Archived posting to the Leica Users Group, 2005/03/19
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Adam, For a fast lens you typically have a large diameter rear lens element. Yes, the light going through the center of the lens will stay the same. But consider the rays coming from the outer edges of the rear element and refracted into the off axis region of the sensor. This light is also striking at a relatively high angle and may not reach the sensor behind its lens and in the well. This effect will increase as the focal length of the lens decreases; a 200 F2 will have almost full speed, a 24 F1.4 may be as much as a half a stop off for a full frame sensor. This is one reason the Olympus efforts at lens design are worth looking into, their whole line was designed for a specific sensor size with known physical properties. Don dorysrus@mindspring.com -----Original Message----- From: lug-bounces+dorysrus=mindspring.com@leica-users.org [mailto:lug-bounces+dorysrus=mindspring.com@leica-users.org] On Behalf Of Adam Bridge Sent: Saturday, March 19, 2005 3:22 PM To: Leica Users Group Subject: Re: [Leica] Digital cameras with large aperture lenses Okay - I STILL don't understand what you say is happening. I can understand that less light may be captured by the microlenses over the sensor elements located at the edges of the sensors because the lenses, I suppose, are designed for light arriving perpendicular to the plane of the sensor when, in fact, they are not. BUT how does this affect what's going on in the middle of the sensor? It doesn't make any sense to me at all. If you open from f2 to f1.4 you should receive twice the number of photons arriving at the micro-lens (since the lens works identically as that for film up to this point.) So you are saying that something non-linear is happening at this point. What would this be? Is the reflection at the air/microlens interface involved? The microlens/sensor interface? It's about photons, right? I can't believe we've dropped into the quantum realm where QED explainations are required in order to understand the interactions. But I sure could be wrong. anyway - I'd like to understand the physics and so far it's all hand-waving and assertions. There must be a way to do some science here - but I think the camera software, even in RAW mode, tends to cover up any effects that might be happening. I'm really curious and dumbfounded - I'm not doing this for the sake of argument. Adam _______________________________________________ Leica Users Group. See http://leica-users.org/mailman/listinfo/lug for more information