Talk:Canon EOS-1D Mark IV

Commons Categories

FYI to all. I have made a commons category for this camera here. Any images of the camera should be placed there. Also I have made a Category for photo's taken with the camera here. Thanks. Nebrot (talk) 18:06, 20 October 2009 (UTC)

Correct Resolution

Which resolution should be listed? Canon's press release claims 16.1 MP, however they also state the max resolution is 4896 x 3264. Well, 4896 x 3264 = 15.98 MP which, out to 1 decimal place, would be 16.0 MP. I've seen the same problem on some other cameras, so can someone please explain which is correct based on Wikipedia guidelines, or maybe explain how Canon's funny math works? Cp82 (talk) 01:31, 22 October 2009 (UTC)

I see your point...something isn't adding up (no pun intended). However, all of Canon's documentation that I've seen states that the sensor is 16.1 effective MP. Maybe it's an error that Canon's press people have made. So, I think we should stick to official figures for now, unless there is some guideline that says otherwise. [SCΛRECROW]^{Cross-Com 2.0} 06:31, 22 October 2009 (UTC)

Works for me – as I mentioned, I don't know what the guidelines state anyway. I was just curious since Canon seems to do this regularly, and I figured I was missing something in the math. But then I was also wondering what the rules dictate if this is just Canon inflating numbers for marketing purposes. Cp82 (talk) 07:11, 22 October 2009 (UTC)

The resolution or number of recorded pixels is 15.98 mio, the number of effective pixels (pixels getting light through the lens) is 16.1 mio, and number of total pixels on the sensor (some not getting any light) could be even higher than that; there is a standard for that [1]. Obviously marketing prefers the bigger number, even though it's quite meaningless for the photographer (I think). Does someone know why not all effective pixels are used for the recorded image? Rror (talk) 08:39, 22 October 2009 (UTC)

Excellent, thanks for the explanation. To answer your question, I've just learned that demosaicing would create image artifacts if pixels were recorded all the way to the edge, thus some pixels are not recorded[2]. That reference also states that JPEGs require image resolutions to be in multiples of 8, so some pixels may also be trimmed to conform to that.

With that said, would it be better to use the term "effective megapixels" in all places where 16.1 is listed? "Effective" is used under Features, but not in the other parts of the article. Cp82 (talk) 09:08, 22 October 2009 (UTC)

Right, I also didn't consider that the discrete cosine transform in jpeg works on 8x8 pixel blocks - now things are making sense :) We should add those things to the effective pixels article. --- Yes, 'effective' should definitely be added. Rror (talk) 12:27, 22 October 2009 (UTC)

Very interesting. Will keep that in mind for future editing. [SCΛRECROW]^{Cross-Com 2.0} 22:12, 22 October 2009 (UTC)

I don't think even canon really knows what it is, :). We will see what the "Technical Report" says. But even the 7D report has continuity problems. here it says 18 megapixels at the top, but further down it says 17.9. An exact calculation is 17,915,904. Nebrot (talk) 15:37, 23 October 2009 (UTC)

I wouldn't expect mathematical exactness from a table that uses 'approx.' in both places... the table makes sense to me. To sum up the above: effective pixels are pixels on the sensor that see light, but those are not mapped 1:1 to pixels in the output file because of technical obstacles. Rror (talk) 16:18, 23 October 2009 (UTC)