Megapixels versus picture quality. Read more....?

Question

Looking at digital cameras I get confused about megapixels versus picture quality. I have noticed that taking smaller pics uses less pixels (ie. 640 x 480 = .3M = 4 x 6 in. pic). Taking larger pics uses more pixels. I find that the ratio of pixels stays the same when changing the size which makes me think that all the pics of different sizes will have the same quality. Of course, I realize that having a higher megapixel rated camera allows you to take those larger pics. So if someone is satisfied with taking 4 x 6 prints those expensive 6 megapixel cameras aren't really worth it (everything else being equal like zoom or other goodies). Now, if someone were to double the size of a pic (after taking the pic) does so without increasing the pixel count and make the pic look worse, will halving the size keeping the same pixel count make it look better by incresing the pixel density? Please reply to all my comments. Thanks.

Answer 1

I have a very old Sony Cyber Shot 2.1 mega-pixel and a new high-end Nikon 8 mega-pixel. It all depends on the camera quality. For 4x6 prints I still think my old Sony does a far better job. It won't, however, allow for enlarging.

Answer 2

You are correct in figuring that the quality of the print will be the same, so long as the pixels-per-inch are constant. You just can't enlarge the pictures at all if you want to hold quality constant.

If you always plan to compose your pictures perfectly, you don't need a whole lot of pixels. These days, I'd say that 5 MP or even 4 MP is fine for the average snapshooter and this can be obtained without unreasonable expense. If you want to allow for cropping, which means enlarging only a portion of your image, the more pixels the better.

Imagine taking a scenic view and then noticing that the middle 20% of the photo would make an even better picture. Suppose you take a picture of a whole group of people and Aunt Clara really, really looks great in the picture, but everyone else looks lousy. If you have the pixels to work with, you can still make a decent print of Aunt Clara that she would be happy to have. If you buy an 8-to-10 MP camera and don't want to TAKE large photos, you can always set the camera to a lower file size. You can never go the other direction, though.

Unless the cost is a major issue, buy the camera with more pixels. You will never be sorry that you did, but you might one day be sorry that you didn't.

Having said all that, though, pixels are not the only measure of image quality. The sensor size is important as well as the image processing softare inclluded in the camera. You need to read reviews if you want a critical understanding of image quality for particular cameras. Try http://www.dpreview.com/reviews/ for more information on the cameras you are considering.

Answer 3

You can't directly compare the physical size of a print to the pixel size of the file. The important number is instead the ratio of the two which is dpi (dots per inch) It is suggested that when you print pictures you have a dpi of no less than 100, which is about what you get with your example. However, 300 dpi is the threshold for "professional quality" printing. Which would require a resolution of at least 1600 x 1200 for a 4 x 6 image.

As well 6 mega pixels is no longer the high end expensive camera. 5-6 mega pixels currently gives you the best quality for your money. 8 mega pixels and above is where you are spending much more money than you need to unless you want large prints.

Answer 4

A sensor that is small has the pixel cells packed together densely. There can be overspill of light and electrical interference from one cell to its neighbour, this causes noise. Noise is what destroys picture quality. The difference between your hypothetical camera sensors if they are in a compact camera will be negligible. There will perhaps be more difference if the camera has a larger sensor such as in a DSLR I use a DSLR: nikon d40, 6.1mp a pocket camera by Casio and a couple of other compacts ranging between 8mp to 16 mp. The Nikon outperforms the compacts. If you zoom into the picture the nikon pixellates sooner as you would expect, but without exception the others lose definition and noise increased well before the pixellisation. Interestingly I have a Nikon D3100 camera too and theres not much to chose picture quality wise between the two nikons. I will just mention I am talking about image quality where it relates to pixel size. Other factors are involved such as onboard image processing and lens quality. A bridge camera uses a compact camera's sensor. The Nikon 1 has a sensor smaller than some phones. There must be a serious amount of processing to give that camera a good image. Specially considering its price. I hope this answer is simple enough for you. Get a DSLR Canon or Nikon, both are excellent, even entry level models (such as mine)

Answer 5

In regards to your questions. I myself take alot of smaller yet sharp pictures to use on eBay while selling items. I have found that most digital cameras have certain settings you can adjust when taking large or small pictures. Depending on your camera you should be able to adjust the mega pixels, zoom or micro settings, usually the larger pictures requires less pixels as you stated. Maybe you can read up on your camera setting a find some solutions or you may require a newer camera to fit your needs a site that has alot of variety in cameras is: www.nextdaypc.com/greatbuys Check It Out

Answer 6

For standard 4 x 6 prints, 3.2 Mega pixels is all you need. But you already mentioned making enlargements, so more MP will give you a better pic. Also. you sometimes snap a pic and would like to cut a smaller portion of the pic out and make a 4 x 6 print of it. Again, more MP is needed. I have a 5 MP camera, and it works fine for all instances I have mentioned.

Answer 7

For good normal photos, 8x11 max, your quality is not going to improve with anything over 4 to 5 pixel resolution. You have reached a saturation point and anything over will actually degrade your quality.

The only purpose for larger amounts of pixels are larger photos such as poster size etc.

High pixel cameras are just a marketing gimmick and only used by graphic artists etc.

Answer 8

if you are looking to but a camera always remember that the more pixels thee better the quality of the picture so no matter the size of the camera the lens or the picture display the mega pixels will determine the quality of the camera

Answer 9

the pixels is the size of da pictures, u may set the quality to be normal, fine, or superfine on some cameras, which changes the compression of the pictures.