Re: Bayer sensor and MX
- From: "Sosumi" <sosumi@xxxxxxx>
- Date: Fri, 8 Feb 2008 22:56:00 -0000
"ben brugman" <ben@xxxxxxxxxxx> wrote in message
news:74353$47acac5b$53557893$7430@xxxxxxxxxxxxxxxxxxxxxxxxxx
"Sosumi" <sosumi@xxxxxxx> schreef in bericht
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The way the Bayer sensor works, it "makes up" color information depending
on the surrounding pixels. But if you do multiple exposures with exactly
the same scene, the picture gets more sharp according to the amount of
exposures.
No the picture does not get more sharp. If there is a lot of noise in one
normal
picture, the definition of the picture get's a littlebit better, but for
most normal
pictures (in normal light) taking more pictures of the same scene does not
make
it sharper.
You're wrong. I took several pictures and the more MX times, the sharper the
picture. Less noise is sharper. If you blow the pictures up to 100% you
clearly see normal noise, grain or pixels, while with the MX pixtures,
pixels are hardly visible: it's much smoother.
In theory small movements of the camera and adjusting for these movements
when adding the pictures, will give a better picture and less risc of
moire.
In theory this method can even make pictures sharper, but then you need
a very large amount of the 'same' pictures to get the pictures noticeble
sharper.
With 5 -10 exposures on one picture the differense is already very
noticeable.
Much is due to the fact that noise is distributed randomly and hence, theMultiple pictures will reduce the noice, but with correctly exposed
same place where a "piece" of noise was before, it's over written with
data the next exposure.
pictures
there is not a lot of noise. (Long exposure pictures will benefit from
multiple
exposure, but not normally exposed pictures).
No, you're wrong. See above.
--What I was wondering: do the pixel interpolation always work the same
way? Or is this also slightly random (shifting)? So do you, in fact, get
more information or only less noise? It just seems hard to believe, that
every take of a picture would give exactly (I mean pixel deep peeping)
the same result.
And also: do all Bayer sensor work exactly the same, or is there a
difference in Nikon, Canon, older, newer models?
There are some variations.
Most sensors have 2 greens, 1 red and 1 blue for every four cells in a
square.
There are sensors where the second green is replace by another color.
There are sensors which are not RGB, but YMC, but I haven's seen them them
lately
in camera's.
Normal Bayer sensors
GRGRGRGR
BGBGBGBG
GRGRGRGR
BGBGBGBG
Interpolation which is most simple is that, on each pixel
Green pixel (position).
Green = G (from the pixel)
Red= (Rl+Rr)/2 from the left and the right
Bleu = (Bu+Bd)/2 from the up and down bleu.
Red pixel (position).
Green = (Gl+Gr+Gu+Gd)/4
Red = R (from the pixel)
Bleu = (B+B+B+B)/4 from the 4 corners of R
Bleu pixel (position).
Green = (Gl+Gr+Gu+Gd)/4
Red = (R+R+R+R) /4 from the 4 corners of B
Bleu = B (from the pixel)
This is without sharpening or any other fancy stuf.
(In general sharpening subtracts a little bit of pixels laying further
away).
When using multiple exposure with shifted pixels, something similar is
done,
with far smaller pixels, where the 'large' pixels are shifted over the
small pixels.
Using sharpening this will result in a slightly sharper picture.
As you can see the Red and Bleu pixels (positions) get the information of
the
Bleu and Red colors from quite some distance.
The resolution for red only or bleu only is significant less than for
black and white.
ben
Sosumi
.
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