Monday, December 21, 2009

Part 2: Photography with Imre Z. Balint: Episode 6 - Metering and Exposure

Well I have to admit that I didn't think Episode 6 was going to be this long! And I tried to keep to the basics as much as possible too. Perhaps this is perfectly normal though, as indeed getting your exposure just right (or the way you want it) is really not that simple.

In the video I covered five different methods of controlling exposure: 1) Metering modes, 2) Locking the exposure, 3) Using filters, 4) Using a light meter, and 5) Using the exposure compensation button (that one with the +/- sign on it). By the way, EV = exposure value.

Before moving on to further details, I would like to add that I could have mentioned exposure bracketing, which most dSLRs support. What exposure bracketing does in general is that your camera will take 3 to 5 photos (depending on the setting) in rapid succession using various exposure compensation values; those values can be set to your liking on most cameras. So for example, if your camera is set to take 3 photos from -1 EV to +1 EV, then you'll get one photo with a -1 EV, another with 0 EV (or no compensation), and the third shot at +1 EV.

So why use this method? Well there are situations where if the shot is important enough to you, then utilizing bracketing may yield that "right" image. Perhaps there are some nice clouds in the scene, but you're not sure which compensation value would be proper to ensure they aren't blown (in other words, you generally don't want your clouds to be completely white, because that's usually not pleasing and cannot always be corrected via software such as Photoshop, even if you shoot RAW). Now because you have several images to choose from, it's more likely that one of those will have a properly exposed sky. Another reason to use bracketing is that it's quicker than taking a shot, making a change to the setting, then taking another shot, then... you get the idea. And there some photographers out there who like to create high dynamic range images (usually just referred to as HDRI). In general you can almost never properly expose the entire image (some things will always be too dark or too light), so by using HDR techniques, you can create a photograph that more closely resembles what our wonderfully adaptive human eyes can see. Personally I like HDRI, as long as the photographs don't look over-processed with that odd halo around contrasting areas; done right though, they do look quite amazing. Here's a link to a website with some HDR shots: http://hdri.wordpress.com/

Some Guidelines
Even though it is somewhat difficult to provide some concrete numbers for exposure compensation and rules for using certain techniques, there are some general ones I would like to share from my experiences and from what I've seen some other photographers use. Keep in mind this is by no means a complete list, but at least is a start for some of you readers out there.

Landscapes: If you're the type of photographer who likes dramatic lighting, then you'll likely be faced with bright skies and dark lands. This poses a problem as most cameras will expose for the brighter sky, leaving the ground almost black and detail-less. In cases like this, I would suggest using a graduated neutral density (ND) filter, and adjusting your EV compensation as needed; perhaps -0.3 EV to ensure the sky doesn't blow. The filter will help even the brightness levels in your photo, to get a more pleasing shot. But depending on what I've shot, multi-metering has been half-decent at getting good results, and center weighted has been quite useful too.

High-Key and Low-Key Photography: High-key shooting in essence means slightly over-exposing your photos, and low-key is basically the opposite, slightly under-exposing your shots. This deliberate act can produce very moody images if you choose your subjects wisely. Often times, portrait photographers use these methods, but keep in mind that you don't have to limit yourself to just people. A dirty downtown back alley may look more ominous if shot low-key, for example. Although values vary from photographer to photographer, for high-key EV compensation is usually pushed to about +0.7 or +1.0, and low-key the same but in negative values (-0.7 or -1.0). Here's an interesting link: http://www.diyphotography.net/lighting-high-key-and-low-key

Birding: In cases like this, I have usually found the most success by using spot metering, and compensating my EV as necessary. At least when I've shot some birds, they tend to be against a very bright sky. If I use multi-metering or center weighted, then I usually get a perfectly exposed sky, with a bird in silhouette. Although that might be nice in some cases, I usually prefer to get the details on the fowl; its feathers, colors, etc. Now of course I have to change my tactic if the bird is smaller and off-center in the photo, as the spot metering will miss the creature entirely, but here's where I can use that auto-exposure lock (AEL) button. I move the spot over to the bird, lock the exposure, then move back to frame my image, and click! Or in this case, I could also use the shutter button by pressing down half-way, which would also lock the focus perfectly on the beaked individual.

Macro: Again, depending on exactly how big your subject is, its placement in the frame, and tone (how dark or bright), I've noticed that center weighted metering, along with EV compensation in either + or -, has yielded good results for me. Usually macro friendly subjects, like flowers and insects, take up the majority of the image, but again, I'd rather expose them properly versus the thing(s) behind them. Spot metering usually doesn't work in these cases as the area the camera's meter samples is far too small, and mutli-metering can be hit and miss, either getting it just right or, or taking too much of the subject's background into the exposure calculations. But again, if you haven't done a lot of photography yet, you'll soon find yourself messing with the settings quite often; that's half the fun of it.

I'd also like to suggest trying out various settings on your camera that are in regard to when you take a photo. In my case, I have my camera (usually) setup so that when I hold the shutter button down half-way, only the focus is locked. When I press the shutter button down all the way to take the shot, then my camera will expose the image (in other words, determine the EV). My logic is that since more aesthetically pleasing images have the subject off center, and more often than not the subject is also in focus, I can shift over to lock the focus where I want it, and then take the shot so that the focus stays, but the exposure is overall correct for the scene. Again, I often break the rules here to, as I'll still likely use EV compensation or lock the exposure on the subject.

I could probably keep writing until the sun comes up tomorrow, but hopefully this will give you a decent start. Bottom line, as mentioned in my video, is to practice and experiment with various settings, to learn how your camera behaves and to get accustomed to different exposure techniques to enhance your photography skills.


Web Resources:
http://en.wikipedia.org/wiki/Exposure_value
http://www.cambridgeincolour.com/tutorials/camera-metering.htm
http://www.chem.helsinki.fi/~toomas/photo/ev.html
http://www.dpreview.com/learn/?/key=exposure
http://www.dpreview.com/learn/?/key=exposure+compensation
http://www.digicamhelp.com/taking-photos/advanced-techniques/ev/
http://digital-photography-school.com/ev-compensation-explained

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