What does a lens being labeled “2 megapixel” or “3 megapixel” actually mean?
Asked 1/21/2016
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I understand megapixels on a camera sensor, where they refer to the number of photosites/pixels. But I also see some small CCTV or C-mount lenses advertised as “2 megapixel” or “3 megapixel” lenses. Since a lens doesn’t contain pixels, what is that label supposed to mean? Is it a real technical specification, a rough indicator of lens resolving power, or just marketing?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
2 Answers
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Both Samsung and Edmund Optics use the name "Megapixel" or "MegaPixel" to describe lenses they sell for C-mount and CS-mount cameras, but in both cases the term is used like a brand name rather than a description of any technical aspect of the lens.
There's also a perceptual megapixel concept developed by DxOMark to describe lens sharpness in a way that's supposed to be more accessible than traditional MTF charts. As far as I can tell, this "P-MPix" rating hasn't really caught on yet even though it was introduced a few years ago.
The example you cited is a very small, very cheap (under $6!) lens meant for a closed-circuit TV camera. It's hard to tell exactly what the "3 mega pixel" descriptor really means, and in fact it may not mean much of anything. It may mean that the lens is sharp enough to work with 3MP sensors, or that it's sufficiently unsharp enough that you shouldn't use it with anything better than a 3MP sensor.
Originally by user4262. Source · Licensed CC BY-SA 4.0
user4262
10y ago
0
Generated from our catalog & community — verify before relying on it.
A lens does not literally have megapixels—only the image sensor does. A lens is continuous optical material, not a grid of pixels.
When a lens is labeled “2MP” or “3MP,” it usually means one of three things:
- Marketing/branding: sometimes “Megapixel” is just a product name.
- A rough resolution claim: the maker may be implying the lens is sharp enough for use with a sensor of about that resolution.
- Vague spec language on cheap CCTV lenses: in low-cost listings, it may not be a precise or standardized technical measurement.
In reality, lens sharpness is better described by optical performance measures such as resolving power or MTF, not megapixels. A lens can blur fine detail because of optical imperfections and diffraction, but it does not have a fixed pixel count of its own.
So for lenses—especially inexpensive security-camera lenses—“megapixel” is best treated as an approximate compatibility/quality claim rather than a strict specification directly comparable to sensor megapixels.
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