Camera and digital zoom
 

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?

Re: Camera and digital zoom
 

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.

Re: Camera and digital zoom
 

Hello CodeMonkey

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

http://talk.maemo.org/attachment.php...1&d=1272707174

and

http://talk.maemo.org/attachment.php...1&d=1272707174

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).

Re: Camera and digital zoom
 

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

Re: Camera and digital zoom
 

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!

Re: Camera and digital zoom
 

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.

Re: Camera and digital zoom
 

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.

Re: Camera and digital zoom
 

and @rickysio


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

/oxpo

Re: Camera and digital zoom
 

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

Re: Camera and digital zoom
 

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:
http://peltsip.pp.fi/samplet/1F7B7662.JPG
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.

Re: Camera and digital zoom
 

4 Mpix? N900 has 5 Mpix.

Background out of focus has nothing to do with pixel counts but with depth of sharpness -- and for many scenes from a camera with such a short focal length (about 5 mm) the depth of sharpness is far to long, with too many objects being within the focus range. So you photo is technically quite good: Motion blur but the seagull completely sharp ...

Well, I have done more specific tests: Indeed, the N900 zoom is a digital zoom without any additional pixels available. So the differences visible in the first samples must be related to image processing only. However, it is not understandable, why non-zoomed images are processed so much worse than zoomed images so that details show difference in image quality. Would be interesting to save camera raw images ...

The 2 images attached to this post are again:

1. Detail of an image taken with N900 zoom 1x but exploded by 3 at the computer
2. Detail of the same image taken with N900 digital zoom 3x

(The original was a sheet of white paper with just black lines on it.)

http://talk.maemo.org/attachment.php...1&d=1272746886

and

http://talk.maemo.org/attachment.php...1&d=1272746886

(PS: The differences between the 2 images of my first post are even bigger in the original files. Unfortunately, talk.maemo.org has converted the png files to jpg and thereby compressed heavily.)