Confusion over digital camera megapixels

To the best of my knowledge a film camera has the capability dependence on its lenses while the digital camera's dependence on the photo sensitive Charge coupled device that records the picture. The film that captures the picture with capability like your eye and it is like an analog audio signal that you can listen directly depending on your ear's capability while in a digital camera megapixels mean like the analog signal being processed digitally and heard through the speakers.
A film camera is best for printing very large size (Posters) pictures while the digital cameras usually provide pictures of sizes usually defined in several megapixels which can be handled digitally by cpus.
You are right when you say number of picture cells per unit usually defined in terms of several 1000000 picture cells per sq inch.

The number of megapixels shown in the specification of a camera is the total number of pixels (dots of colour) contained in the image. For instance, a 5Mp camera is capable of producing a picture of a size 2560 pixels across x 1920 pixels down which equated to about 5 megapixels. This is quite sufficient to produce a reasonable quality up to A4 photo. The number of pixels remain the same but get larger in size as the photo is zoomed in, eventually reaching the point where they can be seen individually.

A megapixel refers to one million pixels,and is commonly used in reference to digital cameras as an indication of resolution capability. A pixel is a tiny square on a computerized display that is so small it appears as a dot. The display screen is a solid grid of these squares or dots, which can be easily seen with a magnifying glass. The more pixels or dots that make up the display screen, the clearer the resolution or image will be. Greater numbers of dots or pixels allow for more refinement of the image, which results in higher, truer image replication.


When it comes to digital cameras, the picture quality capability is measured in megapixels. For example, a 3.1 megapixel camera can take pictures with a resolution of 2048 x 1536, which equals 3,145,728 pixels. That is, the resulting image will be made up of 3.1 megapixels, or over three million dots. Printers measure quality in DPI (dots per inch). A printer capable of only 300 DPI will not print the 3.1 megapixel image in its native high quality. It's simply not capable of reproducing the fine detail. Instead the image may appear grainy. If you wish to print photos, be sure the printer is well suited to the capabilities of your digital camera.

The number of megapixels required to suit your needs depends on what the camera will be used for, and what size prints are desired, if any. The higher the resolution ?- or greater the megapixels ?- the more flexibility the camera will have in terms of being able to deliver high resolution prints in large sizes, such as 8x10.

For those who do not wish to print digital photos at all, but prefer to view images on the computer or television display, purchasing a high megapixel camera is not required. Even 1.5 megapixels will suffice. That said, most cameras as of fall 2005 are 3.1 megapixel or better.

If you are planning to print pictures in sizes up to 8x10, experts recommend a camera with 4-5 megapixels, or a resolution of about 2500 x 2000. For prints up to 12x16, look for resolutions of 3200 x 2400 or better, which translates to a 6 megapixel camera or greater. As a comparison, many professionals use 11 megapixel digital cameras for maximum resolution and clarity even in large printed displays. If you don't plan to print enlargements, paying for more megapixels than you need will be a waste of money.

Ok, simple. 36 mm film. is 3600 pixels. great for normal stuff. 120 film. big film, big prints.
You want poster, use 120.
3mp or whatever, 3000. 6=6000. the larger the number is how big u can go.
1.2mb can do say grainy 36mm shots. the larger the number the bigger u can go.
i went from 2.5 t0 7, shots on jpeg go from 800+600 now to 5000+4000,
Bigger the number, bigger the print.
pixel. get photo program and zoom in, one dot is one pixel.
simple

It's actually the number of pixels at a given sensor size. Compact cameras have very small sensors (do you remember the 110mm size film?), bridge cameras and vast majority of SLR cameras have APS-C size sensors (much like APS film size), and high end SLR cameras have full frame sensors (35mm film size). Now you really need to get you head around this; if all types (compact, bridge/SLR, and Pro-SLR) have say a 10mp count you would think that they would all produce equally good results that can be enlarged by the same amount - wrong! Just like film, the more you enlarge the original, the more noise is introduced (hence 110mm film could never look as good as the same image taken on 35mm film).
The photo sites on a digital compact camera are smaller and packed more densely than on a digital SLR camera. Because the photo sites are smaller then they are less sensitive to light, the electronics in the camera needs to amplify the signal from each site much more than on the larger photo sites on say a pro-SLR, this creates more noise and in turn degrades the image.
Another thing to take into consideration the the lens. A bigger diameter lens fitted to a SLR captures more light and focuses more accurately than say a camera phone or a compact camera.
If you want a camera that fits in your pocket and you only take snaps and aren't too bothered about overall and absolute quality then go for the compact route, but find something with a good lens. If you don't mind something bigger then go down the SLR route and enjoy better quality pictures, that have accurate colours and little or no noise.
A compact camera with a good lens would usually suit most people for most occasions. I however use my SLR camera for all types of high quality image capture from portrait to landscapes to nature, and so I need various lenses to suit - a compact cant compete at this level.

Pixel Count, expressed as Megapixels

Pixel Count, expressed as Megapixels, is simply multiplying the number of horizontal pixels by the number of vertical pixels. It's exactly like calculating area. A 3 MP camera has 2,048 (horizontal) x 1,536 (vertical) pixels, or 3,145,728 pixels. We call this simply 3 MP.
Resolution is how many pixels you have counted horizontally or vertically when used to describe a stored image. Digital cameras today have between 2,048 and 4,500 pixels horizontally. 3 MP cameras have 2,048 pixels horizontally and 14 MP cameras have 4,500 pixels. They have fewer pixels vertically since the images aren't as tall as they are wide.

Instead of giving long-winded explanations, I prefer to refer you to Ken Rockwell's article at http://www.kenrockwell.com/tech/mpmyth.htm; it is exhaustive, and sound.

The "film" in a digital camera is a tiny panel holding millions of light-sensitive dots, each wired to a tiny computer in the camera.
The manufacturer tells you how many dots, or pixels, are on that panel, in total. The numbers are big, so they count them by millions, using the prefix "mega". So, a "1 megapixel" camera has one million such dots, perhaps arranged in 1000 rows of 1000 dots, or 800 rows of 1250 dots. Now, that's all the dots you get, there is no function of area.
You can think of such a camera as dividing your picture into a million pieces and saving it for later viewing or printing. Obviously, the more pieces the picture is broken into, the greater accuracy the picture will be saved with. So 10 million pixels, or 10 megapixels, will represent your scene far more accurately than 1 megapixel. It's like using a large format camera instead of a 35 mm.
For printing, or enlargements, even a 2 megapixel camera will produce passable snapshot-sized prints, but not very good enlargements. Happily, such cameras have become archaic, and even point and shoot cameras regularly contain 8- , 10-, even 14 megapixels. These all produce passable 8 x 10's. BUT! - the true advantage of digital photography is the ability to "crop" your pictures and deal with a small section of it to print or view. It's easy to crop a 5 megapixel image to a point where the accuracy is unacceptable. So, yes, more is better.
One last factor is the pixel size, a cost factor in more expensive cameras. Bigger pixels are available in these cameras, and each pixel has a larger light-gathering surface for increased accuracy. A great explanation of this is found at
http://www.cambridgeincolour.com/tutorials/digital-camera-pixel.htm

PIXELS VS 35MM FILM: Megapixels (Mpx) are millions of pixels. Pixels are image dots, and for resolution they are the digital equivalent of negative film "lines". In negatives the maximum resolution is about 200 lines (or pixels) per mm, using the very best professional film and equipment. For a 35mm photo with its negative "height" 24mm, this amounts to a total of 200x24=4,800 lines or pixels. To get that resolution in a typical digital photo with 4:3 ratio you need to consider a picture "width" of 4,800x(4:3)=6,400 px. The total picture pixels are now 4,800x6,400=30,720,000 i.e. 30 Mpx. However, the above negative resolution is very ideal and it includes negative "noise". More realistically, the valued I once measured from my semi-pro camera+film was about 100 lines/mm. For a 35mm negative height of 24mm, this implies a total of 100x24=2,400 lines or pixels. With 4:3 ratio, the picture width is 2,400x4:3=3,200 px. The total pixels in the picture are now 2,400x3,200=7,680, or about 8 Mpx. CONCLUSION: The 12 Mpx of many present-day digital cameras reproduce quite accurately the quality of 35mm negative film, while 8 Mpx is almost as good.

PIXELS VS 6x6CM FILM: What about this larger negative format so popular among professionals? Let us assume again a ratio of 4:3 and consider the width which is now the limiting dimension. With similar calculations as above, 200 lines/mm are the equivalent of 200x60=12,000, then 12,000:(4:3)= 9,000, finally 12,000x9,000=108,000,000, i.e. 108 Mpx. For a more realistic 100 lines/mm we get instead 27 Mpx. CONCLUSION: You need 30 Mpx or more to reproduce the resolution of professional 6x6cm film.

PIXELS IN MONITOR DISPLAY: So much about film/digital equivalent. What about practical needs? A top-quality modern PC monitor with 4:3 ratio shows very sharp and realistic pictures with 1,600x1,200 pixels: this is only 2 Mpx. HOWEVER, most cameras below 5 Mpx have the resolution limited by the lens: they will produce a 1,600x1,200 picture, but its quality will be significantly below what the monitor can display. For best results on a monitor it is good to take the picture at about 1.5 times the vertical and horizontal resolutions: this implies about 5 Mpx. CONCLUSION: For monitor display a 5 Mpx camera is all you need.

PIXELS FOR PRINTING: As for printing photos on the computer, for the popular usual 4x6in (10x15cm) prints, a very good quality is 600 dpi (dots per inch), equivalent to between 24 pixels/mm which imply 8 Mpx. For the larger 18x24cm (7x10in.), 24 pixels/mm imply 25 Mpx. For an A4 print you need 36 Mpx for a really stunning printout. It has to be said however that we humans tolerate less resolution as prints get larger, and 12 Mpx is usually enough (occasionally one gets quite acceptable A4 printouts from a good-quality digital camera with only 5 Mpx).

Summing up, the nowadays-popular 12 Megapixels are the equivalent of 35mm to all practical purposes.

Regards

Claudio

Claudio Di Veroli, PhD
Seattle PC Service
Bray, Ireland

The megapixel rating is the number of individual elements on a camera's sensor or CCD, with each element representing one pixel. The term 'megapixel' or MP, describes this in millions.E.g., 6.8MP is 6,800,000 pixels.

Higher MP ratings mean more detail that the camera can pick up, but this figure should not be used alone to determine the overall image quality. Good optics also play a part. A decent 6MP camera employing high quality optics (the lens) will outperform a cheap 8MP camera with poor optics.

Camera manufacturers also quote the CCD array size in inches. Generally the larger this is, the better, as this affects how well the camer's optics work under different lighting conditions.

This is how I would explain; if you have ever pumped a tire or blown air into a balloon, then think about how much air you would need in a smaller tire/balloon compared to a bigger one. The more megapixels you have per square inch or per square centimeter, the more you will be able to get a bigger print and still have a good crispy clear and sharp image. I hope this helps you a little bit.

I always understood that the number of megapixels was the number of pixels in the image. So a 12 meg camera would produce an image 4000 x 3000 pixels (assuming a meg were 1,000,000 - not 1024 squared). A six meg camera would produce an image half that resolution or about 2000 x 1500, and so forth.

In viewing a photo on the computer screen, your display is set to a certain resolution. If the number of pixels in the image can fit on the screen, you get exactly the resolution that was provided by the camera. If the size must be increased or dedreased to display on the screen, the pixel content of the image displayed will be changed (with interpolation) to display the image. Similarly, your printer is set to a given dots per inch resolution. It takes multiple dots close together to make our eye see the specific color in a pixel (or the pattern of colors in adjacent pixels). To some extent the resolution of the photo determines the accuracy of the pattern printed, but once the picture being printed is small enough that our eyes cannot (even subconciously) see the individual pixels as separate squares or spots, the pixel resolution becomes less important than the quality of the interpolation by the display or printer

At the sizes most of us view or print photos, the number of pixels in the original photo does not have to be so very large. I usually archive the original photo at full resolution, but use reduced resolutions for sharing on-line and even for the small (4"x6" or less) prints that I paste in my albums.

That's my take on it. You will hear from others with more precise explanations, and maybe some modifications of what I have understood to be the case.

The terminology of 'pixels' refers to 'ONE' singular picture element or 'sensor' / 'display' element in a digital camera's light (image) recording sensor unit, whatever it's size might be, or the display grid on a computer monitor or High Definition television (usually LCD) flat panel.

Since most digital cameras (video cameras) have CCD picture recording sensors (Charged Couple Device) as opposed to old format VIDICON, or CMOS sensors, you have to imagine what a 35mm film area would look like on a typical SLR camera which used Kodachrome film, or even a motion picture camera which still uses roll film to record theater 'movies'.

The RESOLUTION or MEGAPIXELS terminology is determined by the SIZE of the RECTANGULAR image area .. horizontal vs. vertical.. and the number of CCD elements (1 Pixel size each) running the entire horizontal and vertical area of the sensor. The horizontal number is multiplied by the vertical number i.e. 800 horizontal x 600 vertical equaling 480,000 pixels for the entire image.

So for a typical 8 Megapixel digital camera, the H resolution would be 3,264 pixels x the V resolution of 2,448, giving a number of 7,990,272. pixels (which is rounded up to 8 million (Mega) pixels).

The AREA of the sensor times the number of pixels or the SIZE of each pixel will determine how finely the camera is able to resolve the image. Hence if the sensor is 4 x 3 inches and has only 8 million pixels the image will be much coarser (less fine or resolving power) than if the same number of pixels were crammed into an image sensor size of 4 x 3mm ....

That is why the larger the flat panel screen is in size, having the same pixels of resolution, the bigger those pixels will be, and the need for greater distance in viewing to get the apparent sharp image, compared to a smaller screen at closer distance of viewing.

A pixel (short for Picture Element) is the smallest part of a digital image. This equates to a single grain in a photographic image.
So a Megapixel is 1,000,000. A good Kodachome slide taken on a top quality 35mm camera would require 50 to 80 Megapixel to record the same image BUT current digital cameras cannot record the same density range as film. To add to this confusion most people want prints not slides. and a print density range is a lot less.
As a guide a 6 Megapixel Camera would give a very acceptable 10 x 15 cm print (6x4 inches if your still in the dark ages). I have A3 prints from an olympus 7 Magapixel camera and they are quite acceptable because you view these from further away!
I would suggest with current camera's a 10 Megapixel is suffient for most needs. If you are a professional look at higher resloution but most professionals have 12 or 15 Megapixel cameras.
One final note is camera megapixels is the total number of pixels in the camera and do not always have a co-relation to the size of the image sensor.

A pixel is one dot in the final image, defined by a value for red, a value for blue, and a value for green (RGB). Sometimes the megapixel value represents the number of pixels generated by the sensor, sometimes its the number in the final image (slightly less than the aforementioned), and, in the case of the Sony Foveon sensor, its the number per channel (RGB) - the real number being a third of the advertised number. Lens aside, it is the ratio of sensor's physical size to megapixels that is a prime determiner of all aspects of image quality except sharpness & detail (the other determiner is the sensor quality/technology). It is the megapixel count alone that is the primary governor of sharpness & detail, along with the optical resolution of the lens. In general, the higher the megapixel count the more sharpness/detail, but more noise at high ISO, worse dynamic range, and other image quality anomalies. Conversely, lower mega-pixels means potentially not as sharp or as much detail, but otherwise better image quality, especially at higher ISO. More mega-pixels is often better for enlargement and/or cropping, since it reduces enlargement interpolation artifacts and also because noise gets enlarged along with image data, and less enlargement need be done when starting with more mega-pixels, thus smaller noise.

Definition: Mega-pixel war - camera manufacturers increasing megapixel counts for marketing to mis-informed consumers despite image quality drawbacks. In the earliest of days, megapixels was synonymous with image quality - since it was the weakest link. It is not the weakest link anymore; lenses, and sensor's physical size & quality have become more critical now. Reminiscent of CPU megahertz wars, where in the earliest days, CPU clock rate was the bottleneck in computer performance, but its not anymore, at least not for the majority of computer uses.

DSLR manufacturers and users have understood the down-side of more mega-pixels for years, which is why they've not participated in the megapixel wars. Consumers of compact cameras are starting to catch on, and Canon is the first to respond - its flagship compact went from 15 to 10 mega-pixels this year - the G11.

Rob Cole
www.robcole.com

I'll keep this as brief as possible.

First of all, here's a link to a chart that might serve you well that gives various megapixel resolutions and the quality of the images that you can expect at various enlargement sizes.

http://www.bhphotovideo.com/FrameWork/charts/resolutionChartPopup.html

The comparison of megapixels in digital images to film size in film cameras is not exactly accurate. While negative size does contribute greatly to enlargement quality, a more accurate comparison to megapixels would be the camera's speed. An ASA 64 film, for example, is "slower" than ASA 200; because the grain is finer in 64 film than it is in 200 film. Consequently, the slower film takes longer to expose than the faster film. The faster the film, the courser the grain, and the poorer the image quality, especially on large-scale enlargements. One of the most beautiful examples of this that I've seen was an image shot on 35mm Kodachrome 25 film and blown up to a whopping 30x60 feet image that was on display in Grand Central Station for awhile. The pic was of pink flamingos, and the image quality was outstanding for ANY size format. Better quality could not have been achieved with even a large format camera. If it had been shot on ASA200 film, the image would have been unusable at 1/4 that size. The slower the film, the finer the grain; the finer the grain, the better the image quality. It's similar with megapixel ratings of digital cameras.

No matter what your choice of digital camera, though, film negatives and transparencies (slides) are still far and away superior to digital images of even the best, highest-megapixel camera. Keep in mind that the size of the sensors in the digital camera will determine image quality, too. Larger sensors collect more information about what the camera is seeing, and therefore produce a better quality image than a camera with smaller sensors; so it is probably a good idea to stay away from the super-compact cameras and go with one roughly the size of a 35mm camera.

My advice is to go by the chart and choose the megapixel range that suits your particular needs, then buy a well-known brand name that has been known for quality in the photographic world since before digital cameras existed. The makers of quality film cameras will put as much pride of workmanship and consideration of quality into their digital line as they have for their film cameras over the decades.

If it's just for snapshots and close-ups of flowers, insects, your significant other's face, and other general amateur photography as keepsakes, a 6 Megapixel camera is fine in my opinion. I have a Kodak Easyshare 6.1 Megapixel camera, with a zoom lens; and I am just tickled pink with the quality of images that it produces. I get excellent prints up to 16x20 inches with it. I especially like it's anti-shake (or anti-blur) feature and its close-up settings for really small little critters that I think my grandkids would enjoy seeing up close when they come to visit.

The other consideration would be budget and getting the most bang for your buck. The Kodak Easyshare camera I have had for awhile. I think I paid around $125 for it, and it has been well worth the money. For what I do with it, it's every bit as good as my 35mm film cameras. I carry a couple of 3 and 4 GB memory cards in the case when I'm traveling so I have plenty of space to put the images in case I go crazy. That's another thing: memory cards take up WAY less space in the camera bag than rolls of 35mm film--and they're reusable, unlike film.

Oh. It makes very good quality sound movie clips, too--for as long as the batteries hold out.

On that token, you should consider getting two or three sets (it takes 2 AA) of rechargeable batteries; because buying batteries can be expensive, depending on your personal resolution settings, which can be changed, too. I've even taken timed night shots of the moon and other things that slither, crawl, hop, and fly outside at night. You'll need a tripod for that, though.

I like a digital camera, because it interfaces with the computer with a simple USB cord; so the images can be loaded onto the hard drive and edited with your favorite image editing/retouching software--no more scanning the images and all the other work that goes into scanning prints or negatives.

I hope this helps.

Megapixels for a digital camera are often publicised as a measure of resolution. However, the number actually describes the pixel-count, obtained by multiplying width and height of the picture, that camera can build.
For example, Cameras A, B, and C can build pictures of different heights and widths.
A. Width=2,048 ; Height=1,536 ;Width x Height=3,145,728= 3 Meg-pix
B. Width=2,464 Height=1,648 ;Width x Height=4,060,672 = 4 Meg-Pix
C. Width=3,872 Height=2,592 ;Width x Height=10,036,224= 10 Meg-Pix
Apart from pixel count, many other factors are considered(e.g. sensor size, sensor design, how pixels are organized, interpolation algorithm quality of lens etc.) to calculate a final value for resolution.
An excellent article on this subject may be found here:
http://www.luminous-landscape.com/tutorials/understanding-series/res-demyst.shtml

OK, Here's the deal. I work retail, but i know a lot about what customers need vs what they want or are told by "sales" people. Megapixels is how many millions of pixels make up the image. In THEORY a high megapixel means a better quality image. However, there are many factors. First and foremost the lens. I dont care if you see a cheap digital camera that boasts 8 megapixels for 40 bucks. chances are the lense is plastic and crap. so you will get a really high resolution image.. of a terrible shot. Next thing to note, many cameras bost insanely high megapixels.. but the default shooting mode is 5MP. You'd have to change it. And the speed of the camera is rated on its default settings. the bigger the file, the slower it gets. Unless you are using an SLR. Another thing.. most high quality photoprinters max out at 600dpi. At 5MP you can make a perfect 8x10 image. at 10MP you can make a really nice 24x36 poster.
What i'm trying to say is, don't pay too much attention to how many megapixels if you are using a point and shoot camera. All Dig camera's are more than 5MP these days and thats plenty for good pictures for the average shutter bug. Higher megapixels arent worth paying for. Instead look for a good lens, a nice optical zoom, an actual viewfinder, image stabilization. Yes, more MP is better.. but will you actually take advantage of it? probably not.

See this arthicle (spanish)


http://www.dzoom.org.es/noticia-4326.html


Remember: More Megapixels not equal better camera
Regards

I read it somewhere actually. Its the total no of pixels used by your camera to describe a picture.... if it is 2 Mp it can be 2^11 * 2^10 (width * length).

Yes there is an equivalence in number of megapixels to picture quality.

If you don't crop and print only 4x6 inch photos or you look at your shots on a 17" computer monitor, 3 megapixels will do nicely.

Think of 3-6MP as 35mm format. A high quality camera in this class will easily produce beautiful 8x10 prints.

A 10-12MP camera will give you outstanding 16x20 prints - even bigger if you want. Think of this as a medium format film camera equivalent.

If you're a serious pro who NEEDS very big, highly detailed images, there are 50 MEGAPIXEL cameras that cost $35,000. These are easily equal to a 4x5" negative of old.

For most of us, a 10MP camera is about as much quality as any of us need.

Do you realize that an HDTV that mesmerizes most of us is little more than 2 megapixels at 1920 x 1080 on a screen that measures up to 70 diagonal inches?