• Eyepoint Revealed
• Digital Projection Format
• Memory Card Considerations
  

I’ve been investigating digital SLRs and have come across a term I don’t understand. What’s eyepoint and why is it important?

Eyepoint is a measurement of how close your eye needs to be to the viewfinder in order to see the entire image presented by the viewfinder. For example, if you hold a camera a few inches away from your eye, you’ll be able to see only a small portion of the center of the viewfinder image. As you move the camera closer to your eye, you’ll get to a point where you’ll be able to see the entire view without any vignetting.

The eyepoint specification is measured in millimeters. The higher the number, the farther away from the camera your eye can be. If you wear glasses (and a lot of great photographers do), having a higher eyepoint means that you can see the entire viewfinder image while still wearing your glasses.

Projector manufacturers originally developed these units for PowerPoint displays and weren’t considering photographers’ needs. Unfortunately, I don’t know of any square digital projectors.

As to your last question, you have to examine the differences between manufacturing a slide projector and a digital projector. Instead of projecting light through an image provided by your transparency, the digital projector has to re-create the photograph on its imager.

The imager used in the digital projector typically is a piece of highly complicated silicon. The manufacturing line for producing this silicon is called a foundry, and foundries are very expensive to create and run. Manufacturers have to appeal to a wide market in order for a product to be profitable. Until the market creates a significant demand for square-aspect projection or the imagers become very inexpensive, the standard 4:3 horizontal rectangle will likely be the only way digital projectors will be sold. This situation probably won’t be helped with the advent of high-definition video, which has an aspect ratio of 16x9 (a horizontal rectangle).

Memory Card Considerations

I’m considering buying an 8-megapixel digital camera. These high-megapixel cameras are no doubt memory-hungry, so I’d likely buy a 2 GB card for whatever camera I purchased. Regarding Lexar’s Write Acceleration (WA) card, Lexar’s ad makes it sound like the WA feature is something that works with WA-enabled cameras. Are they talking about cameras with some special kind of buffer? They state that in cameras without WA, the card still functions at 80x speed. Can you explain this? 

How would this card compare to the SanDisk Extreme 2 GB card? It has transfer rates of 9 to 10 MB/sec., while the Lexar states a speed of 12 MB/sec., but I don’t know if that’s the 80x speed or the WA speed. Finally, what about Microdrives?

Memory cards that support Write Acceleration depend on technology inside the camera to take advantage of speed improvements. The current cameras supporting WA include all Kodak Professional cameras and pro camera backs, the Nikon D1x, D1H, D2H, D100 (with firmware upgrade), Sanyo DSC-MZ3, Sigma SD9 and SD10, Pentax *ist D and Olympus E1.

The 80x specification uses the same speed ratings as optical drives like CD-ROMs. When CD-ROM read and write speeds are specified, they’re given as 12x or 32x, and the “x” refers to 150 KB/sec. At 80x, you’re talking about 12 MB/sec. While you might get close to this speed when you use a card reader attached to a computer, the speed will be less than half of that with most 8-megapixel cameras.

As for Microdrives, they will be slower than the cards you’ve listed. Also, since they’re actually miniature hard drives, they have moving parts and can be delicate pieces of technology. If you’re expecting your media to go through any type of rough treatment, I’d keep that in mind.

Regarding memory cards, you’re correct that the cameras need lots of memory. One thing to consider is using several smaller cards, rather than putting all your money into one large card. There are several benefits. If you lose a card or one fails, you won’t lose all of your images or your ability to take pictures. Smaller cards also mean shorter download times per card.

Finally, depending on your workflow, archiving can be a little easier if you have cards that are about the size of your archive medium. For example, I travel with a couple of 1 GB cards. I never fill them up all the way. After I edit out the bad images, I can archive the good ones to a CD.