Need help with camera aperture settings?

I seem to be unable to get my Nikon D90 DSLR to adjust aperture settings no matter what program I use. Have tried the A, M and P but no matter how I set it I end up with a full focussed frame and the camera only seems to recognise shutter speed settings. I'm trying to achieve a blurred background and have tried 3 different lenses, turning off AF and fiddling with every program on the camera! I'm guessing I'm missing something simple!

The one simple thing that is most likely to be missing
is You Reading The Owner's Manual.

How can I tell?
Easy.
You said you fiddled with the camera.
Reading the manual would eliminate any reason to fiddle with things.
You would quickly learn Exactly what to do and how to do it.

Sit down with the camera and the book and try everything described,
in order, exactly as it says.

Check the article at the link below

Once you have understood how to set the camera when using those lenses, remember that the big aperture numbers (such as f11, f16) mean a small aperture, and thus large depth of field. To get blurred backgrounds use a large aperture, small number such as f2.8 or f1.8. Use a "long" lens, i.e. Longer than standard, and keep the main subject well forward of the background. Wide-angle lenses are less useful for blurred backgrounds.

Here is the list of tips to do this…

Use longer focal lengths
Wider apertures
Keep the subject closer to camera
And have the background further away

Getting that blurred out look is done by creating a shallow depth of field using a combination of three things: focal length, focusing distance and aperture size. You basically want to produce a depth of field that is about as deep as the subject, if not shallower.

Focal Length: Longer the focal length, the shallower the depth of field for any combination of focusing distance and f/stop used. If you are using an 18-55mm kit lens and you've set it to 18mm, you're not going to be able to get a blurred out background unless you're super close to the subject. The shots that you see with the great bokeh are done with focal lengths of 50mm or longer.

Focusing Distance: Closer you are to your subject, the shallower the depth of field. To this I would say that it's just as important to have a long distance between your subject and the background. Remember, you're goal is to produce a shallow area that's in focus. The further away the subject is from the background, the more the background will not be in focus. Keep your subject within 10', and your background as far away as you can.

Aperture: The larger the aperture, the shallower the depth of field. Again, if you're using your 18-55mm kit lens which has a relatively small aperture of only f/3.5~5.6, you can't get the same blurred out effect as a 50mm shot at a larger aperture, say, f/1.4. Most of the time we can't control the focusing distance. We may not be able to move closer, or don't want to for compositional reasons. Add in the fact that longer focal lengths flatten the perspective, which by doing so makes people look more attractive than they may in real life, and you're left with a situation where you can't adjust the focal length or focusing distance. Therefore, the aperture the main adjustment for controlling the depth of field.

If all you own is an 18-55mm kit lens, the best thing you can do is use the 55mm position, put the subject at 10' away or less, and use aperture priority then select an aperture of f/5.6. You want to use aperture priority to prevent the camera from choosing a different f/stop. You want this so that you not only produce the shallowest depth of field (most blur possible) but you also so that all of your images have a consistent look. If does not produce the level of blur that you want, then you must buy a lens that has a longer focal length or a larger aperture (e.g. 50mm f/1.8) or both like an 85mm f/1.8, 24-70 f/2.8 or 70-200 f/2.8. Whichever lens you choose, you will get the best results with a lens that is longer than 50mm AND has an aperture of f/2.8 or larger.

To blur the background, set the lens to it's longest focal length (zoom out) if it's a zoom lens. Set the camera to A mode then set to the smallest f/number available (without changing zoom if it's a zoom lens). Stay as close to the subject as possible with subject as far away to the background as possible. Take the shot.

To check if aperture size indeed changes with your camera, set camera to M mode. Set aperture to largest f/number (f/22? F/32?). Set shutter speed to 1 or 2 seconds (1" or 2"). Hold the camera as if taking a selfie, facing the lens. While looking inside the lens, press the shutter release button. Take note if the hole inside the lens becomes smaller, much smaller in such way that you see the blades close in. If that does not happen will all the lenses you have, the aperture motor of your camera is broken. Have it fixed at the service center.

Before anything, allow me, please, to explain something. Blur is the effect caused by camera shake or if the subject moves and the shutter speed is too slow. OUT OF FOCUS is when the person using the camera does not focus properly or focuses on something else… Or the subject is NOT WITHIN the area of the Depth of Field (of Focus). Look up "Depth of Field" at Youtube.com and you'll understand the concept.

You have a nice camera but you are not getting the most out of your camera… You are not aware of all the features, functions and options your camera offers you for best photographic results, and you don't know where to find the features, functions and options or when and how to use them. YOU MUST READ your camera's Instructions Manual. IF you don't have the camera's Instructions Manual, you can buy one at any large Photo shop like B&H or you can download a copy from the Internet, and make a hard copy for you to read and carry with you.

IF you wish to get the subject in focus and the background "blurred" out (out of focus), then you need to set a large aperture on Aperture Priority and have some distance between the subject and the background. You can also use a short telephoto lens to achieve the same effect. Just remember, for apertures, large numbers (like 5.6) represents a SMALL aperture size, while a 1.8 or 2.8 are the larger aperture sizes. This is explained in all "How to…" Photography books you'll find in the library and also at Youtube.com in any number of the Instructional and/or Tutorial videos you'll find there. A 1/2 of a pie is a larger piece than 1/5 piece of pie, yes or yes?

IF you're using Manual Mode to get a blurred image to show action but your camera overrides you and renders a perfectly exposed, well-focused image instead, then you may want to check the lens' barrel and check the camera body on the right side of the lens mount… Some lens barrels and some camera bodies have an "M/A" switch… "M" for "Manual" and "A" for "Automatic." You can find out about this by reading the camera's Instructions Manual.

You are trying to have a "depth of field" effect. A minimal depth of field.

To get this, you want the aperture wide open. The smallest F stop.

With an automatic camera, the more you open the aperture, the more light goes in, and therefore the faster the shutter needs to go.

In bright light, you will run out of shutter speed quickly.

With film, you use a slower speed film.

I'm not sure how you do it with a digital camera. I'm an old, old-fashioned, film photographer.

Your desired effect was my favorite effect for portraits.

You can also use a telephoto lens, then merely back up far enough until your subject fills your frame. Again, open the lens to maximum aperture.

You are having a ratio between the distance to the focused subject versus the distance to the background. The bigger the ratio, the blurrier the background will be.

The wide open aperture is the first way to minimize the depth of field. The ratio of distance to subject vs distance to background is the second way.

To get a blurred background with my Nikon D90, I set the rotary switch to A, press the shutter half way and release it, rotate the front dial to the largest number that shows up in the LCD on the top of the camera. I zoom in on the subject as much as I can, and get as close to the subject as I can. And then take the photo. It also helps if you can separate the subject from the background as much as you can.