I thought of another consideration for depth of field context. This is when using a smaller point and shoot camera. These cameras have put photography in the hands of almost everyone who walks in public. You cannot go out without seeing a tourist pointing a camera. Thus I wanted to address how depth of field occurs in these cameras. As you probably know, the lens on them is very small. If you are not familar with focal lengths, basically it is defined as the distance from the focal plane(where the pictures actually gets recorded – film if you will) to the end of the lens. It is usually calculated in millimeters for standardization. For reference, a macro or wide lens in photographer terms usually is anything 35mm or less. The next is called a normal lens and is 50mm for a standard SLR camera. Another term used is telephoto lens which usually means greater than 80mm. A note, these numbers are for SLR cameras only. Calculating the focal length totally depends on what format of camera being used. A large format camera has a normal lens which is different than 50mm. If you wish to know how to calculate it, read this Wiki Article. Also you might wonder what f-stop means when referring to aperture. Well the formula that yields the f number is focal length divided by diameter. Ok back to lenses. The average point and shoot usually has a small zoom lens which varies from 12mm to 35mm give or take a few. In other words, a wide lens. So as you learned in the discussion about depth of field, wide lenses, other factors ignored, yield a high depth of field (totally clear background). So when shooting photos with a point and shoot, most of the situations will make it difficult to get a shallow depth of field if that is what you are after.? Another note about point and shoots is that the f-stop generally cannot go smaller than f6 and often not even that small. I have found even if the camera is set to its automatic portrait mode, you still see a clear background, as in the above example. My face, sunglasses, eyes, nose, and other attributes along with everything outside the train window are clearly identifiable.? If for example I wanted the window and outside to be blurry, I would have needed a smaller aperture and/or a longer lens which is unavailable on point and shoot cameras.? The programmed f-stop for these cameras is usually between f2 to f6 if that depending on the zoom level.? So because of both of these factors, it is nearly impossible to get a shallow depth of field unless your subject has his nose pressed to the camera lens :)? I hope this information has been helpful for novice photographers.

A fairly simple way to determine Depth of Field (DOF) when using an SLR camera is by following some simple steps.? There are three factors which determine how ‘deep’ or ‘shallow’ your photo is rendered.? First is the distance between the focal plane(camera) and the subject.? If you are close to the subject, say a few feet, without other considerations, you will get a low DOF or in lay terms, the background will be blurry.? If you are far away, say across a large room, again other factors aside, you will get high DOF or in lay terms, the background will be clear.? Second is the focal length of your lens.? At shorter lengths (for sake of discussion 20mm-100mm approx) , other factors ignored, you should get deep DOF (clear background).? At longer lengths (for sake of discussion 200mm and up), you should get shallow DOF (blurry background).? Third is aperture (the size of that tiny hole that opens and closes).? If you use an f-stop of f2 or f4 you should get shallow(low) DOF (blurry background).? If you use an f-stop of f16 or f22 you should get deep(high) DOF (clear background).? F stop is the size of that hole and the numbers start from largest opening (f1) to smallest opening(f32 for most SLR lenses).? So those three factors being said, if you combine them, here is what you should get:

• Focal Length (short) + Aperture Wide(f2) + Distance from Subject(close) = Blurred background(low DOF) mostly because of the wide aperture
• Focal Length (short) + Aperture Wide(f2) + Distance from Subject(far) = Blurred background(low DOF) mostly because of the wide aperture
• Focal Length (short) + Aperture Narrow(f32) + Distance from Subject(close) = Clear background(high DOF) mostly from the narrow aperture
• Focal Length (short) + Aperture Narrow(f32) + Distance from Subject(far) = Clear background(high DOF) mostly from the narrow aperture
• Focal Length (long)? + Aperture Wide(f2) + Distance from Subject(far) = Very blurred background(low DOF) because of the long focal length and wide aperture
• Focal Length (long)? + Aperture Wide(f2) + Distance from Subject(close) =not possible, subject cannot be close with this focal length
• Focal Length (long)? + Aperture Narrow(f32) + Distance from Subject(close) =not possible, subject cannot be close with this focal length
• Focal Length (long)? + Aperture Narrow(f32) + Distance from Subject(far) = Fairly clear background(low DOF) mostly from the narrow aperture(the long focal length should lessen clarity)

Of course the in between values here will yield different results but hopefully if I explained well enough you should be able to calculate it approximately.? For example, 22mm lens, f8, subject=close should give you moderate DOF (somewhat clear background).? If you wanted it totally clear, use a smaller f stop(f16,f32,f64).

A few more examples: 300mm, f4,? subject(far) should give you a very blurry background(low DOF). 300mm, f16, subject(far) should yield somewhat clear background(moderate DOF) due to aperture.? See where I am going with this.? In general, mostly you will not determine subject distance.? What you can vary is the aperture and the focal length(possibly with a zoom lens).? In Summary,? to get more DOF(clearer background), use a small aperture and/or short lens.? To get less DOF(blurrier background), use a large aperture and/or long lens.? Typically for portraits, 100mm lens, f2 or f4, subject at moderate distance should yield a very blurred background(low DOF).? Hopefully my experience with these variables will help you to be a better photographer.