Light is the fundamental aspect of photography that matters. The amount of light that records the sensitive material (sensors in digital cameras) is what determines the exposure. Exposure you decide where each of the tones of the scene set yourself: has nothing to do with the available light in the scene. In other words, the available light due to a physical matter, while exposure with the light made available is a completely creative question therefore personnel. Understanding exposure must be the first objective of anyone interested in photography. It is the basis for everything else.
In the cover photo, I decided it was important to preserve the texture of the clouds. For this I measured the light in the upper right, the brightest, placing +3 EV exposure. The rest fell tone which I was interested. In the digital development slightly I increase the brightness of the grass in the foreground to highlight it.
When we talk about Expose, we talked about Place your scene Tones
Light from a scene can be measured with a hand photometer, which measures the incident, or the camera meter, which measures the light reflected light. All cameras incorporate a scheduled photometer to measure the light reflecting objects. By convention, the cameras measure the 18% reflected light, that is, what is called a medium gray 18%. When speaking of exposure normal tendency is to think, first, in adjusting camera parameters (shutter speed, aperture and ISO); although, in reality, these three settings are the tools that cameras and lenses, available to us for exposing any scene.
Therefore, the first important issue to consider is that when we talk about placing expose the tones of the scene, which has nothing to do with adjusting the camera settings. An obvious proof is that a night scene, with adequate exposure time, can become a very bright picture, even appear to have been made during the day (almost). The aim was to preserve the soft lines that drew clouds; if that texture is lost, the picture does not make sense to me. I performed the measurement in the area lit clouds. The sun in front produces a strong backlight that generates flare in the lens, although I do not dislike.
The objective of this picture was to preserve the soft lines that drew clouds; if that texture is lost, the picture does not make sense to me. I performed the measurement in the clouds illuminated area. The sun in front produces a strong backlight that generates flare in the lens, although I do not dislike.
Early last century, the American photographer Ansel Adams set a tone measurement criterion called the zone system. This system, still used today, provides 11 zones ranging from 0 to 10 (from 1 to 10 are numbered with Roman numerals). More comfortable is the system that sets a standard with 6 possible levels: black, second shadows, shadows first, first light, second light and white. The medium gray area lies V, in the zone system, and between the first shadows and the first light in said other system. We use the system we use, all agree on three benchmarks: the black, medium gray and white.
|All shades of any scene are between black and white|
In this photo we have several clues tones. Misty landscapes often have a small dynamic range, which easily has no place in the sensor. Therefore, I usually expose for smog + 2EV. If it were clear, no haze, the grass is closer to the center of the image has a tone slightly above halftone we could have used to expose; as well as the ocher center of the image, in this case, slightly below.
Do not be scared, but you need a little theory of Color
Simply put, the tone is each of the colors of the visible spectrum. Are all major, secondary and intermediate colors of the color wheel, without being mixed with white or black. Saturation is the purity of a color such that the maximum saturation of a color match the wavelength of the color spectrum. The brightness is adding white or black to a color to make it lighter or darker, respectively. Therefore, a medium gray -the reflecting 18% of light-has a brightness of 50%, which is to say, that its exposure stood at 0 EV.
What if there are no white or black? For what already mentioned, the palm is +1 EV above middle gray. In this case I used moss, brighter than the grass. I chose a medium gray area as and explained thereafter. Derechear I took to get greater exposure and shadow detail. So clouds background are burned, but do not matter in the image.
Exposing: The Possibilities of Medium Gray location
The exhibition shows the camera with the meter set to 0, always shows a reflectance of 18%, regardless of color or tone of the real object. Therefore, leaving aside the creative issues and focusing on the accurate record of the tones of the scene, recording the camera exposure suggests three possible scenarios:
- The tone that suggests -the gray tal camera matches the tone of the scene. In this case, we get an exact reproduction of all shades of the scene that fit into the dynamic range of the sensor.
- The tone that we measured as medium gray and it has not caused a shift towards black tones, resulting in underexposure of the tones of the scene. In this case, we have to compensate the exposure with a positive value. This is because the measurement was performed in a medium gray to lighter shade.
- The tone that we measured as medium gray and it has not caused a shift in the tone of the scene at the target, resulting in overexposure of the tones of the scene. In this case, we have to compensate the exposure with a negative value. This occurs because the measurement has been made in a darker shade of gray than the average. The darker the higher the displacement.
How We place the tone where it belongs?
Compensating the exposure. If we measure a medium gray tone without compensation and we want to have a lighter shade can open the aperture, use a slower or may even raise the ISO speed. Conversely, if we get a darker shade, we close the diaphragm or use a faster speed.
Therefore, we can say in general that:
- A medium gray needs a compensation of 2.5 steps in a positive light as to leave no white texture. About 2 steps to get some texture, but being still white. X area in the zone system for white; VIII and IX, for some textures, that is, the second lights.
- A medium gray needs compensation -3 steps of light (negative) to leave as black without any texture. If we need to retain some texture offset somewhat less about -1.5 or -2 steps. Zone 0 and I, for absolute black; II and III, for some texture, that is, the second shadow.
Therefore, if at any stage we have a black or white color tone, since we have a reference for proper exposure (I repeat, according to the tones of the scene, without any creativity).
This bronze sculpture "Charon" Ramon Conde, I was interested to catch the maximum texture eye area, where there is the approach. The white face is 1.5 EV because if any white located on your site, background light would have eliminated the small silhouette of the Tower.
Criteria to consider in deciding the tones Let's Get the Picture
There are several criteria that we consider when we decide where to place the tone.
- The former may be aesthetic criteria. For example, in fashion photography where overexposure of skin tone are used to obtain a washed texture.
- Another criterion could be creative, in which we are forced to use a particular aperture to achieve shallow depth of field or lot. Or a certain speed to record movement or freeze.
- Technical criteria, imposed by the dynamic range of the sensor. If not all large we would like, it can cause a compression in the tones of the scene - especially in those very any supporting that requires us to decide between keeping the lights or shadows.
In this image, the lights illuminating a castle produce some colorful reflections in the water contrasting with the deep blue of the night. Color is the main reason for the photo and the boat, only a visual anchor. Therefore, exposure record chasing gold and orange hues, without being burned. The top black are lost, but a slight blue tone of the night remains reflected in the sea water.
Taking all this into practice
All the comments must be translated into appropriate for the purposes we pursue exhibitions; nothing is right or wrong, if the result is the result of reflection and application of knowledge in the making of the photograph. Therefore, as I told you, the key is to measure correctly. My choice is the spot metering in all cases. There is much literature on the subject, so I will not dwell, but I do believe that total control involves working in manual mode and spot exposure. From there, once we have acquired the knowledge on how to display properly and how to use the parameters offered by the equipment for it, you can opt for the use of semiautomatic and even ISO in AUTO mode.
No need to look for objects of medium gray to 18%, identify the tones of the scene through the information you provide each. For example, a landscape where there are white clouds illuminated by the sun, can make measurements on these clouds and place about 2 or 2.5 steps above the middle gray. If we are in the snow, we can measure the snow and make two steps, to maintain its texture. Another reference, the green of the grass-always that the directors do not give them enough sun approaches the middle gray. And one more if any scene, we measure the light in the palm of the hand and we place a step above 0 which marks the middle gray in our exposímetro- have fairly tight tones scene.
In food photography it is essential to be precise with measurements to properly locate each tone in place. Therefore, if we do not have a precise reference in the scene, the use of at least one gray card is required. If you do not disponéis one you can use a white sheet and use it to expose the still life properly.
Conclusions and Some Tips
- Speaking of tones and black, medium gray and white, some may think that we refer to the photograph in black and white. Nothing is further from reality, all the colors of the scene fit into the dynamic range of the scene, that is, they are represented in some way to an existing tonal gradation between the extremes, black and white.
- By exposing we decide where we place the tones of the scene.
- It works in a timely way to have total control of the measurement.
- Separate measurement of the shutter button, so you have even more control. I remember that when you work in manual mode button does not work exposure compensation, since you decide about all exposure parameters.
- Each camera has a different dynamic range. You will have to test and verify where the highlights are burned and where blacks are pasted (the detail is lost) to your computer. If the tone of the scene you're going to record fit into the dynamic range of your camera sensor, derechea exposure.
All image from dzoom.org.es