||Thread Tools||Search this Thread|
|Feb 8, 2005, 2:47 AM||#1|
Join Date: Feb 2005
Considering the ISO performance of two cameras using sensors with different pixel size within the same graph, is like testing two cameras with different film, ISO 100 and 400 for instance.
It is known to everybody that the ISO 100 film is slower but with finer grain than the ISO 400 film, relatively faster and coarser grain
Viceversa, we can normally say that coarser grain film is faster and finer grain film is slower.
Furthermore, it is possible to obtain larger prints at the same quality level from finer grained fim than coarser grained, otherwise nobody would use ISO 100 film and everybody would be using ISO 400 and more.
Again, when we talk about comparing different sensor sizes, in a way it is like comparing an Hasselblad 500c to a Nikon F2, most reviewers would put in light the fact that they are different formats.
So a wise reviewer should say comparing camera x and y:
camera x has a poorer ISO performance but this is balanced by reaching the same resolving power using shorter focal (smaller and hopefully cheaper) lenses, or by having lenses with same resolving power and more opening.
camera y has a better ISO performance but will need longer focal lens to resolve the same detail.
the aov (angle of view) seen by each pixel is proportional to the focal lenght and pixel size.
The amount of detail equivalent to each single pixel is proportional to the pixel size and focal lenght.
That is the detail is the same for a 5µ pixel with a 100mm lens and a 10µ pixel with a 200mm lens.
Looking around have found :
E-300 pixel size 5.4µ
300D pixel size 7.4µ
7.4/5.4 = 1.37 let us call this ratio 1.4 for convenience.
Focal lenght vs f-ratio
(f) is a function of focal lenght and aperture of the primary lens, f = focal lenght/aperture, therefore for a given primary lens aperture the f varies accordingly to the focal lenght.
That is, the primary lens aperture (size) is the same in a 50/1.4 and a 100/2.8.
Altoghether the same size of lens will give the same detail on a 300D than on an E-300 if the focal lenght is 1.4 times longer.
But when the focal lenght is 1.4 times longer, the f-ratio is 1.4 times lower !!!
It is like loosing one stop.
50/2 on the E-300 and 70/2.8 on the 300D can have the same size of primary lens and obtain same resolving power.
If you prefer, a 500/4 and a 700/5.6 should have the same filter size...
Viceversa, if we use a 50/2 on both cameras, the resolving power of the E-300 will be 1.4 times higher than the 300D.
Olympus way should be to make available to the public the short-medium focal lenses, that are quite unique to the Four Thirds, like the 14-54 and so on, covering that market while for the long end it should be quite simple for manufacturers like Sigma, Tamron, Tokina, Cosina to just add another mount to their range.
Today the E-300 is built like the 20D, not origami like the 300D, the E-1 like 1DsII, and have an overall performance not inferior, basically superior to these (except pixel count difference E-1 1Ds at way lower price...)
|Thread Tools||Search this Thread|