I don't understand the meaning of "DX and FX are equally sharp". The "sharpness" of a sensor depends on the AA filter and the sensel size, not on the size of the sensor.
However, an important consideration is, how good a given lens is with the sensor; this does depend on the sensor size. Many lenses excel with the cropping sensors, while they are soft with full frame; this is only natural. For example for me (dedicated to panoramas) the cropping cameras are the uncontested winners because of the edge sharpness.
Re the IQ: there can be no serious discussion about the superiority of the "pixel quality" of the D3 (= D700) compared to the D300, due to the size of the sensels. Nikon fanboys are in for a rude awakening with the high-pixelcount successor of the D3.
I do not agree that 'all' full frame DSLR sensors, in themselves, are less sharp at the edges - Nikon's D3 sensor technology has proved this. This notion is still banded about because Canon sensors take a nose dive at the edges of the frame, even when using prime telephoto lenses.
My bread and butter lenses, since 1993 (covering professional sport full time), have been super telephoto lenses. In the past 20 years I have owned several versions of Nikon, and Canon's super-telephoto lenses. An interest in optics I have been in a position to test all manner of lenses under very carefully controlled tests (time permitting). I have examined over 150,000 sporting images, on slides, with 4X and 8X loupes, for critical sharpness (library selection edits) and in addition captured thousands of images digitally since 2000.
I recently moved back to Nikon after extensively using Canon 1DS MKI, 1DS MKII and 1DSMKIII cameras. Several top, internationally known, sports photographers (that I know, and not rumour) use FF cameras, more than those, who are not in this section of the industry, may realise.
In the case of super telephoto lenses, such as the 'superb' new Nikkor 400mm F/2.8 VR, Nikon have noticeably improved he edge quality of this lens. Additionally, and Importantly, Nikon's D3 sensor technology retains edge resolution across the sensor, in an efficient manner, in comparison to either the 1DS MKII, or 1DS MKIII - this is not pixel peeping, but by a noticeable margin. I relate my experiences using third party RAW converters, such as RPP, that do not use any lens tags inside the RAW data designed to correct for lens errors.
With the Canon 1DS MKII, even using the stellar Canon 300m F2.8 IS lens (very good edge performance on film), the edges are poor; you can virtually draw a vertical line, from about 15-20% in, from either end of the frame, to indicate where the sensor dramatically dips in quality. Even at F5.6/F8 the edges of the image look as if a very mild motion blur filter 'effect' has been applied. The Canon 16-35m MKII lens makes the effect look like a much stronger version of a motion blur filter -even with a good copy of this lens.
I recently carried out a very accurate edge-to-edge test with my Nikkor 400mm VR lens, at F/8, on some roof tops to see of Nikon's MTF claims were born-out - I was killing time as the sunlight wouldn't play ball for the wider shot I wanted. The image is no masterpiece but nicely demonstrates the edge-to-edge quality achievable with the Nikon D3.
I can say without question that the Nikon D3 sensor, whilst it may not seem that revolutionary to some, has raised the bar with regard to edge-to-edge sensor performance - lenses, if anything (with the D3), will be the limiting factor - telephoto lenses fairing better than wide angle lenses for obvious reasons.
At the Tokyo launch of the D3 a senior Nikon spokesman went as far to indicate that Nikon were using gap-less, double micro lens technology on the Nikon D3 - one micro-lens on the top, and one inner micro lens to boost the efficiency of the photosite; the rest has been kept under wraps since its launch - some recent additional Nikon info [a href=\"http://imaging.nikon.com/products/imaging/technology/d-technology/imagingsensor/resolution/index.htm]http://imaging.nikon.com/products/imaging/...ution/index.htm[/url]
I do not have any direct comparisons from my Canon IDS MKII with fixed focal lenses (only the canon 70-200mm F2.8IS - hardly fair) but I found exactly the same results during prime lens use as Bjorn Rorslet -http://www.naturfotograf.com/index2_PC.html
Home page on left hand column click on Reviews>Nikon D2X (near bottom of page)>see section 'Taking on the Canon 1DS MKII' -towards the bottom of this page, D2X with Nikkor 200mm F2 lens and 1DS MKII using a prime Canon 300mm F2.8L - Periphery examples from the FF Canon, are similar to my experiences.
MTF ratings from lens manufacturers don't tell he whole story, and in many cases derive from computer simulations. However MTF figures given for the new Nikkor 400mm F/2.8 lens, against its predecessor, the Nikkor AFS 400mm, vindicate Nikon's claim regarding improved edge performance, and higher resolution 30 lpm, are born out.http://imaging.nikon.com/products/imaging/...8g_vr/index.htmhttp://imaging.nikon.com/products/imaging/..._if_2/index.htmhttp://www.usa.canon.com/consumer/controll...mp;modelid=7317
- Canon's full frame sensors wreck the respectable edge performance of this lens.
The Nikkor 14-24mm lens is another example of an excellent edge performer, on full frame, that puts the Canon 1DS MKII and 16-35m MKII combination to shame at the edges of the frame.Both systems bank cheques so this is 'strictly' not a Canon versus Nikon post and merely to highlight sound developments in sensor and lens technology.
PS. The first two crops are 100% views from the very corner of the frame and the third crop near the centre of the frame.