To reply to you question... I wonder if you ever shoot film.... Haiz.... anyways.... I use to shoot film...
Well.. Thinking of how to say it in a way that is less insulting....
1. Light from a 'FF' Lens that falls out of a DX Sensor at f/2.8 will mean that there is less Vignetting/ light fall off. f/22 produce less vignetting than f/2.8. So by Theory and test, a 17-55 f/2.8 has more vignetting at f/2.8 on a DX Sensor compared to a 17~35 at f/2.8 on a DX Sensor. as.. the rear glass is bigger.
http://kenrockwell.com/nikon/20mm-comparison/falloff.htm
2. Lens does not 'suck in' light.....hmmm maybe I used the wrong word... ever played with magnifying glasses. Does it burn??? Every tried pointing your lens at the sun... does it increases the power of light that can almost 'torch your eyes'... Why the spot of glasses are usually brighter... Why Glass, not plastic... hmmm...
3. Sensor... maybe I use a wrong word again... I study about films and sensor... when you expose the sensor longer.. don't you get over exposure??? Isn't a sensor like a light sponge.... if you poor red colour dye on it you get red... when you poor more red it becomes 'redder' .Do you know that by exposing a colour to a sensor over a longer period the colour becomes more vivid.. I shall not tell more of the technic to do so...since you already have them.
I think you you write without first thinking... It's 2 am now.. maybe I am not thinking too... :bsmilie:
Anyways. DareDevil has Good Pictures. :-}
Yes. I shot film. And I am an engineer by training and profession (in my past career at least). I was just replying to your insinuation that FF glass will somehow give you a lot more light to work with. To which I responded yes, but that light is wasted on a smaller sensor.
Yes, vignette thing I agree. There is more possibility of vignette and fall off for a smaller glass. But there is always a design choice to prevent vignetting. It is all about choices of the manufacturer's design over cost. So a DX does not mean it will definitely vignette. But this is separate issue from what we were talking about. Having shot film, I can honestly tell you that there are quite a number of FX lenses out there that are dogs in IQ and light falloff contrary to what you claim. So, in your contention, since using FX lenses with DX bodies is so advantageous by maximising light, FX DSLR users should downgrade to DX bodies to get better IQ?
On your magnifying glass example, I am not sure what you are trying to say. Are you saying that a bigger magnifying glass will yield more power in that burning spot? If that is what you are saying, yes, I agree that a bigger magnifying glass will yield more power in that situation. But, we are talking about a camera here, where the plane where the sensor sits, is not where all the light concentrates. If you move the magnifying glass higher past the "burn" point, you will see a minaturized inverted image of the picture. That is what lands on the sensor. And if you notice, the bigger the glass, the bigger the image at the same distance - meaning more power spread over a bigger area so light per sq inch remains the same compared to a smaller glass of equal IQ. So if your sensor is smaller, you capture less of the image (i.e. less of the light).
Film and sensor differ in the way they react to light. Sensor is not a light sponge. It does not absorb. It has light sensitive diodes that creates a current when light falls on it. each color diode is set to react to one color (usually total 3, red blue and green). Film is different, mainly made of light sensitive chemicals that react to light. Very different. That is why a film image is so different to a digital one. Even till today, some people still swear by film.
I am not insulted. If I am, I wouldn't be bothered to reply. I find that by talking about these things, we are actually educating other readers here which I think is important. Whenever I write, I think. Especially how people will perceive my choice of wordings, and also if what I say or write is fundamentally sound, and if what I write serve a purpose, either to support my argument, or to make a specific point.
I am not trying to start an argument here. It is just simple physics.
BTW, thanks for viewing my pictures!
