Received emailed question - "Expose for the sky?"

Scott_Quier

I received the following via e-mail. Rather than share what little I know with just one person, I figured it might be a good idea to post a thread and let others chime in with better information:

Hi Scott. I have a question that I already think I know the answer to but here
goes. When I read comments like "expose for the sky & use fill flash" how
exactly are you exposing for the sky? I guess i need help w/the terminology.
1)Meter reading: half shutter to take the reading?
2)Expose for the sky: Same as above?
3) Fill flash: What setting on the flash should be used for fill? TTL,
Backlight...?I just don't do much outdoor shooting.

1. Meter Reading - I would set the camera to manual because that is the only way you are going to get a reading in on area of the scene and have it stick somewhere else. Here's how:
   1. Set to manual mode
   2. Select eitiher the shutter speed you want or the aperture
   3. Zoom so the sky fills most/all of your frame. This, essentially turns your camera into a spot meter.
   4. Adjust the other control so that you get a meter reading you like
   5. Done, now you know the exposure for the sky
2. Expose for the sky - Just keep the exposure you got from your meter reading above - eazy breezy:D
3. Fill flash - Fill flash is designed to reduce shadows without completely nuking them. So, you are going to want to set your Flash Exposure Compensation (that's Canon jargon - don't know what Nikon calls it) to somewhere between -0.5 and -1.5 stops. This makes the flash such that it does not dominate the main light (in this case the light from the sun).

Eric&Susan

I'm no expert but that is how I do it also.

Eric

cmason

Well, this is how I usually do it, and it seems to be reliable:

I usually shoot in Av mode, so I choose my aperture based on composition. I select the aperture, aim the camera at the sky. Focus on the sky, then press the FEC button (the * on Canon).

I then compose my shot of the subject. I leave the flash in ETTL, but reduce the power to -1 2/3 on bright days, perhaps -1 to -1 1/3 on overcast days.

Focus and compose, take the shot. I find that reducing the power on the flash is the most reliable way to get outdoor fill shots. I have found full ETTL too overpowering for my tastes.

Scott_Quier

cmason wrote:

Well, this is how I usually do it, and it seems to be reliable:

I usually shoot in Av mode, so I choose my aperture based on composition. I select the aperture, aim the camera at the sky. Focus on the sky, then press the FEC button (the * on Canon).

I then compose my shot of the subject. I leave the flash in ETTL, but reduce the power to -1 2/3 on bright days, perhaps -1 to -1 1/3 on overcast days.

Focus and compose, take the shot. I find that reducing the power on the flash is the most reliable way to get outdoor fill shots. I have found full ETTL too overpowering for my tastes.

You're right. This will work quite well if you are shooting Canon and you haven't mucked with CF4 (which can be used to move the AF actuation from the shutter button to th FEC button) like I have.

The person who sent me the e-mail question did not indicate camera brand, model, or anything else. So, I went with the generic solution that I believed to be available to all with an SLR.

Blackwood

Scott_Quier wrote:

1. Fill flash - Fill flash is designed to reduce shadows without completely nuking them. So, you are going to want to set your Flash Exposure Compensation (that's Canon jargon - don't know what Nikon calls it) to somewhere between -0.5 and -1.5 stops. This makes the flash such that it does not dominate the main light (in this case the light from the sun).

Does that affect how the flash fires?

I always assumed exposure compesation affected, well, exposure, and didn't function in manual mode.

Scott_Quier

Blackwood wrote:

Does that affect how the flash fires?

I always assumed exposure compesation affected, well, exposure, and didn't function in manual mode.

Your assumption is correct. In manual mode, EC is a NOP function - it doesn't make sense. Exposure compensation (EC), when in Av or Tv mode (and, maybe, the programmed modes - I don't know as I have never used them), will vary either shutter speed or the aperture to increase/decrease the exposure.

I was discussing Flash Exposure Compensation (FEC). FEC will increase/decrease (when set to something other than zero) the amount of light emitted by the flash by increasing/decreasing the duration of the flash.

pathfinder

Blackwood wrote:

Does that affect how the flash fires?

I always assumed exposure compesation affected, well, exposure, and didn't function in manual mode.

Mark, there is a wealth of information about the EOS flash system here - http://www.dgrin.com/showthread.php?t=70330

When shooting with the flash in ETTL or ETTL II, and an EOS camera in manual mode, the exposure for the subject will be controlled by the lighting from the flash, correctly, and the background will be exposed according to the settings you chose to use in manual mode. This gives you total exposure control of the background and the fore ground. FEC can be used to alter the lighting for the subject as it is controlled by the flash output ultimately.

Be aware, that when shooting sky, you may need to use High Speed Synch, as otherwise, in manual mode, with an EOS flash, you cannot use a shutter speed higher than 1/200th or your camera's native flash synch speed ( which is 1/250th for some Canon cameras).

You can set the shutter speed higher than 1/200th in manual mode, but with an EOS flash mounted, when you press the shutter in non High Speed Synch, the camera resets the shutter to 1/200th even if you loaded 1/1000th. This can lead to over exposure if you do not fully grasp why this is happening.

But once you understand this, you can expose the subject with the flash correctly, and under-expose the background 1, 2 or 3 stops or more of your chosing by the settings used in manual mode.

Blackwood

Thanks (both of you).