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Thursday, February 21, 2013
Nikon DSLR Abandons OLPF
Nikon follows Fujifilm steps and abandoning optical low-pass filter in its new 24.1MP DX-format DSLR D7100. Nikon's PR says: "The innovative sensor design delivers the ultimate in image quality by defying convention; because of the high resolution and advanced technologies, the optical low pass filter (OLPF) is no longer used. Using NIKKOR lenses, the resulting images explode with more clarity and detail to take full advantage of the 24.1-megapixel resolution achieved with D7100’s DX-format CMOS sensor." No further details of these "advanced technologies" are given so far.
I think that means the pixels are so much smaller than the best-case lens spot size that a OLPF isn't required.
ReplyDeleteThe pixel size should be about 3.9-4um, not that small (24MP in a DSLR with 1.5 crop factor).
DeleteNikon's D800E has removed the OLPF since last spring.
ReplyDeleteD800 was manufactured in two versions. The no OLPF version was presented as an option for those who prefer sharpness over moire. The D7100 uses no OLPF in the mainstream version, and says this is possible due to some "advanced technology".
DeleteThe pixel pitch is the same as the D800E. Moire is there if you look for it but under fairly limited circumstances. Nikon is probably betting that the average consumer will not recognize it when it is there. And just to clarify, if they did the same thing as the D800E they did not remove the filter bit rather canceled it out with a second birefringent plate.
ReplyDeleteAny info yet on who makes this sensor? Many have jumped to assume that it's the same Toshiba sensor from the D5200, but it seems at the official launch Nikon said this was a newly developed sensor:
ReplyDeletehttp://www.youtube.com/watch?feature=player_detailpage&v=m_RqsrIPCLo#t=24s
Which they'd probably say anyway if it was the same sensor from the D5200 but without the OPLF...
Fujifilm removed the OLPF but thanks to the excellent X-tran pattern doesn't have much issue with Moire. At least color moire is reduced by the low spatial resolution in color.
ReplyDeleteFor Nikon D800E, it's a different topic because even if it's a Bayer, the resolution is 50% higher(36MP), so color Moire is less visible when output image viewed at lower scale to fit a "low" monitor resolution.
With resolution increasing, removing the OLPF should be the trend.
"At least color moire is reduced by the low spatial resolution in color" in Fuji Xtrans.
ReplyDeleteNot much a trade off: the chance of moire (and other aliasing issues like stairstepping ... which I do see too) for "chroma smearing" even straight out of camera in lots of images with high detail.
Dropping the OPLF is a triumph of marketing over engineering that based ont he idea with most users not knowning what aliasing looks like (it's not just color moire :-) and of color moire being infrequent.
Initially I though that Fujifilm had an otaku hidden away who had really though the Xtrans and it's demoasicing algorithms through (e.g. look at the pattern and there a smaller 3x3 pattern that rotates around a center in four different rotations ... an interesting symmetry).
Now I think it's been driven by marketing and the wish to be "different". The problem is being differently worse.
Regarding who makes the sensor. Nikon always claims it's "theirs" even when it's clearly shown to be comprehensively someone elses tech. Given the D7000 and D5100 shared the same 16Mpx Sony sensor the guess that D7100 shares the D5200 (given the specs) Toshiba sensor is probably not too far from the mark. But we need a teardown to be sure.
Color aliasing is often considered as less accepted than luma aliasing. Ok, it's a bit subjective here.
ReplyDeleteWhen revieviewing IQ, it's fair to sort artifacts from natural to not natural effects. Probably luma aliasing more accepted than color errors.
About OLPF, makes sense to remove it specially if the aliasing filtering is managed by the image processing in an adaptive way. Something that is not possible by the systematic low pass OLPF. Image processing should help to recover more resolution/acutance, minimizing aliasing error.
But of course nothing is perfect.
Last and not least, most users are not displaying images at 100% scale, and viewers are adding low pass filtering to avoid unresolved aliasing to create artifacts.