Digital Camera Memory Card Tips

Editor,

This is in regard to the post in "Backscatter" "Do Digital Camera Memory Cards Cause Image Fading."

Since the current discussions have started, I have been thinking about doing a write up on the use of digital cameras for data taking. So I have been doing some research on digital cameras and how the data is stored and compressed.

Most consumer digital cameras today output the image in the JPEG format. This format uses what is referred to as lossy compression. That is information about the image is lost or thrown away when the data is compressed. The way the JPEG compression works makes it likely to remove subtle color variations as would be seen in a rainbow.

Roughly the way JPEG works is to look at blocks of pixels. It makes the blocks with similar color the same color. It then uses a Huffman compression algorithm on the resulting data. Huffman depends on runs of the same data to be effective in compressing the data.

Another problem with JPEG is every time you make a change to the image, crop it, change the contrast, etc., it has to be recompressed and further degradation of the image will occur. So this is very likely the reason the rainbow has disappeared and is not a problem with the memory card.

If you are going to do any editing of JPEG images, it is best to convert them to a lossless format, bit map or TIFF and do all your editing and saving in this format and only convert back to JPEG if you must.

Here are some tips on getting the best out of your JPEG images:

Some cameras and image editing software have settings for the "quality" of the saved image. If you are going to take or work with an image that needs subtle color, set the quality setting to its highest setting. This will make a bigger file (less compression), but the image will look better.

The performance of image viewing and processing software varies in its ability to compress and expand JPEG images. Since the math that does the compression is complex, some people take shortcuts when writing the software. It pays to compare.

Some tools even have a choice of using floating point or fixed point arithmetic in the calculations. The floating point calculations will give better results but are slower. So if you can find a setting in your toolbox, choose floating point calculations.

Jim Hannon

More About Airborne Particulate Matter

Editor,

I recently returned from a trip to Milwaukee. While there I had an opportunity to look for artifacts in the sky (see John F. Green, "Sunlight Artifacts and How to Observe and Photograph Them," The Citizen Scientist, 24 February 2006).

I noted that though the high temperatures were in the 30s [F] and that though there has been no plant growth or any insect activity since about last October, there was plenty of flotsam in the sky. Now while I am sure that some plants continue to release seeds even while inactive, one would think that their numbers would surely be diminished by the long winter season. This does not seem to be the case.

Also I saw what seemed to be spider silk. If this stuff is being replenished, it must be coming from hundreds if not thousands of miles away. Even here in central Florida the activities of plants and insects are considerably subdued in winter.

John F. Green

Thanks for this report from a northern site. In South Texas, airborne particulate matter is visible throughout the year. Spider silk is especially common during spring and fall. Editor.

Methane Emissions from Oil Wells

Editor,

I am Joe Harrer, an environmental geologist. Prior to college, I worked as a roughneck on local (south Louisiana) oil wells. I personally witnessed the off-gassing of oil formations to relieve pressure on the underlying liquid petroleum so that it could be sucked out of the ground. The off-gassing of methane lasted several days. The methane was not "flared" or burnt but was released directly into the atmosphere. I discussed this practice with some of my friends who deal in air quality laws and permitting, and they indicated that these activities are not regulated and that the amount of methane released is not measured. I believe that such off-gassing if practiced world-wide could be a major and unaccountable contribution to the human effects on the volume of greenhouse gas accumulation.

Joe Harrer, MS, PG

Thank you for sending this observation. In addition to methane, outgassing can also release volatile organic compounds (VOCs), which can play an important role in the synthesis of ground-level and tropospheric ozone. Editor.

Update from James Farr on Cooperative Competition

Editor,

I decided through much deliberation that the best way to study any type of cooperative competition between closely related flatfish populations and/or turtle populations on Long Island creeks would be to see if any hybrids exist, including whether the two common winter flounder species Plueronectes americana or P. pleuronectes have crossed or interbred.

Spotted turtles and the painted turtles could interbreed. I thought if I found anything, the idea that there was some cooperation between these species in sharing food or habitat would definitely be proved.

This letter is in response to the Backscatter letter from a herpetologist, who I remember very well as a top researcher. He suggested tagging turtles. I feel that my resources are best used through my own study design.

I'll keep you informed with any new find of a hybrid.

James W. Farr

From the LABRats Files

Dear Dr. Shawn,

I don't think I can commit myself to the principle of continual self-improvement. Learn something new every day. Pursue an interest every day. Practice a skill every day. And work to perfect within myself the virtues shared by all great scientists... honesty, integrity, perseverance, tolerance and public service.

[Name deleted]

Shawn Carlson Replies

Dear [deleted],

Sure you can!

Over 17,000 of your fellow members of Labrats have already. Do any ONE of those things you mentioned and you'll be a better and more capable person when you go to bed than you were when you woke up. Surely you can learn one new thing every day: Watch the history channel or the science channel for 10 minutes, and you can probably do that. Surf the web for the answer to something that's been nagging you. And so on. Do you play a musical instrument, or have a hobby that you enjoy? Practice it, get just a bit better on days when you don't want to learn something new. And it's always easy to consciously commit yourself to be honest with your dealings with other people, to have integrity, to not give up when you set you sights on some important goal, to be tolerant of others and to see your life in the grander context of the world in which you live.

Just look within yourself to make the commitment to make yourself a better more capable person all day, and you will find it. It only takes a second, and it's really not hard at all. Just commit yourself to making yourself more capable each day, and opportunities to do so will open all around you.

Trust me. You'll see.

Take care,

Dr. Shawn

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