04-21-2013, 07:18 PM
With all this math mambo-jambo you, popo and brightcolours, just seem to forget:
There's not such a lens for APS-C like there are some very pricey ones for FF - and to use them, you just need to get an also pricey FF-body. Which, following Klaus' post are overrated and overpriced anyway, so all the people buying these are just wasting money?
I don't get the point trying to calculate equivalence for FF, this is not a question for an APS-C shooter how "lame" this lens is compared to what is available for FX. At the moment it's just outstanding for APS-C and if it can be used at open aperture, it still gives 1.5 f-stops more than the usual 17-50/2.8 "fast standard zooms" which I don't find that overpriced (except a Nikon 17-55/2.8, ok, point taken).
And DoF? At 18mm and open aperture it's 0.86m, not breathtakingly narrow. f/2.8 (with APS-C and same focal length) would give 1.47m.
One can ask if a Sigma 17-70/2.8-4 OS couldn't be a bit more useful, because of the OS which compensates more than the 1.7 missing f-stops (I was interpolating until 35mm) - but there's no other way to get a narrow DoF and short shutter speeds.
And, by the way, it's not correct to calculate those ISO differences like you did: the borders between the sensels keep the same size, more or less, so in reality the sensitive area decreases more when the sensors get smaller with the same pixelcount.
"The sensor gets MORE sensitive. If you have more surface, the sensor will catch more light. If you have bigger pixels, the pixels will catch more light. Hence: the FF sensor is MORE sensitive by definition."
So a film 8×10 inch and 100 ISO is per your definition much more sensitive than a film 135 with 100 ISO?
Strange - my old spotmeter didn't list film formats as parameter. Must've been a cheap one...
It will capture more photons, in absolute numbers - but not more on the same area than the smaller frame will catch, too.
There's not such a lens for APS-C like there are some very pricey ones for FF - and to use them, you just need to get an also pricey FF-body. Which, following Klaus' post are overrated and overpriced anyway, so all the people buying these are just wasting money?
I don't get the point trying to calculate equivalence for FF, this is not a question for an APS-C shooter how "lame" this lens is compared to what is available for FX. At the moment it's just outstanding for APS-C and if it can be used at open aperture, it still gives 1.5 f-stops more than the usual 17-50/2.8 "fast standard zooms" which I don't find that overpriced (except a Nikon 17-55/2.8, ok, point taken).
And DoF? At 18mm and open aperture it's 0.86m, not breathtakingly narrow. f/2.8 (with APS-C and same focal length) would give 1.47m.
One can ask if a Sigma 17-70/2.8-4 OS couldn't be a bit more useful, because of the OS which compensates more than the 1.7 missing f-stops (I was interpolating until 35mm) - but there's no other way to get a narrow DoF and short shutter speeds.
And, by the way, it's not correct to calculate those ISO differences like you did: the borders between the sensels keep the same size, more or less, so in reality the sensitive area decreases more when the sensors get smaller with the same pixelcount.
"The sensor gets MORE sensitive. If you have more surface, the sensor will catch more light. If you have bigger pixels, the pixels will catch more light. Hence: the FF sensor is MORE sensitive by definition."
So a film 8×10 inch and 100 ISO is per your definition much more sensitive than a film 135 with 100 ISO?
Strange - my old spotmeter didn't list film formats as parameter. Must've been a cheap one...
It will capture more photons, in absolute numbers - but not more on the same area than the smaller frame will catch, too.