Why only 4.6MP?
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From: Martin Brown on 1 Mar 2010 04:04 David J Taylor wrote: > "Alfred Molon" <alfred_molon(a)yahoo.com> wrote in message > news:MPG.25f4dc1d2b7a4fab98c23c(a)news.supernews.com... >> In article <hmdjf1$g7l$1(a)news.eternal-september.org>, david- >> taylor(a)blueyonder.co.uk.invalid says... >>> I suggested comparing today's cameras >>> of similar effective resolution (citing a 4.6MP Foveon and 12MP Bayer as >>> such cameras) >> >> 4.6Mp is not a "similar effective" resolution as a 12MP. A 4.6MP full >> colour camera has a similar effective resolution of a 7MP bayer camera >> (rough guesstimate, which obviously depends on the scene photographed). >> But comparing a 4.6MP (full colour) camera with a 12MP bayer camera does >> not make much sense. >> >> A 10MP full colour camera would be competitive - at least for what >> concerns the resolution - with the current crop of 12-15MP DSLRs. It >> would have larger pixels, far fewer aliasing problems and not put such >> high demands on the optical resolution of the lens and diffraction would >> be less of a problem, meaning that you could use smaller apertures. >> -- >> >> Alfred Molon > > If, as you say, it only needs a 7MP Bayer camera to equal a 4.6MP Foveon > camera, then Sigma has already lost the battle. > > My original question remains, although I choose to rephrase it: how big > a print and how close to it do you need to be (more accurately, what > angle does a pixel subtend) to see the extra colour resolution in > today's Foveon cameras versus today's Bayer cameras? You have to be close enough to see individual pixels (or at least be able to tell the difference between one pixel black and one saturated red vs two pixels half brightness red. Fine detail like black veins on a red flower like a poppy will show significant artefacting. But most of it is down to the JPEG decoder and 2x1 chroma subsampling no the sensor. The win lose for Bayer vs Foveon is extremely sensitive to the material being photographed. The testing case is fully reolved fine black liens on a saturated red background. The only time I have had real problems with Bayer sensors was photographing in monochromatic red light. Obviously operating with half resolution in both dimensions. The effects and limitations of the demosaic were obvious - although even then *most* of the defects in the final image came from systematic faults in the publicly available JPEG decoders as currently implemented. If someone wants to photograph a subject that is challenging for Bayer sensors with both a good 8Mpixel Bayer camera and a Foveon I will decode the Bayer image to demonstrate that most of the benefit Foveon devotees are claiming is actually down to 1:1:1 chroma subsampling and a fault in the JPEG decoder spec for chroma subsampling as presently implemented. Regards, Martin Brown
From: nospam on 1 Mar 2010 05:48 In article <OqLin.882$cp7.294(a)newsfe23.iad>, Martin Brown <|||newspam|||@nezumi.demon.co.uk> wrote: > If someone wants to photograph a subject that is challenging for Bayer > sensors with both a good 8Mpixel Bayer camera and a Foveon I will decode > the Bayer image to demonstrate that most of the benefit Foveon devotees > are claiming is actually down to 1:1:1 chroma subsampling and a fault in > the JPEG decoder spec for chroma subsampling as presently implemented. can you use the samples from dpreview or another review?
From: Pete Stavrakoglou on 1 Mar 2010 10:20 "nospam" <nospam(a)nospam.invalid> wrote in message news:010320100310444789%nospam(a)nospam.invalid... > In article <hmfn20$7ch$1(a)news.eternal-september.org>, David J Taylor > <david-taylor(a)blueyonder.co.uk.invalid> wrote: > >> If, as you say, it only needs a 7MP Bayer camera to equal a 4.6MP Foveon >> camera, then Sigma has already lost the battle. > > exactly. > > when the sd14 came out, most reviews said it was comparable to 6-8 mp. > unfortunately for sigma, competing cameras at the time were 10 mp and > half the price of the sd14. plus, those cameras actually worked and > didn't lock up. You keep stating this but you are incorrect. Can you cite the reviews? It was the SD9 and SD10 that was compared to six-eight MP Bayer cameras. From my earlier post, the dpreview of the DP2 which has the same sensor of the SD14: "Even so, the level of detail being rendered is clearly very high and not dissimilar to that of a well-processed image from a camera with a 12mp conventional sensor such as the E-P1. Per-pixel sharpness on the DP2 is way ahead of the E-P1 and even in a large print it seems ulikely that the extra pixels on the Olympus sensor would give you any advantage".
From: Pete Stavrakoglou on 1 Mar 2010 10:30 "SMS" <scharf.steven(a)geemail.com> wrote in message news:4b8801f1$0$1595$742ec2ed(a)news.sonic.net... > nospam wrote: >> In article <4b860fa5$0$1663$742ec2ed(a)news.sonic.net>, Ray Fischer >> <rfischer(a)sonic.net> wrote: >> >>> Besides, the problem with Sigma cameras isn't the sensor. >> >> that's one of the problems. >> >>> It's everything else. >> >> that's the rest of the problems. >> >>> Their cameras are really kind of crappy and do not >>> stand up against similarly-priced models from Nikon and Canon. >> >> they don't stand up to *any* models from nikon or canon, regardless of >> price. >> >> let's not forget that the sd14 initially sold for $1599 > > No they didn't. That was the asking price. Now the asking price is $660. > If they can get it down to about $300 they might have a market. Yes it did initially sell for $ 1,600.00 Try getting you facts right, it might do something for your lack of credibility.
From: Pete on 1 Mar 2010 11:09
Martin Brown wrote: > You have to be close enough to see individual pixels (or at least be able > to tell the difference between one pixel black and one saturated red vs > two pixels half brightness red. Fine detail like black veins on a red > flower like a poppy will show significant artefacting. But most of it is > down to the JPEG decoder and 2x1 chroma subsampling no the sensor. > > The win lose for Bayer vs Foveon is extremely sensitive to the material > being photographed. The testing case is fully reolved fine black liens on > a saturated red background. The only time I have had real problems with > Bayer sensors was photographing in monochromatic red light. > > Obviously operating with half resolution in both dimensions. The effects > and limitations of the demosaic were obvious - although even then *most* > of the defects in the final image came from systematic faults in the > publicly available JPEG decoders as currently implemented. > > If someone wants to photograph a subject that is challenging for Bayer > sensors with both a good 8Mpixel Bayer camera and a Foveon I will decode > the Bayer image to demonstrate that most of the benefit Foveon devotees > are claiming is actually down to 1:1:1 chroma subsampling and a fault in > the JPEG decoder spec for chroma subsampling as presently implemented. Martin, my question is not related to the subject of this thread, but what you've written may explain an ongoing problem I've had with some software. I'd been assuming that the rapid degradation with JPEG load-then-save cycles, at highest quality setting, was caused by a level mapping error when this software converts JPEG to linear and vice versa. My simple tests use a lightly saturated green/magenta diagonal gradient and combinations of JPEG and 16-bit TIFF input and output: it appears that the software has a small error on linear to JPEG conversion, but most of the error is when reading a JPEG and converting to linear. I set the colour space to sRGB for image, working space, and monitor, to remove as many variables as possible. My extensive Web searches have not revealed a tangible explanation, probably because my keywords are limited by what I know. I'm attempting to learn something new therefore I don't know suitable keywords. Any help would be greatly appreciated. Pete |