Light #8 - Weather

[redkate]

Richard, thank you for this very clear, informative series on light. As a new photographer, I often find it difficult to deal with light conditions, so this is really useful information. Thanks also for including the exif information with each shot - it helps when I'm trying to set up a shot.

[RichardTaylor]

Thank you, and glad to be of help..

[btwien clicks]

Thanks for posting this. I have a question ... how do you choose the 'right Exposure Bias'?
And when?

[Doug Sundseth]

Experience: "In this light condition I've always needed +1-2/3 stops of exposure bias, so I'll start there."

Chimping: "Looks blown out on the back of my camera; I'd better dial in some minus EC and reshoot."

Histogram: "All stacked up on the left side, I'd better brighten it up a bit."

Or in post, but that can fail pretty badly.

[RichardTaylor]

@ btwien clicks

In addition to doug's comments.

"When"
Probably easier to say "when not"
(1) Shooting manual
You will still need to take the nature of the scene into account.
(2) camera dependant, in a scene mode where you have very little control over the camera settings.
(3) When you are looking at an "average scene" ie; not a lot of contrast and not a lot of real bright subjects (snow etc) or real dark subjects (a black car for example).

#9 An average subject. This is a B&W conversion of a basically colourless subject shot in overcast lighting conditions so no harsh shadows. No exposure compensation.
Even though it was shot in auto the exposure is ok.



Camera Canon PowerShot G11
Exposure 0.017 sec (1/60)
Aperture f/4.0
Focal Length 6.1 mm
ISO Speed 200
Exposure Bias 0 EV
Flash Off, Did not fire

------------------------

"how do you choose the 'right Exposure Bias'?"

If you are shooting with a the aid of a live histogram you can just dial it in as needed whilst watching the histogram.

If you don't have a live a live histogram you need to ask a couple of things.
(1) Do I want negative or positive exposure compensation?
(2) Are there any highlights that may blow out?

If you are shooting a predominately dark subject the camera will think the picture is too dark and will try to lighten it by increasing the exposure - so a black car may come out grey or dark grey.
So you will need to reduce the exposure to compensate. How much depends on the subject. This was probably one of the more extreme cases (along with the train picture above). Normally for the subjects I shoot it is around -2/3

#10 Here the subject was mostly darkish green and black engine. Light was diffused as it was morning fog.



Camera Canon EOS 5D
Exposure 0.003 sec (1/320)
Aperture f/10.0
Focal Length 75 mm
ISO Speed 800
Exposure Bias -5/3 EV
Flash Off, Did not fire
Exposure Program Shutter speed priority AE

Conversely if the subject is mostly very light, like snow or a beach in daylight, the camera will think the scene is over exposed and it will reduce the exposure making the scene look dark.
You will need to dial in positive exposure compensation. How much depends on the scene. I havn't shot in snow but I would be looking at possibly two stops.

#11 The light wall in the background made the camera think the scene was brighter than it was.



Camera Canon EOS 40D
Exposure 0.003 sec (1/320)
Aperture f/5.6
Focal Length 400 mm
ISO Speed 200
Exposure Bias +2/3 EV
Flash Off, Did not fire

#12 Sometimes with high contrast scenes you may need to make a decision on what detail you want to preserve. Stopping the whites blowing out was the main concern here as it didn't really matter if the background was a little dark
Notice the exposure compensation..



Camera Canon EOS 40D
Exposure 0.001 sec (1/1600)
Aperture f/8.0
Focal Length 400 mm
ISO Speed 250
Exposure Bias -4/3 EV

Keep in mind there are other techniques you can use when shooting.
(1) In difficult lighting conditions you may be able top bracket your exposures.
(2) Using a different metering metering method (ie spot, instead of evaluative/are/matrix) may reduce the need to dial in any exposure compensation at all.