Megapixel Question with DSLR lenses

[JFPhotography]

I'm still fairly new to the world of photography and DSLR. I got a Nikon D5300 a few months ago and I love the camera and it's great as I'm learning. I've been reading about lenses lately and read something about how the 18-55 kit lens only shoots around 9 megapixels even though the camera is capable of 24 MP. I have two questions:

1 - Is that actually the case with the lens?

2 - When looking to upgrade my lens at some point, what technical spec should I look for, say on the website for Nikon, Tamron, Sigma, etc...to see how many MP the lenses are capable of?

Thanks. Sorry if it didn't make a ton of sense the way I put it.

 

[zombiesniper]

This is kind of true but not really.

When someone makes a MP description with a lens, it's not that it's a 9mp lens. What they are saying is that the quality of the lens is such that it is reducing the image quality down by a certain percentage. This in turn takes the 24mp camera's detail and degrades it to that of a 9mp camera.

Think of it as the difference between the cleanest glass imaginable compared to wax paper. One will give you near 24mp, the other 1mp.

So to answer the two questions.
1 - yes the kit lenses are not the best quality and don't give you the best performance but if you're just starting out it will do you just fine to learn with.

2 - For the upgrade you'll want to look at a few things such as image sharpness across the frame, vignetting etc. Image quality for some lenses is the top feature while others have a look or feel that is more important.

At this point I would just learn the most you can with what you have. Figure out where you're kit is letting you down. Then you can narrow your selection and have a much smaller selection of things to research.

 

[nerwin]

Welcome to the forum!

Stop looking at silly MTF charts. Your camera will shoot at 24MP regardless of what lens is attached. While it's true lower end glass will have less resolving power than higher end glass, it's really something you don't need to worry about right now. I honestly never cared about it.

At this point in your journey of photography, don't worry about your lens & megapixels. Just get out there and shoot.

That's my best advice.

 

[JFPhotography]

Thanks guys! I really appreciate the information. I'm out and about shooting pretty much everyday. I've just been reading a lot too, perhaps too much, haha. Not close to upgrading my lens yet, just trying to learn about how everything works and I was really wondering if having that kit lens was a major issue. Apparently not!

 

[Alexr25]

I've been reading about lenses lately and read something about how the 18-55 kit lens only shoots around 9 megapixels even though the camera is capable of 24 MP. I have two questions:

Which just goes to show you should not believe everything you read, especially if its on some dubious web site. First off lenses are never specified in megapixels the term is meaningless when applied to lenses. Lens resolution is normally specified in line pairs per mm but resolution is only one factor in the overall performance of a lens, other factors such as distortion, various aberrations, and vignetting also affect performance

1 - Is that actually the case with the lens?

The Nikon 18-55mm kit lens may be cheap and plasicky but optically it is quite a good lens and has more than enough resolution for the D5300 24Mp sensor.

2 - When looking to upgrade my lens at some point, what technical spec should I look for, say on the website for Nikon, Tamron, Sigma, etc...to see how many MP the lenses are capable of?

By the time you come to upgrade hopefully you will know a lot more about lens performance and specifications so you won't be looking for lens MP capabilities, cos you ain't gonna find em.

 

[JFPhotography]

I've been reading about lenses lately and read something about how the 18-55 kit lens only shoots around 9 megapixels even though the camera is capable of 24 MP. I have two questions:

Which just goes to show you should not believe everything you read, especially if its on some dubious web site. First off lenses are never specified in megapixels the term is meaningless when applied to lenses. Lens resolution is normally specified in line pairs per mm but resolution is only one factor in the overall performance of a lens, other factors such as distortion, various aberrations, and vignetting also affect performance

1 - Is that actually the case with the lens?

The Nikon 18-55mm kit lens may be cheap and plasicky but optically it is quite a good lens and has more than enough resolution for the D5300 24Mp sensor.

2 - When looking to upgrade my lens at some point, what technical spec should I look for, say on the website for Nikon, Tamron, Sigma, etc...to see how many MP the lenses are capable of?

By the time you come to upgrade hopefully you will know a lot more about lens performance and specifications so you won't be looking for lens MP capabilities, cos you ain't gonna find em.

That makes sense, Alex. Thank you!

 

[astroNikon]

The information you are reading is probably gleaned from the Dxo website.
Nikon AF-S DX Nikkor 18-55mm f/3.5-5.6G VR mounted on Nikon D5300 : Tests and Reviews | DxOMark

For example, that 18-55 lens mounted on a D500 yields
Sharpness 8 P-Mpix
Transmission 5.1 TStop
Distortion 0.3 %
Vignetting -0.7 EV
Chr. aberration 9 µm

where as mounted on a D5300 yields
Sharpness 9 P-Mpix
Transmission 5 TStop
Distortion 0.3 %
Vignetting -0.7 EV
Chr. aberration 9 µm

so essentially the same. though the higher MP of the D5300 (24 vs 20) yields a higher sharpness rating.

Compared to a much more expensive lens
a $1,600 58mm/1.4 has 15mp resolution on a d5300 ==> Nikon AF-S Nikkor 58mm f/1.4G mounted on Nikon D5300 : Tests and Reviews | DxOMark

or 25mp resolution of the 58/1.4 on a d810 ==> Nikon AF-S Nikkor 58mm f/1.4G mounted on Nikon D810 : Tests and Reviews | DxOMark

some camera bodies also force the owner to upgrade the lens. The D8x0 comes to mind with a 36mp lens. Some older lens don't resolve well on newer bodies. My old Nikon 75-300 AF lens was fine on a 16mp D7000, but was mush on a 24mp D600, which ironically has larger pixels per density.

To a more extreme comparison, the 55-200 @200 compared to a 200mm prime
What you are basically asking is why does a top of the line prime 200mm lens cost $6,000 versus the 55-200 at $150.
That 55-200 @200 has a resolution of 9mp
Nikon AF-S DX VR Zoom-Nikkor 55-200mm f/4-5.6G IF-ED mounted on Nikon D5300 : Tests and Reviews | DxOMark

That 200/2mm has a 28mp resolution on a d800 ==> Nikkor AF-S Nikkor 200mm f/2G ED VR II lens performance | DxOMark

it's all not Apples to Apples though. When you buy a lower end consumer camera you get price points, and at those price points it includes lenses to fit those price points. At the upper end there really is no price point, it's about quality.

But as others have said, I wouldn't worry about it.
Work on lighting, composition, etc

And when you really do want to move up in lenses, just remember that $$$ you kinda get what you pay for if you really want the best.

 

[fmw]

1 - Is that actually the case with the lens?

No the pixel resolution is in the sensor not the lens.

2 - When looking to upgrade my lens at some point, what technical spec should I look for, say on the website for Nikon, Tamron, Sigma, etc...to see how many MP the lenses are capable of?

Assuming we are talking about plastic zoom lenses the important specs are the zoom range and the maximum aperture. For best performance you want the smallest zoom range that will work for you and you want the fastest lens you can afford because the manufacturers put their best technology in the faster lenses. All lenses that are compatible with your camera will use whatever pixel resolution your camera sensor has - 24 mpx in your case. All the brands you listed are competent.

 

[Derrel]

What you are seeing is basic science: a crap lens resolves wayyyyyyyyyyyyyy less information than a superb lens. It's simple: take a 24-million-pixel sensor, and test it with the $149 Nikon 55-200 kit zoom lens, and you might find that the lens is NOT GOOD ENOUGH to deliver all the resolution/information/fine detail/contrast/resistance to flare/resistance to CA that the 24-MP sensor could theoretically provide. THEN, take the same 24-million-pixel sensor, and put a top-class prime lens on the camera, something like,say, the Nikon 200mm f/2 AF-S VR-G. You will ____immediately_______ and literally "SEE" the difference. One lens will be "okay"....the other will be STELLAR. One will have good information in the image file: the $6,000 lens will be overflowing with fine,fine details, strong contrast, superb microcontrast, and will be virtually perfect.

Let's put it this way: a top-class lens like the 200/2 will make even older cameras, like the 6-MP Nikon D70 look good; it will make the 12-MP Nikon D2x look excellent: it makes the 24-MP Nikon D3x look extraordinary; it makes the 36-MP Nikon D800 series look simply astonishing. I owned the first version of this for over a decade. It was a stellar, albeit huge and heavy lens. I also shot the doggy 55-200 Nikon kit zoom as well....Ughhh.

One of the biggest issues with digital sensors is that "simple", non-aspherical wide-angle lens designs do NOT perform very well, due to the steep angle the light rays hit the sensor at, and also, because W-A lens designs for mirrored cameras are VERY complicated and costly to make. The wide-angle end and the zoom range of a lens like the $99 18-55 is brought down by the weaker focal lengths tested...this is a weakness that zooms will always show: the weaker-performing regions of focal length and f/stops will bring the lens's overall average down (hence why DxO Mark show the "best at" results).

What DxO Mark has mathematically described has been known about since digital sensors came onto the scene: that "some" lenses perform very,very poorly on some sensors. And that there are varying degrees, from bad to superb, of lens/sensor compatibility and performance. One of the worst areas for lens performance is found in cheap $99 to $149 lenses with wide focal length ranges (like the 18-55mm, and most-especially, in wide-angle focal lengths, wide-range zooms.

Normal length, tele, and super-tele prime lenses perform the best, and can "translate" (which is what a lens does!) all the imformation in a scene into light rays that hit the sensor at a fairly straight-on angle of incidence, across a fairly narrow angle of view, and can do so with high resolving power, good contrast, and good levels of micro-contrast.

 

[Ido]

You probably saw this on DxOMark, or read/heard someone quoting from that website. They do fantastic work with their testing, but the scores are, I think, way too simplistic and can cause confusion.

When you shoot with a Nikon D5300, and choose either the full-size JPEG or RAW (NEF), you get a 24MP image. All this means is the image is made up of 24 million pixels — if it's exactly 24MP, that should be an image that measures 6,000 pixels by 4,000 pixels. The lens you use cannot change that.

Some lenses can produce a sharper image than others. The same lens can produce varying degrees of sharpness when you change the focal length or the aperture. DxO tests that; you can see different representations of that if you switch to the "MEASUREMENTS" tab, then to "Sharpness," and then one of the tabs below. I find it's only useful to look at those measurements in comparison to something you're familiar with. The numbers themselves don't tell me much, but if I add a camera-and-lens combination I'm familiar with to the graph, I know if it's sharper, and can better estimate what the difference is.

DxO explains how the scores are calculated on this page. About the sharpness/P-Mpix score:

"For each focal length and each f-number, we first compute sharpness and then weight it throughout the field, tolerating less sharpness in the corners than in the center. This gives one number for each focal and aperture combination.
"Then, for each focal length, we select the maximal value of sharpness over the range of available apertures. We average this value over the whole range of focal length to obtain the DxOMark resolution score that we report (in P-MPix)."​

What I've found, though, is that I get a lot more information about a lens from viewing sample images.

 

[greybeard]

I kind of went through this a few years ago. My D7000 came with a plastic mount 18-105 and I was just certain that the much more expensive 16-85 3.5-5.6 would be much better, it wasn't. I also had access to an 18-55, and believe it or not, I couldn't see any IQ difference between it and the other 2 lenses. So what was the big difference, build quality. The 16-85 has a metal mount, rubber dust gasket, metal parts, and has a much more solid feel than the rattley plastic 18-55 and 18-105.

 

[JFPhotography]

Thank you everyone for all the great information! You've cleared things up greatly for me.