Originally posted by falconeye Hi thePiRaTE,
you are totally right. Of course, we must assume both the same pixel density for the sensor and the same MTF (resolution) for the lenses. Otherwise, we would compare apples with oranges. The very best 35mm lenses (ZEISS, Leica) are able to deliver about >100 MPixels while most lenses in use are inferior to 20MPixels (assuming full frame).
Now take as resolution the smaller of the two measures, (1) lens resolution and, (2) sensor resolution. Then, a 300mm FF image gives you 125% more information (more pixels or whatever) than a 200mm APS-C image.
If both sensors have 12 MP, then both images with have 12MP. Where did the extra 125% come from?
Perhaps a browse through this
Understanding resolution and MTF
Would be useful some time. When you find the bit about calculating system resolution and working out the linear resolution for a sensor let me know.
Well your formula is not quite correct is it. A 12MP APS sensor has more resolution (more pixels per linear mm) which exactly cancels out the shorter length (22 vs 36 mm) to get the same number of horizontal pixels.....
OK lets compare actual 12MP APSC and a 12MP FF camera then, from DP Review, and perhaps you can explain.
Absolute res Extinction res
H Canon 5D 2300 lppm 2500 lppm
V Canon 5D 2000 lppm 2500 lppm
H Sony A700 2200 lppm 2900 lppm
V Sony A700 2100 lppm 2800 lppm
Almost an exact match. Hmm. How can that be? By your "theory" the 5D should have quite a lot more resolution. In fact the tests were performed using a FF 50mm lens! If a dedicated APSC lens were fitted to the Minolta it may beat the Canon by more still.
Hey let go REALLY crazy and compare it with a 12MP digicam with a titchy 7.2mm side sensor...a Canon G9...
Absolute Extinction
H 1950 2400
V 1900 2400
Wow - not bad huh - its got a wonky 4X zoom lens stuck on the front and its almost matching a Canon 5D for resolution. Guess Phil must be lying huh!
When the tests of the Nikon D3 and D300 come out it will be interesting to compare wont it.
Originally posted by falconeye Hi thePiRaTE,
The images will look the same until you need maximum detail. Denying this would mean denying that middle format cameras can deliver better IQ than 35mm.
MF cameras using FILM yes. A given film emulsion had the SAME grain density whether it was MF of 35mm therefore a MF negative has far more grains overall. But we are talking about 2 sensors with the SAME number of photosites, therefore the smaller sensor has a higher pixel density/resolution! At the end of the day you still get 12MP from both cameras assuming lenses that are decently sharp.
In fact lens resolution for an APS dedicated lens can be higher than for a FF lens because it does not have to cover such a wide circle and requires less correction for spherical aberation. Check
Canon EF-S 18-55mm f/3.5-5.6 IS - Test Report / Review for resolution figures for Canons new APSC kit lens vs one of their top FF primes. Its actually higher even though its a cheap little zoom.
Youll also find the same generally happens if you compare the newer Pentax DA zooms against the older FA zooms. More resolution. Its not because they are higher quality its just easier to design lenses for smaller image circles.
And finally, because the sensor resolution is so much higher, APSC sensors can generally get away with slightly weaker AA filter which makes them sharper on a per-pixel basis.
So before you go on about FF sensors at least know your facts and learn a bit about the physics.
The real advantage of a FF sensor compared to an APSC one is that it should have less noise at high ISO for the same number of MP (2X the pixel area = about a stop) or double the resolution (2X as many pixels) for the same noise. However this will present more of a challenge because you are using full image circle lenses. I would lay bets that the 24MP Nikon D3X does not double the res of the D3.
However there are real disadvantages too. Larger sensors with larger pixels suffer from more aliasing, moire, light falloff and edge softness. An FF image taken with a less than stellar lens (or any lens wide open) will not look too hot around the edges. It will also get hotter faster and live-view will be harder to implement as a result. It may even cause low ISO noise to be higher than an APSC equivalent.
Also, advances in sensor design have also delivered a 1 stop improvement in noise for APS sensors. They are just a year or so behind.
So, the advantage at low ISO is minimal, the advantage at high ISO is about a stop (using identical sensor design). On the other hand you have a bigger mirror box (slower shutter) and around a $1500 premium over price of an equivalent APS camera (Canon 30D --> 5D or Nikon D2X --> D3). Assuming most of that premium is the sensor and mirror box upgrade, then any FF camera is likely to cost around $1500 more than a similarly specced APS version. Thats a lot to pay for a stop less noise which will be wiped out in a year....