Sigma/Foveon Questions
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From: Ray Fischer on 18 Apr 2010 19:01 nospam <nospam(a)nospam.invalid> wrote: >In article <4bcb5b3b$0$1636$742ec2ed(a)news.sonic.net>, Ray Fischer ><rfischer(a)sonic.net> wrote: > >> >> A 4.6MP bayer sensor does indeed have lower resolution than does a >> >> 4.6MP foveon sensor. >> > >> >slightly. >> >> It's significant. > >no it isn't. > >> >it's certainly not 1/3rd or whatever other silly math the foveon >> >fanbois claim. >> >> It is actually not too far from 1/3. > >it's approximately the same. both bayer and a foveon sensor with the >same number of pixels will resolve approximately the same, roughly >70-80% of nyquist. Tests show otherwise. >> >> But notice how many cameras have 4.6MP Bayer >> >> sensors. >> > >> >and then look at how many have foveon. it's not even 1/2 of 1%. >> >> Not the point. The point is that cameras with Bayer sensors are >> generally 10MP or more, easily outstripping any benefits seen from >> the Foveon sensor. > >that's true. the best foveon sensor is still 4.6 megapixels, while >bayer is 18-24 megapixels. -- Ray Fischer rfischer(a)sonic.net
From: nospam on 18 Apr 2010 19:11 In article <4bcb8f32$0$1651$742ec2ed(a)news.sonic.net>, Ray Fischer <rfischer(a)sonic.net> wrote: > >> >it's certainly not 1/3rd or whatever other silly math the foveon > >> >fanbois claim. > >> > >> It is actually not too far from 1/3. > > > >it's approximately the same. both bayer and a foveon sensor with the > >same number of pixels will resolve approximately the same, roughly > >70-80% of nyquist. > > Tests show otherwise. which ones?
From: Alfred Molon on 20 Apr 2010 14:10 In article <B6ezn.63223$vC3.49470(a)newsfe04.iad>, Martin Brown says... > It isn't the Bayer mask that fails in this particular case it is the > chroma subsampling. No problem if you shoot RAW and then postprocess with 1x1 chroma subsampling (vs 2x1). -- Alfred Molon ------------------------------ Olympus E-series DSLRs and micro 4/3 forum at http://tech.groups.yahoo.com/group/MyOlympus/ http://myolympus.org/ photo sharing site
From: Alfred Molon on 20 Apr 2010 14:14 In article <190420101220067533%nospam(a)nospam.invalid>, nospam says... > > Luminance requires all *three* colour components. If you do not capture > > all three colour components at each pixel, you do not capture luminance > > at each pixel. > > you may not capture full luminance but you do capture enough > information to calculate the correct value. the system works. Bayer does not capture the luminance at the pixel level, period. However the green channel is a good estimate of luminance and half of the pixels in a Bayer sensor are green, which is why the performance of a Bayer sensor is not as abysmal as the lack of 2/3 of the colour information would imply. -- Alfred Molon ------------------------------ Olympus E-series DSLRs and micro 4/3 forum at http://tech.groups.yahoo.com/group/MyOlympus/ http://myolympus.org/ photo sharing site
From: nospam on 20 Apr 2010 14:28
In article <B6ezn.63223$vC3.49470(a)newsfe04.iad>, Martin Brown <|||newspam|||@nezumi.demon.co.uk> wrote: > >> There are a handful of cases where the Foveon sensor might give a better > >> image and one of those is when photographing fine black detail on > >> saturated red or blue flowers. Rest of the time it is all marketting. > > > > black detail on saturated colours should be ok with bayer because > > there's a big luminance difference and bayer generally gets that right. > > It isn't the Bayer mask that fails in this particular case it is the > chroma subsampling. bayer samples colour at half the rate of luminance. humans can't see the difference, but some think they can (like those who can 'hear' differences in speaker cables). > Try it on a test chart with a Wratten 25 filter and > you will see what I mean. There will be a factor of 2 difference in the > effective resolution between horizontal and vertical in the red channel. if you filter only red, you will reduce the resolution of the sensor but that's not a real world scenario. > Foveon save their images as fully chroma sampled JPEGs so the issue of > errors in the subsampled chroma decoding approximations do not arise. that's a plus but humans can't tell the difference except in extreme (i.e., not real-world and contrived) cases. > > where bayer has a problem is with two different saturated colours, such > > as red/blue, especially if the luminance is similar. the human eye > > can't handle that particularly well either. > > The problem arises later in the imaging chain. Bayer sensor struggles a > bit with a pure red (or pure blue) monochrome images because it has > fewer independent pixels. true but nothing in this world is 'pure saturated red' (or blue or green). even bright red objects have a little blue or green in it. > Normally the luminance channel is able to hide > these defects, but when the situation arises where the luminance channel > is corrupted by the chroma channels then you lose detail. and that only happens in edge cases, like red/blue test charts. that's why the foveon fans love those tests, despite it not being relevant to real world photography. |