Unshielded Bodies?

Here is a detailed article by Peter Zheng about the internal dissections and PCB layouts of different DSLR models of different brands, namely, Pentax, Canon and Nikon ones:-

http://docs.google.com/View?docid=df2k6qz2_89db3xzcdq

In the beginning of his article, an excerpt of a Japanese interview with the Pentax imaging department, about the concern of EMI (Electro-Magnetic Interference) of the Pentax DSLR bodies, is also quoted.

One important thing was found and is noted: Pentax's internal circuitries and PCBs (Printed Circuit Boards, and of course those electronic components inclusive) are NOT shielded *whilst* all other models made by Canon and Nikon are well shielded, grade and price regardless. In fact, this could cause EMI issues, also as admitted by the Pentax official in the interview.

The author further writes that Pentax DSLR bodies, from *ist Ds to K10D, are all unshielded. Although he writes no further information about if the K20D, K200D and K-m are shielded, it would be fairly reasonable and safer to assume that they are also unshielded. Nonetheless, it still has the (minimal) chance that Pentax would have already improved the design, by adding a metallic shield like the other DSLR makers have been doing (since long ago), but none of us is for sure unless there is anyone who has dissected one of the three newer Pentax bodies and let us know.

According to the IEC standards, the formal term used on describing devices and appliances should not interfere with each others, electro-magnetically, is called the "Electro-Magnetic Compatibility", or just called EMC in short-form. And, EMC compliance is validated only if one of the following two conditions are fulfilled:-

1. The device does not interfere with any other devices nearby;

2. Any EMI existent in the environment which the device is placed, should not interfere and affect the normal operations of the device.

There is a third case which is not mentioned in the IEC standards, though (but indeed it is not needed to be mentioned, but it is crucial!), that is, the device should not interfere itself and the inside electronic components of the device should not interfere each others amongst themselves. In fact, this is just something that is closely associated with the PCB and component layout design. And of course, the PCB metal shield (as shown in other C and N DSLR models) should help, and in most cases, as it helps to suppress EMI from "flying" around inside the body, once those are arisen, and could eventually be picked up by the PCB traces and/or other electronic components. As for the Pentax cases, you can see some examples of strange interferences which could affect the final images here and here (cases of the K10D and K20D respectively).

Now, let's look at the operating frequencies of a typical 10MP DSLR, say, with the most "popular" Sony 10MP CCD imager. First of all, the CCD is operating at a clock frequency of 25MHz, for the pixel signals to be "clocked" out in a chain (of waveform). Secondly, the CPU and IPU and internal memory RAM etc. of the camera are operating at much high frequencies, usually from several hundreds of MHz to a few GHz nowadays (the lower GHz range is well known as Microwave in dailylife term). For the former 25MHz signals, any external EMI at that *base* frequency could severely affect the signal. However, EMIs with higher frequencies could also affect the signal waveform as the 25MHz is only the base frequencies and there exists higher harmonics (in multiples of the base frequency) contained in the actual signal to be transmitted (which is generated out from the CCD imager, and to be received for second stage processing). As a result, the final transmitted/received signal is distorted (in addition to signal loss and other imperfection of the electronics and circuitries), which eventually to appear as noise, and even worse, in bandings or pattern noises. Similarly, the same case applies to the CPU and IPU which are operating at the GHz levels. The only difference is that the CCD signal (same case for CMOS as well) are just primitive analogue devices which are even be more susceptible to those EMIs and especially they are the heart of the DSLRs as the imagers are just for receiving the raw image and light data afterall.

Well, still remember the IEC EMC standards and the two prime and essential requirements? The other concern is how an (electronics) device which is EM compatible should NOT interfere with other appliances. In the above case, the DSLRs with the (most popular and common) Sony CCD imager could affect FM radio and other RC controlled devices or communication systems in range of tens of MHz or higher (in multiples of that base frequency, even worse, if mixed with other EMIs with other frequencies, in the new intermodulated frequencies as well). And, the much higher CPU and IPU EMIs could affect other devices which are operating at GHz frequencies, e.g., mobile phones, indoor DECT phones, PC and notebooks and so on.

So, afterall, why not shieldED the PCBs?? Even Canon and Nikon DSLRs that are having a metal outer body shells are shielded. How come Pentax DSLRs with only metal INNER frames but all plastic outer shells are NOT be shielded??? Well, I must agree this is a huge concern and issue as raised.