F Stop Numbers and Blurred backgrounds?

Question

It's my understanding that a lower f-stop number will result in a blurred background and a higher number in an all around in focus shot. BUT why is it that I am seeing these photos online that have nice blurred backgrounds that were shot at f-14? What gives? I want to use this info for wildlife photography.

Thanks!!

Answer 1

Your general statement is generally correct, but that is just a starting point. Look at this image: http://www.flickr.com/photos/samfeinstein/487790706/

It was taken at f/16, which would give you fairly "deep" depth of field rendering most things in focus, except that the point of focus is very close to the camera lens. If I was 5 or 6 feet from the bee, pretty much the whole scene would have been in decent focus.

See this example: http://www.flickr.com/photos/samfeinstein/511707803/

The closest flag is about 5 or 6 feet from me. This is the same lens as the other example, although the aperture is set on f/22 instead of f/16. It's the distance from the camera to the point of focus that "shifts" the depth of field in these examples.

Wikipedia does pretty well on the subject of depth of field. (I'm sorry that Y!A is not presently allowing me to post that link!)

See also: http://www.photo.net/learn/optics/dofdigital/

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tigerrrrrgrrrll is right. I looked over your other questions and I see you have a Fuji S700. This camera's sensor is of the smallest size commonly used. When you started talking about apertures, I incorrectly assumed that you had an SLR. Here's my stock answer on depth of field for point and shoot cameras.

It's going to be darn hard to "de-focus" too much using a digital camera while keeping the main subject in sharp focus. The smaller the sensor, the greater depth of field you will have. Generally speaking, the smaller the camera, the smaller the sensor. Most of the pictures you take with a digital camera are quite sharp from near to far distances and there is a reason for that which I will explain.

While we speak in terms of the 35 mm equivalency of digital lenses, don't forget that the digital sensors are usually smaller than a full-format 35 mm frame. Most of the more popular point and shoot cameras have the smaller sensors. It's only about 5 mm wide and 4 mm high. The lens on required to cover that angle of view is an ACTUAL 6-17 mm zoom lens. At these focal lengths, the background is going to almost always be in pretty sharp focus.

In other words, if you WANT to defocus the background, you are going to have to work pretty hard at it. You would have to zoom to the longer end of the lens and set the aperture open as wide as it will go, if your camera even allows you to control the aperture, and get pretty close to your main subject while having the background a fair distance away.

The bigger the sensor, the easier it will be to achieve pleasing bokeh. This means moving to a dSLR, which all have sensors about 20 times bigger than the typical P&S digicam. If you want to really go for brokeh (very bad pun intended), you can get a Canon 5D and you will get exactly the same effect you are accustomed to in a 35 mm camera, since the sensor is the same size as 35 mm film.

Answer 2

Smaller the aperture size (higher the F stop number) the more in focus the background will be. f/32= very sharp background. Larger the aperture size (lower the F stop number) the more blurred your background will be. Now, if there is a small aperture (high F Stop) that means there is very little light coming through the lens. So you must compensate with a slower shutter speed. Use your light meter and remember that if you have a correct exposure at,say, f/2.8 with a shutter speed of 1000... that same exposure can be reached at f/32 if you push the shutter speed 1 stop slower for every higher f stop. (generally that is... there are a very few exceptions when it gets into high-end dslrs and really great glass...) If the exposure is too long, and you want to use a high f/stop though, put the camera on a tripod. And spend $20 on a cable so as to nearly remove all movement of the camera during a long exposure. General rule of thumb for most: anything lower then 1/60th on a lens without a form of image stabilization- Use a tripod. No use in having blurry photos that could have been damn sharp :-)

Answer 3

(Cut and pasted from another answer I just gave)

Depth of field is controlled by a few things:

1. Aperture size. Remember that the smaller the f-stop, the larger the aperture. Larger aperture = smaller DOF. However, when you change the aperture you change the amount of light that gets to your film or sensor. This means that you will have to adjust either the sensitivity of the film/sensor (ISO) or the shutter speed to compensate. For a given exposure and ISO, if f-stop goes down, shutter speed goes up, and vice-versa.

2. Focal length. A telephoto lens will give you a shallower depth of field than a wide-angle lens.

3. Distance from subject. When you get really close to a subject, the depth of field decreases. If you get REALLY close, the depth of field can get razor thin even with a small aperture.

FWIW, the distance of the subject from its background also affects the *apparent* DOF. If your subject has, say, one inch of total DOF, and the background is just past the focus point, there will only be a slight blur. If the subject is many feet from its background, the background will have a much stronger blur, even though DOF is actually the same.

Here is a calculator to figure out depth-of-field:
http://www.dofmaster.com/dofjs.html

Answer 4

f/14 isn't deep enough to exclude all background elements from focus, it is a middle range aperture used mainly for stoping down bright scenes like shooting in open sunlight and will effect overall depth of field depending on the lens used, particularly whether the lens is a wide or telephoto lens. DoF decreases with telephoto lenses over 70mm, and with a long lens focused closely, you will get background blur even at f/14. It would help if you had posted an image with your question.

Answer 5

F14 can still create blurred backgrounds under several circumstances.

1. Macro photography where the DOF usually only covers fractions of an inch

2. Long telephoto shots that compress the DOF

3. The background was a long way away from the subject

I have an in-depth article on my site http://photography.about.com that covers the type of information you need. The link is: http://photography.about.com/od/takingpictures/ss/DOF.htm

Best of luck
~Liz
http://photography.about.com

Answer 6

One of two things prob happened - either they used a very long telephoto and the subject is some distance from the background (telephotos give more bur to the bg than wideangles)

Or they photoshopped the background.

A third possibilility - you're looking at f1.4, not f14. Or the background is in motion - to shoot at f14, they would have needed a flash or had to use a slow shutter speed in most cases.

Answer 7

I'm surprised that no one has mentioned sensor or film size. On a digital P&S, the sensor is very small. This usually means that shallow DOF is hard to get no matter what f-stop. dSLRs have a bigger sensor which helps quite a bit. My Holga (medium format) and my Polaroid 250 are both fixed at F8 and yield beautiful bokeh because the film is so large.

Answer 8

Most likely "f 1.4", not "f 14". "F one point (decimal) four", not "f fourteen".

In traditional times and even today, "f 14" is an unusual aperture to quote, and would only result in a blurred background with a very long telephoto lens.

Answer 9

Go to expoimaging.net and order their ExpoAperture2 "Depth of Field Guide". $29.95 + shipping.

You can read a review of it in the Oct. 2007 issue of Shutterbug Magazine (shutterbug.com).

Answer 10

the answer is because you dont understand, apeture/focus/depth of field...........or you cant read and its actually F1.4 (theres a point in there)

if you use F22 and focus on something close, then there will be a shorter depth of field

also if exstention tubes or close up filters are being used the depth will be shorter

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