WINTER EXPOSURE

Have we had enough of cold and snow yet? Unfortunately, it doesn’t look like it’s going away any time soon.

So – if you have the itch to get out and take some photos anyway but are disappointed with the results, the problem may be with exposure. The photographic kind, that is. The camera meters (measures) the light coming through the lens and tries to ‘average’ the exposure to a mid-grey (referred to as 18% grey).

With Evaluative (Canon-speak) or Matrix (Nikon-speak) metering, the camera reads the light over several zones in the viewfinder. If a bright scene covers most of these zones, the computer in the camera will calculate the exposure based mostly on these bright zones. In winter scenes – guess what – snow tends to dominate the scene and the camera tries to expose it to a mid-grey. So, if your winter shots are a little dark, that’s the reason.

There are two fixes for this: spot/partial metering and exposure compensation. I find the latter is the easiest solution so I’ll address it first.

 
Exposure compensation is a means of overriding the camera’s metering, by allowing you to over- or underexpose by an amount chosen by you. It’s normally controlled by pressing the +/- button and turning the command wheel on the camera. As you do, a bar graph (depends on the camera) will indicate by how many stops you are changing the exposure.

Since the snow caused your camera to underexpose, you need to dial in some overexposure or + exposure compensation. I typically use about one and two-thirds stops, but you may need to use something different depending upon how much of the scene is occupied by snow. Just don’t forget to dial it back to zero when finished, because it won’t go away when the camera is turned off.

 

Partial or Spot metering relies on something that has a mid-grey tone (although it can be a colour like facial skin) centred in the viewfinder. It effectively ignores all the white snow around it and exposes based on the face or mid-grey object.

I hope this helps, because there’s nothing I can do about the weather. If you need a little more help,  check out my photography courses at www.filmscapes.ca

NEW LIGHTING COURSE IN 2013

Many people have taken my Digital Photography for Beginners course to overcome their reluctance to take their camera out of Auto mode and take control of exposure and depth of field.

For those who are starting to feel comfortable with their camera's creative modes and now want to take portraits or product shots aided by low cost lighting equipment, this 3-hour course should fit the bill.

Dubbed 'Lighting for the Beginner Photographer', the course provides plenty of hands-on practice using equipment the student may not yet own. All that is required is to bring along a digital SLR and to have an understanding of the basic concepts in the Digital Photography for Beginners course. You can also bring a hot-shoe flash if you have one.This is taught in my home in London, Ontario.

To register for the course, please visit http://filmscapes.ca/html/photography_courses.html

Here is an outline of the course (subject to change):

1.       The Camera’s Creative Modes

a.       Review of Aperture Priority, Shutter Priority, Program and Manual Modes

b.      When to use these modes in available light

c.       When to use these modes with fill flash (built in to the camera or external)

d.      Taking control of light and depth of field in the studio with Manual mode

e.      Flash sync and its relationship to maximum shutter speed

PRACTICE: Using fill flash in various creative modes. Observing shutter speed limitations with flash.

2.       Light Sources and Exposure

a.       The meaning of colour temperature and its relationship to outdoor and artificial light

b.      Selecting white balance for the light source (outdoor light/flash/indoor lighting)

                                                               i.      Preset vs. auto white balance

                                                             ii.      Custom white balance: when to use and how to set it

c.       The hot-shoe flash vs. the built-in flash

d.      Strobes (optional)

e.      Continuous (hot) lights

f.        Guide Numbers and Watt-Seconds

g.       Use of the light/flash meter (optional)

h.      Camera metering modes

i.         The histogram as an exposure tool and the meaning of 18% grey

PRACTICE: Experimenting with White Balance presets. Setting a custom white balance. Shooting without flash using various metering modes and comparing results in the histograms.

3.       Remote Triggering of Flash/Strobe

a.       Radio triggers and adapters for flash mounted on light stand

b.      Optical triggering

c.       Controlling the flash in manual mode

d.      Controlling the strobe output (optional)

PRACTICE: Setting remote flash output. Triggering from camera with radio trigger or optically from camera’s flash.

4.       Introduction to Light Diffusers and Reflectors

a.       Umbrellas

b.      Soft Boxes for strobes and hot-shoe flash

c.       Reflectors and Absorbers: outdoors with/without flash; in the studio

d.      Diffusers for harsh daylight

PRACTICE: Take a portrait shot/object shot with remote flash, with and without umbrella Repeat using available light and reflector, then diffuser.

5.       Basic Portraiture Methods

a.       Background stands

b.      Choice of material and colour for the type of shoot (including green screen)

c.       The role of depth of field and lens choice

d.      Using natural light

e.      The single light setup

f.        The two light setup

g.       Balancing sources for intensity

h.      Mixed light sources and the importance of custom white balance

PRACTICE:

-          Portraiture/object shoot using window light and choice of background (try black then white)

-          Portraiture/object shoot using window light, reflector and/or absorber and choice of background

-          Portraiture/object shoot using window light and single hair light (custom white balance)

-          Portraiture/object shoot using single light in studio setting (custom white balance)

-          Portraiture/object shoot using two lights with umbrellas/soft boxes in studio setting (custom white balance)

-          Experiments with other combinations

Getting Exposure Right

For those of you who attended one of my beginner digital photography courses, you may recall me harping on about the camera's metering always trying to achieve 18% grey average exposure.

So what does that mean, really? Well, if you were to examine the histogram (that funny looking graph on your camera's LCD screen) for a picture you just took, 18% grey falls smack dab in the middle. When your camera evaluates the light in the scene before you take the shot, it measures the light over several points in the scene and makes a decision about the settings required to make the average value of the exposure fall at the middle of the histogram. This is called evaluative (Canon) or matrix (Nikon) metering.

The reason for this is to try to ensure that the shadow and highlight areas of the scene remain within the left and right ends of the histogram to prevent loss of detail. Remember, the left end of the histogram represents the darkest shadow detail that the camera can capture, while the right end represents the brightest highlight it can handle. If the histogram is not centred, and the graph is rammed against one end or the other, then chances are you've lost some detail. In short, the best histogram is one whose graph trails off smoothly at both ends, barely touching the sides.

There are times when this brainwork by the camera can do a disservice, however. If you're shooting a scene that's 90% snow or white sand, for example, the camera will try to average the exposure to 18% grey. That means your snow or sand comes out a dull grey because it dominates the exposure, and the camera wants to expose it to mid-grey. Not only that, but if there is some deep shadow detail in that remaining 10% of the scene, it may be pushed against the left end of the histogram and be lost.

Knowing this, camera manufacturers provide an exposure compensation button, pictured below. Typically, you push and hold this button while you turn the command wheel and read the exposure compensation on the LCD screen. In the snow scene example, you may need to overexpose (+) by 1 to 2 stops. Now you're ready to take the shot and check the resultant histogram to see if the white end of the graph ends up close to, but not touching, the right end of the histogram. If not, adjust the exposure compensation and try again.

Remember, most cameras do not reset exposure compensation to zero after you turn off the camera. Reset it manually to ensure you don't wreck the next day's shoot.

You can also use the camera's other metering modes, such as partial or spot, to meter the light only in the very centre of the scene. A typical use for these is where you are taking a picture of someone who has a strong backlight directly behind them. Evaluative or matrix metering would read the backlight and most likely make the face very dark. You could use exposure compensation in this scenario, but partial or spot metering will do the same thing by measuring the light reflected from the face (assuming you centre it in the viewfinder) and make it mid-grey. Again, in these metering modes, the camera takes what it measures and tries to average the exposure to 18% (mid) grey.

As with exposure compensation, don't forget to reset the metering to evaluative or matrix when you're finished with partial or spot metering.