June 2004 HelpLine

Resizing Images

    * Disappearing Photos
    * IRIS In Digial Cameras
    * Acronym Acrimony

Resizing Images

Q)  I’m in the process of scanning my 35mm slides, negatives and various prints for which I have no negatives. Ultimately, I want to burn them onto CDs. I’m using the highest resolution that my scanner allows for the type of medium I’m scanning; with the negatives and slides, it’s 2400 dpi; with prints, it’s 300 dpi. Since I don’t expect to print any of them larger than letter size, should I leave the files at their present size or resize them to letter size at 300 dpi before burning them to CDs?

Bob Bella
Via e-mail

A)  First, let’s deal with resizing your image before writing it to CD. If you do so, you may add artifacts to the image during the resizing process (if you simply change resolution, pixels don’t change; however, if an image is sized up or down so that pixels are increased or decreased, artifacts can cause problems). Once written to CD, these artifacts are permanent even if you scale the image back down to its original size. This applies to digital camera images as well as scanned photos.

I recommend that you resize the image just before printing. At print time, then resize the image for a specific print size based on the original image file. As advances in picture processing continue, there’s also the possibility that in the future there may be better algorithms for interpolation of pixels during the resizing process that won’t harm the image as much.

If you’re scanning small images, say, old 3×4-inch prints, and think you might like a larger size, you need to scan them at a higher resolution than 300 dpi. I’m not sure you’d be happy with them scanned at 300 dpi, then blown up to 8×10. You could increase the size—say, 4×6—by resizing to 200 dpi or go even bigger by printing at 150 dpi, and you’d still get good results. However, by simply scanning at 600 dpi or higher from the start, you’ll have more printing options in the future.


Disappearing Photos

Q)  I recently talked my wife into converting from the conventional 35mm to a digital camera. Everything was going great with the camera; my wife was taking all kinds of pictures and having fun. Then we shot with a new memory card, but it wouldn’t download to my laptop. We reviewed the pictures on the camera and noted 100-plus pictures on the memory card. I took it to Wal-Mart and they weren’t able to view any pictures on the chip either. Do you have any ideas?

Steven A. Trainor
Gordon, Wisconsin

A)  Before looking for solutions, let’s look at the reasons for losing your images. I think there might be three possibilities. First, while rare, memory cards sometimes are defective, which is a good reason to always test new photo and digital products before using them for something significant. This is no different from film days—it always was best to test a film before using it for an important vacation, for example.

Another possibility is that the card has bad formatting. Formatting in the camera will give you the most reliable results. If the card was used and formatted elsewhere, such as a computer or media player, you can have problems. Finally, there could have been an interruption during the write cycle. This could be caused by removing the card before the camera finished writing or by letting the battery power get so low that the camera shut down during the write. This might be compared to opening the film back before the film was rewound.

Now, onto possible solutions:
1. Recovery of the data through software programs. Many memory card manufacturers offer them, so check out their Websites for a link to file recovery software you can purchase.

2. Recovery of the data by a third party. There are companies that will recover media cards for you. You can find them online by doing a search for “file recovery,” “data recovery” or “SD recovery” (www.flashcardfix.com is an example). You simply mail your card to them and they will send you a CD with any files they were able to recover.



3. A lot of cameras that have onboard memory have a way of copying images from it to the memory card and vice versa. Since you can view the images on the camera, see if you can copy some of them to onboard memory. Then remove the faulty card and use another memory card to copy them to.

IRIS In Digital Cameras

Q)  Do digital cameras actually stop down their lenses, or is this just a manipulation of factors to control the chip download speed and interval? For example, does the aperture-preferred exposure mode mean the lens actually stops down to give me greater depth of field?

R.E. Jackson,
Collingswood, New Jersey

A)  For those of you who aren’t familiar with the term, depth of field is the distance between the farthest and closest points in your scene that are in focus. It’s controlled by the focal length of the lens, the aperture (or iris) of the lens, the distance from your camera to your subject and the size of your final print. The aperture settings are measured in ƒ-stops. The ƒ-stop number actually is derived from a ratio between the focal length of the lens and the diameter of the aperture.

Okay, enough of the definitions. Just remember that the larger the ƒ-stop number, the smaller the opening in the lens. When you “stop down” a lens, you’re closing the iris of the lens, which increases your depth of field, which, in turn, increases the range of objects that will be in focus in your scene.

It’s easy to assume that digital technology has replaced all the features in film-based photography with electronic wizardry. (Accommodating changes in light color temperature through white-balance settings versus putting a filter on the lens is one example of “doing it with electronics.”) However, this can’t change the optical path of the lens, which is where the iris is located. While digital cameras can adjust the apparent sensitivity of the chip, “stopping down” the lens is still done where it has always been done—in the lens.



In aperture or aperture-preferred mode, you can set your exposure based on the aperture that will give you the depth of field that you want and let the camera pick the shutter speed to match the ƒ-stop you’ve selected.

Acronym Acrimony

Q)  When I was researching my next big CompactFlash card purchase, I came across a “feature/benefit” on one manufacturer’s card called MultiWord DMA. What is that?

Rowen G.
Via e-mail

A)  Let’s break apart the term—MultiWord and DMA—and deal with the two components separately. DMA stands for Direct Memory Access, a technology that has been used for years in the computer industry. The concept is a fairly simple one. In the early days of computers, the CPU, or central processing unit, was more like a central control unit that did everything.

As computer manufacturers started making computers faster and faster, they recognized that they had to offload some of the more mundane tasks to separate computer chips. That’s where DMA comes in. Instead of the CPU’s controlling the writing of each bit
of data in memory to the hard drive, a separate chip directly accesses the memory without the intervention of the CPU.

Now on to MultiWord. In computer speak, a “word” is another way of saying a group of bits (of data). When DMA was first developed, it used the typical method of transferring one “word” at a time. Think of each word as a package of information. Each package has to be wrapped, sent from memory to the storage device, unwrapped and acknowledged that it was received.



Unfortunately, a “word” is a very small amount of data. The overhead in sending each “word” makes the process a little inefficient. What if you could put more “words” into each package? That’s just what MultiWord does—it allows multiple “words” of data to be sent during each transmission. When you put MultiWord and DMA together, you get a technology that removes the CPU from the task of writing to memory and also speeds up the process.

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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