why cant i blur background with my Nikon d7200?

The shopkeeper obviously doesn't know much about cameras except what he's read on the Internet.

As for getting a shallow depth of field (DOF), shoot with the largest aperture (smallest f-number which varies with zoom) and a zoom setting of 50 to 105mm. The background needs to be far away from the subject in order for it to be blurry (example, subject 8 feet away, background 20 or more feet away). It's all about the ratio between the background and subject. You need to experiment to see what works for you.

While a lens with a larger aperture will give you better control over DOF, you can use the 18-105 if you understand how to set up your shoot properly.

There are plenty articles on the Internet discussing DOF.

Unless money was an issue, I'm amazed that they sold the 18-105mm lens as it isn't up to the capabilities of the D7200. That lens limits the quality of the image (sharpness and contrast). You would have been better off with the 18-140mm which is optically better.

With that lens you can blur the background, but you have to observe a few conditions.

1] Use the lens at 85mm or 105mm. Indeed at the wide-angle setting (18mm) no lens of any sort can seriously blur the background, unless it is focussed very close - 2 feet or closer.

2] Set max aperture - thus f5.6 for 105mm, not f11 etc.

3] Have the main subject well forward of the background you want to blur.

4] Have the main subject fairly close to the camera.

So check my suggestions first before immediately going out and spending lots of money on a lens.

Indeed a lens such as the 85mm f1.8 will make blur easier, but if you had it, you would still need to bring the main subject well forward of the background, and to use a high aperture such as f1.8, f2.8, or f4.

ALL lenses are capable of blurring the background.

IT's just harder to do it with some lenses (wide angle) compared to others. With your lens, I advice you do this outdoors under the sun. Make sure the distance of the background from the subject must be much farther than the distance of the camera to the subject. Zoom the lens to the max at 105mm, set to A mode, select the lowest f/number available (f/5.6) then shoot.

Take note also that all lenses have a minimum focusing distance. This is the reason I'm asking you to use 105mm outdoors. You might not have enough space inside your bedroom. If you can't seem to focus, step back and try again.

Finally, always mind the light. What is low light to you may as well be pitch black darkness to the camera already so again, the reason why I asked you to shoot outdoors under the sun. Indoors, always use flash.

It's not true to say that you can't get a blurred background with that lens, but you won't be able to get a blurred background in every situation - chances are you described what you were trying to do and it really isn't possible. You need to learn how to control depth of field before you invest in what will probably be a relatively expensive lens - google terms like "depth of field", "aperture", "focal length", "hyperfocal distance" and "circles of confusion" (if you want to understand the physics of what's going on). There are some excellent YouTube videos that will take you through it as well - just search for "control depth of field".

The shopkeeper is stupid. You certainly can get a blurred background with that lens, *if you know how*.

You have to use the smallest available aperture, which varies with focal length on that lens. You also have to have some distance between the subject and background. How much distance varies with aperture and focal length.

The 50mm f/1.8 is a very popular for this use, as your subject can be much closer to the background and still provide blur. Any lens with a wide aperture makes it easier.

I'm surprised someone that sells cameras would tell you such a thing, unless they were just trying to make a sale.

Blurry background is an effect of Aperture. Use your manual to determine how to adjust aperture. The lower the number, the wider the aperture, and the shallower the depth of field. But you have to focus right. Use manual mode. Hold the shutter button down half way on the subject. After you've adjusted the aperture down to like 5.6 or lower, the photo should have that bokeh effect.

It will work fine with practice.

Keep the subject closer to camera

Select locations with backgrounds further back

Use wide apertures

Add an ND filter if necessary to prevent overexposurer

Practice...

Get a nikkor 85mm 1.8, that will solve your problem