Why are the photos taken from my Nikon D5100 not very sharp?
They are not as vivid as I like? Any tips on how to achieve sharp photos, especially for people's faces?
Should I buy a new camera?
It's not the camera… I use the D5100 and it's never disappointed me…
Do you wear glasses? You might need to adjust the dioptre adjustment slightly if you do… It's in the manual.
It's hard to advise and retiredPhil is spot on suggesting a quick course… I'd try an evening or weekend course in a local college, shouldn't cost much and they can be lots of fun.
What you need to buy is a photography course.
To shoot people's faces, focus on the eyes and then reframe the subject.
Picture control settings are explained starting on page 92 of your manual.
Blurred or out of focus shots are caused by one or more of:
Dirty lens, filter or sensor. Use a microfiber cloth or lens pen to polish up your lens front element and/or the filter if fitted. Thereafter keep your grubby greasy fingers off the glass ;-) If the sensor needs cleaning get it done by a pro - whatever you do DON'T TOUCH THE SENSOR
Check the lens for a white bloom on the inner surfaces - if you have that it is fungus and effectively kills a lens.
Inaccurate focusing. Focus on the eyes. Don't let the camera decide - it will always choose the bit nearest the camera - the tip of the nose or the ear! See also depth of field.
Inadequate depth of field. A wide aperture gives a nicely out of focus background but that comes at the cost of a shallow depth of field that may not render the whole face in focus. Use F/5.6 or f/8 if this is the issue.
Shutter too slow - camera shake is reduced by stabilisation but people also move and that will cause motion blurr if your shutter is too slow. Don't shoot portraits any slower than 1/125th, preferably 1/250th
High ISO causing noise - the sharpest shots will be at ISO 100. At ISO1600 the noise starts to really degrade the image.
Poor quality lens - if you have a £$10 1970's Russian 42mm screw thread lens attached via an adaptor then you can't expect good results. Entry level Nikon, Canon etc are good but not excellent. Excellent costs a few £$€.
Notice that none of these causes is the camera! Except maybe high ISO performance or clumsy cleaning of the sensor that has caused damage. So buying a new camera will probably not cure your problem because 99% sure it is operator failure.
I'm using a 18-55mm kit lense. I do focus on the eyes but the photos come out dull and I have to do post edits all the time.
The D5100 is a great camera. So it must be the person using it.
Have you read the manual? Now is the time to do so. It maybe a lighting issue. Or you're not giving the camera time to focus.
I love the " for dummies " series of books. I'd suggest you buy a copy of Nikon D-5100 for Dummies ".
They publish books that are written in more simple terms than the cut and dry owners manual.
User inexperience. Time to read the manual.
Your camera is likely working fine. A common beginner error is to not provide enough light. Just because you can see well with a desk lamp on doesn't mean that it is bright enough for the camera. Try taking shots in bright daylight. If you need to shoot indoors, learn how to make best use of flash, or look into buying some studio lighting (or even a high-intensity work lamp from a hardware store).
Without enough light, you will get motion blur (from too long a shutter speed), short depth of field (how much of an image can be in focus; short because the aperture is too wide open), and more image noise (too high ISO sensitivity). Some models might not even take a shot if it is too dark to focus.