Digital cameras forum: Confusion over megapixels vs. megabytes

Hello John,

The number 14.2 refers to the number of PIXELS which can make up the picture your camera can take at its' HIGHEST QUALITY image setting i.e. 14.2 megapixels - which means 14.2 million pixels. Each pixel is a tiny part of the picture.

The 'size' of the picture e.g. 3.2meg or 1.8meg refers to how much space the picture takes up on any memory card i.e 1.8 or 3.2 megabytes (megabytes and megapixels are NOT the same thing).

By way of explanation the more pixels a camera uses to make and take a picture, the better the picture quality should be, but the more pixels there are in a picture the larger amount of space it will take up on the memory card that the camera uses.

I don't know what size or type of card is used in your camera, but if your camera is used at its highest quality image setting of 14.2 megapixels, then I would expect each picture to take up MORE space than 1.8 or 3.2 megabytes. Therefore setting that your camera is using to create a picture of 1.8 or 3.2 MEGABYTES in size is probably NOT the highest quality setting.

Your camera may have settings that allow you to adjust the picture quality in several steps from the best quality (most pixels - and therefore largest size IN MEGABYTES) - down to the 'lowest quality image' which will take up the least amount of space on the card IN MEGABYTES that the camera uses - which will have the effect of allowing you to take more pictures using the said card if the settings of the camera are left at the 'lowest quality image'

As an example I still use a Canon Powershot G5 (which has 'only' 4 megapixels) with its highest image quality setting (called 'superfine') and my pictures are stored on a couple of 128 Megabyte cards. The size of these pictures (at about 2 or 3 megabytes) is about the same as that on your camera, which uses three times as many pixels. These cards are quite small compared to what you can get nowadays, but I can still get loads of good quality pictures on them. If I used a 1 or 2 Gigabyte card I could get hundreds of best quality pics on it.

In the case of your camera with 14.2megapixels, the smallest card you should want to use if the camera is at its' highest quality image setting would probably be about 512 Megabytes or 1 Gigabyte (1 Gigabyte is approximately 1000 Megabytes) to get a decent number of best quality pics before the card is full up.

Also your camera having 14.2 megapixels also means that it should be able to use a much bigger card (for bigger read 'more space' not actually physically bigger) than than a camera with say about 4 or 6 megapixels.

The more spacious the card the more pictures you can put on it at the highest setting, but the more the card will cost.

I hope this info helps, and is not too confusing

Rob

You're getting mixed up between how the picture is put together, and how much memory is needed to store it.

Pictures are put together in little dots, or pixels (you can see them if you look closely at your monitor, or at the TV screen). Your 14.2 megapixel Nikon uses 14.2 million of these dots to make up a photo.

When you take a photo, what the camera sees is converted into these dots, and the "colour" of each dot is stored in memory. When you want to view the picture, your computer (or whatever you use) goes to the memory and finds out what each dot should look like for that photo, and puts it up on the screen, thus reconstructing the photo.

You can imagine that it would take a lot of computer memory to remember what 14.6 million dots look like. In your Nikon case, it takes 1.8 megabytes of memory. That's where that figure comes from.

By contrast, your Kodak camera has 12 million dots per picture, and this takes 3.2 megabytes of memory to store. Why is it more memory for fewer dots? One reason is that some computer chips are more efficient than others, but the other may have to do with your "resolution" settings.

"RESOLUTION": You can change the memory needed for each photo by altering what's called the "resolution" setting on your camera. That is, if you like, how many dots you want your camera to remember when you take a photo. It doesn't have to remember all the available dots (you might tell it to just remember half of them, for example), but if you choose to do this, you will lose a bit of sharpness. This is called "lowering the resolution", which you might do to save on memory (or megabytes - your camera, like your computer, has a limit).

You might have heard of a photo looking "pixelated'. This is when very low resolution has been used (relatively few pixels), and you can start to see the individual pixels or dots when you look at the photo.

Fewer dots remembered means less memory (megabytes)used, but loss of sharpness (this is low resolution). More dots remembered means a sharper picture, but more memory used (this is high resolution).

It's always best to use high resolution for your photos, but you have to remember that you can't take so many photos like that - you will run out of memory sooner. If you think you might run out of memory, then you need to lower the resolution and put up with photos that are not quite as sharp. Much of the time this won't matter, as they will still usually be very good.

Remember also that you will need to store your photos somewhere, so the memory capacity of your storage must also be taken into account.

Final note: the resolution setting on your camera might not mention the word "resolution". One I'm looking at now says "Quality", and tells me how many "frames", or photos, I can get for each quality setting. Higher quality = fewer frames. Another camera I have seen gives the resolution in: pixels across times pixels down. So it might say 1536 x 1180, which would be 1.8 megapixels (1536 x 1180 = 1 812 480). Your camera manual will help if you can't figure this out.

A very good, clear description and explanation.

Nice one.

Mark

Well said. My one comment is about his 14.2 megapixel camera creating an image file size of 1.8 megabytes being dependent on his Nikon. Actually, file size is more dependent on the amount of detail in the picture taken, which would affect the amount of compression that the jpeg algorithm could do. Think of a highly detailed photo of a dense wildflower field compared with one of a beach scene with white sand, dark blue water and light blue sky. The former will require lots of pixels (and bytes of storage) to maintain a decent picture, while the latter could be compressed significantly and still look great. It's all about adjacent pixels being very similar or quite different.

A pixel is ONE piece of a picture. PIX ELement.
Take a very close look at any video monitor. You will see either three color dots in a triangle or three color lines next to one another. These dots or lines are repeated over the whole screen.
If the resolution of the monitot/tv is full HD it is 1920 by 1080 which means one picture contains 2,073,600 pixels. (1920 times 1080).
In camera terms 14.2 megapixels is the # of sensors vertically times the # horizontally behind the lens.
When this image is recorded in a file, the size of the file is determined by the TYPE of file that is saved. It could be RAW (no compression), it could be TIFF (little to no compression but with less pic info than RAW, or it could be JPEG (little to a lot of compression).
The other factor is that each color of each pixel is saved as a separate byte and the luminance info is saved as another byte - the color may be saved as 2 bytes.
A RAW file with a 14.2 MP sensor will be very large.
A JPEG file will be more the size you are getting. The exact size depends on the QUALITY you have selected and the resolution.
Try setting your camera for the highest quality, the highest resolution, and RAW if available, or TIFF. If neither of those formats are an option, then it will compress it to JPEG with highest quality or most bits per pixel.

In a simple way:
Megapixel: is related to the photo size (inch size)
Megabyte: means how bulky will result your photo.

Megabyte depends on the camera manufacturer for the compression level applied to the photo, for that reason two images of equal megapixel but different brand cameras have different size in megabyte (because are using different programs for compressing the images)

Megapixels and megabytes aren't really related at all.

A pixel is a very small block of colour. A digital photo is made of thousands or millions of individual pixels. The more pixels an image contains, the greater its detail (quality). One million pixels equals one megapixel, so a 14.2 megapixel digital camera can take photographs that contain more than 14.2 million pixels.

A megabyte is not representative of the quality of your images, it measures the file size. The more megapixels contained in a photograph, the more megabytes (MB) it will consume. (The better the quality of the image, the larger the file size.) The file format also has a lot to do with the file size (megabytes) of your image. E.g. a 14.2 megapixel photo saved as a jpg might take up about 3 megabytes but the exact same photo saved as an uncompressed tif file might be about 15 megabytes.

Hope this helps

The 14.2 Mega pixels refers to the photo diode array that captures the picture. The mega byte size of the picture is the photo quality. You can't change the former but you can change the setting of the latter by adjusting the camera settings. As has been said many times, "When all else fails, read the instructions." You'll need to read how to adjust the picture quality. Undoubtedly you are saving pictures in a low quality JPEG format. You can probably increase that to 4.7 megs per picture with the camera settings. Or, you can change the format to TIFF which will provide a 9.8 meg picture.

Your camera with 14.2 mega pixel photo diode array is very good-----a high end amateur camera. This will allow you to blow pictures up to 12 x 18 with great quality and even larger for a little sacrifice in quality.

Someone said earlier that the quality of an image from a 14 megapixel chip is better than others of a smaller megapixel, say in this case, 8 megapixal. This is all down to the size of the printouts made.
At around 5x7" printing you won't see the difference between an image taken on either camera, as the 8mp chip is still within its range of producing a good image at that size.

When you decide to make a 16x20" print there may be a difference, as whilst the larger chipped camera can still cope, the 8mp is over its limit. The 8mp is a little like the old 110mm film format, and if you can remember going into the old processors many would pull a face and say "this won't print too big you know", whereas a 35mm neg would print that big (the 14mmp chip)comfortably.

The megapixel size could also be described as the chips "potential" to hold information for full a sized print if stored at its least compressed as a Tiff or Raw file only.

The chip, unfortunately holds other information on this chip in relation to the actual processing of the image, therefore 2 cameras which boast exactly the same megapixels can still produce differing "potential" images. One chip may devote more of its space to mundane processing tasks such as storing the auto whitebalance and automatic contrast of each jpg, whereas the other may find a more effective way of storing this information in favour of storing more "size" into the image.

This is why it is always best to clue-up on what the camera you want is offering. This "wastage" is known as the difference between ACTUAL megapixels and EFFECTIVE megapixels. This can be reduced a little if shooting in RAW, as most of the calculations a camera makes in its set programmes can be replicated out of the camera with software such as Photoshop and the like.

Megabites are a totally different kettle of fish which has been covered already, and I'm sure you've sussed out by now. In face I may have even repeated what has been said already here but didn't get chance to read all the posts

Hope this helps
Glenys Sheffield

Does one pixel occupy one byte? If not, how much pixels occupy one byte?

With a 14 MP camera, are each and all photos are composed/recorded with 14 Mega dots (if setting is not changed?

When we order for a print of different sizes, say 4X6 or 8X12, do prints of all such sizes constitute same (14) MP?

Megpixels refers to the number of pixels in the image...it's akin to screen resolution. The higher the megapixel rating...in theory...the better quality picture you get. There are also other factors involved that effect that as well. Megabytes is the size of the file. Just becaue you have a camera that is 14 megapixels doesn't mean the resulting image will be 14 megabytes. The two are totally unrelated. Now as far as why one takes a pic that is smaller in size than the other depends on setting like resolution, compression, colors, etc... One of your cameras might be using an older compression scheme that isn't as efficient so it produces a larger image.

A pixel or megapixels is the tiny dot that comprises a picture. You can see it only if you magnify the picture. A byte or megabyte is the measure of disk space that a file will consume. A poster picture will have more megapixels than a tiny picture. But a simple picture, let us say a black straight line on a white background will require less memory than a colorful scenery even if they have the same megapixels.

The term "megapixels" is simply a measure of how many MEGA (or million) PICTURE ELEMENTS, (or "PIXELS") there are that make up the photo. It's a simple multiplication of the number of pixels wide by the number of pixels high.
EXAMPLE: If your camera is set to shoot a photo 1600 pixels wide and 1200 pixels high you would multiply 1600x1200=1,920,000, or about 1.9 million pixels (megapixels) in the photo.

The term megabytes (or Mb) is in reference to the amount of storage space your photo takes up on your hard drive. Each pixel does not equal one byte, so it follows that 10 million pixels (or megapixels) don't necessarily require 10 mb of storage space on your hard drive. The JPEG format of saving photos also does a lot of compressing. The more similar adjacent pixels (same color, same texture) the more compression you get.

So although the more megapixels you have in the photo, the more megabytes you will need to store the photo, it is not a one pixel for one byte relationship.

Boy, this thread is loaded with allot of techno jargon, some of it useful, and some of it pure guessing, or nonsense.

Simply put, a camera Megapixel rating is a measurement of the cameras maximum image size (Width X Height) in pixels.

Megabyte is the memory used to store the image. This varies with file format, and content of the image.

John; Mega is a numerical statement. Pixels are the dots used to make up a digit picture. Bytes are the amount of memory used to save the pixels. 1.8 megabytes is about the same memory space equal to one hole 3.5 inch floppy disc. So, if you were to put your pictures on floppy discs you could only fit one picture per disc. 1.8 megs is a large file for one picture.

Rich