The larger format camera (and it is assumed the size of the lens is going to match the size of the sensor)...
Why is it assumed that the smaller format must be equipped with a smaller/lesser lens? My point is that we should break those 'rules' to get a better picture.
What are the equivalents of 35mm f/1.4, 85mm f/1.2, 200mm f/1.8, 400mm f/2.8, 600mm f/4 or 1200mm f/5.6 in the Medium Format?
The larger camera is generally more expensive, bigger, heavier and can therefore 'hold' more technological wizadry.
I rather think a manufacturer that has large volumes can put more technological wizardry in its products, as Canon does
(its CMOS, noise, processing power, etc... is quite exciting) whereas medium backs are specialized products optimised for high quality photography: they use higher quality components and can avoid degradations required for other types of shooting
(handheld low light, speed...) like the use of microlenses, the fast read-out speed, etc...
About different systems comparisons: by using the 'same FoV, DoF, Speed' equivalence
(ie: same amount of light, different ISO), I compared samples from a lot of digicams/DSLR and found that the sensor used in the Fuji F30 (6MP 1/1.7") is quite efficient, the latest Sony 1/2.5" and 1/1.8" are close and the Canon CMOS used in APS format are also very good.
I believe the sensors used in the 1D2/1Ds2
(and even 5D) are not quite so light-efficient, Nikon/Sony DX as well as sensors used in '4/3' are behind. Kodak/Dalsa sensors for MF are probably even less light-efficient as it is not their priority
(ultimate quality is).
This is not exactly a scientific test, but it gives some interesting trends: light efficiency is not related to sensor's size, but rather to the R&D/Production effort the manufacturer put into it
(ie: the level of technology). There is no limit at 5 or 6.8 micron... as the excellent results from the 2.6 micron Fuji F30 shows
(OK, This 1.75 micron CMOS sensor is probably pushing the envelope at this time).
By the way, I propose a much better one: "A larger lens is better"! (and really: it's quite accurate as the lens diameter for a given FoV will be rather well related to the amount of light reaching the sensor... whatever the sensor's size)
I can't see any logic here. Whatever the size of the lens, equal DoF and equal FoV means equal aperture diameter. The amount of light the lens lets through is then governed only by the shutter speed in these circumstances. For example, the diameter of a 50mm lens at f8 is 50/8=6.25mm. The diameter of an equivalent lens at f64 for 8x10 format is 400/64=6.25mm).
Ray:
- Do you agree that same FoV, DoF and shutter speed give the same image
(or 'as close as could be') and same Signal/Noise whatever the sensor size?
- Do you agree that for a given FoV, when light is lacking (ie: camera or subject movements), you will be better off with a lens of large aperture diameter on APS rather than with a lens of smaller aperture diameter on 645 to get a picture with little noise/blur?
The logic is to replace the usual "a larger sensor has less noise" which is not true by "a larger lens has less noise" which is really more accurate in those situations.
Olivier