What is the deal with megapixels?

Shawnster

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Hi every one I have a weird question, why does my 6 megapixel $60 digital rebel take better photos than my 18 mp rebel t3i and my 24 mp nikon D3200? I know megapixels isn't everything, but this seems very odd to me? The photos are just clearer with less artifacts in them. I have not compared prints, but they definitely look better on the computer monitor.
 

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When you look at the photos at 100% view your 6mp image is much smaller than your 18mp image. Look at the size and you'll see taht the 18 is something like 5000+ pixels on the longest side, whilst the 6mp is going to be under 2500. So when you set it to 100% view and thus each pixel takes up the same amount of space you've blown the 18mp image up to more than double the size of the 6mp. So it will show more artifacts and appear softer.

It's not actually the case, if you resize, edit and print or display online the 18mp will be as good if not better than the 6mp. Myself I find that with my Canon 7D I view at 60% more than at 100% (100% is for sharpening and noise removal stages) because its more akin to the view my 400D gave me. You might find that 60% or 50% is a more comfortable viewing size for reviewing your photos on your larger mp cameras.
 

Solarflare

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Thats exactly what the deal is with Megapixels: the more pixels you have, the less quality the single pixel will have. Thats simply because:

(a) the optics used arent perfect and the more Megapixel you have, the more you will see their shortcomings (Also effects like diffraction. Compact cameras are often already at the diffraction limit simply because the sensor and thus also the pixels are so small).

(b) the individual pixel is smaller, thus will have a worse signal to noise ratio, i.e. the image quality will be lower.
 

KmH

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As MP increases, so do the demands on lens quality.
At some point image sensor resolution surpasses lens resolution. By using lenses having insufficient resolution to utilize image sensor resolution image quality is compromised.

Image quality is affected by a variety of technical factors, image sensor mega pixels being just one of them.

Other factors are: image file type (Raw, TIFF, JPEG), image file compression (if any), how aggressive an image sensor's anti-aliasing filter is (if it has an AA filter), the camera image processor CPU and image processing settings, the exposure settings (shutter speed, lens aperture, ISO) used, and the quality of the device an image is displayed on (if electronic).

Photographer skill and knowledge have a major influence on image quality.

Digital Camera Sensor Sizes: How it Influences Your Photography
Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks
Camera Lens Quality: MTF, Resolution & Contrast
Bit Depth
 
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GWAC

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Thats exactly what the deal is with Megapixels: the more pixels you have, the less quality the single pixel will have. Thats simply because:

(a) the optics used arent perfect and the more Megapixel you have, the more you will see their shortcomings (Also effects like diffraction. Compact cameras are often already at the diffraction limit simply because the sensor and thus also the pixels are so small).

(b) the individual pixel is smaller, thus will have a worse signal to noise ratio, i.e. the image quality will be lower.


I feel as if there is a ton of important information left out in this. Such as the fact that the signal to noise ratio is going to depend on the amount of available light to expose the image, and the stress the sensor has to undergo to expose that image.

I agree with KmH. Higher resolution demands a higher quality lens. I do not believe that, in all cases, the smaller pixel produces a lower quality image. I would certainly put the 100% crops of my D800 and 70-200 2.8up against the 100% crops of your D600 and 70-200 4 any day. I just wouldn't do it in low light situations. Studio or outdoor with plenty of light, though, and I'll take that bet any single day of the week.
 

Monday

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As others have pointed out higher mp requires better glass. A recent friend asked me the same question. Turns out he upgraded bodies but kept his old cheap kit lense (his only lense) to swap between the two. I let him borrow some nicer glass and he came back preaching!

Lots of other factors also as mentioned above.
 
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Shawnster

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Thanks everyone! I guess that must be it, I cannot afford any L series lenses so I'm using kit lenses a 40mm STM lens a long with a few m42 takumars and a T mount zoom lens. None of which do the 18 megapixel sensor justice. But still I am impressed with the quality of 6.3 mp digital rebel I hope the prints look as good as the photos on the computer screen do!
 

dennybeall

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One small point is that pixels can help make up for not having a longer lens handy. If I take a long shot with 6 mp and a long shot with 24mp I can use the center of the 24mp shot since it still encompasses a lot of pixels while the 6mp center only has a small amount of pixels in the same area. In effect digital zoom. Not ideal but can help at times.
And start a lot of conversation I guess.....
 

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