I've been wondering for some time what the best resolution is for me to use when shooting digital cameras, when I'll be resizing the final image to a Web quality resolution with a size of around 640x480. 72 dpi is a given, but I often shoot around 1280x768, then resize in my image editing software. Do I gain anything by this, or should I just shoot at 640x480 to begin with? Note: these images will not be output to a printer; just viewed on-screen.

-- Mike Henderson (mhenderson@matric.com), November 18, 1999

Answers

This is a really good question with an unintuitive answer. Short answer: If you will not be modifying the images, you are definitely better off going straight to 640 X 480 from inside the camera, instead of resizing down from a 1280 X 1024 jpeg.

Long winded answer: Compare both methods, each ending up with 640 X 480 -- camera CCD -> 640 X 480 vs 1280 X 960 jpeg -> 640 X 480. Which is a better source image to compress down to 640 X 480 from, the in camera CCD RAW image, or the 1280 X 768 JPEG? No question the in camera CCD RAW image has better and more information. Even if 1280 X 768 is the max res of your camera, the in-camera CCD image still wins, because CCD RAW has more information than the jpeg. Remember that each "pixel" in a camera only represents one color, and cameras do interpolation to get their max resolution even before lossy jpeg compression kicks in.

Going to 640 X 480 from a jpeg ends up with two lossy jpeg compressions, going straight from the camera you only get one go through the lossy jpeg sieve.

The jpeg compressor you use may be better than the one the camera uses, but your 1280 X 1024 jpeg already went through the cameras jpeg algorithm, probably nullifying whatever quality advantage a photoshop compressor might offer.

The question gets a lot fuzzier when you're considering modifying the image beyond a resize, then you might well be better off with a 1600 X 1200 original to work from. But you'd have to decide whether the final quality is critical enough to bother with that.

-- benoit (foo@bar.com), November 18, 1999.

All the above assumes you don't have an uncompressed mode on your camera. If you do, your photoshop compressor might well be better than the cameras.

-- benoit (foo@bar.com), November 18, 1999.

This may depend on what camera you own. For example, Sony Mavicas have an e-mail option that records a 6-8k image of a photo as well as whatever other resolution you have chosen. The e-mail copies are stored in a separate folder on the floppy disk. The extra space used for the e-mail images is so small there is no need to ever not use this option thus you can always have a ready made e-mail version of every photo you take. If you don't have a Mavica, check your owner's manual to see if your camera has a similar option.

Rodger

Rodger

-- Rodger Carter (rodger.carter@wpafb.af.mil), November 18, 1999.