How many megapixels do I need in a digital camera?

Ray Nelson October 25, 2011

I have a monitor that has a  pixel resolution of 2040×1080. That is around 2MP. Is there any benefit to having 8.5MP pictures if the detail can not be displayed? Would the detail show if I used zooming software?

  1. HildyJ
    October 30, 2011 at 3:16 am

    The short answer is that more pixels allow finer zooming and bigger enlargements. The real answer is that you're looking at the wrong spec for your use. For digital photos that get passed around the digital world, how sharp the lens is will affect the picture much more than the pixels. The other thing to look for is how accurately the camera captures color. Basically, no number of megapixels will help if the buildings are blurry and the sky has a green tint.

  2. Ray
    October 28, 2011 at 2:45 pm

    I understand and have to work with what the industry tells me.  I now understand the .28 dot density (or what ever) we should seek when purchasing visual displays....  

    I hope your discussion helps others.  I also know the Premium a friend of mine paid for a camera with something like 18MP, (knowing the person's needs) is way overkill....

  3. Mike
    October 27, 2011 at 10:25 am

    The article is correct for what it is trying to express.

    The problem is that over time people started to exchange technical terms with logical terms to make things easier to understand.

    For example assuming you have a Full HD display at 1920x1200 and view a photo in fullscreen:
    A 2MP photo from your mobile phone will probably look bad.
    A 2MP photo from your compact camera will probably look ok.
    A 2MP photo from your DSLR will probably look good.

    The reason being that each image sensor delivers a different quality of image. However when cameras where developing a higher image size required a better image sensor so the market started to use MEGAPIXEL to express the quality.

    Back to the numbers: 
    What we call resolution for photography is really just an image size wherein DPI/PPI expresses the resolution. 
    An 1000x1000 (1MP) image at 144 PPI will result in a 2000x2000 pixel sized image on a 72PPI screen. Again, neither really expresses the actual quality.

    For displays it's different: 
    What we call resolution e.g. 1920x1200 is really just a logical resolution (or image size) layed over the actual displays size and pixel count.. 

    There are 24" TFT displays with 1920x1080, there are 17" notebook displays with 1920x1080 and there are 52" TV displays at 1920x1080. All of them obviously have different Pixel Per Inch. 
    However if you connect them to your Windows PC all of them will display a logical 96PPI resolution (default of Windows).

    The result being that we draw XX logical inch per YY actual inch on the display. 
    Since we can't change the PPI/DPI of the display panel and we get confused just by thinking about "Inch per Inch" we started to simply use the term resolution for the logical image size.

  4. Mike
    October 27, 2011 at 12:36 am

    You try to combine two different "worlds" ~ or actually three... relating to your previous comment:

    1920x1200 is a monitor or image resolution
    8MP or 4272 × 2848 is a pixel count

    Your monitor running 1920x1200 doesn't have a pixel count of 2.304.000 or 2.3MP. It's pixel count is a product of it's dimensions and pixel density. (width * PPI) x (height * PPI)

    Your photo doesn't have a screen resolution of 4272x2848 but a size of that measured in pixels. At 96 PPI that size would be 44,5" x 29,67"

    Last but not least the third one is that the actual quality of pictures depends on the pixel count and the image sensor. Consider this:
    Two cameras with the very same image sensor, one sold as 4MP, the other one as 8MP. That's a normal appearance on todays market. 
    In most cases the first one will result in better quality images because the very same detail the sensor can produce is pushed into a smaller amount of pixels.

    Whether you can spot the difference of a 4MP camera vs a 8MP camera depends on your photographic skills and your screen. If you have some sub 150$ TN-panel display you probably won't. If you look at the pictures on an IPS panel you don't even have to zoom to see the difference.

    • Ray
      October 27, 2011 at 5:48 am

      I understand almost everything you said.   And I thank you for your patience.   What I have not seen is anything relating to the PPI for my monitor.   Everything is in what looks like the numbers representing Pixels.  

      Even windows settings are related as such with the recommended one matching the maximum on the sales literature for the monitor.  I have displayed several picture comparisons, and don't see any difference above around 3MP.  

  5. Ray
    October 26, 2011 at 11:58 pm

    Man, I am sorry I did not read that first article.  My fault.   It does a superb job of getting to the detail of what I was thinking...   The most telling statement, and I quote, 

    "the maximum megapixels you need is FOUR. Yes, a 4 megapixel digital camera is really sufficient for all your daily needs and you won’t even notice that it’s a 4 megapixel camera if I scratch the label out and write 12 megapixels on the lens. "

  6. Ray Again
    October 26, 2011 at 10:33 pm

    I can definitely see how if you zoomed in on a part of the displayed image and had sufficient detail, the display could be much better with the higher MP...  I don't know if software such as the native Windows Photo Viewer does that.

    Everyone is pushing high end MP's.   Just really wondering if most people are getting any benefit, especially me.

    • Jay
      October 26, 2011 at 10:37 pm

      I gave you the image to test it, so you can see how an 8 mp image will be displayed on your monitor,
      you can download them from attachments from my comment above.

      and also, mentioned the zooming thing, if you read.
      yes, microsoft image viewer can zoom in and zoom out ,  open an image, and see the option below the image.

      • Ray Says Thanks.
        October 26, 2011 at 11:52 pm

        Thank you Jay.    Simple answer....  

        • Jay
          October 27, 2011 at 3:40 am

          Yes, it's really simple. Test it to know it :)

          You can zoom the image according to its quality on your monitor.

  7. Ray
    October 26, 2011 at 10:28 pm

    Was not really talking about any camera.   Was referring to the displayed image of a picture..  

    As I understand it, the resolution on my monitor correspond to a grid of Pixels...   

    Simply wondering how the """detail""" from a camera that is shooting at say 4272 × 2848 resolution = 12.2mp could possibly be displayed on my monitor with 1920x1200 resolution.

    I understand that printing especially large formats is different.    

    The images from these wonderful camera's are huge.   I don't print them...  Thought someone could say, Yea or Nea and were the crossover is...

  8. Mmynhier
    October 26, 2011 at 6:34 pm

    Long answer short: It depends. If all you are going to do is view images on your desktop, then you don't need more than the minimum you can buy...right now that is way above 2 megapixels. BUT, think of it this way...on your stereo you seldom, if ever, turn the sound up to max, so why bother being able to put out more than you will ever use. The answer is the same for both. You are using a percentage of what you "need" to allow for a better product. Your images will be nicer, if you have a higher megapixel camera. Don't be fooled into thinking that the 8 megapixel camera on your phone and the 8 megapixel SLR are the same, either. It is all about size. Chip size, in this case. You don't need to chase megapixels (you will never catch up unless you have an unlimited source of which case: can you share?), but you do need to hit that happy medium where quality and price meet. Generally, 8.1 megapixels is equivalent to 35mm, 200 ASA color film. That is a good place to sit for the time being. It isn't very expensive and it provides a good quality.

  9. Jay
    October 26, 2011 at 7:44 am
    2040×1080 = 3MP

    You can view a picture captured by an 8MP camera on your monitor, then you can decide. I found some pics, of the same respution, you can check them .

    you are right about Zooming.
    you will get a clear pic when yo zoom, if the pic is really high quality.

    Read this :

  10. Anonymous
    October 26, 2011 at 7:26 am

    Think of it this way: you say you can't see more than your desktop resolution. Well, even if you still had a 4:3 1280x1024 screen, you'd still benefit from having more MPx. Don't go overboard, though, a soapbox (pocket camera) that boasts 16MPx still won't compare to an older 6Mpx DSLR (the big ones, with interchangeable lenses).

    Theoretically, a 6MPx camera should be enough to have some space to maneuver - because this is what you're basically after: being able to shrink the image to improve quality, or crop it, to improve composition (the arrangement of the subject in the photo). 6Mpx ~ 3000x2000, which is enough to give you a little room to spare.

    The main question, however, is what you want to use the camera for. If all you're looking for is a traveling camera, a pocket camera or a bridge (slightly larger cameras, such as the Nikon L120) is more than enough. If you want to learn photography, you will need bigger and better (and much more expensive) equipment, but all that comes with time. You can learn photography even with a mobile phone camera, provided you read into it, and actually go out and shoot almost every day.

    If you only want facebook photos, you need not worry about MPx.

    When you reply with what you actually want from a camera, we may be able to provide more information. As for what MPx can do for you, please see FIDELIS' link (posted earlier).


  11. Anonymous
    October 26, 2011 at 7:14 am

    sure you will get benefit but there is also quality/noise ratio, this will depend on your camera specification and manufacturer. The pattern noise is caused by pixel non-uniformity, dust specs on optics, interference in optical elements, dark currents...

    An important camera factor affecting the quality of the final image is the image sensor size, bigger sensor gives less noisy ("grainy") image.

    high-medium frequency component of the pattern noise of CCD/CMOS arrays can be used for very reliable camera identification and can even distinguish between camerasof the exact same model.

    October 26, 2011 at 6:05 am

    Hello, I would read what is said on the following link to understand a little bit more about megapixels and what is the best compromise:

  13. Mike
    October 26, 2011 at 2:09 am

    I'm not an expert on photography but as far as I know you cannot directly compare the megapixels of a camera to screen resolution.

    Even if you have a screen at 2560x2048 a 1MP photo should look rather good on-screen because computers use interpolation to fill in the missing information and the screens PPI. But yes, the quality especially in zoom will be better at higher megapixels.

    The megapixels are mostly important for printing. Professional and quality printing is usually done at 300DPI wherein on-screen usually is 96/72DPI (actually PPI, Pixel per Inch).

    For example if you have a 8MP photo with 3192x2512 dimensions it's sufficient information to fill a 72PPI screen of 44" (112cm x 88cm) wherein a 300DPI printout would only be high quality up to 10.6"x8.4" (27cm x 21.3cm, A4/Letter)

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