Exposure Control (Bracketing)

July 09, 2013  •  Leave a Comment

Exposure Control (Bracketing)
© Terry Mercer.com

So, you have an important shot... big money and/or reputation rests on THE PRESS OF YOUR SHUTTER. You know what shutter speed you need, you have calculated the DoF you'll have to have (aperture), and you have the ISO set to the lowest you can. And your test shot looks great. HOWEVER, there are some extremes fixing to be added into the frame... either really bright whites (such as snow, flashy wedding bright white wedding dress, or shiny white car)... and/or some dark darks (night sky, dark room, black clothing, even a really dark skinned person next to a very pale person/object) setting the exact right exposure for the WHOLE IMAGE may seem impossible. Too light and the whites get blown out. Too dark and the blacks & shadows have no surface or details.

You have ONE CHANCE for that group to be together (teams, weddings, graduations, etc.) and it will never happen again. What do you do??

Try Bracketing - it uses something called 'EC" (Exposure Control/Compensation). The shutter speed remains the same, the ISO stays the same, and the Aperture isn't changed....

But is a very under utilized feature most all dSLR's have, related to the 'in camera' light meter. It's that little 'grid' at the bottom of your view finder with the hash marks, and the 'highlite' little square (or dot) that shows you where the camera thinks the exposure is, based on your settings (ISO, shutter, f/stop (aperture)). It's the 'forth dimension' - and something very few people ever pay attention to or use (including many professionals). However, it enhances creativity, reduces errors, and allows you to capture some otherwise almost impossible shots.

Each stop of EC provides either a doubling or halving of light compared to what the in camera metering mode would have done otherwise. A setting of zero means NO compensation will be applied (default).

Exposure of an image can be adjusted in post-processing, using good editing software. However, there are obvious and real limitations: lightening an under-exposed shot will exaggerate any noise, while 'blown out' (over-exposed areas) are impossible to recover.

In most dSLR's (and some of the higher end Point & Shoots that also capture in RAW) you can select something called 'bracketing' - which is necessary for HDR, but more importantly, helps insure you’ve got one that’s correctly exposed – especially if you choose to shoot RAW files.

What it does: It captures THREE FRAMES of the same image... you set the brackets, but they are usually -1 0 +1 for the exposure. Your high end cameras allow for .5 +/- to 2 +/-  (a few allow a 3 stop option). Many landscape photographers using bracketing use a +/- 2. Which means that one shot will be over exposed by 2 stops, one under exposed by 2 stops, and one where you (or the camera) has the exposure settings set at. The HDR photographers use these brackets to 'pull' the dynamic color range, and to get the sharpest, highest contrast areas of the greatest range of shades possible. They are multiplying the the color range by at least a power of 2 (if not 3). You have the 0 compensated 16.7 Million colors, and the +/- version of those 16.7M colors.

Think of it like walking into your living room in the afternoon... consider that 0. Turning on the lights, +2. Turning off the lights and putting on sun glasses, -2. That will help you understand the different shades of lights and colors you'll be able to see. The modern cameras are able to do that by using bracketing. Isn't it time that you stepped up to play with an often under utilized feature??

Next, is 'STACKING' - that is what the HDR photos do with the bracketed images. Literally stacking them on top of each other, allowing the sharpest and most dynamic colors (shades & shadows) to show through. But, one step at a time... start with bracketing, and see the difference. AND SHOOT IN RAW!

 


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If you have any questions about photography, please feel free to ask. I might not know the answer off the top of my head, but odds are I can either help you find the answer or know someone that knows the answer. After nearly 45 years of playing with hundreds of different cameras, both film and digital, I probably don't know specific 'make and model' info... but I UNDERSTAND PHOTOGRAPHY, and the PRINCIPLES & CONCEPTS of capturing and creating good to great images.
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