The meaning of Megapixels in smartphones

[Antonio65]

For the technology experts of TCS

I am a bit confused about the meaning of MP for cameras in smartphones.
I have a reflex digital camera with a 24 MP sensor, which gives me photos of 6000*4000 pixels, up to 12 MB of file size (jpg), and this is exactly what I would expect from a sensor like that.
All the smartphones I had so far would say they have 40 MP, or 80 MP, even 108 MP, like the one I currently have. As for this last one, it was advertised as a very good camera phone, with so many pixels to give back wonderful photos. Nonetheless, the photos I take with those smartphones are small sized, both in file size and in MP. For instance, one of the last photos I took with my phone is 4000*1800 pixels (equals to 7.2 MP), file size 1.9 MB. And the quality, well, quite disappointing, very little details and if I zoom in on the display, the photo gets blurred.
Where have the other 101 MP gone? Can you help me understand?

I also thought the very high number of MP in my phone was for the digital zoom, so that the camera could zoom in 6x and still have a good resolution photo. The reality is that if I take a photo with the zoom at 1x, the photo is rather good, but gets blurred if I zoom in on the display. If I take a photo with the zoom at 2x, the photo is still the same file size, but the details are gone. So, it doesn't seem that those MP are being really used.

I'm attaching the last photo I took this morning, one of my feral cats while she was waiting for her morning meal. One is the original file, the other one is a cropped photo. You can see how bad they are. Those photos are actual size, not resized, to let you appreciate them fully.

 

[tabbytom]

I'm attaching the last photo I took this morning, one of my feral cats while she was waiting for her morning meal. One is the original file, the other one is a cropped photo. You can see how bad they are. Those photos are actual size, not resized, to let you appreciate them fully.

I'm no expert but I'll try to explain.

Cameras and phone that comes with cameras, they need pixels to make up the photo or image. Having said that, pixels need a sensor to capture the image. The bigger the sensor, the better the resolution of the photo and the manufacturer can squeeze in as much pixels as they can onto the sensor.

All cameras comes with sensors of different sizes from size of a postage stamp to the size of your thumbnail. So, the bigger the sensor, the better quality will be the photo if it can store millions of pixels.

As with any sensors, the bigger the better and better for cropping. Let's say you take a 1x1 cm sensor and crop 50% and another 4x4 cm and crop 50%, which do you think will yield a better cropped photo? The smaller the sensor, the more you crop, the more sparse will the pixels be and therefore you get a more pixelated and not clear and not sharp photo provided it was well taken and if it's badly taken, the results will be adverse.

Most compact cameras and phones with cameras comes with digital zoom which is not what you expect as they gives you 10x, 30x 50x zoom as the zoom effect is digitized as compared to this that are optical zoom, which is more expensive but gives a better zoom image as compared to digital zoom.
If you view the photo you've taken either on a camera or phone and preview through the the LCD screen, it looks good till you blow it up. Same as when you view it on your computer.

Looking at you photo, you cropped maybe 50% and you see that the photo starts to degrade.

So the thing here is sensor size and any conversion, you'll loose pixels. Once you loose pixels, you loose image quality.

 

[Miathebsh]

Well the smartphones companies don t focus on the megapixels as the professional cameras are doing . Everything is about the lens, image quality, lights and etc . You will never compete with a phone that is created for multi-tasking with a professional Canon (for example) that is strictly done for photography . If you would look into Iphone cameras(as an example) your front one is having like 12 mp but the quality of the photos is very good for a phone . Also, videos done in cinematic mode will take you a big amount of space depending the quality chosen . Every time you will try to move a photo from phone to a desktop they will lose quality . This happen too when used application that don t support the 4k images done .
i attached a photo done with my phone .(4.4mb size)
I tried different phones and i really sticked with the iphone because the stability of the images, videos, applications running . Indeed, they don t have good quality on the zooms but for me are fine .
some phones are adaptive when you try to crop/zoom an image that meaning the quality of the image will remain the same (even details) but the size will get bigger I tried to attach the same images zoomed but the size is too big (6.6mb)

 

[Antonio65]

Let's say you take a 1x1 cm sensor and crop 50% and another 4x4 cm and crop 50%, which do you think will yield a better cropped photo?

Yes, I know that sensors in phones are very small and not ideal for taking photos, and I do know that cramming millions of pizels on a small sized sensor will lead to low quality photos, because every pixel would have caught very little light and information.

Most compact cameras and phones with cameras comes with digital zoom which is not what you expect as they gives you 10x, 30x 50x zoom as the zoom effect is digitized as compared to this that are optical zoom, which is more expensive but gives a better zoom image as compared to digital zoom.

I also know that digital zoom is nothing more than a crop of a wider image and not a physical/optical zoom. That's why I thought that having so many pixels was a way to still get a very good image even when cropped/zoomed in.

My original question is why I never get a 108 MP photo from a camera with a sensor that format? All my photos are 4000*1800 which is 7.2 MP.
Where are the other 101 million pixels?

 

[Antonio65]

You will never compete with a phone that is created for multi-tasking with a professional Canon (for example) that is strictly done for photography .

I'm aware that I couldn't expect the same quality from my phone like I do from my reflex Canon. But I just don't understand what the 108 MP are there for when all files from my phone are just 7.2 MP.

If you would look into Iphone cameras(as an example) your front one is having like 12 mp but the quality of the photos is very good for a phone . Also, videos done in cinematic mode will take you a big amount of space depending the quality chosen . Every time you will try to move a photo from phone to a desktop they will lose quality . This happen too when used application that don t support the 4k images done .

I know that iPhones give excellent photos, but they are also much more expensive than an Android phone. I always appreciated and envied the quality of the photos that iPhone people get.

 

[tabbytom]

Not sure if these articles helps :-

truth-behind-108mp-smartphone-cameras

how-to-get-full-resolution-images-out-of-your-mobile-camera