Is RED One Really a 4K Camera?
Sunday, September 16, 2007 at 4:08PM Anyone interested in the RED One camera should read this comparative review/diary of the Sigma SD14 and the Canon 5D (the latter of which I am a delighted owner).
Both are SLRs, both are a few years old. But the 5D has a 12.7 megapixel, full-frame chip, where the Sigma produces a mere 4.6 megapixels. Why bother even comparing them?
The reason is that the Sigma has a Foveon sensor rather than a CCD or CMOS. This sensor can capture distinct R, G and B light information at every pixel. The 5D's CMOS chip can record luminance at every pixel, and uses the common Bayer pattern of color filters at the photosites to capture RGB color, intermingling color fidelity and spatial resolution in a way that must be decoded by software using some math, some compromises, and some guesswork.
One way of looking at this is that the 5D spends three of its 12.7 million pixels to accomplish what the Sigma achieves in only one. If the 5D records 12.7 million tiny little light records per image, then the Sigma records 13.8 million (4.6 x the unique R, G and B records per pixel).
But that's not entirely fair. Our eyes tend to perceive detail more in luminance than in color, and the 5D is recording much more luminance information that the Sigma. For black and white photography, the 5D truly is a 12.7 megapixel camera and the SD14 truly is a 4.6 megapixel shooter.
So the truth lies somewhere in between—the SD14 is neither the 5D's equal in resolution nor is it possessed of one third the pixel count.
In one very real way the RED One is a 4K camera. It creates 4K images that look damn good.
And in another equally real way, the RED One is not a "true" 4K camera, as each of the 4K's worth of pixels it creates for each frame is interpolated (from compressed Bayer data at that).
And that's probably just fine—a topic for another day.
Reader Comments (9)
first off, a friend of mine has the 5D and it is indeed an awesome camera.
as far as the RED goes and any other "digital" or "4K" camera there has to be a break even point between price, performance, and image. we as humans can only perceive so much.
its the same in the audio world where people argue over 192 vs 44.1 and all that jazz. there can only be so much data captured and re-interpolated before it becomes a total waste of money/resources/workflow.
j
Hi Stu,
In my opinion, the only things that a pixel count is a good metric of is storage requirements. Beyond that, if resolution is actually a factor in the decision-making process, there are a number of other factors that play critical roles in effecting resolution, sharpness and MTF, including the presence and properties of a low-pass filter in front of the lens, the lens itself, the aperture (f-stop) used, any filtration, etc.
Personally I would consider the Red a legitimate 4K camera even if the limiting resolution or MTF are less than is achievable in a 4K film scan. The fact of the matter is that you (can) end up with 4K worth of data generated by 4K worth of photosites. Now whether or not that is actually superior for a given application to a lower-resolution solution made with co-located photosites is another question that must be determined by testing using criteria determined by the requirements of a specific job.
Nicely put Jesse!
The issue with the Sigma, and why it's images are sharp is actually more to do with it producing heavily aliased images, rather than it's Foveon sensor. Resolution comparisons are only meaningful if you can avoid aliasing artifacts.
True, film probably still has (a bit) more resolution than 4K. But it's as probably de facto degraded due to the inevitable grain structure. What delights me so much about the RED is how clean, clean, clean the images are. It's truly an amazing sight.
(And if you can't live without your grain, just hang in there. Someone will eventually get http://grubbasoftware.com/index.html" REL="nofollow">this kind of plugin movin' in Color. Graeme?)
As for resolution, somebody passed on to me that some very well informed folks pegged typical 4 perf 35mm film as good for about 3.2K of true, optical resolution. What does Red generate in terms of optical resolution? I don't have a definitive answer on that yet.
4k or not you guys may want to check this stuff out.
Here's to awesome DPs.
http://www.reduser.net/forum/showthread.php?t=4910
There is a simpler way to measure true resolution on a bayer sensor. LPH or LPIH, which stands for lines per image height. DPreview.com has reviews that provide that measurement on most high end digital cameras. This is a true, final measure of luminance resolution. Having looked at the numbers I have found that the black and white resolutions of a bayer sensor is no where near its cited resolution. I love my bayer camera, I just think of it as a 1.5 mega pixal camera, not a 6 mega pixel camera.
Ryan, your calculations are somewhat off, and you're missing the point that most cameras use optical low pass filtering to stop aliasing entering the sampled system. Aliasing has a number of problems in moving images that you don't need to worry about so much in stills, not least that aliasing is more visible on movement, and it can confuse compression schemes and reduce image quality.