1. Are you ready for the Galaxy S20? Here is everything we know so far!

Does S20 really contain 64 MP?

Discussion in 'Android Devices' started by Sudhakar Reddy, Jul 9, 2020.

  1. Sudhakar Reddy

    Thread Starter

    In S20, when u set the camera for 3:4 64 MP, the zoom goes only upto 6X. In other settings using 12/9 MP, it goes all the way upto 30X.
    Now, when you have 64 MP at your disposal, this format should be more amenable for 30X than when only 12 or 9 MP format.
    Further, I find that 64 MP, 6X does not produce any better image than 12MP, 6X. After 6X, the resultant image with 12 MP contains 2MP & with 64 MP, it should contain 64/6 = 10.6 MP & so the latter is expected to show much greater detail without pixelisation. But actually it's not so.
    I really doubt if it contains 64 MP.
    What is your opinion?
     


  2. dontpanicbobby

    dontpanicbobby 100% That Guy
    VIP Member

    The screen is great.
     
  3. Screen looks perfect!!:D
     
  4. Hadron

    Hadron Smoke me a kipper...
    VIP Member

    Do you know when it means optical zoom and when it means digital (i.e. cropping plus interpolation)?

    Rather than try to summarise it, read this page of a review: https://m.gsmarena.com/samsung_galaxy_s20-review-2083p5.php. Basically there is a 64MP sensor on there as well as 2 12MP sensors, but Samsung are less than transparent about how they are used in the different modes.

    Or if you want a more detailed discussion of the cameras, look here:https://www.anandtech.com/show/1560...ynos-snapdragon-review-megalomania-devices/12
     
  5. Sudhakar Reddy

    Thread Starter

    Thanks for the info. Extensive discussion indeed!
    But my question, why in 64 MP setting, zoom is capped at 6X, remains unanswered.
     
  6. Hadron

    Hadron Smoke me a kipper...
    VIP Member

    Well your main question was whether there was a 64MP sensor there ;).

    You'd have to ask Samsung why they made certain decisions, but the first thing to remember is that this isn't a 64MP telephoto camera: it's a 64MP wide-angle camera (almost as wide as the primary) and that the zoom comes from cropping and software interpolation (i.e. digital zooming). The difference is that the 64MP gives you a bit more scope for cropping before you start to rely heavily on software for the zoom (there is no real optical zoom on the S20(+), only on the Ultra).

    So as for what's happening, I don't have one of these cameras so am just working from what I can read plus a bit of educated guesswork. But here goes:

    The first thing to note is that you won't get 2MP from a 6x crop of as 12MP image, nor will you get 10MP from a 6x crop of a 64MP image. When people talk about zoom ratios they refer to the angle of view, i.e. the linear magnification, while 12/64MP refers to the area. So a 6x zoom by cropping a 12MP image would give you a 0.3 MP image (VGA resolution). So digital zoom isn't simply cropping: they crop and then they do a software interpolation to scale that back up to a higher resolution. Try taking a picture, zooming by a factor of 2 then taking another, then look at the properties of the images: you'll find that they both say they have the same number of pixels - that's using software to "scale up" the resolution back to what you set it to. Of course you don't get extra information this way, so the real image quality is always inferior with digital zoom compared to a true optical zoom.

    So my guess is that if you select "12 MP 6x zoom" it will produce a 12MP image using software zooming (about 4000x3000 pixels). Now set it to 64MP and tell it to take a 6x zoom image: what resolution does it say the image has? Does it give you a 64MP zoomed image, a 12MP one, or something inbetween (for small zoom factors)? My guess is that it will rescale to 64MP, to be consistent with what the setting said (you asked for 64MP so the camera gives you it), but I'd be curious to know whether I'm right. If it does something different then it changes what I speculate below.

    Then it gets more speculative: you say that you get 30x zoom in the 12 MP setting. What resolution are the 30x zoomed images? My guess is 12MP. Now an actual 30x digital zoom would be utterly worthless: a 30x linear crop contains 1/900 of the original pixels, so scaling that up to the original resolution is going to look like crap. So my theory is that the "30x zoom 12MP" is actually using the 64MP sensor, just rescaling back to 12MP rather than to 64MP (it will still look like crap, but not as bad as doing it with the 12MP sensor would).

    As I say, I don't have one of these phones to test, so I may be wrong. But my guess is that it will do something like this:

    * When you select 12MP or 64MP you are not so much choosing which sensor you use but what resolution the image is.

    * If you set 12MP mode and start zooming, at some point it will switch from using the 12MP sensor to using the 64MP sensor, but it will always rescale the zoomed image to 12MP. At what point it will switch I don't know (6x would be an obvious guess, given where the 64MP mode ends, but it might happen earlier - it might even happen the moment you start to zoom).

    * If you set 64MP mode it will use a digital zoom up to 6x, rescaling the image to 64MP. Above that it will stop because the image quality loss is too large for it to be worth rescaling up to 64MP, and so if you want a > 6x zoom you have to choose lower resolution (i.e. 12MP, even if that actually uses the 64MP sensor for part of the range).

    But as I say, that's only a guess. It could even be that they just use digital zoom on the 12MP sensor all the way to 30x and the purpose of the 64MP sensor is to give higher quality zoom images, and they cut that at 6x because anything more than that is losing too much quality. But given how outlandish a 30x digital zoom is my guess is that they actually use the 64MP sensor for that then rescale to a lower resolution - at least if you asked me to implement a 30x zoom with that hardware, that is the way I'd do it.
     
  7. Sudhakar Reddy

    Thread Starter

    Thanks for writing such a detailed explanation. Really enlightening.
     
    dontpanicbobby likes this.
  8. Sudhakar Reddy

    Thread Starter


    Hadron,

    "So a 6x zoom by cropping a 12MP image would give you a 0.3 MP image (VGA)"


    May I know how did you arrive at this figure?
     
    #8 Sudhakar Reddy, Jul 29, 2020 at 3:42 AM
    Last edited: Jul 29, 2020 at 3:47 AM
  9. MeganAlsopTXO

    MeganAlsopTXO Lurker

    I think there is written it has 64 MP but actually it does not.
     
  10. Hadron

    Hadron Smoke me a kipper...
    VIP Member

    Zoom refers to the angle of view (linear magnification), so when you zoom by cropping the number of pixels along 1 axis scales (inversely) with the zoom factor. The total number of pixels in the image depends on the area of the cropped image, which scales as the product of the number of pixels along each axis. So if you crop to produce a 6x zoom you reduce the number of pixels in x by a factor of 6, the number in y by a factor of 6, and hence the total number in the image by a factor of 36.

    This is why producing a large zoom factor by cropping will always hurt image quality badly.
     
  11. Sudhakar Reddy

    Thread Starter

    That means even a 4X zoom of a 12MP image, will reduce it to 0.75MP (12/16).

    What happens if I save an image at 12 MP & then crop it to 1/4th? Will the resultant image contain 12/4 = 3 MP?

    Likewise, will a 10X crop of a 64 MP image after saving, produce a 6.4 MP image?

    If it's so, does cropping after saving at higher resolution, produce a better image than zooming while taking the picture?
     
    #11 Sudhakar Reddy, Jul 29, 2020 at 1:48 PM
    Last edited: Jul 29, 2020 at 1:54 PM
  12. Sudhakar Reddy

    Thread Starter

    You are 100% correct. Whatever be the zoom, the resultant image still gives the same number of pixels we set (12/64).

    Secondly, as we increase the zoom, the main 12 MP camera is automatically shifting to 36 MP camera at 3X. However, the resultant image still contains 12 MP.
     
  13. Sudhakar Reddy

    Thread Starter

    After posting the last but one post, I realized that the image size of 4X zoom while taking the picture & 1/16th crop after saving will produce the same picture. However, the pixel count is different. Please ignore the post.
     
  14. dontpanicbobby

    dontpanicbobby 100% That Guy
    VIP Member

    Try some clamp on lenses.
     
  15. Sudhakar Reddy

    Thread Starter

    Any suggestions available in India?
    Will the clamp not damage the front glass over the display?
     

Samsung Galaxy S20 Forum

The Samsung Galaxy S20 release date was March 6th, 2020. Features and Specs include a 6.2" inch screen, 64MP camera, 12GB RAM, Exynos 990 or Snapdragon 865 processor, and 4000mAh battery.

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