March/April 2005 HelpLine

Memory Cards Vs. Film

    * When Digital Film Isn’t Film
    * Caught In The RAW
    * Making It On Television
    * ƒ-Stop Exposé

When Digital Film Isn’t Film

Q)  Does it make a difference in picture quality if we use the nonbranded (cheaper versions) of memory cards? Are the super-speed SD better than the normal SD?

Doreen Chan
Via e-mail

A)  It has become a convenience to refer to memory cards as “digital film,” but that analogy falls apart quickly in one area: picture quality. Sit at a table with a few film photographers, start asking about the best film, and you’ll hear lengthy discussions about Fujichrome Velvia’s color rendition or Kodak Ektachrome’s tonal range. Sit at a table with a group of photographers shooting digital, ask about memory cards, and you might hear discussions about reliability or write speed, but nothing regarding picture quality (if you do, move to a different table, fast).

In short, there’s no difference in picture quality between the cards; they’re simply storage devices for image data. Once the camera processes the image (whether a lot with JPEG or minimal with RAW), it’s just writing data onto the card. There isn’t such a thing as a high-resolution card or a low image-noise card.

Cards vary as to reliability and how well they work under different conditions, however. Certain memory cards are rated for use under very hot or cold conditions—for example, conditions beyond the normal range of card use. Branded cards, as a whole, are very reliable, and you can count on them working and not failing on you.

 


Card speed has no affect on image quality or a camera’s speed of taking pictures. Card speed refers to how fast a memory card can move images from the camera’s buffer to the card. Whether it makes any difference to your camera really depends on whether the camera can take advantage of the higher-speed cards. Most small digital cameras can’t write quickly to a memory card, so card speed has little effect. High-end digital SLRs are definitely affected by card speed, but they also have large buffers, so card speed affects how many images can be taken by the camera before the camera has to stop to catch up on recording files from the buffer to the card.

Caught In The RAW

Q)  I accidentally took digital pictures in the RAW format and now I’m having a hard time doing anything with them. I used the RAW image converter for my camera and converted them to TIFF, but I still can’t e-mail them in that format.

Karen Mowry
Via e-mail

A)  Many cameras offer an image quality setting for storing images called RAW. RAW files offer some advantages as far as changing white balance after the fact and can allow for greater control of the image processing. Unfortu-nately, this all comes at a price.

Unlike JPEGs or TIFFs, the RAW file format isn’t a standard. It’s not even the same among a few manufacturers, so even if you tried e-mailing them, the people receiving the photos probably wouldn’t be able to view them.

 

 


There’s more. Since there’s not much in-camera processing on RAW images, they may require processing in an image editor before they look good. The files aren’t compressed, so they take up much more room on your memory card. And they will take longer to write to a memory card.

Luckily, many popular image-processing programs will be able to take your RAW file and save it as a TIFF or JPEG file. Most image editors also have a batch function that will take a whole folder of images and create copies in the format you need. You also should be able to use the batch function to convert your TIFF files to compressed JPEG for e-mailing.

Making It On Television

Q)  I’ve been trying to make a slideshow on a VCD of the pictures taken from a digital camera so that my family can view it on the TV using a DVD player. The problem I’m facing is the loss in the picture quality when viewing the same images on a TV; the pictures when viewed on the computer are sharp and clear, but when I create a VCD and test-run to see them on the TV, the pictures aren’t as clear and are choppy.

Navin Nawani
Bangkok, Thailand

A)  The image quality problem you’re having is caused by the fact that VCDs use a low-resolution format. Consider a typical computer setup (if there’s such a thing as “typical”). The display resolution may be set to 1024 x 768 or even higher, and your display may be 17 or 19 inches measured diagonally.

Believe it or not, a VCD image size is only 352 x 240 in NTSC (the television standard used in the United States) and 352 x 288 for PAL (the standard used in many other countries). That’s approximately one-tenth or less of the computer screen resolution. When you convert your images for recording to a VCD, you’re immediately throwing away at least 90% of your resolution. You have no choice because of the format. Then you’re blowing up the image to display it on a TV screen—probably larger than your computer monitor. You can see, then, why the image quality suffers!

 

 


A Super VCD (SVCD) might be an option for you, provided that your friends and family have a player. The SVCD standard is still only 480 x 480 in NTSC and 480 x 576 for PAL, but it eliminates some of the scaling artifacts you’re noticing.

Another approach is to use DVD. Its higher-resolution format—720 x 486 NTSC or 480 x 576 PAL—is still smaller than your computer’s screen resolution, but this now takes advantage of all a standard TV can handle. The drawbacks are that DVDs require software to author the disc and need to be played on a DVD player or a computer’s DVD drive.

ƒ-Stop Exposé

Q)  Is there an optimum aperture to use for composing landscape images with a digital camera?

Howard J.
Via e-mail

A)  The aperture is a camera setting that adjusts the amount of light reaching your image sensor. The aperture, measured in ƒ-stops, is controlled by the iris (a part of the lens with a variable opening, just like the iris in your eye). A wider opening of the iris is represented by a smaller ƒ-stop number, so a set-ting of ƒ/4 would have a larger opening and let in more light than an ƒ/16 setting (a larger opening also is called a faster aperture).

Before deciding which aperture to use for landscape images, you must consider depth of field, which usually is defined as the distance from front to back in which the objects in the scene are in focus. In reality, there’s only one plane that’s in focus, but the depth of field is the range in front of and behind that focus plane that’s acceptably sharp in a photograph.

 

 

What kind of depth of field do you want? That is, how much of the image do you want to be in focus? If you want as much in focus as possible, use a smaller aperture such as ƒ/11, ƒ/16 or higher (ƒ/8 for advanced compact cameras; they often don’t have smaller ƒ-stops, but because of their lens’ size, depth of field is still very high). Smaller apertures increase depth of field. (It can be confusing to think of a smaller aperture as requiring a larger ƒ-stop number; however, the ƒ-stop actually is a fraction. (If you’re not good with fractions, just remember that the higher the number, the smaller the opening and the deeper the depth of fiel
d.) To limit depth of field and throw more of the foreground or background out of focus, use a large aperture (a smaller ƒ-stop number).

If you have any questions, please send them to HelpLine, PCPhoto Magazine, 12121 Wilshire Blvd., Ste. 1200, Los Angeles, CA 90025 or helpline@pcphotomag.com.

 

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