Confusion over digital camera megapixels

Do you know what a pixel /is/?

Anyhow, in a Bayer-pattern sensor, half the pixels are green, and one-quarter each are red and blue. This is because the eye has greater sensitivity to green light and sees more detail at green wavelenghts.

The number of pixels has a strong bearing on image quality. The more pixels, the more you can enlarge the image. However... the output of the sensor requires processing, and the quality of the processing affects the quality of the image. In addition, the smaller the sensor for a given number of pixels, the noisier the image is, and the less it can be enlarged. So, you can't automatically assume that more pixels will necessarily give better image quality.

That's about as simple an explanation as you can get. Please get a book and read.

Megapixels rarely make a difference for the average person who only print 4 x 6, 5 x 7 or 8x10 pictures. They only really make a difference with large prints (poster size) and cropping. More megapixels is not always better either. Take the Canon SX IS line: The SX10 IS has 10 MP while its successor, the SX20 IS has 12.1 MP. They both use the same sensor therefore the SX20 has poorer photo quality, especially in low light, due to the increased demand on the sensor compared to the SX10 IS. Similar to the digital cameras that claim they have 1600 ISO that is completely unusable! Just another "stamp" to put on the box and in their specs that catch your eye yet really mean nothing for 99.9% of the population. There are other specs that are more important such as the sensor type, zoom capability, video capability, variety of settings, performance in different lighting situations, etc that have more of an impact on the quality of the photo you take than the MP.

When shopping for a digital camera don't rely on the manufacturer's hype - read reviews. You can find them just about anywhere and don't just go by numbers or star ratings - read REAL reviews that you can decide if the person's approval/disapproval of an item is warranted. Sometimes people give poor reviews for things like slow shipping, etc, which has no bearing on the product.

A great site to see side by side comparisons is:
http://www.digitalversus.com/duels.php?ty=1&ma1=1&mo1=649&p1=4503&ma2=60&mo2=583&p2=3727&ph=15

Just click continue - don't click on either link or you'll lose the page. Here you can see differences in photos taken under several conditions with different models side by side.

another great review site is: http://www.dpreview.com/

Don't get bogged down by the numbers, there are great 10 MP cameras and bad ones. If you are looking for something for leisure, you surely don't need more than that (probably could even go lower). Just do some research, go to local stores to see the cameras and try them (bring a memory card with you - most use SD cards, take some shots, download them when you get home and compare) and you'll have a much better idea of what is right for you than by going purely by numbers.

My first digital camera was a 3.2 megapixel. It has always taken very nice photos. I still use many for my computer screen wallpaper, and I've never seen another camera that shows finer close-up detail(as in dust particles). My more recent cameras have been 9 and 12 MP, which is all well and good, but if you want better photos, sensor size counts for a lot more. You will find that cameras with larger sensors cost more, and for good reason. They produce better photos, no matter how many megapixels you have. By the same token, lots of megapixels with a smaller sensor will not give impressive results.

The things that first determine the overall quality of any camera are the quality of the lens assembly and the build quality of the body. This is basically why SLRs win out over compact cameras even if the compact boasts say 12Mpix and the SLR even just a measly-sounding 6Mpix. So if you have the option and the quality of the images are important to you go first for a "large" format camera (as opposed to compact) and work from there. The benefits from available choices of interchangeable lenses, filters etc will more than compensate for any deficit resulting from less Mpix.

Given that, your questions about format size are relevant. Each type of camera (from webcam to cellphone to compact to SLR etc) has a different physical size of the sensor that detects light.

If you have eg 10Mpix sensors in a larger and a smaller sensor size then it follows that in the larger size each pixel can be physically bigger and be more separated from its neighbours. These factors straightaway improve image quality because of noise reduction particularly a kind of "crosstalk" between pixels called dark current noise. This noise is a big problem when many pixels are crowded on a small sensor array. The noise that results in the image from this (particularly colour noise) is very ugly.

If you have the same size sensors one with a lower pixel count than the other you should also be aware that the one with the greater number of pixels will be less sensitive to light simply because the available light is being divided between more pixels. To compensate for this a greater demand is placed on the quality of the accompanying optics to gather more light accurately and this demand is often not met between models that differ only in the pixel count. This is simply so the marketing people can fire a bigger shot in the megapixel wars.

In short, go for build quality and lens quality first, sensor size second, and probably pixel count last of all.

Finally remember that a 12Mpix camera, for example, would (if the pixels were used to their maximum limit of resolution in reproducing an image) produce an actual viewable image (on a screen or on paper) that would be absolutely huge. Poster size at least. Ask yourself if you really need that!

Hope this is coherent enough to help... Steve C

The above posters have given some really good technical explanations. But let me give you some practical comparisons.

There is no standardization for the MP vs film formats.

But if you look at today's market, a true full frame 35mm equivalent D-SLR usually will have 21 to 24 MP (the older Nikon D3 however only has 12 MP but has lower pixel density and excellent images).

The medium format digital cameras have 33 to 60 MP (the 645 cameras).

There is no real large format digital camera out there yet, you still need to use film.

Will you really need all those MP? Depends on who you are. There are certainly pros who get barely satisfied with the Mamiya or Phase One 645 cameras with 60 MP. They have their reasons and they do large prints for a living.

Currently the entry and midrange D-SLR are all small format APS-C size sensors that are smaller than the 35mm film format (usually 1.5 to 1.6x crop factor). For these cameras, 8 to 12 MP are enough. We used to think that more MP with higher pixel density will increase noise, but the new Canon 7D proves that newer sensor technology can control noise quite well at higher pixel density. Most people don't print larger than 8x10, so 8MP is actually quite enough. I do a number of 13x19 prints at home (for my own use), and photos taken by my older 8MP Canon 30D still looks very good (even when viewed close-up). But the prints from my 21 MP Canon 5D Mark II are slightly better with finer details when viewed close-up at that print size. When I hang them up the wall and view from a distance, they don't really look much different.
As always, a good photo with good exposure, color and sharp focus can be enlarged quite a bit and still looks great. On the other hand, a poorly exposed or focused photo will look bad even at thumbnail size. So MP is not the most important determinant, it is good technique and good composition that matter more. MP mainly gives you an estimate how large your print can be. But on the other hand, your perception of the details depends on the distance you view the photo. The larger photos are meant to be viewed farther away, so you really do not need a lot of MP if you have a good photo.

The larger the megapixel the larger the photo can be printed,most used by professionals for not nescessary for every day pictures.
I use one megapixel on my fuji s7000 and get great results,if focusing is working correctly it looks very good.the feature i find most useful is spot beam for focusing in the dark.

A megapixel is one million pixels(picture elements). This of course would be obtained by multiplying pixel width x pixel heighth. For example, 3 megapixels would be 2048x1536; 6 megapixels = 3008x2000; 10 megapix = 3872x2592; etc. Usually the literature for the camera will give you these dimensions, too. As a professional, I prefer to print at a resolution of 300ppi(pixels per inch). You can get acceptable results at 200-250ppi. So, if you want to print an 8x10, you would want your file to be 2400(8x300)x3000(10x300). Higher resolutions come into play if you need to crop your image, as you will lower the pixel dimensions unless you use some kind of interpolation to upsize it again. That having been said, most people these days buy cameras with much higher resolution than they need. I often find that they lower the quality of the images to save on file size. Never lower your quality setting! You are much better off shooting high quality at a lower resolution. Keep in mind also, that a crappy 10 megapixel image = a crappy image. If you give me a sharp, well-exposed 2 megapixel image, I'll print you a billboard from it. In other words, spend your money on a camera with a quality lens instead of the highest megapixel count you can find. I hope that helps.

the number of megapixels is simply the total number of dots used to make up the picture, this is calculated as width times height in pixels or dots. so a camera with 3000 (wide) x 2000 (width) dots would be a six megapixel camera, e.g. 3000x2000=6,000,000.

So a camera with more megapixels has finer resolution, basically.
The sensor size has no direct bearing on the resolution - a 1.5" x 1" sensor with 3000x2000 resolution would have the same theoretical resolution as a 3/4" x 1/2" sensor with 3000 x 2000 pixels.

Now there are advanatges to a larger sensor and that is the noise is lower because the image sensing spot is larger and spread over more area. of course the penalty for larger sensors is camera size grows and cost grows.

Pixel is shorthand for picture element, which is the smalles point of light or dark that a portion of the picture can be seen having. You take a pixel and try to maginify if to greater detail, and it just expands out as a blot, with nothing new seen inside. The thing is though, while one camera may have more pixels that it can break a certain viewed image into, unless you elect to magnify it up in scale, it will seem to be about as resolute as a camera with a lower pixel count, as long as the pixel counts do not go down too low,

And yes, you can consider the Megapixels as an indicator of the resolution that can be had in a given camera, but much depends on how the results will be viewed as to whether that higher resolution counts for much. For instance, the resolution of your monitor screen, the resolution of your printer, and the scale at which you decide to view the picture at are factors as well.

Plus, what additional features are offered by the camera, such as ability to be stablized internally during the shot, or the way it performs a zoom when trying to get a closer picture, even the accuracy with which it handles shades and hues of light. The best answer to most people is what looks best to them, meets their other requirements, and justifies the difference in price. But you are at least partly correct in thinking that higher pixel count does count for something.

The number of megapixels shown for a digital camera is the maximum number of pixels per photo which the camera takes. A 'megapixel' is one million pixels as stated by SI unit prefixes. The number of pixels in an image is calculated by multiplying the height of the image in pixels by the width of the image in pixels. This is called the resolution of the image. Manufacturers display the maximum resolution their cameras can take as a normal specification. It is better to have a higher resolution camera, but once past 8 or 9 Mpixels you don't really need larger photo sizes because you will have to resize them quite a bit. I find 8 Mpixels to be more than enough and I still have to resize the images to send them by email and upload them to the internet.

Hope this helps
Tom

Megapixels is the amount of light sensors on the CCD (charged couple device image sensor) on a digital camera. More is better, but you don't have to go out and buy a 8MP or higher camera for vacation/everyday photos - although I do think those are the mainstream now. I've taken some really great pictures from the top of Diamond Head with a 4MP camera suitable for 8 X 10" framing, and I've managed a very nice family picture at 16 x 20". Additionally with more megapixels the bigger the size of the photo file will be on your computer and the bigger print you can make. Although all cameras have a way to change your picture resolution modes resulting in ether really big file sizes or ones around 1Mb.

Check out the reviews at cnet.com, digitalcamerareview.com, and dpreview.com on what's popular.

PPI pixels per sq. inch