Digital cameras-what's the difference?

[John D.]

I've seen digital cameras that advertise 3.1 megapixels and 4 megapixels. I know that 4 is better, but by how much? Does the 3.1 match the quality of an average 35mm camera?

[Salvage]

The quality of digital cameras go on a camera by camera basis. eg one 3.1 Mpix cam could be better than a 5.2 Mpix cam. Many of them are great in high light conditions but aren't that great in low light conditions.

You'll need to look for specific reviews.

[Peter Smith]

Originally Posted by John D.

I've seen digital cameras that advertise 3.1 megapixels and 4 megapixels. I know that 4 is better, but by how much?

4.0 is exactly 0.9 better than 3.1. Sorry, I couldn't resist that.

I am sure Salvage is right. Look at reviews. Resolution is one thing, and quality is another.

I haven't bought a digital camera yet because every time I get into the reviews I am overwhelmed with detail and decide to postpone it. I do know that optical zoom is much better than digital zoom, that you should strive for as much picture quality and color fidelity as you want to afford (look carefully at reviews with graphical examples), you should consider how many megapixels you really need for typical shots, and you should consider memory requirements to hold X number of shots at Y megapixels each. Each pixel is probably 24 bits or 3 bytes, depending on various factors such as compression method. So, 4 megapixel == approximately 12 megabytes per shot. Buy extra memory capacity - they never come with enough.

Consider that megapixels goes as the square of the linear pixel dimension. Thus, 800 x 600 is 48000 pixels = .48 megapixels (1000000 / mega). 1600 x 1200, twice the linear dimension, = 4 times the megapixels or 1.92 megapixels. Proceeding in this vein, 4 megapixels at that same 4/3 aspect ratio would be 2309 x 1732, whereas 3.1 megapixels would be 2033 x 1525. So, you see, there is only a 14% difference between the two in terms of resolution (dots per inch).

Most cameras come with a way to shoot at various resolutions. I know someone with a 5 megapixel camera who told me that is good for very high quality images that will be blown up a lot, but for normal snapshots he always shoots at much less to conserve memory. Here is a table I got off the web of image size vs megapixels for photographic quality:

1 megapixel 4"x 6"
2 megapixel 5"x7"
3 megapixel 8"x10"
5 megapixel 11"x17"

That's all I know about digital cameras.

[Old Man]

Sorry Peter, I didn't bother to wade through all your details so if I'm repeating ... but I'm in your exact position here. I still haven't bought one. Most of them do one form of compression or another. The average SLR image suitable for slides has about 20,000 pixels (Or is that 20 megapixels? Been a while. That's the scale anyway.) so digital cameras are still a ways short of this. However, for everyday use they are suitable it seems going by the pictures I've seen first hand. There are professional quality digital cameras easily identified by their non-consummer pricing if that's what you're looking for.

What was even more interesting to me is that photo developing retailers are now offering digital image printing for reasonable cost -- about $.25 each! So, you don't really need your own printer for this.

I have decided to go ahead though. Just waiting for more available time. I found one that allowed full, uncompressed or high quality low compression image storage on the camera. Sony IIRC. But I need time to get back on the internet and find it again. Take care, though, this storage method doesn't allow too many images to be kept on the camera before it fills up. Gotta be in a position to offload them to my PC regularly. Then I'm not quite sure if I can use the retail printers if I don't have the images on the camera or memory sticks. Should be able to drag a CD- or DVD-RAM there and get them printed off that way but I haven't checked that out yet.

[Salvage]

It's rare to find a high Mpixel camera that offers a lossless format and has good quality all round.

I found this page to be of help when searching for the features I wanted in the camera. Of course I had to do some extra searching to find good reviews.

Pictures at 3.15MPix and 2048x1536 are between 700kB and 2MB, usually closer to 2MB. I believe the compression is at 90% to get those numbers but I'm not completely sure. A 64MB card will get you around 40 pictures at that setting.

When I was looking several months ago I found the HP Photosmart R707 looked pretty good from the reviews as far as IQ was concerned, although it was reported as being physically flimsy by users.

[Peter Smith]

Thanks for the correction, Salvage. I had forgotten about compression.

I think that I would be tempted to get more memory to give greater flexibility. There is a certain advantage to storing, say, 200 pictures rather than 40, or having the flexibility use more megapixels or less compression if that suits you. I would get at least 256 MB, myself. Newegg is selling 1 GB cards for less than $70.