16 July 2011

Depth of Field

15 July 2011

The depth of field is the amount of your image beyond and before your focal point that will be in focus.  Normally, for landscape, you want a large depth of field and to have everything in focus to capture the beauty of the scene.  In portrait photography, a small depth of field is often used to limit distractions of the background  from the main subject.

There are a few factors to determine your depth of field:

1)  Your aperture
2)  Your lens
3)  the distance from your subject.

The Aperture
The aperture controls the depth of field, which is what is in focus in your image.  You can draw attention to one subject, with a blurry background using a low f/stop or to focus everything in an image with wide f/stop. 

This is f/5.6 with a close distance

  Here I widened the apurture to 7.1 and stepped away a few feet. Notice how the baby's hand is not in focus, this is because my focal point was broader than the movement of the hand.

•    The higher the number for your f/stop the wider your depth of field (f/16) the lower the number for your f/stop the more shallow is your depth of field. (f/8)
•    The closer to your image, the shallower is your depth of field as in using a micro lens for nature photography. 

Here are some other shots, showing the depth of field using higher/lower f-stops.
This image was taken at f/16 a smaller aperture. Notice how you can see more details of the dark Cyprus trees in the background compared to the image below taken at f/13.  This image has a "broad depth of field"

Taken at f/13 you can still see the background, but the trees and wall are not as "sharp" in focus as the f/16 shot.  I call this a "medium depth of field".
This image was taken at f/8 you notice how the garden in the front is the main focus, while the background is blurred.  This image has a "shallow" depth of field"

Your lens:

•    The longer your lens (200mm) the more shallow will be your depth of field.   The shorter your lens (55mm) you will have more depth of field.  This is termed as Focal Length.

The Distance:

•    The closer you are to your subject, the less amount of depth of field you will have.  The farther away, the more depth of field.  (as described in the image of the baby's hand and other image with the mother above)
Related lessons:
Aperture and f/16 Rule
Shutter Speed Basics

Depth of Field
Focused Bracketing or Photo Stacking 

14 July 2011

Focus Bracketing or Photo Stacking

Focus Bracketing: (or Stacking)
Susan Brannon

This is useful with limited depths of field mostly used in macro photography where you can focus the subject at different positions.  Take several images of the same subject each with a different focus spot.  For example, take an image of a flower and let your camera automatically bracket your image.  You will notice that the image may be focused in the front (closest) to your camera, and blurred at the back.  Now, take that same flower, and bracket focus on the back of the flower instead, manually.  The front of the flower is blurred, while the back is in focus.

There is a term “focus stacking” that by taking a sequence of various parts of the subject in focus and combining them together to create the entire subject in focus.  This is not easy to do, because it requires delicate use of PhotoShop to combine the images!

Some tips:
1)  Focal length -  The longer your lens, the more shallow your depth of field is.
2)  Distance to the subject:  The nearer you are to your subject, the shallower your depth of field is, especially with a macro lens. 
3)  Aperture settings:  The more you open the aperture, the shallower your depth of field will be.

How do you do this?

A)  Use a steady tripod.
B) A macro lens, to get really close.
C) Super precision:  Lock your camera on your tripod, so you cannot move your camera. 
And rely on your in camera focus points to focus on different parts of the image.
D) Patience:  This process takes quite some time
E)  Post processing software, that can handle focus stacking.
F)  Create a file with layers, stacked on each in a linear arrangement.  Do not jumble the sequence of focused images.
G)  Align layers
H) Blend layers

Image below from Wikipedia:

Related lessons:
Aperture and f/16 Rule
Shutter Speed Basics

Depth of Field
Focused Bracketing or Photo Stacking 

13 July 2011

Tips for Night Photography

Susan Brannon
26 July 2011
It is difficult to take images at night and in low light, but to do so, is the fun challenge in photography!  Once, you set out and “practice” you will find your technique and afterwords there will be not a time in the day when you think, “I cannot take a photography because of the light!”

1)  For night photography, you will definitely need a tri-pod!  This will stabilize (duh) your camera and allow for longer exposures!

2)  Take if off Auto mode (you can keep the focus on Auto mode and place with the focal point)  This way you can play with your shots, reduce the brightness of the lights, and add some creativity to your images.

3)  Set your exposure to -2 or -1

4)  Avoid using flash.  This flushes out the natural light, and it may overexpose the image you are trying to shoot.  (Or flood out the background)

5)  Set your ISO to the maximum.  The higher the shutter speed the shorter the exposure you can use.  This is important for night photography.

6)  Experiment, take as many images as you can, alternate your exposure levels and doing this will increase your understanding in night time photography.

Tip:  If you are out running around in a beautiful place and decide that you really want to take some images but do not have your tri-pod.  You can always find a flat spot to place your camera that just may steady it enough to allow you to take your shot!

Remember:  Check the weather, for rain and/or clouds.  See when the sun sets and the moon rises.  Think of where you want to set up shop, and bring bug spray for the summer!

This one was not taken in the summer, but when it snowed in Florence, Italy I could not but help to run outside to capture this moment.  However, my film was black and white, so the glow from the night time light did not bounce off of the snow.

For this image I wanted to capture the glow of the buildings. The camera was set at: f/5.6; 1/6s and ISO 640

A rare moment in Florence History, The Duomo covered in Snow, with a beautiful orange sky in the background. This image was taken at f/5.6; 0.4s and ISO 640

Related lessons:
Aperture and f/16 Rule
Shutter Speed Basics

Depth of Field
Focused Bracketing or Photo Stacking 


Susan Brannon

Cameras do not see the world the way that we do, and sometimes we find that an image is too dark and you cannot distinguish any detail.  The camera is based on the different hues of gray. You use bracketing when the lighting condition is difficult for your sensor to read, creating under or over exposures.  For example, taking images in the snow, you camera will automatically make things darker.  How do you resolve this problem?  You must tell the camera what exposure you want to use. 

Slide, film and digital work in different ways.  Slide is very sensitive and where you would set your exposure for your digital, will not work for the slide; your image may not even show up!  Film you only see the effect when it is pronounced.

The term bracketing usually refers to exposure bracketing: the photographer chooses to take one picture at a given exposure, one or two brighter, and one or two darker, in order to select the most satisfactory image.  Many digital and film cameras, can automatically shoot a bracketed series of pictures. 

Exposure bracketing is dealing with high-contrast subjects with a limited range or sensor.
Exposure bracketing is using your camera to create a high dynamic range that exposes the portions of the image by different amounts.  (Also see exposure)

You can set your bracketing setting on your camera to different stops,-4 stops -2 stops, +2 stops etc…This is what allows different amount of light into your sensor and changes your exposure. 

Like This:

This is at the automatic setting with zero adjustments for exposure

Related lessons:
Aperture and f/16 RuleShutter Speed Basics BracketingDepth of FieldFocused Bracketing or Photo Stacking Exposure