TheDman Loc: USA

That can affect megabytes. Megapixels is just the number of pixels, which is determined by your sensor.

gvarner Loc: Central Oregon Coast

Terms are confusing. MP for megapixels. MB for megabytes. MEG for mega which is a million. So be careful and precise when asking a question like yours. A pixel is like a dot that contains data. A byte is harder to visualize but it is an electronic signal that is either on or off. A color pixel has 3 bytes. Roughly, a camera sensor that's 20 megapixels (MP) in area can create a photo file that is 60 megabytes (MB) in file size. So your 5.47 MP file would be about 16.41 MB in file size. Roughly. Maybe. But it's complicated.

BebuLamar

It doesn't affect the number of megapixels but it does affect greatly the number of megabytes if you save them in a compressed format like JPEG. For example I can create an image which is only white of 6000x4000 pixels or 24MP and the image is 24MP but when I save it as JPEG the size of the file is only 366KB that is very small.

Kuzano

No...
5.47 Mp

shelty Loc: Medford, OR

I'd blow them up big enough so you can see them and then count them.

Stardust Loc: Central Illinois

You are correct - I was going for a simplified suggestion based on an assumption from the original question and the "good size" comment, plus the 1584 of the size was a little "slim". And, since she said they were wanting to buy the digital image, then obviously there is a chance they want to crop or have at the 300 PPI, etc. So, it was just easier to say it might have to be double dependent on the use.

Stardust Loc: Central Illinois

Interesting thread - photographers apparently are like electrical engineers. Ask them where the light switch is and pretty soon they are explaining the flow, amps, etc. The original question was simply how to take 1584x3456 and convert it to megapixels and now I see answers to how many bits are in a byte and whether they are turned on or off (1 or 0). Reminds me of the little boy that asked his mother where he came from? After an in-depth hour explanation of the birds & bees & birth, she asked if he understood. He said. "No... little Mary across the street came from Cleveland, where did I come from?"

David in Dallas Loc: Dallas, Texas, USA

I didn't see where anyone defined how many bits are in a byte (8). Someone did mention that "kilo" as in kilobytes was actually 1024 instead of 1000, but that does not extend to any other use of that prefix (and I've always considered it an aberration in the first place).

frankraney Loc: Clovis, Ca.

No, you are talking about computer language bytes, or the size of a file stored. Pixels are a completely different unit of measure. Pixels are just the size of the picture in pixels physically. Bytes are how it is stored on the computer, they are different.

frankraney Loc: Clovis, Ca.

Here are some good articles on ppi and print sizes.

https://pagemaster.ca/printing/technical-info-for-file-submissions/photo-resolution-sizes-needed-for-printing-your-images/

http://www.vivyxprinting.com/how-big-can-i-print-my-digital-picture.asp

https://photographyicon.com/enlarge/

Do not assume, just ask what size they want in pixels what format they want it in, ie Tiff, jpeg etc.

wesm Loc: Los Altos CA

No. There are a fixed number of pixels (buckets collecting photons) on the sensor.
The translation to colors and luminosity requires a certain amount of information per pixel, I think 10 or 12 bits per pixel. This is largest contributor to the file size.
But the values of color and luminosity don't matter as long as we're talking about lossless RAW files (no compression). For a completely monotone image (all pixels one single value), you would only need about 4 bytes to represent the whole image (length X width X value of any one pixel). But as an uncompressed RAW file, it's the same size as any other image taken with that camera with the same settings.

wesm Loc: Los Altos CA

That's because every other common use of the word implicitly assumes decimal numbers (powers of 10).
However, at the raw machine level, everything is encoded in binary. So powers of 2 are the natural arithmetic units. 1024, or 2 raised to the 10th power, is the closest power of 2 to 1000. Hence KB means 1024 bytes, MB means 1024x1024 bytes, etc.

David in Dallas Loc: Dallas, Texas, USA

wesm, I know why the multiplier is 1024 instead of 1000, but that doesn't mean I have to agree it was a good idea. Back in the 1960s, when the memory of the big SAGE computer was the largest that had ever been put into production (256x256 words x 33 bits/word), it was described as a 65Kword memory (not a 64K one) because there were 65,536 words in the memory. (We could have called it 66K, I guess, but no one did.) Words in that machine were 32 bits (4 bytes) plus a parity bit (which usually were not counted when giving the size); the Big Memory, therefore had 4x65536=262,144 bytes and we called it 262Kbytes (if we bothered to use that unit). By current terminology, it would be said to be 256KB. The change to use 1024 as the "kilo" multiplier for memory size began, I think, when the 1401 and 1620 computers came along and people started stating memory size in bytes instead of words. Prior to that time, computers were "word-oriented" machines, and the major players were IBM (32 bits) and Honeywell/GE (36 bits). Also, prior to that time, the "shorthand" for notating values was typically "octal" instead of "hexadecimal"--Honeywell words were expressed as 12 octal digits and IBM words were broken into 2 "half-words" described as 5 octal digits plus a sign each. By the time of the 360, hexadecimal notation was firmly in place for specifying values.

gjgallager Loc: North Central CT & Space Coast Florida

I'm surprised this topic only generated 3 pages of responses!

frankraney Loc: Clovis, Ca.

Quite simply multiply the two numbers, 1584x3456=5,474,304pixles divide by 1,000,000(meg) = 5.5 mp(megapixles) rounded.