06-15-2016, 05:40 AM
Quote:Equivalent iso setting is not valid, from a "sensitivity" or light ratio POV.That, of course, is incorrect.
It is very valid for light.
An equivalent focal length, gives the same field of view.
An equivalent f-stop setting, gives the same depth of field.
An equivalent ISO setting, gives the same amount of light.
Quote:Iso equivalence is only related to sensor noise, nothing else.The "only" part is nonsense...
The whole single reason it is "related to sensor noise" is because equivalent ISO settings will form the image with the same amount of light.
Quote:With a 4x smaller sensor you need a 4 times (2 stops) lower iso to have the same noise at the same size image, compared to FF, that's all.Because you used the same amount of light.
The way isos and light are related is in amount of light per square standard area size (f.e., per square mm).
Light per square area size is.... totally not interesting in any way. The paradigm has shifted going from film to digital. With film, when using the same film, it made some sense. When using two totally different films, not so much.
Quote:This is why you get exactly the same exposure parameters (aperture and shutter speed) for the same iso with any format camera, wether it is 4/3, APS-C, FF, MF, large format. or anything else for that matter.ISO is not based on amount of light per square mm. You made that up... Or just misunderstood things that way.
There is indeed less total light captured, but that is purely because of the sensor or medium size. Amount of light per square mm, which is what iso and metering is based on, is still the same.
Quote:However, a 4/3 sensor is 1/4 of the area of a FF sensor, and hence if one makes an enlargement to exactly the same size as, e.g., an image from a FF sensor, say a 20x30, the FF image print will have 4x less noise, as it has been enlarged 2x less linearly (4x area) provided of course the sensors are of comparable quality.
This is where "iso equivalence" originates from - not real iso equivalence, but equivalence with regard to noise.
It should also be noted that equivalence should always be specifically referred to, as an F/1.4 4/3 lens is still an F/1.4 lens, whether it creates an 4/3 image circle or not. Due to the smaller image circle and shorter absolute focal length, it just has more DoF.
BTW, it is entirely possible to get similar narrow DoF on micro 4/3 as on FF, more or less anyway: just use a Metabones Speed Booster Ultra 0.64x, with FF lenses. Works like a charm. My 85 F/1.2 becomes a 54.4 F/0.8 lens, or a 108.8 F/1.6 in equivalent terms. This is narrow enough to struggle to get a single eye in focus in a tight portrait setting. And sharpness is incredible, as resolution increases with the compression of focal length.
In short, I now have the benefits of both worlds, FF with all the stuff I like to do, but with heavy equipment, micro 4/3 with light equipment with increased DoF, or micro 4/3 with a similar playing ground as with FF when i need that, just that the equipment becomes quite heavy again (but that is ok when you really need it).
Kind regards, Wim