jeep_daddy Loc: Prescott AZ

The wider open the aperture, the less depth of field your image will have. So you need to be precise on you focusing. With a long lens such as a 200mm and shooting portraits, if you were to shoot a portrait or head shot, you might focus on an eye but an ear may be slightly out of focus when shooting wide open. You can look at a depth of field chart to see how much depth of field you have at certain f/stops and focal lengths, at so many feet or inches away from your subject.

SharpShooter Loc: NorCal

Thanks D!! :thumbup:
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jimmya Loc: Phoenix

You have the basic concept and that's good. To me this question is way over analyzed to the point it's made so complicated it makes my head hurt. It's not that difficult to do or think about.

Here's a tip to practice on. When you're setting up just watch your view finder while changing your f/stop to a wider setting. You'll notice if you do this in aperture priority that the background will become farther and farther out of focus (that's called the Depth of Field or DOF). Setup, do the aperture settings and shoot the one that looks the way you want it.

I get very nice DOF with my 50mm f/1.8 and I've got some nice ones with my 18-200 as well. Good luck

gessman Loc: Colorado

Experiment, discover, practice, and learn here:

http://camerasim.com/apps/camera-simulator/

CatMarley Loc: North Carolina

The longer the focal length, the less depth of focus. i.e wide angle lens=deep depth of focus, tele = less depth of focus. Small aperture = more depth of focus, large aperture= less depth of focus.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Cat, that is not exactly correct, though it does seem that way. It is all about magnification which implies distance, and aperture.\

If you take a shot with a 200mm lens, and without moving the camera take the same shot with a 24mm lens, and you crop the wide angle shot to the same area as the shot with the 200mm uncropped, the DoF will be virtually the same.

Here is a great tutorial and excellent reference:

http://www.cambridgeincolour.com/tutorials/depth-of-field.htm

canon Lee

You are correct that a large aperture opening will blur the background. Another factor to blur the background is distance from the subject. The closer you are to the subject the more blurring will occur. It is a balance of both that will give the preferred blur (Bokeh). A fixed aperture lens will allow you to zoom in and out and maintain the same aperture setting. DOF settings allow a photographer to be more creative.

Ansel Rosewater

“Blurring the background After the Shot”

This recommendation is slightly tangential to the subject of aperture and the necessary accompanying change in shutter speed to get the desired effect of a proper exposure and altering the depth of focus.

In many cases, the photograph is taken under circumstances or a time constraint that doesn’t permit changing the aperture and speed. This brings up the question of digitally altering an existing photograph to blur an uninteresting or distracting background or to give depth to a picture.

Using Photoshop, it is possible to blur the background by masking and blurring the masked area. For those interested, here’s my method:

= Using the Quick Selection Tool, I mask the area I wish to blur. If the tool selects some of the foreground one wishes to keep sharp, there is the minus selection tool to remove that area of the foreground from the mask.

=Next, go to >Filter>Blur >Gausian Blur. This brings up a menu. Check the Preview, and put the cursor on a section of the background you wish to blur. Then slide the slider to increase or decrease the blur. Blur which is accentuated can detract from the overall picture. A slight blur will give excellent depth to a photo. The prevue section will show exactly the degree of blur. Finally > OK.

Note: in some photographs it is possible to give different degrees of blur to different areas enhancing the apparent appearance of depth.

.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Be careful. A variable aperture lens, let say like a Nikon 24-85 F3.5 - F4.5 - will allow you to set the aperture to F4.5 and zoom in and out and keep the same aperture.

CatMarley Loc: North Carolina

Well yes because the whole thing depends on the angle of view, doesn't it? the tele has a very narrow angle of view, and therefore is looking at a very small area. Everything will be proportional within that area. both width and depth. Small width AND small depth, so for practical purposes you have less depth of focus with the tele BECAUSE you have a small angle of view, but in practical terms, which is what the man wanted to know, the depth of field is smaller, the longer the lens, even though in real terms this is only an illusion caused by the narrow angle of view. The effect still is that the background will be blurrier if you focus on an object at 4 meters with a 200 mm rather than a 20 mm!

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

It really depends on how you look at it. But in absolute terms, not at all. In practice of course it does. :)

lighthouse Loc: No Fixed Abode

Simplistically.
The closer you are to your subject and the further away the background is, the more the background will be blurred and possibly the smoother the bokeh will be.

chazz4623 Loc: Prairieville, La

Please dont crucify me, I'm just learning (relearning) these principles. My expression of it is that a lens' purpose is to bend light that passes thru it. This effect is stronger the further from the center to the periphery of said lens. When reducing the aperture, one effectively reduces the focusing or bending effect of the lens ( light going thru the lens at and near the center is bent the least. A pinhole focuses from 0 to infinity, a larger opening focuses less and less the bigger the opening, therefore the need to 'bend' the light to keep focus. This necessitates those pesky things called lenses. Begin pulling out hair.

travlnman46 Loc: Yakima WA

Hi Brenz:
Try this website from Cambridge in Colour... I does a pretty good job of explaining depth of field, with some pretty good graphics... http://www.cambridgeincolour.com/tutorials/depth-of-field.htm If this site doesn't help I can give you a couple more refrences that might explain it better..

SharpShooter Loc: NorCal

Cat, Brenz is no more MAN than YOU are, that is assuming your avatar is YOU!!! :lol: :lol:
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PS, there, that's MY big contribution to this complex subject!!! :lol: :lol: