I wonder if you can comment on the technical and business feasibility of making a digital camera body that has, like the lens and memory, an interchangeable image sensor and image processor? It makes sense from the consumer side, to protect the value of our camera investments.

The concept of interchangeable image sensors and image processors sounds like a great idea in theory, but the realities of a competitive market make it highly unlikely. First of all, there's a lot more to the design of a digital camera than lenses, sensors and processors. What about things like size, weight and cost? What about improvements in the design and performance of other components like the camera body and LCD screen, etc.? Frankly, in my opinion it makes a lot more sense to give camera designers a clean slate to work with so that they can take advantage of technological developments not only in sensors and processors, but in all other areas of product development as well. History clearly shows that every significant expansion in the digital SLR market has occurred due to the release of new products that provide better features at lower prices than previous models. Locking in on a single body design just to support the ability to upgrade internal components would almost certainly cost customers more money, while simultaneously leaving them behind the curve in terms of technological evolution.

One of the first pro bodies I ever owned was the Canon EOS 3. I loved it quite specifically because of the Canon-exclusive Eye Controlled Focus. Not sure if I'm alone in this but, doing mostly documentary work, it was incredibly useful. Focusing became more instinctual the more I used the camera, allowing me to concentrate on the content of my work. Is Canon considering bringing Eye Controlled Focus back to any of the digital EOS bodies? Is there some technical limitation? I think that specific feature is one that photojournalists in particular would really appreciate.

At this point, it is reasonably clear that the absence of Eye Controlled Focus (ECF) in EOS digital SLRs is a marketing decision. There is no point in ruling out the possibility that ECF may be introduced in future EOS models, but I don't expect it to appear unless a sufficient level of market demand is perceived. So far, that has not happened, but your request has been forwarded to our Product Development Center.

It would be interesting if Canon could build a fixed focal length pocket-sized digital camera as a high-quality snapshot compliment for SLR users. Replacing the usual zoom for a higher quality "L" fixed focal length lens (say 35mm equivalent), combined with a 3:2 ratio "SLR" type sensor, would appeal to those looking for a higher image quality pocket camera at around a $500-$700 price point. Contax successfully did that for film users back in the '90s with the Zeiss-lensed T1/T2 series 35mm compacts. What do you think?

A high-quality compact digital camera of the type you propose has been suggested to Canon many times over the past several years. If we ever release such a product, I am certain it would be well received by savvy photographers all around the world. That being said, I'm not so sure that sales volume would be high enough to justify the required investment, unless the market price is sufficiently affordable. This creates a dilemma: the lower the price, the less compelling the feature set for a camera that virtually by definition is not designed for the masses. However, it's still a tempting idea! Thanks for the suggestion.

I work as a photojournalist on several newspapers in Brazil. Recently I bought a Canon EOS 30D. I know that's not what Canon recommends for this kind of photography. For sports and action in general I should have an EOS-1D Mark II N. That being said, I should tell you I'm very pleased with this camera and its possibilities. After reading October's Tech Tips I started wondering about LCDs and stuff. And I have to ask you this. Why doesn't the 30D's LCD show exactly what I've shot? I say that, because every time I shoot an underexposed picture, it looks OK on the LCD screen. Only when I transfer the images to a computer do I see that they're underexposed. The opposite is not true, though. When it comes to overexposure, they look far too white on both the LCD and the computer screen.

I understand your concern here. You'll be pleased to know there's a solution to this issue: Use the EOS 30D's histogram display. It provides a reliable indication of exposure accuracy. For what it's worth, it is important to understand that the 30D's LCD screen is intentionally designed to take maximum advantage of its limited brightness range in order to provide a readable image for photographers while they're working in the field. The enhanced brightness of the image makes it easier to check details in an image, such as facial expressions, sharpness, etc. The trade-off for this is that some images appear darker on a computer monitor than they do on the camera's screen. But when checking exposure accuracy is the priority, the camera's histogram display is a valuable tool.

I work as a news photographer in Auckland, New Zealand, and I use a Canon EOS-1D Mark II N. Other photographers and I have found that the images taken on RAW are not as sharp as images taken on JPEG, and the focus tracking seems slower on RAW. Is there a reason for this?

In order to preserve the maximum amount of image information, raw data is intentionally unsharpened. It is up to the photographer to decide how much sharpening to apply when rendering a JPEG or TIFF image with conversion software such as Canon DPP or Adobe Camera Raw, etc. On the other hand, in-camera JPEGs shot with an EOS-1D Mark II N are typically sharpened if the camera is left at its default Standard picture-style setting. This difference is usually not a big obstacle for most photographers who shoot RAW images. Once they find a sharpening setting they like, they can lock it in on their conversion software and simply apply it to all rendered images. Similarly, the Mark II N allows photographers to adjust the sharpening on in-camera JPEGs. The standard setting is level 3, which is essentially mid-scale between 0 and 7. The image quality setting (RAW or JPEG or RAW+JPEG) has no bearing whatsoever on autofocus performance.

Can you explain to me why, when shooting in RAW on the EOS-1D Mark II or Mark II N, I would not have focus tracking problems? I think I know the reason but I need something from an expert to show the photo staff here. We have started shooting all our work in RAW and the photogs say that is impossible in this mode as the camera does not keep up with the focus.

Focus tracking and lens drive operation are completely independent from the photographer's choice of recording formats. After all, from the camera's point of view, every exposure starts out as raw image data that is subsequently converted to JPEG or recorded as a RAW image according to the image quality setting on the camera. Therefore, setting the camera to record RAW or RAW+JPEG has no effect on focus tracking or lens drive. However, because of the larger file sizes involved, it does have an effect on the number of images that can be recorded in a burst, and how long it takes to write the image data to a memory card.

Here's a more detailed explanation: The EOS-1D Mark II N can nominally capture 48 consecutive Large/Fine JPEGs, but only 22 consecutive RAW images, or less when the camera is set for RAW+JPEG. This occurs because RAW images require more storage capacity than JPEGs, but the buffer memory capacity of the camera is fixed. Under these circumstances, it may well be that photographers who are used to shooting JPEGs are noticing that the camera's buffer fills up much more quickly when shooting RAWs. This problem can be minimized somewhat by using fast memory cards, but ultimately the photographers must come to terms with the fact that they cannot shoot as many RAW images in burst mode as they might wish. Clearly, though, the choice of image recording formats has nothing to do with focusing accuracy.

I have a Canon 20D that I sent in for repair. I did not include a compact flash card. When I got the camera back, the image sequence number and the folder number were way different than what is in my database. How can I reset the sequence number and folder (less important) back to the original sequencing?

Here's what to do if you still have a CF card with images that are exclusively from the initial file numbering sequence, ideally from the end of that sequence:

1. Find a spare CF card that you don't mind formatting.
2. Set the camera's file numbering setting to Auto Reset.
3. Format the spare CF card. This resets the file numbering sequence to 100-0001.
4. Set the camera's file numbering setting to Continuous.
5. Replace the spare CF card with the CF card that has the last image from the initial file numbering sequence. The camera will resume file numbering from that point.

I recently purchased a used EF600mm f/4L USM lens (non-IS), and am using it with my EOS 30D. It has provided great pictures in my resolution tests so far, even when using stacked 1.4X and 2X extenders, but I am concerned that the focusing ring only seems to work in manual mode. Since I don't have the lens manual, I don't know if this is a defect in the lens (which I have about five days left to return), or whether it is the way it was designed. I have heard that on some camera bodies it is possible to enable manual focusing after AF is complete -- does the 30D support this function? (I've mislaid my instruction manual for the camera as well.)

The EF600mm f/4L USM (the non-IS version) has an electronic manual focusing system that requires electrical power to operate. As you say, the focusing ring is functional when the focus mode switch on the lens is set to M and the lens is mounted to an EOS body that's on. There are also two ways to operate the manual focusing ring when the focus mode switch is set to AF:

1. Set your EOS 30D to Custom Function 4-1 or 4-3. This optional setting initiates autofocusing from the AE lock button on the back of the camera, while making the manual focusing ring of your lens active even in AF mode.

2. Set your EOS 30D to Custom Function 4-0 (the default setting) or 4-2 and set the camera for One-Shot AF. In this configuration, the manual focusing ring will become active in AF mode after autofocusing is complete, while the shutter button is pressed halfway and the green in-focus indicator dot in the viewfinder is visible.

The EOS 30D instruction manual is available online at Canon USA's Web site. You can order a copy of the instruction manual for any EF lens through Canon USA's Customer Support Center at 1-800-828-4040.

Thanks for reading Tech Tips! That's it for now. See you in December!

You are invited to submit questions about photo equipment, imaging technology, or photo industry trends that may have a bearing on your work or interests. I cannot promise to answer everything, but I pledge to do my best to address the issues that concern you. (Please use the e-mail link provided at the end of this article.)