Saturday, October 10, 2015

Megapixel lens ratings - 2MP = 1080 HD

Just went through a little learning curve and I want to document it for future reference. For the first time I ran across something called the megapixel rating for lenses. I didn't really know exactly what a megapixel is, but I do know that my G1 has 12 of them and the GH2 has 16. So just now I was on the verge of buying what looked like a really decent 6.5mm wide angle when I notice it's rated for only 2 MP. Wait, what? Seriously!!?? I mean, isn't that like - totally 10 years ago or something? Who has a 2 MP camera?

A little digging turns up that while many cameras have high MP ratings for still photos, 1080p HD is only just about 2 MP. Ok, actually it's 2.07, but apparently a 2MP lens is good enough for shooting HD video at full 1080p. Though I wonder if a hacked GH2 might be trying to capture more detail than a 2MP lens can resolve? Would using it basically negate the hack? Like putting a low flow shower head on a high pressure hose?

Possibly, to some extent. I don't know tech stuff (love that line from the Terminator - use it every chance I get). But then I have some 1/2" format CCTV lenses that resolve only a small image circle in the center of the G1's sensor, and need to be severely cropped, which reduces the resolution to probably around 1MP. I'm not a pixel peeper or a perfection junkie, I believe as long as it works then it's fine. Hell, I love a lot of old films shot on 16mm film handheld with bad exposure and all that stuff - it can give a film a visceral punch in the gut kind of feel as opposed to a careful, overproduced and over intellectualized feel. Screw it, I'm gonna get it.

No good for stopmotion - the really wide lenses capture stuff that's all around you and almost behind you - you'd need a wraparound set including a sky or ceiling and to have the camera jammed way back into it so you don't end up seeing the basement walls over the edges, and a set like that would make it hard to reach in and animate, unless of course you're building a massive set that the animator can walk around on like a Laika production. But anyway, it would be good for some live action video stuff.

"In a megapixel (MP) camera such as the GoPro Hero line, the focal plane spot size of the lens should be comparable or smaller than the pixel size on the sensor. So if you are capturing high MP media you should use a lens that will resolve the pixels for the resolution you are capturing. MegaPixel ratings of a lens relates directly to the image sharpness, the ability to resolve pixels at a particular resolution. Using a lower MP lens than the MP rating of the mode you're shooting in will still work, though the media may be a little fuzzy (less sharp).

For GoPro Hero 4 & 3 video modes, here are the pixel measurements:

4K = 3840x2160 pixels 8.3MP (16:9)
4K Cin = 4096x2160 pixels 8.9MP (17:9)
2.7K = 2716x1524 pixels 4.1MP (16:9)
2.7K Cin = 2716x1440 pixels 3.9MP (17:9)
1440p = 1920x1440 pixels 2.8MP (4:3)
1080p = 1920x1080 pixels 2.1MP (16:9)
960p = 1280x960 pixels 1.2MP (4:3)
720p = 1280x720 pixels 0.9MP (16:9)
WVGA = 848x480 pixels 0.4MP (16:9)

For GoPro Hero 4 & 3 photo modes, here are the pixel measurements:

12MP Wide: 4000x3000 pixels
11MP Wide: 3840x2880 pixels (11.1MP)
8MP Medium: 3200x2400 pixels (7.7MP)
7MP Wide: 3000x2250 pixels (6.8MP)
7MP Medium: 3000x2250 pixels (6.8MP)
5MP Wide: 2592x1944 pixels
5MP Medium: 2592x1944 pixels

To figure out the MP of a photo or video resolution, you would multiply the pixels by each other. For instance, shooting a video in 1080p means you'll use 2,073,600 effective pixels (1920 x 1080 = 2,073,600). That 2,073,600 pixels is 2.07MP, or "mega pixel". So that means that if you plan to mostly shoot in 1080p (like we do) you'll simply need a 2MP or higher lens. The higher the MP rating of a lens the sharper the captured media will be, assuming you're capturing at a high MP that you'll be able to notice any difference. Using a 12MP lens (such as the stock one) to capture 1080p (2MP) content is theoretically not that much better than using a 2MP lens. There are other factors which affect image quality, such as the diameter of the outer glass element, anti-reflective coatings and of course the quality of the optics used (i.e. glass vs plastic)."

1 comment:

Shelley Noble said...

"...can give a film a visceral punch in the gut..." Amen. Yaaaas to "... as long as it works then it's fine."