Thanks Jim, as you can probably tell we are "Newbies" with a dig camera...have purchased a 256 and a 512 as we are going to Alaska next week :-) ..
Great! I hope you get some nice photos.
Just using the 16 to try things out....sure have learned a lot thru Steves website...want to be able to take 400 + pics while in Alaska....again, we will go back to the std paramaters and see how many we get on the 16 and if the ISO change affected it...will change to HQ also
My guess is that you set the camera to SHQ by accident, and this mode produces higher image quality compared to SQ. As a result, the file sizes are larger and you won't get as many photos on a memory card.
As for ISO speed, I wouldn't set it any higher than you need to. Each time you double the ISO speed, the camera can use shutter speeds twice as fast for any given lighting condition and aperture setting.
But, this comes at the expense of higher noise levels (similar to film grain). So, it's a tradeoff.
If you're shooting in lower light (and/or longer focal lengths), you may need the faster shutter speeds to prevent blur from camera shake. So, yes, ISO 400 can be useful in some conditions (noise is often preferrable to blur). But, I wouldn't use it unless absolutely necessary.
Chances are, your camera is increasing ISO speed to around ISO 200 using Auto ISO in low light. But, it probably would not use ISO 400 unless you set it that way.
...we havent figured out what a card reader does yet....does it speed up transfer to the PC ( something we will want when we get home )...
When you insert a card into a reader, it looks like a removable disk drive to your PC (just like most cameras appear now). They are typically much faster compared to the USB interface built into a camera. Another reason to use one is because you'd be discharging your camera's battery while transferring images without a reader (which may or may not be an issue to many users).
Make sure to buy a USB 2.0 (or firewire) reader, versus an older USB 1.1 reader (which will be slow). Also, make sure that it supports xD Picturecard (many readers don't support this format).
We have a review of some card readers here (but most of them a bit dated now, so you'll find newer models from the popular manufacturers like Sandisk and Lexar on the store shelves):
A card reader is not absolutely necessary. Some users never bother to get a card reader. But, they are relatively inexpensive. So, I'd be inclined to get one if I planned on transferring a lot of images frequently.
BTW, there are ways to transfer images to other types of storage devices while you're on vacation. A number of products are available now designed specifically for portable image storage. These products typically have a small form factor hard disk drive and a built in card reader. So, you don't need a PC to transfer the images to them. Some have color LCD displays, too. Check carefully for xD PictureCard compatibility when looking at them, though. Most will require an Adapter (for example, an Xd Picturecard to CompactFlash adapter) for this media type.
You'll find some reviews of Portable Image Storage Devices here (some are a bit dated, so check with manufacturers for newer products):