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Photo Forum / Digital Photography / DSLR Cameras / August 2005Question for the geeks "Effective Pixels"
I recently bought a D2X Nikon camera. Beautiful camera. Lovely pictures. The best wedding digital I've owned. Nikon blurb refers to 12 megapixel images being blah, blah, etc. Delving into the fine print, I come across 12 million "effective pixels". Alarm bells ringing here. The images won't enlarge past about 900mm wide (10D's limit) without losing definition. Me thinks they have undergone some peculiar post processing in the camera which my Interpolation algorithm doesn't like. Genuine Fractals doesn't handle it too well either once you go into the realm of wall size prints. No problem with Canon (1D)files. Fuji's S2/S3 series cameras are 6 MP cameras with 12 Megapixel "effective" images. They are interpolated in the camera. Can anyone say with conviction what size the sensor in a D2X actually is? I'd hate to think Nikon stooped to Sigma levels and started inventing specification just to match numbers.  SignatureDouglas, You never really make it on the 'net until you get your own personal Troll. Mine's called Chrlz. Don't feed him, he bites! > Fuji's S2/S3 series cameras are 6 MP cameras with 12 Megapixel > "effective" images. They are interpolated in the camera. Can anyone say > with conviction what size the sensor in a D2X actually is? I'd hate to > think Nikon stooped to Sigma levels and started inventing specification > just to match numbers. Every camera, Canon included, has some rating of "effective" pixels. It's the number of pixels actually being used to create the image, as opposed to how many are physically present. The Canon 1Ds2 has 16.6 million "effective" pixels, but 17.2 million actual sensor photo detectors. There is nothing funny going on in the D2x. It has 12.2 million "effective" pixels and 12.8 million actual photo detectors. SignatureJeremy | jeremy@exit109.com > Every camera, Canon included, has some rating of "effective" pixels. It's > the number of pixels actually being used to create the image, as opposed > to how many are physically present. The Canon 1Ds2 has 16.6 million > "effective" pixels, but 17.2 million actual sensor photo detectors. Little niggle with your post: The effective number of pixels is the resulting number of pixels in the image after interpolation. ALL the sensor pixels are used to create the final image. Signaturehttp://www.pbase.com/bcbaird > The effective number of pixels is the resulting number of pixels in the > image after interpolation. ALL the sensor pixels are used to create the > final image. True, I guess some number of the edge pixels are used to facilitate the interpolation (de-mosaicing) of the edge areas. Some of the extras may also be used for things like determining black level, though. SignatureJeremy | jeremy@exit109.com >> The effective number of pixels is the resulting number of pixels >> in the image after interpolation. ALL the sensor pixels are used [quoted text clipped - 4 lines] > Some of the extras may also be used for things like determining > black level, though. Correct, and some pixels are sacrificed to allow JPEG compression on 8 or 16 pixel boundaries, and then there is also aspect ratio preference. Bart > > The effective number of pixels is the resulting number of pixels in the > > image after interpolation. ALL the sensor pixels are used to create the [quoted text clipped - 3 lines] > interpolation (de-mosaicing) of the edge areas. Some of the extras may > also be used for things like determining black level, though. Black level depends on the sensor. I think Canon does it per-pixel, other manufacturers may have different methods. Signaturehttp://www.pbase.com/bcbaird >> > The effective number of pixels is the resulting number of pixels in the >> > image after interpolation. ALL the sensor pixels are used to create the >> > final image. >> True, I guess some number of the edge pixels are used to facilitate the >> interpolation (de-mosaicing) of the edge areas. Some of the extras may >> also be used for things like determining black level, though. >Black level depends on the sensor. I think Canon does it per-pixel, >other manufacturers may have different methods. Canon has black (unexposed) pixels on a horizontal and a vertical edge, for determining blackpoint. Blackpoint is determined globally for Canon software and firmware. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< SNIP > Canon has black (unexposed) pixels on a horizontal and a vertical > edge, for determining blackpoint. Blackpoint is determined globally > for Canon software and firmware. Correct, with the addition that for long exposure times (usually longer than 1 second) a dark frame subtraction is performed, which in a sense is a per pixel recalibration. Bart > > Canon has black (unexposed) pixels on a horizontal and a vertical > > edge, for determining blackpoint. Blackpoint is determined globally [quoted text clipped - 3 lines] > longer than 1 second) a dark frame subtraction is performed, which in > a sense is a per pixel recalibration. That's what I was thinking of. Thanks for the correction. Signaturehttp://www.pbase.com/bcbaird >>The effective number of pixels is the resulting number of pixels in the >>image after interpolation. ALL the sensor pixels are used to create the >>final image. > > True, I guess some number of the edge pixels are used to facilitate the With dcraw as a raw converter you get several extra edge pixels. > interpolation (de-mosaicing) of the edge areas. Some of the extras may > also be used for things like determining black level, though. SignaturePaul Furman http://www.edgehill.net/1 san francisco native plants >The effective number of pixels is the resulting number of pixels in the >image after interpolation. ALL the sensor pixels are used to create the >final image. No; most DSLRs have a strip of unexposed pixels on two perpendicular edges of the sensor, and even amongst the ones exposed to light, a thin band around the edges are not usually rendered in the output. The actual number of exposed pixels dropped depends on the software. The "effective" is probably how many are used by the firmware for JPEGs, and the MFR's RAW converter. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< > Delving into the fine print, I come across 12 million "effective > pixels". Doug, the edge pixels must be discarded on ANY Bayer-type sensor due to color and luminance interpolation. Can you say... duh?! As for your enlargement issues, sounds like something else is going on. Signaturehttp://www.pbase.com/bcbaird Edge pixels have to be discarded because they don't have any surrounding pixels from which to determine their color. They're only used by the inner pixels so that the inner ones can determine their color. > > Delving into the fine print, I come across 12 million "effective > > pixels". [quoted text clipped - 3 lines] > > As for your enlargement issues, sounds like something else is going on. Effective pixels can be nonsense; especially so when deployed in ads like the Bell + Howell crap that's now appearing in various media. These ads tout 10.0 mega pixels (for $249) and the camera is most likely only 2 to 3 MP. Caveat Emptor! > I recently bought a D2X Nikon camera. Beautiful camera. Lovely pictures. > The best wedding digital I've owned. Nikon blurb refers to 12 megapixel [quoted text clipped - 14 lines] > think Nikon stooped to Sigma levels and started inventing specification > just to match numbers. Relax, Doug, read this excerpt from DPreview: "Nikon has today revealed the sucessor to the D1X. The new D2X Professional digital SLR has a 12.4 million pixel DX format CMOS sensor, by default the D2X can shoot at 5 fps, however it has an interesting 6.8 milion pixel option which reduces the sensing area (to a FOV crop of 2x) but increases the frame rate to 8 fps. Hence the D2X can be seen as two cameras in one, a 12.4 million pixel high resolution shooter and a 6.8 million pixel high frame rate shooter. Obviously the use of CMOS is new to Nikon but also new on this camera is a four channel read-out from the sensor and the ability to perform WB correction to the analogue data before it is digitized. Also new is the WT-2 wireless transmitter with 802.11 b/g support and wireless Capture Control (Nikon Capture 4.2). Phil: Although the cropped 6.8 megapixel mode sounds odd it's actually very easy to use as the area is indicated by a box on the focus screen (view through the viewfinder). It's just like a "sports finder" in that mode and of course means that your 300 mm lens produces the same FOV as a 600 mm lens, at 6.8 million pixels." Colin D. > .... Fuji's S2/S3 series cameras are 6 MP cameras with 12 Megapixel > "effective" images. They are interpolated in the camera. Just yesterday I met a photographer who had done some favors for a friend and he said he had a 12 Meg.pix. camera- the Fuji S2. I recall discussion of this before the NG was inundated with -er, other issues. Can anyone recall the gist of the Fuji mathematics? SignatureJohn McWilliams > Just yesterday I met a photographer who had done some favors for a > friend and he said he had a 12 Meg.pix. camera- the Fuji S2. I recall > discussion of this before the NG was inundated with -er, other issues. > > Can anyone recall the gist of the Fuji mathematics? There is an interpolated mode. http://www.dpreview.com/reviews/specs/Fujifilm/fuji_s2.asp You're friend should be touting the dynamic range (esp. in the highlights) of the camera and not the pixel count in interpolated mode. S3 too: http://www.dpreview.com/reviews/specs/Fujifilm/fuji_s3.asp Fine cameras. Cheers, Alan Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. >> Just yesterday I met a photographer who had done some favors for a >> friend and he said he had a 12 Meg.pix. camera- the Fuji S2. I recall [quoted text clipped - 12 lines] > > Fine cameras. Yes, it appears they may well be, as he is serious about his work. He is also a very nice guy, so I don't want to get into a big to do about interpolation, etc. But its 6.1 "Effective Mega Pixels" is the number that's comp. to Nikon and Canon's figures, I'd bet. It also lists 12.3 million "Sensor photo detectors", but I guess that uses two different angles of light striking the sensors (to double the 6.15 effective pixels), used in the interpolation? Thus accounting for more dynamic range? SignatureJohn McWilliams |
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