Even with the camera set consistently at the highest JPEG resolution, compressed file sizes will vary depending on the complexity of the information being captured. An image that’s predominantly composed of a single color, such as a gray card, will be more compressed by either camera; a more complex image, such as a hillside of wildflowers, will yield a larger file. If you were to take exactly the same picture with each camera, the file sizes likely be would different, however, because the image and the number of megapixels on the sensor are only two of a number of factors that affect the file size. The two cameras have different-sized sensors (the Nikon’s is slightly larger and actually uses 10.2 megapixels vs. Canon’s 10.1), different processors and, as we’ve noted, different compression algorithms.
I don’t know if anyone has done the kind of test you’d need to do to determine which camera actually puts more JPEG images on a 4 GB card—that is, to take exactly the same series of images with both cameras. But I do know that it’s not really that important when it comes to image quality. I’ve examined the output from similar cameras of both manufacturers, and there’s little discernable difference due to compression. The differences you can detect are most likely due to other features, such as optics.
Out, Darned Spot! Q I have a Canon EOS 30D, and its warranty expired a few weeks ago. All pictures taken with it have a spot in the upper-right corner. I thought it was dust. I attempted to blow the sensor off with air, but the spot still remains there. What would you recommend I use to clean the sensor? Should I send the camera in to Canon to repair? K. Lui Via the Internet
A You need to go further with your sensor cleaning. Who knows how this happens, but stuff gets stuck to the sensor, and more than a puff of air from a bulb blower is needed to clear it. (Never use canned air to clean your delicate camera parts, by the way. It’s much too harsh and will leave hard-to-remove liquid propellant on your sensor.) Even your newer self-cleaning sensors can host adhered dust and debris that won’t come off with soft-brush methods. Stubborn spots need a wet method, and there are several options. Go to www.cleaningdigitalcameras.com for a full lesson in sensor care and guides to a number of excellent products.
Worn-Out Imaging Q Is there a point at which it’s clear that rechargeable batteries or CF cards are in need of replacement or disposal? Should I replace at certain intervals? R. Sistare Wilmington, N.C.
A It’s easy to tell when rechargeable batteries have lived out their useful lives and require proper disposal: They stop taking and/or retaining a charge. The new ones last longer, but they still wear out. Batteries are less efficient in cold weather, so don’t assume that the shorter active charge means the battery is gone. When you’re ready to let them go, the best choice is recycling. NiMH, NiCd and alkaline batteries all can be recycled, and some communities have mandatory requirements. You can find out more by going to the website of the Rechargeable Battery Recycling Corporation website at www.rbrc.org.
CF cards last a long time and over many cycles. One problem with them is corruption of the allocation table. To prevent this, always reformat the card when you put it back in the camera after transferring your images to the computer. A number of card manufacturers offer free or low-cost software that will check and recondition cards, as well as extract data from a corrupted card.
Chances are that as you progress with the advancing technology of digital photography, you’ll purchase cameras with more megapixels, which need faster and/or larger media cards. Long before your smaller cards fail, they’ll be abandoned because they’re not up to the challenge of more sophisticated equipment. I have a lot of 256 and 512 MB cards lying around that would only store a couple of images from my newer 21-megapixel cameras.
For information about upcoming seminars and digital-imaging workshops, visit www.geolepp.com. If you have any tips or questions, address them to: OUTDOOR PHOTOGRAPHER, Dept. TT, George Lepp, 12121 Wilshire Blvd., Suite 1200, Los Angeles, CA 90025-1176 or online at www.geolepp.com.
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