OP Home > Columns > Tech Tips > ISO & Digital Image Quality


Monday, October 1, 2007

ISO & Digital Image Quality

Lowest ISOs • Blowin' In The Wind • Stacking Tele-Extenders • Performance In Cold Environments

Performance In Cold Environments

My husband and I are planning a trip to Antarctica this winter. I need advice regarding equipment, as well as the use of digital cameras in that cold climate. I’m a Canon user and have the 5D, the older D60, a PowerShot Pro 1 and a wide assortment of lenses—wide-angle to 400mm. I also have several film cameras. Would film perform better in that environment? I’d like to take as little as possible, but still have what’s needed.
V. Bradish
Via the Internet

Many people are visiting the colder climates while we still have them. The temperature extremes in Antarctica aren’t nearly as severe as you might think; expect ranges from the 20s to 30s, so the only real concern is battery life. Always carry extra charged batteries, generally several more than you’d expect to need. Keep them in a pocket close to your body so they stay warm, and recharge them each evening when you return to your accommodations.

In my opinion, there’s no advantage to either film or digital in this environment, but if you visit colder environments, at zero or below, different problems can be expected. The battery situation becomes more critical. LCDs on the back of digital cameras can become sluggish or nonresponsive, and film can become brittle and even shatter. With either kind of camera, be vigilant about keeping moisture off the equipment surfaces as you move between cold and warm environments. As far as Antarctica trips are concerned, I recommend you take along a dry bag to protect your camera equipment as you transfer from boats to land or for working in rain or snow.

As for essential equipment, I suggest taking your 5D, with the D60 as a backup, and leave the PowerShot at home. You’ll need the wide assortment of lenses, including a 40mm. Take along a light tripod and a flash for fill on bright days. I can’t see any advantage to taking both a film and a digital camera when you have the quality of the 5D. With digital, you also have the advantage of checking your results as you go. It’s hard to return to Antarctica for a reshoot.

The Right Size

Please give me some advice into the sizing of files, from capture to archiving, sending to publishers and e-mailing.
L. Will
Valdosta, Georgia

I always capture at the largest file size possible. Whether you choose JPEG or RAW format will depend on your own work habits and how you want to use your images. Keep the large file size, either in 8-bit or 16-bit, as you work in your image-processing program, even if you intend to make only small prints from the optimized file. You can always resize downward and maintain excellent quality, but enlarging a small file doesn’t give very good results. I usually send files to the printer at 300 dpi sized to the paper.

Be careful that you don’t save the print file with the same name as the master file for the image because the smaller print file will overwrite the larger one, and you’ll lose the full set of information. The full-sized, optimized file should be kept in a .psd format (assuming you’re using Photoshop) so that if you wish to make additional corrections later, all of the layers are still intact. In other words, don’t flatten your optimized file. If you’re shooting in RAW, you also may want to save the original RAW file as a backup to your archived optimized file.

Files should be e-mailed in JPEG format at 72 dpi in a size that will display on the receiver’s screen without scrolling. Use a JPEG-quality compression of about 8 to keep the file size small. If you have the option, it might be best to embed the image within the e-mail rather than to send it as an attachment. Many of us are cautious about opening attachments from anyone these days. When sending images to a publisher or to someone who will be printing from the received file, it's always best to check first to see what resolution and size are preferred.

Editing With LCD Monitors

My computer has a nice 19-inch LCD screen. I bracketed a set of images, but when I viewed them on the LCD, I couldn’t see any difference. When I viewed them on our old CRT monitor, I could definitely see the differences. Are CRTs better monitors for image editing?
L. Heckman
Via the Internet

For editing purposes, the two monitors should perform equally well. I suspect that when you got your new computer and monitor, you also installed new image-editing software and that you have a setting in Photoshop Bridge that’s automatically correcting all of your thumbnail images as they’re loaded for viewing. If so, the correction software is bringing all of the images to the same standard.

Control U in Photoshop CS2 turns off the automatic thumbnail correction. In CS3, open an image in the RAW converter and click on Control K (Command K); unclick "Apply autotone adjustments." This makes your thumbnails in Bridge reflect their true exposure characteristics, letting you choose from among your bracketed images. If this doesn’t solve the problem, your monitor could need repair or adjustment.

For information about upcoming seminars and digital-imaging workshops, visit www.geolepp.com.


Add Comment


Popular OP Articles