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I have a 5MP camera in my phone. The pictures shows good clarity both in the phone screen and my computer screen. But one of my friends has a different camera with the same 5MP in his phone (brand is different and a new one). But the photos taken with that camera are not as good quality when viewed in computer screen. We didn't use digital zoom (since we heard digital zoom reduce the quality).

Why is one 5MP camera so much better than the other? I think not only the megapixel values but also camera lens needs to be considered while buying a camera... right?

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3  
This isn't quite a duplicate of Do megapixels matter with modern sensor technology? but learning that should help you understand this better. –  mattdm Jul 31 at 13:14
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Also worth considering, are you viewing the photos zoomed out to for example fill the screen, or are you viewing them at 100% crop? Hardly anybody views photos at 100% on a computer screen, unless perhaps they are into truly detailed digital retouching work. –  Michael Kjörling Aug 1 at 22:12

5 Answers 5

up vote 23 down vote accepted

You're right. Picture quality is as complex as, say, how well a food item tastes. Megapixels only tell you the number of pixels the picture is made up of, and more is certainly not always better. More pixels on a small sensor means more noise. Megapixels are often used by marketing just because people want simple truths, like 18 MP must be better than 10. However, that's like comparing two cups of coffee based on the quantity in the cup - and saying the one with more in the cup must be better. But, how does it actually taste?

So, like the coffee, what those pixels contain is the critical part. Of course, it needs to be said, what is meant by quality is also subjective. Instagram filters for example often simulate old camera defects, like vignetting, noise and color shift, still they often come across as great looking photos, right?

http://nenuno.co.uk/creative/design/inspiration/10-vignette-photos-for-inspiration/

Underexposed photo with dark corners, i e vignetting. Originally a lens imperfection, it's often used creatively because it helps frame the picture.

Anyhow, subjectivity out of the way. Main factors for pure image quality are:

  • Sensor quality (low noise, high dynamic range, and so on - all of which get better with a large sensor)
  • Lens quality (sharpness, lack of chromatic abberation, quality of bokeh etc)
  • Camera firmware, i e ability to use RAW format, or create JPEG files with good quality.

Also, it's important to understand that lighting plays a HUGE role in how the photo turns out, so if your friend shoots indoors and you outdoors for example, yours are likely going to look infinitely more high quality. Cameras wanna bathe in light! Here's a guy even doing a fashion shoot with his 3 Megapixel iPhone 3GS, and it looks absolutely stunning thanks to high quality lighting, and the camera being just good enough to capture it. https://fstoppers.com/editorial/iphone-fashion-shoot-lee-morris-6173

There's definitely a lower threshold for being able to capture that, and I'd say an old Nokia phone from the late-mid 2000's would still show pretty low quality even in great lighting, it's just really a bad camera.

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To put this into perspective, 2MP = 2 Mega Pixel = 2 million pixels = 1920*1080 = Full HD. I'm not a photographer (nor do I know a thing about photography), but as a programmer I know Full HD is more then enough to create a sharp image with lots of detail (might be different for a photo, but still 5MP should be the highest you will ever need for non-billboard photos). –  Kevin Aug 1 at 8:48
    
@Kevin Well, you're partly right. Most images we're used to seeing on the web though, are scaled down from 3-24 MP photos. A photo viewed 100% zoom level doesn't look that great generally, but scaled down they do, so you "need" a higher MP count. And for print there's the 300DPI thing, which puts much higher demand on resolution. There are many reasons for having a higher MP count than 5, but I guess that's a whole other discussion. –  Jan 'Saffi' Stekelgunsson Aug 1 at 10:37
    
@Jan'Saffi'Stekelgunsson "all of which get better with a large sensor" but sensors don't (always) get larger with higher megapixel count. –  Calimo Aug 1 at 13:40
    
@Calimo - Yes, you are correct. And it's been discussed to death. Eg. here: photo.stackexchange.com/q/14773/15918 –  MarcinWolny Aug 1 at 15:22
    
More pixels also allow you to shoot wide and then crop later, which is very valuable as you don't always have the luxury of perfectly framing your shot before opening the shutter. –  Charles Wood Aug 1 at 17:21

GEEKY ANSWER - you have been warned.

There's much more to the image quality than just lens and megapixels.

The most important factor in any photograph is:

  • Light

You can have the best camera and lens in the universe - and that will still be meaningless if you have no light, or very badly lit subject.

After that comes... lens. Lens is what bends the light, what allows you to grab more - or less of it. Your sensor can capture only as much details and light as your lens will let through.

Then you have camera... but there's much more to the sensor than just resolution - sensor dynamic range, color reproduction, noise, and much much more along with how these characteristics change depending on a sensitivity very much determine image quality. Smartphones are very difficult to judge in terms of image quality, but general rule is relatively simple: bigger sensor is better. Bigger sensor behind brighter lens is much better ;).

And finally, a factor to combine them all, and the once deciding if you're photograph will be poor or brilliant:

  • Skill

Even if you have the best gear in a world, and best lighting one could imagine - you will still make poor photos or none at all if you don't know how to approach subject. Cameras these days offer automatic modes, some are even limited to the automatic modes alone, but you are still the one holding and pointing the camera, choosing perspective, affecting environment around - you can try getting more light in, or dim it down, you are the one in control and ultimately deciding on the outcome.

Less-geeky-answer:

If you want good photos without being bothered much - buy yourself a large-sensor compact (eg. Sony RX100 - you can grab one relatively cheaply off eBay) - they tend to be small enough to fit in a jeans pocket and offer very high quality comparing to any smartphone. If you really need something that you can have with you all the time - buy one of the photo-oriented smartphones, you can find good image quality rankings and reviews of a smartphones on a following websites:

Don't look at the number of megapixels - look how it scores in image quality ratings. Oh, and in general - get more light. ;) Sometimes it's simply so dark that you can't take a good photos with the gear you own - just move on, don't get frustrated by this, simply: learn to shoot when the light is great - and then you can try approaching more difficult subjects :).

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Much will also depend on the accuracy of the focus mechanism and the photographer's ability to hold the camera perfectly still when lighting is challenging to avoid camera shake. –  chili555 Jul 31 at 13:12
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@MarcinWolny: Sorry for the trouble I made. I didn't mean a new smartphone with good camera.. I was looking for a good camera(only camera). I mentioned that smartphone camera for an example, which made me think like MP is just a criteria. –  Nemo Jul 31 at 13:57
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@Nemo - that's why I also suggested RX100 and other large-sensor compacts. These will give you great image quality (comparable with some DSLRs) in portable body. Great to grasp some basics. You could throw yourself right into some more serious business and play with interchangeable lenses - there are obviously DSLRs out there to meet your needs along with tons of publications describing them from any possible angle. But if you're confusing megapixels with image quality - I'd advise good compact first, and things like RX-series, X100 or Coolpix A can really deliver brilliant images. –  MarcinWolny Aug 1 at 15:19

Short(er) non-techy answer, to follow up the other two excellent (but long) replies.

Your camera is as good as the weakest component.

Lets start with a $50,000 Hasselblad H5D-60 as an example. 50Mp sensor, the lens costs more than my motorbike. You won't get better quality outside a research lab.

  • take off the lens and replace it with a plastic one from a 1978 Instamatic. You will now have an ultra-high resolution soft-focus photo with the chromatic abberation (rainbowing) rendered in exquisite detail.

  • Swap the sensor with a 640x480 consumer-grade VGA sensor from a 1998 web camera. The noise, pixellation and wrong colours aren't the fault of the lens. Don't let the Hasselblad team find out or they'll probably hurt you.

  • The camera and the Sports Illustrated calendar crew are sent to a warehouse on a rainy day, along with Kate Upton, Emily Ratajkowski and Jordan Carver. The only lighting they get are three LED flashlights from 7-11, different brands. SI will try to explain the results as being printed on a 30-year-old dot-matrix printer - the "Retro 80's Issue".

  • My sister gets an afternoon in SI's photo studio with her dog as the subject (the girls from the warehouse went into hiding after seeing the proofs). Can't tell if it's the pooch or the rug. Gets worse after she drops the camera a few times.

And in case you are unfamiliar with digital "zoom", it works by simply expanding the middle part of the image. You get exactly the same results by cropping the image, then resizing it to the original size. I've seen "200x digital zoom" video cameras - the resulting image was about 130 pixels resolution, each pixel clearly countable.

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Great post, though I think you under-estimate what a good photographer could do with a warehouse and 3 mismatched LED flashlights. –  AJ Henderson Aug 1 at 14:13
    
Make it brighter? You don't need a photographer if the only thing you have is a warehouse and some LEDs. :P –  MarcinWolny Aug 1 at 15:24
    
@AJHenderson I think a good photographer could do a lot, but an "Alien Autopsy" theme won't go over well with the girls. –  paul Aug 2 at 0:49

Quality and Clarity are, unfortunately, subjective. Why two different cameras of the same megapixel value would have different output could be up to any of the following: * Sensor manufacturer * Software handling of the image * Lens * f-stop, shutter speed or ISO selected by the software.

And if you are talking about cameras with interchangeable lenses, you also need to consider diffraction limited aperture. This is a calculation of where the aperture setting begins to negatively affect the sensor. There is a great article at CambridgeInColor about this.

If you want a real 1-to-1 test, make sure the pictures you are both taking have the exact same values for shutter speed, f-stop, and ISO, and make sure you turn off all filters and software "enhancements". Only then can you get a real comparison. I suggest this because we never know how a different sensor will read a scene and apply software to make it work.

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You must consider the ISO you are using to take pictures.

  1. higher iso reduce definition
  2. lower iso improves definition
  3. higher iso needs less time of exposure
  4. lower iso needs more time of exposure
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Thank you so much for your help.. :) –  Nemo Jul 31 at 15:13
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Do you want to expand your answer beyond just ISO? You should also give explanations of why ISO has the effect it does. –  Andy Blankertz Jul 31 at 15:35
    
en.wikipedia.org/wiki/Iso –  Wavy Crab Aug 1 at 0:11
    

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