I get details can be blurry on a bad lens but how is this like pixel resolution?
CCTV lenses are often 1-5 megapixel lenses. How can a lens have a mega pixel count?
What does it mean for a lens to “resolve” more detail? Is this just about sharpness?
Also when buying DSLR lenses how can you tell what their resolution will be?
>I get details can be blurry on a bad lens but how is this like pixel resolution?
Well, these are two separate things. If you consider the camera system as being a lens in front of a sensor, this is kind of like your eye. The lens in the front of the eye focuses the light onto your retina, which is like the camera’s sensor.
>CCTV lenses are often 1-5 megapixel lenses. How can a lens have a mega pixel count?
It can’t. Lenses do not have megapixel counts. The camera sensor does.
>What does it mean for a lens to “resolve” more detail? Is this just about sharpness?
Yes, it’s about sharpness. Different quality lenses will achieve different levels of sharpness due to their design.
>Also when buying DSLR lenses how can you tell what their resolution will be?
This can actually be measured, if you want to get into the technical details of the lens specs. The simple/practical answer would be to read lens reviews or to watch youtube review videos where they test the lenses.
In photography for example ,there is something we call perceptual megapixels. Let’s say you have camera with 10mp sensor ,if you put some cheap lenses on it you will get for example 4 perceptual megapixels,if you put the best lenses you will get 8-9 perceptual megapixels. The 10 megapixels of detail is what you will get if you had the perfect lenses (which doesn’t exist)
The term you want to look for in the lenses is “circle of confusion”. This is the smallest point of light that the lens can produce. If the size of the pixel in the sensor should ideally match the circle of confusion of the lens.
Having said that, the glass is very durable, whereas the sensors come and go every few years. So when I was buying gear I spent more on good lenses and then getting better sensors as the sensors got better and cheaper. I ended up spending a lot, but only once, on lenses. Then I started with the camera body that I could afford, and got a new body when the old body wouldn’t do what I wanted.
MTF charts for lenses are also worth understanding, and not too much work to get your head around.
This will let you get started with your search and help in making to choices beyond subjective thoughts in review articles.
>Is this just about sharpness?
Imagine a infinitely small point light source, like a star. A lens will focus it to sensor, but not to a infinitely small dot, but more like a blurry round blob like so: [https://en.wikipedia.org/wiki/Airy_disk#/media/File:Airy-pattern.svg](https://en.wikipedia.org/wiki/Airy_disk#/media/File:Airy-pattern.svg)
Now, the question is, how large is a pixel in relation to this blob? If a blob is bigger then a pixel, then limiting factor of resolution is the lens, adding more pixels in the sensor does not get you sharper image.
So the MP rating of a lens is really a recommendation to what sort of sensor it’s built to be used with and an indicator of how sharp and image it can generate.
When sensor resolution started getting better, flaws in lenses started mattering, so a megapixel rating on a lens is basically saying “the lens won’t be the limiting factor for useful resolution up to this megapixel count”… in theory.