 400/800, flash comp e.g. -.3/.7, fixed the shutter speed & aperture depending on the situation.

By the way, both photos above are very very nicely captured and exposed :)

Is the exposure compensation different from flash exposure comp?
Yes, EV compensation is different from flash exposure comp. Not sure of the camera system but on Nikon SB600, it is set on the flash itself.

And if in A mode and using high ISO you still cannot get the background light bright enough, meaning the ambient light is really low, you need to go over to M mode and drag the shutter a little, 1/30 or 1/20 is workable. Remember to turn off your auto ISO.
 

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peterlimyk

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#12
Yes, EV compensation is different from flash exposure comp. Not sure of the camera system but on Nikon SB600, it is set on the flash itself.

And if in A mode and using high ISO you still cannot get the background light bright enough, meaning the ambient light is really low, you need to go over to M mode and drag the shutter a little, 1/30 or 1/20 is workable. Remember to turn off your auto ISO.
Does that mean the EV exposure meter is not working when external flash is being used and I have to trial and error to get the correct exposure?
 

daredevil123

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lil red dot
#13
Does that mean the EV exposure meter is not working when external flash is being used and I have to trial and error to get the correct exposure?
EV still works.

They are 2 totally separate different things.

EV is your compensation for overall exposure because it overrides the meter.

Flash compensation adjusts the amount of light the flash send out based off the TTL-flash metering. So adjusting Flash compensation is actually adjusting the balance between ambient and flash light.
 

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peterlimyk

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#14
thanks for the reply.

I was using diffuser and the light is quite harsh sometimes. Wondering should I go for bounce card??
 

daredevil123

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lil red dot
#15
thanks for the reply.

I was using diffuser and the light is quite harsh sometimes. Wondering should I go for bounce card??
You need to know what a bounce card is for. You see, when using a bounce card, we usually bounce the light off the ceiling, and most of the light is actually coming from the bounce off the ceiling. When bouncing off ceiling, you get shadows in eye sockets of your subjects (aka raccoon eyes). The bounce card is intended to send some light forward to fill in.

Diffuser can work well depending on how you use it. Which one are you using now?
 

Richter

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Sep 11, 2005
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#16
It does not matter if you are using F1.2 or F22. When talking about flash photography, it is the shutter speed that controls the amount of ambient light captured by the camera. Not the Aperture. The Aperture controls the amount of flash that is being capture for a fixed power on the flash.

Above is commented with the flash setting fixed.

You can proof it by setting your flash to manual and vary the aperture and shutter 1 by 1.

Hope this helps.

Experts please correct me if I am wrong so that I can learn.

Thanx
 

Richter

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Sep 11, 2005
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#17
On the EV compensation, please take note that when you set your camera to -1EV, the subject will also underexpose by 1 EV compared to you shooting at EV0. You will need to set the FV(flash value) anything from 0 to +1. No hard and fast rule. It depends on how you want the subject to be lighted.

I am using Nikon. Canon flash and camera may differ when shooting in TTL. Different camera and flash function differently. So you need to learn you own camera and flash how they work when used in TTL.
 

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daredevil123

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lil red dot
#18
It does not matter if you are using F1.2 or F22. When talking about flash photography, it is the shutter speed that controls the amount of ambient light captured by the camera. Not the Aperture. The Aperture controls the amount of flash that is being capture for a fixed power on the flash.

Above is commented with the flash setting fixed.

You can proof it by setting your flash to manual and vary the aperture and shutter 1 by 1.

Hope this helps.

Experts please correct me if I am wrong so that I can learn.

Thanx
ISO, Aperture and Shutter speed together determines your exposure. So Aperture do matter. If your aperture is smaller, you will need a longer shutter speed to get the same exposure (be it the subject or the ambient lights behind). The reason behind a dark background when using flash (TS's problem) is that while the subject is lighted well by the flash, the exposure did not allow for the background to expose correctly. In this situation, if the flash power is fixed (not TTL because TTL is always varying flash power) and keeping the subject in correct exposure, no matter which combination of aperture/shutter speed will have no bearing on getting the background into exposure. The only thing you can do is to lower the flash power. This means, the key is to balance the amount of light from the flash against the ambient light. And once you lower the flash to balance the ambient light in a dark situation, you will need to boost the exposure. How can you boost exposure? 3 ways: 1. up your ISO, 2. longer shutter speed, 3. Larger aperture. We usually leave aperture alone if we want to maintain the same DoF.
 

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daredevil123

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lil red dot
#19
On the EV compensation, please take note that when you set your camera to -1EV, the subject will also underexpose by 1 EV compared to you shooting at EV0. You will need to set the FV(flash value) anything from 0 to +1. No hard and fast rule. It depends on how you want the subject to be lighted.

I am using Nikon. Canon flash and camera may differ when shooting in TTL. Different camera and flash function differently. So you need to learn you own camera and flash how they work when used in TTL.
Edited.

My bad, I stand corrected. EV is just a override to the exposure metering.

So, if you set EV -1 and FV +1, logic says your subject should be similar lighted, but your background will be a lot darker than EV and FV at 0. But if you are using TTL, it is another story, as there is another calculation done by the camera in TTL.
 

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Sep 28, 2008
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#20
It does not matter if you are using F1.2 or F22. When talking about flash photography, it is the shutter speed that controls the amount of ambient light captured by the camera. Not the Aperture. The Aperture controls the amount of flash that is being capture for a fixed power on the flash.

Above is commented with the flash setting fixed.

You can proof it by setting your flash to manual and vary the aperture and shutter 1 by 1.

Hope this helps.

Experts please correct me if I am wrong so that I can learn.

Thanx
wrong . aperture matters.
e.g shooting at f1.2 with flash at 1/250s 50mm will probably over expose everything,
shoot at f11 with flash @ 1/250 might be just nice. this is just an example. the actual correct exposure will have to depend on the amount of ambient light available
 

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