It’s been about four months since Casio showed the prototype of its high speed digital camera last August at IFA in Berlin. Now Casio has announced they're going to push this to production as the EXILIM Pro EX-F1. This is the most exciting amateur camera I’ve seen in a long time.
The camera is based on the Sony IMX017CQE 1/1.8” CMOS sensor announced back in February 2007. This sensor is kind of a “light” version of the Sony 12.5MP APS-C IMX021 sensor used in cameras like the Sony Alpha A700 and Nikon D300.
The design of the CMOS sensor used in the EX-F1 is very interesting. Not only is it a CMOS sensor, as opposed to CCD sensors used in most consumer cameras, but it also integrates some really nice features. Some of the sensor’s highlights include on die A/D converters, 12-bit column A/D converters (operating at 10-bit resolution at higher than 15fps), and a 432MHz LVDS interface. Worth noting here are the column A/D converters. This feature allows the sensor to output captured images at the full 6MP resolution at an amazing 60fps. That’s about 425MBs per second of raw pixel data! Casio aren’t saying much about the image processing engine they’re using in the EX-F1. It sure is a smart design, but I doubt there’s any ground breaking technology here in terms of image processing speed. The mere fact that the EX-F1 is a consumer camera means the Casio engineers don't have a large R&D budget (when compared to professional DLSRs) or designs that require expensive manufacturing processes. To get an idea how much processing power is required to crunch through all the data the Sony sensor can cram out, take the Canon 1D Mark III as an example. With its 10fps 10.1MP sensor outputting around 170MBs per second, the camera needed TWO full fledged DIGIC III processors to be able to go through all that data in realtime. I don’t think that Casio was somehow able to design an ASIC that is several times more powerful than the Canon DIGIC III processor used in the $5,000 MarkIII yet cheap enough to make for them to be able to cram it in a sub $1,000 camera.
So, how did Casio manage to do it? I think the answer lied in the mini site Casio had for the prototype. Unfortunately, now that the camera has been officially announced, that mini site has been pulled down. Within that site was an image of the image processing board for the prototype of the EX-F1. On that board, one could clearly see the image processing ASIC surrounded by two other chips. I think those chips were DRAM chips. Most probably two 2Gbit (256MB) DDR DRAM chips. My theory is that the Casio engineers used a large DRAM buffer to achieve the 60fps at 6MP capability. Using a large DRAM buffer is a very cost effective way of achieving the high performance of this camera. By Buffering the entire burst of images allows the processing engine to take its time to go through the buffered images, process each one into a JPG, and then store it on the SDHC card. My theory is further strengthened by the fact that Casio stated the camera can sustain the 60fps rate at full esolution for only 60 frames. A 1 second burst would fill around 425MBs of a 512MB buffer. Which if true, leaves some 87MBs available, which is plenty for processing each buffered image and the housekeeping functions of the camera firmware.
Funny enough, when capturing video (even high speed video) the image processing engine has to handle less data than when capturing images at its full resolution at 60fps. When capturing full HD video (1080p@60fps) the engine has to handle around 356MBs per second of pixel data. When capturing 512x384 video at 300fps it has to handle around 211MBs of data per second. When capturing 432x192 video at 600fps it handles around 178MB per second. And 138MBs per second when shooting 336x96 video at 1200fps. That’s 83.7%, 49.6%, 41.9%, and 32.8% respectively of what the image processing engine handles at 6MP resolution at 60fps. However, when capturing video, the engine doesn’t have to go through the grueling debayering algorithms used when capturing still images. This is because the sensor is outputting at 2x2 or 3x3 line readout. So debayering becomes a trivial task. There's still the task of compressing the video stream, but that's not much of an R&D problem, as there already are quite a lot of HD video compression engine designs the engineers can choose from. And because of the reduced resolution the higher the frame rate goes in video, the actual workload on the image processing engine would actually be reduced the higher the frame rate goes. I doubt we will be seeing a similar camera based around the Sony IMX017CQE sensor from any other major camera brands like Canon, Nikon, Pentax, or even Sony. Not because of any technical hurdles that would prohibit the development of such a camera, but because such a camera would be competing directly with those brands’ entry level DSLRs. Casio can afford to make such a camera simply because they don’t have to worry about eating away from the sales of any higher model they have. I can't wait until this camera hits the store shelves. And I'm positive that once the price goes down a little(estimated initial retail price is $999), this baby will be one hot seller.