>> From: Vicente <[EMAIL PROTECTED]> >> I think that the problem is the new CMOS AF sensor. It's needed to obtain >> the 7 AF points, but it don't help to low light operation. It's a >trade-off. > >I've read speculations that Elan7's focusing points covers a bigger area, >therefore light need to be spread more, and results in loss as compared to >other cameras with smaller focusing points coverage. >However, I don't understand it at all. The mirror reflects the entire 35mm >frame with even light intensity to the entire focusing screen, therefore >having a focusing point at any arbitrary position of the frame should be >totally independent of the other AF points, no matter how many there are. >Am I missing something? Does SIR have a factor in this? Please enlighten >me.
First point is that AF sensors are not on the focusing screen but under the mirror. The mirror let pass a fraction of the light. When the light hits the mirror it divides in two paths: One goes to the focusing screen and ambiental mettering sensors, and the other crosses the mirror goes to a secundary mirror and reflects into the sensors. The transmision ration off the mirror may change from camera to camera. Moreover, you don't need to have use a full semi-mirror. Part of the mirror can reflect all the light to the focusing screen. The change of technology for the sensors from TTL-CT-SIR on the Elan II to TTL-SIR CMOS on the Elan7 can also change the need of light of the sensors. There are a lot of variables involved in the design. Moreover, the fact that the Elan 7 is not capable of mettering acuratelly using T or M42 lenses makes me think that something has changed in the light paths of this camera. >Thanks, >BlueSky Best regards Vicente * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
