General Photography - Techniques & StylesDiscuss the fundamentals of photography, photographic technique, infrared and macro shooting, and related topics here!
I would like to know how to use it in practice? Do i just point it to a bright area of the scene and press the shutter button halfway and then recompose?
To my understanding, the Auto Exposure Lock button (AE-L) merely locks the exposure or in Manual mode, adjusts the appropriate exposure determined by the camera based on whether the user has preset in the Custom menu for either the aperture or shutter speed to vary, or for both aperture and shutter speed to change (Program Line). The camera default is Program Line.
This has nothing to do with spot metering per se as one could use AE-L with any of the 3 metering methods - matrix, center weighted or spot.
The 3 metering methods provided allow the user to meter according to the subject. Center weighted for example puts emphasis on the center portion of the frame and works well for portraits.
In the case of spot metering, as it allows measurement of a small portions of brightness in a scene. Great for measuring high contrast situations and very accurate but the caveat here is the user has to determine which is the important point to measure the exposure in the viewfinder. AE-L serves the purpose to lock exposure to a defined point in a scene while the user re-composes.
From what i read in the k100ds users manual the AE-L button doesn't lock the exposure in M mode but instead automatically selects an appropriate exposure.
JDG, if you've never seen an 18% gray card, get thee to a photo store and take a look at (or better yet, buy) one. That is a middle tone between pure white and pure black, and it is the tone (brightness) to which your camera meter is calibrated for a "proper exposure," regardless of metering mode.
Learn to see real-world brightness that corresponds to that middle tone (green grass in sunlight is close; a clear blue mid-day sky to the north is real close; the right medium-gray rocks will be close), and learn which other real-world tones are a stop or two brighter or darker. Then, when you use your spot meter (practice in Manual mode until you get good), try to find a tone that you know in your scene, or put your gray card into the light in your scene, and meter on that. Adjust your exposure if you need to compensate for metering on a brighter or darker toned subject. Try a shot, and check your histogram, then increase or decrease your next exposure, or try a different-toned subject to meter. Lather, rinse, repeat...
Build enough experience with this technique, and you'll develop a good eye for the range of light in your photos, for what subject(s) to meter, and for how to anticipate exposure tweaks before you even trip the shutter. After all, that's how we Pentaxians did/do it with our Spotmatics and K1000s!
I use spot metering only on my K10D and tend to look for a lightly shaded part of the frame to collect the proper exposure from, then reframe and shoot. Works out really well for me. I have a gray card for wedding dress shots, or shots where the exposure is jumping all over the place when I'm scanning the scene I want to shoot.
As for collecting off of grass or sky...those are great suggestions that I will definitely be giving a go at.