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Shooting question
I am very new to photography. I took a general class in college and it drew an interest. I see many pictures where the subject in the picture (a person for instance) is very clear and in focus and the background is blurry. What settings do I adjust to have this effect. Sorry for the very basic, general question..

Comments (15)

To do this you need a wide aperture (lens opening). This is indicated by a lower f-number: so f/4 is quite a wide aperture, whereas f/22 is a pinhole-sized opening..

Wide apertures give a narrow depth of field, such that anything in front or behind of the focus point will be out of focus. This can look great, for example, on a portrait shot where you want to throw the background out of focus to draw attention to the subject. In contrast, with a landscape for example, you may want a very big depth of field, with everything from the fence in front of you to the horizon in focus - for this you would use a narrow aperture..

Have a play with this depth-of-field calculator to get a feel for how it works..

Http://www.dofmaster.com/dofjs.html.

Best wishesMike..

Comment #1

Mike703 wrote:.

To do this you need a wide aperture (lens opening). This isindicated by a lower f-number: so f/4 is quite a wide aperture,whereas f/22 is a pinhole-sized opening..

Wide apertures give a narrow depth of field, such that anything infront or behind of the focus point will be out of focus. This canlook great, for example, on a portrait shot where you want to throwthe background out of focus to draw attention to the subject. Incontrast, with a landscape for example, you may want a very big depthof field, with everything from the fence in front of you to thehorizon in focus - for this you would use a narrow aperture..

I only have one lens so I am not sure about this point - but I think some lenses are better are blurring the background than others. For example, a fixed 50mm lens will blur better than an 18-200..

Am I wrong?.

FINE PRINT: I reserve the right to be wrong. Should you prove me wrong, I reserve the right to change my mind...

Comment #2

At the same aperture the effect is similar. A 50 mm with f/1.8 will have obviously a better separation than 50 mm with f/5.VictorBucuresti, Romaniahttp://s106.photobucket.com/albums/m268/victor_petcu/..

Comment #3

I only have one lens so I am not sure about this point - but I thinksome lenses are better are blurring the background than others. Forexample, a fixed 50mm lens will blur better than an 18-200..

Am I wrong?.

The depth of field depends on three things:(i) focus distance.

(ii) f-stop (wide aperture = narrow depth of field; small aperture = much larger depth of field).

(ii) focal length of the lens (wide angle lenses have a greater depth of field than telephotos when set to the same focus distance and same aperture)..

So a 50mm prime lens at f/8 and focussed at 10 feet will give exactly the same depth of field as your 18-200 under the same conditions (i.e. set to 50mm, f/8, 10 feet)..

The difference you are thinking of is probably that a prime (non-zoom) lens usually has a much wider maximum aperture. A 50mm prime lens will generally have a maximum aperture of f/1.4 or f/1.8, which will give a very narrow depth of field, e.g. plus-or-minus a few inches at a distance of 10 feet..

Your 18-200 zoom lens can only open up to about f/4 at 50mm, otherwise it would be very big, very heavy, and very expensive. This will result in a greater depth of field. But that is because of the narrower aperture (f/4 instead of f/1.4), not because it is a zoom lens..

Best wishes.

Mike..

Comment #4

... even though your 18-200 has a narrower maximum aperture than a 50 mm prime, which will give a greater dpeth of field at 50mm, you do have access to a much longer focal length (200 mm) which will give a very narrow depth of field if you stand back from your subject. So to really isolate the subject with your lens: stand a long way back, zoom in, and use the widest aperture you can..

Best wishesMike..

Comment #5

I'll use the word 'portrait' a lot because that's where that blur is most often wanted..

It's a balancing act because :.

(1) to get a really blurred background you need as wide an aperture as possible, meaning the f-number should be as small as possible.

(2) the wider the aperture the smaller the depth of field ( the distance range which is in focus ). So if you use a very wide aperture you have only a very narrow depth of field ( although this also depends on other factors ). Macro photographer often find this a problem ,because the very narrow DOF makes it difficult to get enough of the subject in focus..

(3) Most lenses are actually not at their peak performance ( best sharpness over the best area ) at wide apertures. It is often best to stop a lens down a couple of stops to avoid this. This is less of a problem than it might seem as most portraits ( where that blurry background is most desired ) are not interested in the border area, just the central part of the image. The center is usually OK for sharpness ( not always but often, depending on the lens ), so you can get away with wide apertures even on not so good lenses for portraits. Also portraits do not have to be quite pin sharp - no one likes to see every single pimple and spot !.

(4) The wider the aperture the more light you let in, so the faster your shutter speed has to be. This makes it harder to use a longer exposure ( which is useful for some effects ). You can deal with this by using filters that simply reduce the amount of light without affecting white balance..

That last one is not that big a problem ( not usually shooting for blurry backgrounds on long exposures )..

If you do get a reasonably out of focus background you can enhance this a little by selecting the background in a photo editor and applying a little more blur. It's not quite the same effect, but it helps a little if you need it..

A good 50mm lens on a DSLR is quite a useful portrait lens and they are often relatively cheap..

You will see the term 'bokeh' in relation to that blur. Some people obsess about bokeh and I'm not one. Can't afford to be. .

StephenG.

Pentax K100DFuji S5200Fuji E900PCLinuxOS..

Comment #6

You have to use a large aperturethe hole in the lens is larger (a confusing point is that larger aperture = smaller number...something like 2.8 or 3.5.)..

The aperture affects the depth of field... if the hole is larger, the depth of field is smaller, making your subject in focus, and everything else blurrier. If the hole is smaller (smaller aperture), then you have a larger depth of field, makign the background more in focus..

Hope this helps!..

Comment #7

Oops, didnt see all the replies, didn't mean to be redundant..

Comment #8

Mike703 wrote:.

... even though your 18-200 has a narrower maximum aperture than a 50mm prime, which will give a greater dpeth of field at 50mm, you dohave access to a much longer focal length (200 mm) which will give avery narrow depth of field if you stand back from your subject. Soto really isolate the subject with your lens: stand a long way back,zoom in, and use the widest aperture you can..

As others have indicated, there are several ways to blur the background, yet have the subject in focus..

With your 18-200mm lens:.

1. Use the smallest numerical aperture (biggest physical opening)...that will be f/5.6 to f/6.3, depending on the brand2. Use the longest focal length (FL)...that will be 200mm..

3. Get as close to your subject as the lens will allow..

4. Get the subject as far away from the background as possible..

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/..

Comment #9

I see a lot of discussion of the technical aspects of lens design, but how do you shoot it? You need to set your camera for aperture priority (Av) so you can select the largest aperture and the camera will pick a shutter speed to suit. You can also use manual and select everything yourself..

As others have said, a kit lens or other zoom lens is not going to have as wide an aperture as a single focal length "prime" lens. A 50mm f/1.4 lens is excellent for portraits. A kit lens at 50mm and f/5.6 just can't give the same "bokeh"..

Happy shooting!.

DavidPentax K100D..

Comment #10

There is also a quality called "bokeh". Good bokeh means the OOF (out of focus) areas of a picture are pleasing to look at. That is, the OOF softness feels right and doesn't detract aesthetically from the target. Bad bokeh means the OOF areas aren't pleasing to look at. And if the bokeh is bad enough, it can wreck an image visually..

The extent to which the background is OOF and the background itself contributes to bokeh, but so does the construction of lens, specifically the aperture. Apertures with more blades generally yield better bokeh, making your shallow DOF images more pleasing to look at..

Baloo_buc wrote:.

At the same aperture the effect is similar. A 50 mm with f/1.8 willhave obviously a better separation than 50 mm with f/5.VictorBucuresti, Romaniahttp://s106.photobucket.com/albums/m268/victor_petcu/.

Http://www.pbase.com/digirob..

Comment #11

Some of the responders in these forums are real camera experts and can get quite technical in their replies. I have read all of them posted thus-far and will attempt to keep it as simple as possible..

1. Whichever lens you choose, use your largest f-stop (biggest aperture opening in the lens). Typically this might be 3.5, 2.8, 2.0..

2. Use a relatively long lensa telephotolike a 100, 200, 300mm. Whatever you might have. Use the longer part of the zoom. Use a bigger f-stop on that lens..

3. Make the distance from the "clear" object to the "blurry" background as wide as possible..

4. Try focusing not exactly on the person or object, but slightly in front of it, keeping that person within the depth-of-field sharp-focus zone..

Hope this helps to keep it simple. Once it give satisfactory results, write down your set-up for future reference. Some cameras even allow you to "save" a couple of these "favorite" set-ups.ngk20000..

Comment #12

4. Try focusing not exactly on the person or object, but slightly infront of it, keeping that person within the depth-of-fieldsharp-focus zone..

I'd disagree with this approach. It's way too technical for a beginner ( and I don't accept the technique as valid anyway - it's a waste of forward DOF and makes it harder to get sharp images )..

For a beginner it's more important to just develop a feel for how DOF works and how it relates to aperture and focal length. Experimentation is very important. Take several shots at different apertures and compare them, that kind of thing. It will all come together..

StephenG.

Pentax K100DFuji S5200Fuji E900PCLinuxOS..

Comment #13

Thanks for the responses. I look forward to gaining knowledge of photography in the future. Happy Holidays to all..

Comment #14

Sjgcit wrote:.

4. Try focusing not exactly on the person or object, but slightly infront of it, keeping that person within the depth-of-fieldsharp-focus zone..

I'd disagree with this approach. It's way too technical for abeginner ( and I don't accept the technique as valid anyway - it's awaste of forward DOF and makes it harder to get sharp images )..

I very much agree that this suggestion is not a good one.Regards,Baz..

Comment #15

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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