Its been a while since I’ve written a geek article. Over the last couple weeks I’ve been talking with a peer who is considering getting the new Canon EOS 650D (aka Rebel T4i or EOS Kiss X6i). When I got my Canon EOS 7D, he really envied me—he just couldn’t justify the cost. Well, now he is taking a cruise that will take him to the same vendor I got my 7D at (on St. Thomas island). He has had a number of questions of my experience with the 7D because it and the 650D share some similar specs.
However, we started discussing the “brains” of the cameras. Mine has two Digic4 processors. The 650D has the latest generation of the Digic5 processor, but only one. Supposedly, going tooth to tooth, one Digic5 is 6 times faster in processing the image than one Digic4. Besides speed, improvements in handling noise at higher ISO’s are also noted. There are other benefits, but supposedly those are the big two.
In reading a Wikipedia article, Canon has used those claims with each successive iteration of the processor, but not without justification & good reason. For example, the new 1D series, using two Digic5, can shoot 14 frames a second with an ISO of over 200,000 (204,800). The 650D can shoot at 25,600 ISO. The highest ISO my 7D can shoot at is 12,800, half of the 650D but it can shoot 8 frames per second, three frames faster than the 650D and 6 frames slower than the 1DX.
During my reading/research, I also learned a bit more of the process flow inside the camera. There are three major phases. The first is the image capture. This takes place on the CMOS sensor. Next is the image processing; this takes place in the logic chips (Digic processors), handling white-balance, saturation, color correction & much more. Finally, there is the image storage that writes the image to the memory card.
(The last few iterations of digital cameras, at all levels of consumerism, actually divide the "write" process into two separate pieces: First, the image goes to a buffer that is essentially "live" and "fast" memory. Second, the buffer holds the image while the much slower storage card is written to. If you turn off your camera while the buffer is clearing its contents--sending it to your storage card, the camera is designed to remain on until the buffer is cleared. Thus you are not in any danger of losing an image. If you try taking a set of burst photos, you will audibly detect that the first few shots sound very fast compared to the rest. The reason is that the buffer has become full and the bottleneck of image traffic is slowing down the operation while the data gets written to your card. This is reason enough to ensure that you buy the highest write-rating speed of card for your new camera. Especially with the new 18 and above megapixel cameras. You don’t want your burst photos or movies being ruined by write speeds.)