Depth of Field--photos

So, taking photos of these dinosaurs, showing different depths of fields. Here are 4 photos:

In this photo, I used a greater depth of field, and all the objects are in focus:

This photo shows only the closest subject in focus:

Here, although more difficult to do and it isn't as clear what is in focus, the 2nd subject is in focus, while the others aren't focused as well:

Finally, this photo shows only the furthest subject in focus:

Depth of Field

Depth of field is the range of distance around the focal plane which is acceptably sharp.
The depth of field depends on:
-focal length
-sensor size
-aperture
-focal distance
The depth of field does not, all of a sudden, change from sharp to unsharp. It is more of a gradual transistion. Actually, everything immediately in front of or behind the focusing distance begins to lose focus, although it may be so slight that our eyes or resolution don't perceive it. Since there is no definite point of definite transition between sharp and unsharp, the term "circle of confusion" is used to define how much a point needs to be blurred in order to no longer be perceived as acceptably sharp. This is an exaggerated diagram of circle of confusion. In reality, it would be just a tiny fraction of the camera's sensor area.
An acceptable circle of confusion is loosely defined as one that would go unnoticed when the photo is put onto an 8by10 print, and viewed from 1 foot away.
These are three photos taken from the same point, with different focuses.



How aperture affects DOF:
As the aperture gets smaller, the depth of field is increased. If you want very great depth of field, use a very small aperture. If you want the effect of a blurred background, with a smaller amount of the picture in focus, set a higher aperture. This means to set the f/stops smaller if you want the photo having a greater DOF.

The focal length is how close to the subject your actual lens is. With a longer focal length of the lens, the DOF will be shallower because the lens is closer to the subject. If you use a shorter lens, the background of the subject will be less blurred. If a very long lens is used, the back of the subject will be very blurred, since you are so far zoomed into the subject.

Sensor size:
The actual size of the sensor affects the Depth of Field. The smaller the sensor size, the greater the depth of field is at a given focal length and f/stops. Sensor are classified by their crop factor. Using this, the sensor is compared to a frame of 35 mm film. If a camera has a ratio of 1/4.5 (the one being the comparison to the frame of film) it has a smaller sensor size than that with a ratio of 1/3. The greater the denominator, the less the sensor size.

Homecoming Week

Here are a series of photos from homecoming week, with some pumpkin carving. Enjoy!


Taken after soccer practice on 10/17/07 at about 5 pm at the La Conner Middle School soccer field. This is Hana Van Pelt and Robin Coe, carving pumpkins for LCHS girls soccer team Senior night on 10/18/07. The pumpkins will spell out "Thank You Fans," one letter on each pumpkin.

The LCHS girls soccer team members hard at work, still carving pumpkins. They didn't have any spoons to scoop out the pumpkin flesh, so they did it by hand.

One of the pumpkins, a final result. This is Anna Raymond (left) and Galena Graham's artistic take on the common letter "O."

So that's the end of the pumpkin story. The pumpkins looked great, each holding a candle, in the dark at our Senior Night Game.

I will put the other Homecoming week photo story in another blog a little later.

Exposure

I recently took a series of photos, to find what exposure worked best in the environment I was taking the pictures.

This photo was taken with a shutter speed that was too slow, and the aperture was also too high. The lighting was too bright for the exposure which I set, so the image appears washed out and white.


I took this photo in the same lighting, but the shutter speed was too fast for the given aperture. This is why the photo appears so dark. It did not have a long enough exposure.

Finally, after taking the previous photos, one with an exposure that was too long and one that was too short, I set an aperture and shutter speed to accommodate the lighting. The result is the right exposure ( and therefor right shutter speed and aperture). This produced a clear and detailed image.

Photo techniques

Panning is a technique used in which, when used to capture in an image, the main subject will be clear and sharp against a blurred background. It idea of panning is to follow the subject with your camera as it passes in front of you, and continue following it as you press the shutter, even after the shot is taken. If you pan at the same speed the subject is moving, the subject will appear sharp against a blurred or streaked background. You can do this best by keeping your feet still, and rotating the top of your body as you follow the subject. To make sure your subject will appear sharp, prefocus the camera at a point where you subject will pass. Make sure the background isn’t too light or dark and you are good to go. It may take a couple tries, but panning is a great technique to use.

Stopped action is used to take a photo, mid-motion, in which there appears to be no movement actually in the shot. Usually we know it is taken of an action by the circumstances (such as someone’s leg in the air and a soccer ball above it). Having a very fast shutter speed and anticipating an event or movement achieve stopped action. When the action occurs, the image must be taken with a very fast shutter speed, so that the subject is captured in that small moment in time in which the action is occurring.

Blurred action is used to take a photo of an action in which the action appears blurred because of a slow shutter speed. The image will appear streaked or blurred because the shutter speed is not fast enough to capture the exact moment the action is occurring.

Exposure Basics

Exposure is the amount of light collected by the sensor in your camera during a single picture. If a shot is exposed too long, the photo will be washed out. If it is not exposed long enough, the photo will be too dark. Almost all camera today have light meters which light in a given shot and set the ideal focus automatically.
The primary controls for exposure on a camera are aperture and shutter speed:
Aperture-the size of the lens opening that lets light into the camera. Apertures are measured in "f/stops" ex. f/2.8 is a very wide aperture, f/19 is very small.
Shutter Speed-the amount of time the light is exposed to the sensor. Shutter speed is measured in seconds (or fractions of a second). 1/2000 of a second is very fast and 8' seconds is extremely slow.



This is an example of a photo with a very low shutter speed, and a slightly narrow aperture

The relationship between shutter speed and aperture:

To maintain the same exposure value, if you change one of the two settings, you must change the other value in the opposite direction. Take this situation for example: The camera meter is 1/60th second and f8.0 and you wanted a faster shutter of 1/250th second. To have a faster shutter speed of 1/250th second it is underexposing three stops. So to keep this the same, the aperture must be overexposed three stops. This would be f/2.0. The exposure of 1/60 and f8.0 has an equivalent exposure to 1/250 and f/2.0. This is a table showing the relationship between shutter speed and aperture.

Photos-10/8

This is a flower along a fence in La Conner. These photos were taken last night on 10/7/07 at 6:30 p.m. I tried taking photos without the flash also, but they ended up being shaky and not as focused.




(This is late because of computer trouble I was having yesterday). Thanks!