First of all, I hope you have followed the pointers others have left you in this thread -- fundamentals and specifics about exposure have been worked through many times, and you can get more info by following earlier discussions than a single thread will produce. I'd also encourage you to look at the bottom of this page, in the "related threads" section, and read through the various threads to pick up other thoughts.
samueli wrote in post #7637003
Thanks for all the replies! I thought there would a more mathematical way to do it in manual mode, without the ability to use exposure lock.
Well, I don't know how practical a "mathematical" approach is -- Ansel Adams, working with large format film and specific light meters developed the "Zone System" to identify specific "zones" of light in an image and incorporate them in his exposures, but he also did serious post-processing to fully develop his images. With our smaller/digital format we don't see the same range and you don't see much discussion about the Zone System in actual practice. The idea of metering for highlights (and/or shadows and/or midtones) is still very active, though.
A common "starting point" from the "old days" was the "Sunny 16 Rule", in which you took the idea that on a sunlit scene you could use f/16 and then a shutter speed that was 1/ISO and get a good exposure, but then you have to modify each of your settings according to the particular scene and your requirements as far as specific shutter speed needs, aperture/depth of field needs, and ISO/dynamic range or speed needs. You end up often with settings that don't seem to resemble the Sunny 16 idea much!
I don't really. I read this in some thread as one of the basic rules of thumb for photography - "expose for highlights". Sometimes I will expose both highlights and shadows and try a capture of each. I'm just trying to figure out a way to do this technically. Plus, I've only had spot/center weighted metering for a few weeks, with my new 50D.
I had read in another article that center weighted metering is really the only way to go, and have seen some creative uses of metering on a certain part of an image, locking the metering, then capturing the whole image where the metering would be different.
It's just that in manual mode, there is no exposure lock. So if you meter on a certain area, then recompose/focus, what is the math? In manual mode there is a missing variable to needed add/subtract stops. Or do you meter on several areas of the photo and figure out from there?
One of the conveniences of Manual mode is that you don't have to use exposure lock continuously -- you lock in your settings, period, and only change them when the lighting of the scene or your orientation to the lighting changes.
There are a few practical approaches to using manual that can arrive at the same place -- a good exposure that will take in highlight as well as shadow areas. This involves using your spot (or at least center weighted) meter and identifying an area of a consistent tone in the same lighting that illuminates your scene that you can reasonably identify and adjusting your settings accordingly -- telling the camera that this item is, say, medium or light or dark. You can use various things -- the palm of your hand, a gray card, a white sheet of paper, the sky, snow, as long as you know how the camera should interpret that object.
If left to automatic exposure, the camera tries to interpret everything as "medium" so that, for expample, if you let the camera expose for snow, it would turn the snow gray in the exposure. You have to know that, and, depending on the lighting of the scene, adjust your settings to interpret the snow as bright.
Once you have a balanced setting for the scene as a whole, you can shoot away unless, like I said, the scene lighting changes or your orientation to the light changes.
As far as exposing for the highlights (or in other cases shadows), you can do the above, but you are specifically metering an important highlight and using that to set your overall exposure. In the "snow" example, you want to expose the scene so that the snow will be white, but not "blown white" without any detail, so you set your camera so that the meter scele when metering the snow reads up to but not against your right edge.
Sometimes, when "exposing for highlights" you may find that other parts of the scene are darker than you would visualize, and when I'm against that type of high contrast dynamic, well, first of all RAW is a real necessity, then, I'd pay real good attention to the right side of your histogram, making sure that those highlights are really nudging the right side. Third, I would shoot that scene with the lowest ISO possible because you will get the cleanest results bringing up the shadows in your RAW converter with a low ISO.
As a whole, try to keep it simple so that you can think and act quickly. For handheld shooting, I like the statement "PhotosGuy" FrankC uses: First set your shutter speed and aperture to get the effect you want, then adjust your ISO to properly expose the scene. For shooting with a tripod with a static scene, I mix it a bit: first set the aperture and ISO you need, then adjust your shutter speed to expose the scene. But you want to keep it simple and practical!
Hope this helps a bit!
Mike beat me to it! Thanks!
" Denney
