Confusion

I'm not a technophobe but....

I must admit I am confused by all the issues affecting the performance of digital cameras. I know that noise is a problem especially in low lighting conditions, but I don't understand why a higher resolution CCD may have more problems with noise than a lower resolution one. I also don't know why printed photos show less noise than on-screen - is noise only really a problem when being displayed on screen? Can anyone explain these and other issues, or at least point me to a good reference website or book?

The reason I ask is I want to buy myself a good but compact digital camera and it seems that all current models have flaws in one way or another, so I am finding making a choice almost impossible. I quite like the sound of the Pentax Optio 555, but the price (here in the UK) is too high at the moment at £499. (I have just got rid of my first digital camera - the Fuji F601 Zoom, because I was never happy with the quality of the photos)

scotgotchi said:

I'm not a technophobe but....
I must admit I am confused by all the issues affecting the
performance of digital cameras.

Click to expand...

You're in good company, don't worry.

scotgotchi said:

I know that noise is a problem
especially in low lighting conditions, but I don't understand why a
higher resolution CCD may have more problems with noise than a
lower resolution one.

Click to expand...

All else being equal, the higher-rez sensor will have smaller photosites (pixels). The smaller the photosite, the worse the signal to noise ratio.

Think of it this way: the absolute amount of noise per photosite is approximately constant. The bigger the photosite, the more photons it can capture. Therefore, a bigger photosite will have proportionately more charge from captured photons than accumulated noise.

(It's actually a good deal more complex, once you get into the intricacies of noise reduction, but the same principle holds even then -- anything you can do to improve the s/n ratio of a small photosite you can do for a large photosite, so the large photosite retains its edge.)

scotgotchi said:

I also don't know why printed photos show
less noise than on-screen - is noise only really a problem when
being displayed on screen?

Click to expand...

When you print the photo, the individual pixels will be crammed very closely together. This "averages out" the noise. Something that looks very noisy when seen at 100% "actual pixels" on-screen will look almost noiseless when printed.

Actually, the same thing happens if you shrink (downsample) the image for screen viewing using some halfway intelligent method (such as bicubic interpolation; even better if you use B-Spline or Lanczos).

scotgotchi said:

Can anyone explain these and other
issues, or at least point me to a good reference website or book?

Click to expand...

Try the "123 of digital imaging" e-book advertised here at dpreview. It explains all of this and more in a very clear way, and, even better, explains ways of dealing with the problems in post-processing.

scotgotchi said:

The reason I ask is I want to buy myself a good but compact digital
camera and it seems that all current models have flaws in one way
or another, so I am finding making a choice almost impossible. I
quite like the sound of the Pentax Optio 555, but the price (here
in the UK) is too high at the moment at £499. (I have just got rid
of my first digital camera - the Fuji F601 Zoom, because I was
never happy with the quality of the photos)

Click to expand...

LOL!

The trouble is, they keep moving the goal-posts. Any camera that's great now will be average a year from now and pretty mediocre two years from now. In my opinion, there are very few real dogs left among digital cameras from the major brands today -- the competition is so hard that the actually bad ones have simply gone away.

What exactly didn't you like about the photos from the Fuji? By all accounts, it should be a pretty good camera!

Petteri
--



Portfolio: [ http://www.seittipaja.fi/index/ ]
Pontification: [ http://www.seittipaja.fi/ ]

Thanks for shining some light on the subject Petteri (lol).

Petteri Sulonen said:

When you print the photo, the individual pixels will be crammed
very closely together. This "averages out" the noise. Something
that looks very noisy when seen at 100% "actual pixels" on-screen
will look almost noiseless when printed.

Click to expand...

...so if I print something out large enough, it will look just as bad as on-screen? (This is half my problem I guess - I tend to zoom in to the detail on-screen and think to myself that it doesn't look very good - maybe I'll get a better feel for things when I get around to buying a printer!)

Petteri Sulonen said:

Actually, the same thing happens if you shrink (downsample) the
image for screen viewing using some halfway intelligent method
(such as bicubic interpolation; even better if you use B-Spline or
Lanczos).

Click to expand...

yeah okay... (blank expression on my face)

Petteri Sulonen said:

Try the "123 of digital imaging" e-book advertised here at
dpreview. It explains all of this and more in a very clear way,
and, even better, explains ways of dealing with the problems in
post-processing.

Click to expand...

Thanks, I'll certainly check this out.

Petteri Sulonen said:

What exactly didn't you like about the photos from the Fuji? By all
accounts, it should be a pretty good camera!

Click to expand...

Yeah, it was pretty good I guess. I liked a lot of things about the camera - it is very well made, fast to use, has lots of control features, a good movie capability, but I felt that it was probably ultimately let down by the lens quality. Outdoor landscapes, for example, never seemed to be particularly sharp, and then there were the noise issues...

The other answer to your questions pretty much covered the subject. I'd like to add a few things I've grown aware of after making the transition from film to digital approximately 4 or 5 years ago.

Film could be readily shot at ASA (ISO) 400 to 800 or higher in the pre digital days. I used to push the speed of film to ASA 2400 when developing film from my SCUBA diving ventures. Now those 2400 pushed shots had a lot of objectionable grain. Grain is the film equiv of noise.

Early on you couldn't expect to use ISO 400 with digital. You could get some viewable results by dark frame subtraction shooting at that speed but you'd have a rough time selling prints to buyers unless they were photos of bigfoot!

As the other poster pointed out, these digitals keep getting better. I'm presently shooting a D60 Canon. Now, some people say it's good for ISO 800. Each to his own. I use ISO 800 only when I absolutely need too. ISO 400 is perfectly clean. ISO 1000 is terrible but, again if bigfoot comes buy i'll use that speed!

My younger brother has just bought a 300D rebel by Canon. It shoots a lot cleaner than my D60 at ISO 800 and 1000 is highly useable. Same sensor too. Canon improved the processing algorithms. They aren't saying how but they did. Probably a dark frame subtraction process.

If you don't shoot above ISO 800 or shoot at lower speeds with a tripod you shouldn't experience any problems getting clean images. A program called NeatImage does wonders for eliminating noise. In the next couple years I speculate that speeds of 1600 will be coming out of the camera very clean.

Don't expect to see a clean image such as a full sized RAW or other type of uncompressed file to be pretty. The image size to print would be 48 X 28 inches. By the time you resize it to a maximum size of 12 X 8 or 11 X 14 it'll print out clean as you want. If you tried to print a 35mm negative to 48 X 28 it'd look like he** also.

If a few more were to take note of these practical statements, then they might just begin to concentrate on photography, instead of always agonising over technical issues - especially those new to photography. Buy the best camera that you can afford, learn as much about photography and get that part right first; then start to consider whether you should upgrade your equipment, after you've learned how to use it.