[Smeggypants]

A 100% crop is not a photograph. The question is how will the images from the two cameras compare in the same size prints or screen images. At the same size, more pixels produce better IQ, assuming that there is a visible difference.

Jeff

Complete and utter rubbish!

[30v iPentax]

Uusia Canon harrastajia on tullut mittamaan K-5 vertailua Canon. Itse ostan iPentax ilman ulkopuolista arvosteliaa. 35 vuoden Pentax kokemus, se on tae itselleni, Pentax on minulle tarpeeksi paras omistaa.

[blende8]

Here are the values from DXOmark:
orange 5D, red K5.

[simico]

That said, to me the question is how much of a difference you will see at printing sizes. For most users, they will not be able to see much difference below iso 6400 between the K5 and 5D

Exactly. I've just got my prints (131 pics) for our family album. There are photos taken with K-m and K-5, ISO all over the place from 100 to 3200. Noise is hardly visible at all even on the ISO3200 K-5 shots. Below ISO1600 it's impossible to tell what camera and ISO was used for the shot. Imho if you only care about noise then at the regular consumer printing sizes it doesn't really matter if you used a K-x or a K-5 or a Nikon D3.

[30v iPentax]

En tiedä mihinkä näitä taulukoita käytetään. Mikä on käytäntö ja teoria.

[Jeff Charles]

Complete and utter rubbish!

Should I interpret your response to mean that you do not agree with my statement that "At the same [print] size, more pixels produce better IQ, assuming that there is a visible difference"? There are varying opinions on this topic, but there is definitely support for what I wrote, although in the references cited below, the support is qualified, especially in the last one.

Here are three reference sources about the relationship between number of pixels and image quality. For each, I have pasted the summary or concluding statement. The supporting details are at the linked-to pages. Sorry for pasting so much text, but I did not want to be selective in what I posted.

Equivalence

Summary statement: "So, are more pixels still better? In terms of IQ, yes. But the IQ advantages of more pixels is not as extreme as the difference in pixel counts seems to suggest, due to the fact that lenses are not infinitely sharp and that, unless a higher shutter speed can be used without raising the ISO, the effects of motion blur and/or camera shake may degrade the additional detail afforded by more pixels. But unless the system with the higher pixel count has a less efficient sensor, it will never have lower IQ, and even with a less efficient sensor, may still render higher IQ in many instances. The question, then, is at what point the additional IQ of more megapixels passes the point of diminishing returns and becomes more of a burden than it's worth, especially given that more megapixels requires more memory, more time to process to realize the potential, and likely a lower frame rate. The answer to that question, of course, depends on the size the image is displayed, the quality of the lenses being used, the DOF being used, and the QT (quality threshold) of the viewer. Given that 8.6 MP results in 300 PPI for an 8x12 inch print, for many, we are well past the point of diminishing returns already."

http://www.dxomark.com/index.php/en/Our-publications/DxOMark-Insights/More-pixels-offset-noise!

Summary statement: "Noise measurements in RAW format are indicative of pixel performance, but the viewing conditions of the image must also be taken into account. To compare prints on a given format of cameras with different resolutions, it is more suitable to compute the equivalent SNR of a camera with a given reference resolution. For equal, normalized SNR, a high-resolution camera is still better than a low-resolution camera. While it is always possible to simulate a low-resolution camera using a higher resolution camera (since downsampling is easy), it is not possible to simulate a high-resolution camera using a lower-resolution camera other than by interpolating or inventing data."

Noise, Dynamic Range and Bit Depth in Digital SLRs -- page 3

Summary statement: "Bottom line: Among the important measures of image quality are signal-to-noise ratio of the capture process, and resolution. It was shown that for fixed sensor format, the light collection efficiency per unit area is essentially independent of pixel size, over a huge range of pixel sizes from 2 microns to over 8 microns, and is therefore independent of the number of megapixels. Noise performance per unit area was seen to be only weakly dependent on pixel size. The S/N ratio per unit area is much the same over a wide range of pixel sizes. There is an advantage to big pixels in low light (high ISO) applications, where read noise is an important detractor from image quality, and big pixels currently have lower read noise than aggregations of small pixels of equal area. For low ISO applications, the situation is reversed in current implementations -- if anything, smaller pixels perform somewhat better in terms of S/N ratio (while offering more resolution). A further exploration of these issues can be found on the supplemental page. Rather than having strong dependence on the pixel size, the noise performance instead depends quite strongly on sensor size -- bigger sensors yield higher quality images, by capturing more signal (photons).

"The other main measure of image quality is the resolution in line pairs/picture height; it is by definition independent of the sensor size, and depends only on the megapixel count. The more megapixels, the more resolution, up to the limits imposed by the system's optics."

Jeff

[mjohnsonf15]

Ryan's question is pretty interesting, to me anyway...I've wasted way too much time trying to figure out the answer myself. I hope everyone accepts that full frame images will have less noise and produce files that are on par/better than scanned MF film. So a 5DMkII would provide (other than DOF) a substitute good with respect to MF cameras a decade ago. Current cropped-sensor cameras, with smaller bodies, would seem a good fit for what 35mm photographers have used for decades. That argument, valid or invalid as you may see it, is what led me to use pentax cropped-sensor cameras with limited lenses, despite the temptation to seek the ultimate in ISO...I think this may follow Sean Reid's train of thought with respect to the K-5 as a tool as well, from what I remember when I subscribed some time back. Pay for subscriptions...absolutely better than any magazine I subscribed to, even if you're not into the whole rangefinder thing.
Cheers,
Matt