Thanks to everyone who submitted questions in November! With no further adieu, here are December's Tech Tips:

In DPP 2.0 there is a sharpness slider in the Raw Image Adjustment window that goes from 0 to 7, and there is a sharpness slider in the RGB Image Adjustment window that goes from 0 to 500. I am unable to find any explanation of the differences in those two sliders. Can you assist? Thank you.

In Digital Photo Professional software, the RAW Image Adjustment window supports RAW images only, whereas the RGB Image Adjustment window supports RAW, JPEG and TIFF images, as mentioned on page 2-6 in the DPP instructions. If you are working with a JPEG or TIFF image, you cannot use the RAW Image Adjustment window and are therefore limited to the RGB Image Adjustment window. If you are working with a RAW image, you can use both windows. Assuming that's the case, there is no difference in terms of the sharpening algorithm between the RAW Image Adjustment window and the RGB Image Adjustment window, but as you point out, there is a difference in the number of increments. Incidentally, it's 0 to 10 for the RAW Image Adjustment window rather than 0 to 7 as it is on the EOS 5D and 1D Mark II N, but you are correct that it is 0 to 500 for the RGB Image Adjustment window. The choice between the two is up to you, but the RGB Image Adjustment window offers a finer degree of control over sharpness than the RAW Image Adjustment window.

I just got a new 1D Mark II N, and am in a bit of a panic regarding its low-light autofocus lag. In a two-lamps and TV lit room, my 20D snaps objects into focus with both my 28-70L lens and my 100 2.8 macro (both Canon, of course). The new 1D Mark II N actually takes about one second on all of the same objects. It is fine in high light, but it actually takes about a second or more to lock on the same objects upon which the 20D with these lenses locks almost instantly. Both are in the center-square focus point, P-mode, same ISO, single-shot, etc. ... I'm about to panic. Any info, including if that means a suggestion to have it sent in, will be appreciated. I was expecting at least the same performance as my 20D, and it is acting a bit like a fast D60.

One of the differences between the 9-point AF sensor used in the 20D versus the 45-point Area AF sensor used in the EOS-1D class cameras is the size of the individual pixels on each. The pixels on the 45-point AF sensor are much smaller than those on the 9-point AF sensor, and one inevitable result of this difference is superior low-light sensitivity for the 9-point sensor. This is reflected in the specifications for each camera, which state the 20D's AF sensitivity at EV -0.5 compared to EV 0 for the 1D Mark II N.

However, when considering the overall performance of these cameras, any fair comparison will show that in most light levels other than extreme low light, the 45-point AF sensor is much faster than the 9-point sensor in terms of tracking subject movement, and there is no question that it covers a far greater percentage of the picture area. Moreover, it has 7 cross-type focusing points to the 20D's single cross-type focusing point. Last but not least, the low light AF performance of both cameras can be enhanced with an AF Assist beam, whereas the coverage and tracking speed of the 20D's AF sensor cannot equal the 45-point AF sensor under any circumstances.

Ultimately, the choice is yours, but the kind of photography you do should make a difference. Unless you do a lot of your work in extremely low light without an AF Assist beam, there's really no problem with the performance of the 1D Mark II N's AF sensor.

I'm getting ready to sell what has long been my favorite travel lens: the Canon 28-135 IS. I have noticed that, on occasion (usually in colder weather) the IS system will cause the viewfinder image to vibrate at a very high frequency and emit a sound similar to a vibrating pager or cell phone. I've owned more than one copy of this lens and they have all done this on occasion. I also see questions about this phenomenon occasionally in different forums but never an explanation. Is this a malfunction of the IS or just something that can happen to a properly functioning lens under certain circumstances? I don't want to sell someone a broken lens and I can't seem to get through to anyone at a Canon Factory Service Center who is knowledgeable enough to even guess one way or the other.

The image stabilizer mechanism in any Canon IS lens operates by means of a set of electromagnets surrounding a group of movable lens elements. It's usually possible to feel a vibration through the barrel of the lens or hear an operational noise while the stabilizer is running, although in the case of the EF 28-135 IS, the mechanism is virtually silent due to its relatively small size. If this is all that's happening (i.e., you are feeling a vibration through the lens barrel or hearing a slight operational noise while the image stabilizer is running), it is completely normal and nothing to worry about.

A vibrating image in the viewfinder is another issue altogether. Like you, I have noticed (and documented) the fact that specifically with the EF 28-135 IS lens, the viewfinder image occasionally tends to vibrate at high speed while the stabilizer is running. However, in my observations, this occurs only when the camera is set for AI Servo AF, and then only with certain EOS digital SLRs like the original EOS-1Ds. I don't think that temperature has anything to do with it. If the viewfinder image vibrates at high speed while the stabilizer is running, I would suspect that the camera rather than the lens might be the root cause of the problem. Regardless of where the problem lies, it would be best to have both the camera and the lens examined by a Canon Factory Service Center technician to make sure that it is properly repaired.

I just got the EOS-1D Mark II N and everything is fine except that the file number jumped by about 7300 suddenly. It seems to have coincided with attaching my EF Extender 1.4X plus my EF70-200L IS zoom lens. The number went from 0045 to 7368 or so. Is there a fix coming for this? I can't see any BIOS update for this camera yet. My photography business depends on unique file numbers so this will be a problem. Please let me know what I should do.

This usually happens when another memory card is used after the first shot was taken, and this second card has digital images with higher file numbers on it. Like any previous EOS digital SLR, the new EOS-1D Mark II N looks to two things before establishing a file number -- it already knows the most recent number assigned by the camera (whether it was a moment ago, or months ago), and it also examines the contents of the active memory card to see if it detects any files on the card. If so, it compares the highest file number on the card to the most recent file number assigned by the camera, then selects the higher of the two and adds "1" to it. I can't say what happened in your situation, but this is the only way a properly-working system would "jump" file numbers like that. And be aware, regardless of whether your system is set to Continuous file numbering or Auto Reset, in the scenario I mention here, every subsequent number would be in sequence with the suddenly-higher sequence, even if you changed back to a card with lower numbers you'd shot moments before. The system is designed this way to prevent the possibility of writing duplicate file numbers on the same memory card.

If unique file numbering or filenames are important to you, then your best bet will be to rename your files according to your personal preferences. This can happen either during the downloading process, or after the files have been downloaded to your computer. Canon supports both methods with the software that is supplied with the EOS-1D Mark II N. Use ZoomBrowser EX (Windows) or ImageBrowser (Mac OS X) to rename files during the download process, or Digital Photo Professional (Mac/Windows) to rename files that have already been downloaded.

I have the Canon EOS-1Ds Mark II. I have a job to shoot oil rigs in Calgary ... cold weather. Does anyone have any experience using digital SLRs in freezing and near 0 degrees?

Ah, the notorious "cold weather" question...Hard to believe we're on the verge of another winter season here in North America. Here are some timely "Tech Tips" for winter shooting with digital cameras:

As noted in the instruction books, the limit for guaranteed low temperature operation with any EOS digital camera is 0 degrees Celsius. However, a lot of people have been successful using our cameras in sub-freezing temperatures, as long as they observe the following precautions against condensation and poor battery performance. Here's some background info on cold weather operation:

SHUTTER LUBRICATION: Older cameras like the Canon F-1 had heavy-duty shutter mechanisms that required special modifications in lubrication for cold-weather use. Today's digital SLRs do not require any special lubrication, because their shutters use newer designs with high-performance, lightweight blades and smaller magnets. In terms of shutter performance, no special modifications are necessary for cold-weather use.

CONDENSATION: Even though EOS-1 class digital SLRs are well protected against moisture in the form of rain and snow, etc., they are vulnerable to severe internal damage from condensation, like all other digital cameras. That's the main reason why we recommend placing cameras, including but not limited to EOS Digital SLRs, in airtight plastic bags before bringing them from a cold environment to a significantly warmer one. This allows the condensation to form on the bag, thus protecting the equipment as much as possible.

BATTERY PERFORMANCE: Battery performance drops off as the temperature falls below freezing. Nickel metal hydride and lithium-ion battery packs are better than alkaline batteries in this situation, but even the lithium-ions will eventually stop working once they've chilled long enough. By now, at least one 3rd-party developer (Digital Camera Battery) has produced an external battery that can connect to the EOS-1 class digital SLRs through the supplied DC Coupler, but I don't expect Canon Inc. to either condone this or to make one of their own. In the meantime, the best strategy is to carry a few fully charged spare NP-E3 packs inside your coat, where they can be kept warm and exchanged for the cold batteries from time to time as necessary.

Memory cards are another potential weak link. Canon doesn't make its own, so it's best to check with the card manufacturers and other photographers to get a cold weather rating.

As with current film-based electronic cameras, items such as LCD data displays are the only means available to indicate camera settings such as shutter speeds, apertures, frame count, etc. Digital cameras add another type of LCD for use as a playback monitor. The information normally seen on these displays tends to disappear when temperatures drop below -20 degrees Celsius. LCDs usually start working again when the temperature goes above freezing, but that won't do you much good out in the cold.

Bottom line, it's certainly possible to use professional digital SLRs in freezing conditions, as long as they are handled correctly. The main issues are condensation and adequate battery power, but with a bit of advance planning these obstacles are not insurmountable.

However, there's not much that can be done with existing technology to ensure consistent digital camera performance in severely cold conditions for the reasons outlined above. You are welcome to try EOS digital SLRs in sub-freezing temps, but keep in mind that you're bound to run into some limitations eventually.

Thanks for reading "Tech Tips"! That's it for now. Happy Holidays to one and all. See you in 2006!

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.)