Gary's Parries 12/11/06

November 12, 2006 | Mark Goldstein | Gary's Parries | Comment |

Gary's ParriesThis week’s Gary’s Parries topics are:

1. Concert Audio For Digital Camera Videos
2. SDHC Write Speed For Digital Camera Videos

Introducing this week’s Gary’s Parries column. Everything you always wanted to know about digital cameras, but were afraid to ask. No question too difficult, or too easy. As a Senior Principal Software Engineer, and a former Assistant Professor of Computer Information Systems, as well as a recording studio owner/operator, inventor, and now, a digital camera enthusiast, GARY has more digital camera knowledge in his entire brain than most people have in their little finger. In the unlikely event that GARY would not know the answer to your question, he will answer it anyway, true to the spirit of the word “Parries”, a fencing term which, in this context, implies “cleverly evasive answers”. So let your imagination run wild. Email all your nagging digital camera questions to: , and then, En Garde!

You may also attach to your email an ORIGINAL PHOTO of your choosing. A preview of the photo will be displayed with your question, and a full-sized version will be just a click away. No personal information will be published with your question unless you specifically include it in the text or attached photo of your email, which may be further edited for grammar, content, or other reasons.


garys_parries_121106_q1.jpgI’m a total novice who enjoys recording segments of jazz performances. I’ve been using a Sony DCR-TRV361 camcorder for recording videos, and a Sony DSC-S85 for photos. As camcorders are becoming more and more a ‘no-no’ at performances, and as the S85 fails the photo test in several respects (only 3x zoom, poor low-light performance) I’m ready to move on.

I can live with a few still-camera video segments if I can get sound that is comparable to the marginal audio of the TRV361. Digital camera manufacturers seem to ignore audio specs, so I assume they are very low. The cameras I’m considering are the Canon PowerShot S3 IS or G7, the Sony DSC-H5, and the Panasonic Lumix DMC-FZ50.

Can you provide some clarity on this murky subject?

*** ANSWER 1

Besides camcorders becoming a ‘no-no’ at concerts, I have also heard cases of similar treatment for SLRs. So, even though the Panasonic Lumix DMC-FZ50 has a standout 16:9 (848 x 480 pixels), 30 fps video mode, and a fantastic 12x, image-stabilized zoom lens, great for those distant stage shots, you might not want to take one to a concert, for the simple reason that it looks conspicuously very much like an SLR.

You are also correct about digital camera manufacturers not providing audio specs for their cameras. The exception would be when a camera features stereo vs. mono audio. Of the cameras you mentioned, only the Canon PowerShot S3 IS offers stereo audio.

The biggest advantage of the S3 for the video recording of concerts (besides its stereo audio) is its 12x, image-stabilized, zoom lens (though not as highly rated as the FZ50’s lens). The biggest drawback of the S3 for the video recording of concerts is the fact that, like the FZ50, it is a very conspicuous (almost SLR-like) camera. The Sony DSC-H5 has basically the same advantages and disadvantages for concerts as the S3, except that it does not have the S3’s advantage of stereo audio.

The only camera you mentioned that would even come close to being inconspicuous at concerts is the Canon PowerShot G7. The good news is that the G7 has the highest resolution video mode (1024 x 768 pixels), as well as the best still-camera image quality of all those you’ve mentioned. The bad news is that it has only a ‘6x’, image-stabilized zoom, its 1024 x 768 pixels video mode is only 15 fps, and it does not record in stereo.

One other digital camera you might want to consider for its high-quality audio recording is the Samsung NV3. While the NV3 has only a 3x zoom and no stereo audio, it does have an AGC (Auto Gain Control) to minimize audio noise pickup during recording, and even better, it allows for the use of ‘optical’ zoom during video recording (which is quite a rare feature for digital cameras).

Best of all, the NV3 is a highly ‘concealable’ camera. In view of the fact that most digital compacts now have camcorder-like video capabilities, how long do you think it will be before they too are banned from concerts? :)

[Note: Thanks to Nick in Japan for submitting this beautiful landscape scene taken with his Sony DSC-F828. Get well soon, Nick. We miss you. – Ed.]


garys_parries_121106_q2.jpgYou may recall my question in the September 3, 2006 Gary’s Parries stating that I had followed PhotographyBLOG editor Mark Goldstein’s digital camera reviews for about 2 years in hopes of finding a robust, splashproof, compact digital camera to replace my 11-year-old Pentax WR90 roll-film camera, one with a similar budget (

< £250), but with a slimmer body, and a far improved zoom lens (ideally 28-200mm). As I had said, 95% of my UK photography is on yachts, usually racing, and I had hoped to repeat in a new camera the WR90’s tough, splashproof, polycarbonate case right out of the box (i.e., without the need for fiddly and expensive ‘over-cases’).

Yacht racing aside, however, my immediate need is for a slim travel camera, suitable for an upcoming trip round Brazil. The primary requirement is as previously stated, but with an overriding need to be able to keep the camera unobtrusively in a trouser pocket to avoid the interest of muggers.

I have all but decided on a Canon ‘Digital IXUS 850 IS’ (a.k.a. ‘PowerShot SD800 IS’). The zoom is only 28-105mm, which meets my wide-angle requirement, but not the telephoto; however, I was thinking its so-called ‘Safety Zoom’ could give me an effective 2x ‘digital’ zoom extension to 210mm without, as Canon claim, any loss of image quality (remember it’s a 7.1 megapixel CCD). However, I fear from all the discussions about digital zoom that this may be wishful thinking, and that this ‘safety’ digital zoom may not be one iota better than just plain digital zoom. What do you think?

Another main reason I am contacting you again is because I have a query on the write speed requirement of SD cards for video recording. Since I am limited to 20kg on the flight, I must do all my photography with one camera. Although I will be primarily taking stills (and coming from roll-film, I am frugal, rarely taking a second quick-shot of the same scene), I will also want to make some movies.

Since Canon has raised its movie recording size limit from 1GB to 4GB for the 850, I will want to buy a 4GB SDHC; however, the Canon website spec for the 850 does not state or even allude to what the minimum write speed requirement for an SDHC card would be in order to maintain the 850’s VGA 30 fps performance. I called Canon with this very question, but answers varied from “slow” to “as fast as possible” depending upon with whom you were speaking.

For other cameras, I have seen some reviewers say “need a fast card” while others will say “tried a slow card and did not notice any difference.” Clearly, if money is no object, you can play it safe and buy the most expensive, fast card around, much like people used to say “buy IBM!”

My own thinking as to what minimum SDHC write speed is required to avoid slowing down the camera’s movie record performance is simply this: as I can find nothing in the general Canon brochures on this issue, I see that Panasonic’s brochure offers a handy table of Image Recording Capacity and Movie Recording Time, from which I used the fact that a VGA mode movie at 30 fps will fill 128 megabytes of memory in 83 seconds. That equates to a write speed of (128 / 83 =) 1.54 MB/sec. That implies that an SDHC write speed of 2 MB/sec is okay.

I would be grateful if you could check my logic, and from your experience, whether there may be some other factor that needs to be taken into account. If indeed, an SDHC card write speed of 2 MB/sec is adequate to support VGA movie recording without any slowdown, then I had thought to get the SanDisk 4GB SDHC, which has a write speed of just 2 MB/sec, and rather importantly, is claimed to be actually available. Also, it comes with an included SDHC-to-USB2 adapter.

If 2 MB/sec is not enough, what do you think about ORA Memory? ORA’s 4GB SDHC write speed is claimed to be 15 MB/sec, but it is more expensive, has only a 2 year warranty (vs. lifetime for the SanDisk), and has no USB adapter.

My flight to Brazil is already booked, and I want to order the camera and 4GB SDHC as soon as possible. The issue of the SDHC card type is all that is now holding me back, so I would be grateful for your advice on this matter as soon as possible.

Kind regards,
Leon Gee

*** ANSWER 2

Hold your Mangalarga Marchadors, Leon. :)

You say your primary requirement for this Brazil trip camera is as was previously stated (for your yacht-racing camera), and if I recall correctly, your previously stated primary requirement was that the camera had to be SPLASHPROOF. I hate to break this to you Leon, but the ‘Canon Digital IXUS 850 IS’ is NOT a splashproof camera. So, unless you also intend to buy its optional underwater case (which I seriously doubt based on your previous statements), then I would definitely NOT buy the Canon Digital IXUS 850 IS, as a good a camera as it is.

If a splashproof camera is your primary requirement, and you also need one that is easily pocketable, then your ONLY options are the Olympus Stylus-series cameras or Pentax W-series cameras, none of which even come close to your desired zoom range. This all makes your question about Canon’s ‘Safety Zoom’ somewhat moot; however, I will answer it anyway, just in case I misunderstood about the ‘splashproof’ requirement.

Safety Zoom is nothing more than a ‘smart’ digital zoom, smart in the sense that it does avoid all of the deleterious effects on image quality attributed to ‘standard’ digital zoom. In fact, the only drawback to the Safety Zoom is that you cannot use it at a camera’s full resolution. Rather, you must first select one of the camera’s reduced image resolution settings, and the higher the digital zoom level you require, the lower the resolution you must first select.

For example, suppose you had a 10-megapixel camera, but needed only 5 megapixels resolution for a specific application. One way a camera can reduce its image resolution from 10 megapixels to 5 megapixels is by discarding every other pixel from the original 10-megapixel image, which would yield an image with 5 megapixels resolution having the exact same crop as the original image with 10 megapixels resolution.

Now suppose you wanted to digitally zoom the reduced 5-megapixel image. One way to accomplish this in-camera would be to crop pixels as needed from the outer perimeter of the 5-megapixel image, and then spread the remaining pixels out to maintain the original image size, but then also fill in the resulting pixel gaps with interpolated pixels to bring the image back up to 5 megapixels resolution. It is precisely this interpolation process that causes the observed image quality deterioration associated with standard digital zoom.

However, if instead of digitally zooming the 5-megapixel image, we started back with the 10-megapixel image and discarded every third pixel rather than every second pixel, the resulting image would have 6.67 megapixels resolution. If we now digitally zoomed the 6.67 megapixels by cropping 1.67 megapixels from the image’s outer perimeter, and we then spread the remaining 5 megapixels out to maintain the original image size, the result would still be a 5-megapixel image, even after applying the digital zoom, but this time with NO interpolation.

Similarly, if we discarded every fourth pixel from the 10 megapixel image, resulting in a an image with 7.5 megapixels resolution, we could then apply even more digital zoom by cropping 2.5 megapixels from the outer perimeter of the image, and still end up with a 5-megapixel ‘uninterpolated’ image. The maximum digital zoom we could achieve in this manner would be for the case where we did not discard any pixels from the original 10-megapixel image, but instead cropped 5 megapixels from the outer perimeter of the image. This would yield a 1.4x digital zoom, which is the maximum uninterpolated digital zoom that can be achieved with any digital camera at exactly half of its full resolution.

Unfortunately, Leon, in order to increase the 850’s 105mm maximum optical focal length to your desired 200mm focal length by using the 850’s Safety Zoom (i.e., uninterpolated digital zoom), you would need to select the 850’s postcard image size of 1600 x 1200 pixels. This would then reduce the 850’s resolution from 7.1 megapixels to a mere 1.9 megapixels, which is barely even acceptable for postcards.

But one thing is for sure, Leon. Once you have selected the 850’s postcard image size, there will be absolutely NO degradation of image quality when using the Safety Zoom to digitally achieve a 200mm focal length.

As to your question about SDHC memory cards, keep in mind that none of the current splashproof cameras are SDHC compatible, with the exception of the Pentax W20.  Regarding the minimum write speed required for full throughput of VGA video at 30fps, while there is nothing wrong with your calculations, it is a bit like trying to calculate that 25mph is the minimum speed you would need to travel on a city road in order to get from point A to point B 25 miles away in one hour’s time. There’s a lot that can go wrong between points A and B to increase your travel time.

According to Jeff Keller’s review of the Canon Digital IXUS 850 IS at DCRP, you would want an SDHC card with AT LEAST a 60x write speed. The SanDisk Ultra II 4GB SDHC has a 66x write speed, comes with a lifetime warranty, includes the same USB2 adapter as the SanDisk Standard 4GB SDHC, and will cost only 10% more (MSRP) than the Standard … that is, when it becomes available. Sorry, Leon.

If you can’t wait for SanDisk Ultra II SDHC availability, any reputable brand SDHC with equivalent specs will do, and there will be no compatibility issue, as long as the camera is specified for SDHC (not just SD) use.

P.S.- Fotografar feliz, Leon !!!

[Column photo “The Photographer” by Brenda LaFleur of Brenda LaFleur Photography.]