Today, I am looking at a depth-of-field that leaves a background very out of focus. This is easy to do on my point and shoot camera to wonderful results: 1) Set the camera to macro. 2) Zoom in as far as the lens can zoom. 3) Stand back as far away as possible from the subject while still able to get the desired composition, and still able to focus on the subject. 4) Take picture.

Oh, such a lovely photo taken with an HP Photosmart 735!

Update: I just found that my HP Photosmart 735 captures information about things the user has no control over when photographing! Here it is:

Exposure:

0.008 sec (1/125)

Aperture:

f/5.1

Focal Length:

17 mm

ISO Speed:

141

The same steps work with the Nikon D40 when it’s set on “Auto”. There’s no depth-of-field preview looking through the view finder, but the photograph can be reviewed on the LCD screen immediately after taking a photograph. Even better, all the camera’s auto-selected settings can be viewed, as they are embedded within the photograph’s image file!

I will look at three photographs with a depth-of-field like in the photograph above, and the settings the camera selected to achieve the effect. I hope to learn how to take this kind of photograph with manual settings.

This raises the question: Why? Why do I want to learn to do manually what the camera can do automatically? There are two answers: Knowledge. Control. I want to know what the camera is doing, and how it achieves what it does. This is the knowledge. The power is that there may come a time when I want to take a specific kind of photograph, and “Auto” cannot get me the result I want. I might need to use one of the semi-auto settings, or I might have to go completely manual to get what I want. I’m taking the first steps in learning how to control what I can achieve on “Auto” so I may one day be able to achieve what I cannot on “Auto”.

Here is the first photograph:

When I saw these trees with new, green leaves, and a few old, brown leaves, I knew I had to do a “circle of life” photograph, and I knew I wanted the old leaf to be in focus with the new leaves out of focus. This forces the subject to be the brown leaf without there being a clutter of subjects, as all the other leaves are not in focus.

Here are the settings the camera chose for this photograph:

Exposure:

0.008 sec (1/125)

Aperture:

f/8.0

Focal Length:

98 mm

ISO Speed:

400

I’ll get back to these. First, let’s check the next two photographs and their stats.

Exposure:

0.002 sec (1/500)

Aperture:

f/8.0

Focal Length:

200 mm

ISO Speed:

200

Exposure:

0.008 sec (1/125)

Aperture:

f/5.6

Focal Length:

200 mm

ISO Speed:

400

Okay, we have some interesting things to look over! Where to begin?

I’ll start with the focal length, as this is the part that I manually controlled. The focal length, as far as an amateur with a zoom lens is concerned, is how much the lens is zoomed in. A focal length of 35mm might let you see everything in front of you, but up that to a focal length of 200 mm, and you’ve essentially zoomed in, so you only see a small area in front of you (but in greater detail, and more sensitivity to the camera shaking).

Since I was using a lens that “zooms in” up to 200 mm, two of these photos were taken zoomed as much as possible. This goes back to my instructions of stepping back and zooming in to take a photograph of a subject with the background being very out of focus. The other photos, the brown leaf among green leaves, has a focal length of 98 mm because I didn’t want to zoom in too closely on the brown leaf, as I wanted the green leaves behind it. (I could have still took some steps back and zoomed in more, except I was have started backing off the sidewalk and into the street to get this photograph’s angle!)

Next, I want to look at the ISO speed. The Nikon D40’s “ISO Sensitivity” menu includes thumbnails of photographs depicting the kind of situation when the ISO would be used. An ISO of 200 is shown with a photo of a scene where a ship is on the water, and buildings are in the background, with a lot of daylight. And ISO of 400 shows a zoom in on a boat speeding along the water. Higher ISOs include photos of night time and indoors.

The ISO number represent the camera’s sensitivity to light. If there is a lot of light, a low ISO should be used. If there is little light, a higher ISO should be used. However, a larger ISO results in more noise in the photograph.

I don’t yet understand what exactly the ISO is what how it works, but I do know that a lower ISO is preferred. A higher ISO is used when the camera needs more light to photograph something (would the subject be too dark with a lower ISO in such a situation?). Of course, indoors photography can use the camera’s flash as its light source, allowing a low ISO to be used.

If I set the camera to “P” mode (for “Programmed auto”), I can select the ISO of my choice, and let the camera decide the shutter speed and aperture for me. If I used this mode, I could have set all three photographs to use ISO 200, the lowest the Nikon D40 goes. So long as enough light was available, this should have been suitable for even the two photos where the camera chose an ISO of 400. This mode is good for taking snapshots without having to worry about getting all the settings right manually.

I could be wrong, but I believe the shutter speed is the fraction in the “Exposure” part of the photograph’s meta-data. Shutter speed is an easy one for me to understand.

If the speed is fast, then the photo is taken quickly. Taking a photo of a running sprinkler system with a fast shutter speed will leave a photo where you can see each drop of water. A slow shutter speed means the photograph will take longer to be taken.

Considering if one photographs a freeway at night with a long shutter time to take the photo, the resulting photograph will show trails of light from the headlights and tail lights of all the cars that passed by while the camera took its time taking that photograph.

The photographs above have speeds of 1/125 of a second and 1/500 of a second.

The “S” or “Shutter Priority” mode lets me select the shutter speed, and the Nikon D40 will handle the aperture setting for me. I still have to select the ISO in this mode. This mode lets me pay attention to whether I want a short or long exposure, whether I want a crisp or motion-blurred photograph, without having to worry about the aperture.

The shutter information on the Nikon D40 confused me from the start. The zero looks like a lowercase letter O, and they seem to use a 1 for a capital I. With that in mind, I can continue.

What I need to know is that the ” next to the shutter value marks seconds and the lack of a ” marks a fraction of a second. This means that a value of 30″ means the shutter will be open for 30 seconds (blurring any movement). At 1″, the shutter will be open for one second. A value of 2 will is 1/2 of a second. A value of 4000 is 1/4000 of a second, taking a crisp “moment in time” photograph with no motion blur.

With a speed of 1/4000, I need enough light to take a picture, and the Nikon will tell me if there isn’t enough light. The F value will replace with a LO (or a HI when there’s too much light). In Shutter Priority mode, the aperture will change to compensate, trying to allow just the right amount of light in.

If I want to photograph something like the photos above, I don’t need a long exposure time, I need a short one. 1/4000 probably wouldn’t get the camera enough light. The camera determined that 1/125 to 1/500 of a second was enough time to get the light needed, but the aperture setting will impact this as well.

This brings into play the aperture setting. This is where that F value I mentioned a couple of paragraphs ago comes into play. A value such as F/11 will keep everything in focus whereas a value such as F/4 will keep the foreground in focus while letting the background be out of focus.

The aperture priority mode of the Nikon D40 allows one to set the aperture, and the camera will select the right shutter speed to allow in enough light. The D40 allows from about F5.6 to F36, depending on camera settings.

So, what do I need to know? A “high” number, such as “11″ will give me a “high” range of area in focus. A “low” number”, such as “4″ will give me a “low” range of area in focus.

My photos above have F-values of f/5.6 and f/8.0, which are both on the “lower” end of the numbers, which results in a small area in focus, resulting in the background being out of focus, resulting in the photographs above. This then is the most important setting to achieve the effect in these photographs.

Update: How do the stats of the HP Photosmart 735’s “Auto” compare? The exposure matches at 1/125 of a second. The aperture is a wonderfully low 5.1 (lower than the three taken with the Nikon D40!) The focal length is 17 mm, with the camera’s rance being 5.8 mm to 17.4 mm (and now I finally know what those numbers mean!) The ISO speed is a wonderfully low 141, which I think is lower than the Nikon D40 can go. I’ll have to play with the D40 more to be certain.

Update 2: To give myself a re-cap:

Exposure:

1/500 ~ 1/125 (depending on light)

Aperture:

f/5.1 ~ f/8.0

Focal Length:

(zoomed in)

ISO Speed:

200

Oh, I think this is enough to take in for one day! Maybe I will try to manually set my camera and take a photograph like those above!