The N900 has a digital zoom only, that means: No optical zoom. Right?

This would mean, that the camera crops the images but when zooming should not be able provide more detailed images. However, on a brief test, the zoomed picture showed more detail (and less noise) ... something I only expect from an optical zoom.

Any explanation?

My guess:

Without zoom, a raw picture is taken at resolution x by y. The picture is compressed to jpg introducing some jpeg artifacts.

With zoom, a raw picture is taken at resolution x by y. The picture is cropped to (x - z), (y - z). That image is then scaled up to x by y, losing raw image quality since some pixels are doubled and others might be averages etc. The picture is compressed to jpg, introducing a different set of jpeg artifacts.

I don't think that there would actually be more detail there, but in some cases the application of the jpg algoriithm would be less effective at compressing the image, in which case it would have to leave more of the raw data and not introduce artifacts. The file size will likely be larger (at least for that section of the image, other areas may balance out).

You can probably test further by setting the jpeg compression level to 100 (which I believe is no compression, though it might still apply some even with this setting), and trying your experiment again.
You can set the jpeg compression level in an ini file somewhere - there are a few references somewhere on this forum, but from what I've read the current settings produce a good quality to filesize ratio.

Hello CodeMonkey

To me, the differences appear to remarkable for being simple JPEG artefacts. Compare the two figures below:



and



The first one is taken with zoom factor 1x but exploded 3x at the computer. The second one has been taken with zoom factor 3x. The only other difference between both images is a slightly different ISO value applied (114 for the 1x zoom versus 123 for the 3x zoom image). The camera-zoomed image shows much more detail, for example in the blue upper left area (recognizable in the full size image only) and in the yellow/brown area in the lower center. The increase in detail does not look like just a result of a lower jpeg compression. (The images uploaded are png, in order to avoid any additional compression.)

My guess: The sensor has about 10 MPixel instead of the official 5 MPixel. Hence, when the image is cropped to about 1/3 of the original size, the number of available pixels is not reduced to about 1.6 MPixel but about 3 MPixels (which then are exploded to 5 MPixel to have the same size as an image with zoom 1x).

If it had a 10Mpix sensor, Nokia marketing department would have plastered it all over the place...?

Nokia and N900? Two worlds are meeting? Did Nokia yet realize what they have got with their N900? I do not think so. They treat it more like an orphan, not really knowing whether they want it!

The N900 was never meant for the mass market in the first place...? Nokia had implied that if we wanted something we DO something, not expect them to do something. This is was marketed, and IS a phone for the geeks, the hackers, and the devs. Not the common Joe.

if it has Sensor of more than 5Mp then it will be handy if someone can write a third party camera app to make use of this.

and @rickysio


Does really every thread have to end up about this? Keep this thread on topic (Camera and digital zoom)

/oxpo

I was talking about his comment about N900 being an orphan. Please ask the correct guy to remain on topic.

damn you don't have any clue about real megapixels....


I'd say a normal N900 image compares to ~1mpix (100% crop image quality comparision)

here's my 4mpix for comparision:

background etc is out of focus, white is burned through, ....

so the sensor is probably read and a result is compressed a bit better when zooming digitally. but no, no more megapixels.