Slicing Up Depth Of Field

Formulas And Focus • Size, Weight And Will it Float? • From JPEG To RAW • Charging Overseas Without A Charger • Bifocal Focus

Click Images To EnlargeThis Article Features Photo Zoom

tech tips
Image of flowers at the Denver Botanical Garden taken with a Canon EOS 5D and processed using Helicon Focus Softwa

Formulas And Focus
I shoot a lot of wildflowers and have tinkered a bit with Helicon Focus Software (www.heliconfocus.com). The main objective is, of course, the soft background with a sharp subject. Do you have any formulas for the number of slices at various magnifications? I use a Really Right Stuff focusing rail and a Canon 90mm tilt/shift with and without extension tubes.
D. Nelson
Via the Internet

Helicon Focus is a software program that offers photographers unlimited depth of field, and it’s especially useful with macro subjects like flowers. With the camera on a tripod, the photographer takes a number of overlapping shots, adjusting the focus to achieve a set of sharply focused “slices.” The program processes the images to retain only the sharpest version of each part of the image and assembles a final composite that’s completely sharp. The key to using this program to retain a sharp subject with an out-of-focus background is to never offer a slice with the background in focus. To achieve this, use a fairly large ƒ-stop (ƒ/8) so the subject can be rendered completely sharp with a series of images, with none of the backgrounds in focus. As you preview the image for each slice, remember the viewfinder is showing you the field of focus attainable with the lens in its default widest aperture—less depth than what the set aperture will yield. Use this preview to determine the points of overlap, and your slices taken at ƒ/8 will give you a full set of sharp overlapping images. I don’t use any particular formula to choose focus points other than the process just described. When you get to the last shot with your subject in focus, use the depth-of-field preview to be sure you have the desired background effect.

The focusing rail you describe will work well for this series of images, but the 90mm tilt/shift wouldn’t be the lens I’d use to photograph wildflowers with an out-of-focus background. A longer telephoto (180-300mm) would be better, as it allows you to be selective in choosing sharp and soft elements. The 90mm tilt/shift, coupled with Helicon Focus, would be ideal for sharp rendition of a field of flowers from a close foreground to a distant background.

The attached photo shows a group of flowers totally in focus, while the background is completely out of focus. The image was accomplished using a Canon EF 180mm macro lens and six captures focused on different points in the flowers only. The six captures were processed in Helicon Focus.

Size, Weight And Will it Float?
What are the advantages of a D-SLR over a quality digital compact camera? I’m planning a photo safari to Africa (Malawi and Zambia). Most of the shooting will be from vehicles with other people in them. In Lake Malawi, I have the option of underwater photography. My photo equipment budget is about $2,000, and less is always better. I’d like to capture the best-quality images my budget allows. I’m looking at the Panasonic Lumix DMC-FZ18 for its long lens (28-504mm, 35mm-equivalent), image stabilization, small size and weight, and low price. I’m not sure the advantages of a D-SLR justify the price tag, size and weight. Could you explain some of the more important advantages of the D-SLR?
L. Rhoades
Hawaii, Via the Internet

It all depends on how you’re going to use your images. If your intent is to make smaller prints (8½x11), post images on the Internet and create digital slideshows, the compact camera will do an excellent job. If you plan to make larger prints, and possibly submit them for publication, then the larger sensor of the D-SLR and the resulting digital file are necessary. Other advantages of the D-SLR in shooting wildlife are capture speed (up to 10.5 frames per second) and a shorter time lag between activating the shutter and recording the image. There are many reasons professional photographers and advanced amateurs carry heavy tripods and camera bags—they need to make large prints or provide image files that are marketable in the professional realm. However, with your budget and preference for light weight and small size, the compact digital is a good choice. Achieving the same range of focal lengths in a D-SLR would take a camera body and several lenses.

If you want to do underwater photography, the compact digital camera has another advantage: the availability of underwater housings at a reasonable cost. The particular camera you mentioned, and numerous others, also have a movie mode that can be useful.

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From JPEG To RAW If you’re shooting with a higher-end camera like a Canon 5D or Nikon equivalent and you’re shooting in JPEG, do you really gain anything by converting the 8-bit JPEG image to a 16-bit one in Photoshop CS3 and saving and editing it as a TIFF file?
D. Blackburn
Los Angeles, CA

When you capture the image in JPEG, it’s an 8-bit file, which means it contains less information than if you had captured it in RAW (usually a 12-bit file). Converting the 8-bit file to a 16-bit one in Photoshop doesn’t add information; if you want the best quality, you must capture in RAW. There’s an advantage to converting a JPEG to a TIFF or a PSD (Photoshop file) before you begin to work on it. As JPEG files are saved, they lose data each time. TIFFs and PSDs, however, maintain their quality and layer structure.

As a side note, CS3 lets you open JPEGs and TIFFs in the RAW converter. This doesn’t add any information or enlarge the file, but it does enable you to use some of the useful tools found in the converter to improve your images.

Charging Overseas Without A Charger
I’ll be travelling to England, France and the Netherlands for 11 days this spring. I have a Nikon D80 and a Nikon D100 and two batteries for each. Should I carry the chargers or hope the batteries will last? Will I need adaptors for the chargers to work in Europe? Are there new security concerns with the lithium-ion batteries?
T. Campbell
Via the Internet

Always carry a charger, even if you think you have enough batteries. Batteries fail. They don’t last as long in cold temperatures. You may end up taking more pictures than you expected. And you can’t rely on finding the batteries or the charger you need in foreign countries. Check your charger to see if it has a dual-voltage capability; if it does, it will say 110/220, meaning it will automatically accommodate either voltage. You’ll need a different plug adaptor in most countries outside the United States. These are easily purchased at travel/luggage stores or online.

Effective January 1, 2008, the TSA prohibits transporting “loose” lithium batteries in checked baggage. They must be secured in separate packaging, or tape must be placed over their contacts. The TSA recommends that batteries and battery-operated equipment be carried in your carry-on baggage. You can learn everything you need to know about traveling with lithium-ion and primary lithium batteries at www.tsa.gov/travelers/airtravel/assistant/batteries.shtm.

Bifocal Focus
I’m having major difficulties adjusting to the world of bifocal lenses as related to photography and computers. I’m going to have to replace my current prescription and am hoping you might be able to give some advice, since you also wear eyeglasses. Contacts aren’t an option, and I have a very strong prescription.

I currently wear bifocals, and have had problems focusing my cameras ever since I had to start wearing them. I got a prescription specifically for the computer work, as I felt that another focusing zone would just create more difficulties. That solved the computer problem, but focusing a camera still remains difficult.
D. Gullickson
Fairbanks, Alaska

Many photographers aren’t aware that the camera viewfinder can be personalized to their vision. The part of your glasses that’s used in focusing an SLR camera is the area that’s corrected for distance. This is usually the largest section of a bifocal lens. With the camera autofocused on a subject, look into the viewfinder through the upper area of your lenses and adjust the diopter until you see a sharp image. The idea is that you know the camera is delivering a sharp image to the viewfinder, so adjust the viewfinder until it delivers a sharply focused image to you.

The close-up section of your bifocals will enable you to read the dials, settings and LCD. I have, like you, a pair of glasses with large lenses dedicated to computer work. I might add, however, that my wife has a tiny set of trifocal lenses she uses for everything from photography to needlework to computers to driving, so perhaps it’s a learned skill!

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.

One of North America’s best-known contemporary outdoor and nature photographers and a leader in the field of digital imaging and photographic education, Lepp is the author of many books and the field editor of Outdoor Photographer magazine. One of Canon’s original Explorers of Light, Lepp finds inspiration in advancing technology that fuels creative innovation and expression of his life-long fascination with the natural world.

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