main index NOTA BENE: gli articoli in italiano cominciano qui!


I wrote a number of articles about digital cameras; sorry, this is the only article in English (based on some messages I wrote some time ago) dealing with digital photography.

Anyways, if you can understand Italian or if you want to check something nice using the Babelfish translator, begin here or here...

In this page:



My digital camera produces 1700+ kbytes JPEG images...

The JPEG is a somewhat weird compression scheme, and at high quality settings the file size is not proportional to the amount of details.

Image editors let you specify the quality level before saving a JPEG file (generally it's a 0-100, useful range is 5-95; some programs have different meaning); I use gimp (on Linux) to work on my shots: at levels above 80-85 (photos with plenty of details) the size increases without noticeable differences. The gimp also allows to fiddle with a quality slider while seeing a preview and its JPEG file size.

I guess also that some poor JPEG encoders have some compression/speed tradeoffs. I got often 450+ kbytes of JPEG on a one megapixel camera, which gimp can dramatically reduce (even about 50% of file size, stirring down the quality level of only 15-20 points or less) without apparently loosing any detail.

IMHO I don't think I'll ever need a TIFF (or any uncompressed format) on a camera; to me, it's more important a true "fine" JPEG setting (quality of 85 to 90; having more is useless).


Why digital cameras can't take long exposures?

While the film just accumulates light photons over the time (allowing, in some circumstances, exposures of some hours), the electrical sensors of digital cameras (CCD, etc) accumulate also drift and noise. This means that on long exposures (from a few seconds up), the image quality will dramatically decrease.

Yes, it would be technically feasible and easy to implement - a digital camera firmware could wait minutes, or even hours, in taking a shot - but the resulting quality would made it an useless feature.

A little hint for programming experts: you could shot a number of consecutive photos of the same subject (without moving the camera!), and then create a resulting image by "adding" pixel values, for example:

Note: "luminance" is not just "R/G/B components", and this processing will run decently only on TIFF (or, better: RAW) images. You shouldn't use JPEG images because of its "lossy" compression scheme (that, in the pixel averaging, will add up the compression "noise" and wipe away some fine resolution, even at the highest quality setting).



The sales guy told me that the Panasonic FZ20 isn't that good; you instead are very proud of it; why did he talk bad about it? isn't he an expert? are you, instead, an expert?

Well, er, uhm... don't believe too much in what you read on the net, and do believe (I mean: do believe) in what the Sales Guy tells you, and... and you will make him happy ;-)

You already know that Sales Guys are those people that Talk Big about model X and badmouth model Y, only in the case they have lots of X on stock and/or have bigger earnings on X than on Y.

Then, don't believe in Big Names. It isn't always true that a pricey camera is better than a cheaper one. Have a look to this comparison between a Canon EOS 300D Digital Rebel and a Panasonic Lumix DMC FZ20. Hey, Canon is still Canon, but absolute perfection doesn't exists in digital cameras world... :-)

Also, the FZ20 has a stunning Leica lens system paired with a very good hardware/firmware solution (the Venus II image processor). Some other cameras have cheap hardware/firmware or lenses or both. Maybe the "12×" wouldn't impress you much more than a "10×", but there is a noticeable difference between a "12×" at F/2.8 and one (maybe only "10×") at F/4.7...! Yes, there is some barrel distortion on the wide of most cameras (including FZ20), but this is the price of having such a 12× beast in half a kilogram.

And, remember, the anti-shake system ("Mega OIS", optical image stabilization - a mechanical system!) will buy you out some more F/stops saving good shots that would have been useless without it. This is definitely a must for the photography novice as well as for the enthusiast - in the worst case, it will come in handy for a number of different light situations or telephoto zoom modes...

Don't care too much about people complaining about photo quality after a few shots only. The best camera, in wrong hands, will produce the worst shots, and stupid people will immediately tell everyone they are unhappy with the camera. Be prepared to wipe out at least 90% of your "best shots" - good photographers won't shoot a single photo of an important subject... and shooting much photos with a digital camera is a no-cost operation.

Better: don't trust too much digital camera forums. Most people will cry for "bad shots" or "excellent shots" without ever understanding what does actually good shot mean. A good photographer will spend his time in shooting, and won't spend much of his time on a forum only to proclaim himself (or feel proclaimed by other people) as a Digital Photography Expert.


Duh, the FZ20 has only five megapixels... I think eight is better, ain't it?

Duh, didn't you ever consider the cost and the hassle of having Lots Of Megapixels? Companies shout about their multi-megapixel cameras, as though they were a measure of photo quality, which they actually aren't. And lots of consumers are falling for it, forgetting the usual drawbacks: need of bigger memory cards, more lag between shots, more time needed to open/edit/save photos at home, harder to send via e-mail, etc...

Most people could buy a simple three-megapixel camera and just live happy (because it's twice×twice the most common computer screen, because it's easy to edit photos using a something different than a top-notch-gigahertz computer, because it's cheaper than bigger cameras, etc...)

There is only an issue about getting a "high steroids digital camera". It's for those shots that you won't ever have another chance. You cannot improve a low-resolution photo, and -maybe- in the next 10-20-50 years you could find yourself crying "why did I choose such a cheap camera?".

I only object that if this was the final rule, then even the extreme jerk should buy a top-notch camera, investing just too much time and money to not to say, one day, "duh, I had a decent camera...". Have a look at the weird marketing of the most famous brands, and ask yourself why everyone should continuously buy unnecessary power (for SUVs, computers, software, etc)...?


Which is the actual magnification of the 12× zoom using the 4× digital zoom?

432mm-equivalent × 4 = 1728mm-equivalent.

Anyways this is not a correct indication.

If I shoot a subject with 1×=36mm and then shot the same subject with 12×=432mm, I see actually about 10.7 times magnification (yes, I just counted the pixels); this means that the 12× full optical should be equal to a magnification of about 11× when compared to a "true" 35mm.

You can try it by yourself (be accurate, but don't exaggerate) :-) No, I don't have a true 35mm camera to compare... any volunteers? :-)

And yes, 4× digital zoom is actually four times extra zoom.

I did not (yet) check the 2.2× Raynox add-on lens, but I read some feedbacks about the 0.66× one, which actually "reduced" of 0.66 (getting a true wideangle 24mm-equivalent zoom).


This shot was done with a one-megapixel camera!

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