Playing around with interpolation

[shutterbuggy]

Here's a photo from my FZ5 (shot a few weeks ago when I wasn't quite sure about how to use my cam) interpolated to 10 MP. It shows a nice building in Bad Alexandersbad (a spa). Be warned - it's 2.3 MB:
http://www1.file-upload.net/27.01.06/m72wul.jpg

The original file (1.5 MB):
http://www1.file-upload.net/27.01.06/yvgz5b.JPG

OK, next time I'll use natural instead of vivid mode - too much in-camera processing in vivid mode. The amount of CAs beats me - how to avoid them?

Btw: I think I need a good wide converter for my FZ5 ... :G
The next few days I'll try the same shot in natural mode with manual settings. :?

EXIF data:
Camera make : Panasonic
Camera model : DMC-FZ5
Date/Time : 2006:01:11 13:27:29
Resolution : 2560 x 1920
Flash used : No
Focal length : 6.0mm (35mm equivalent: 36mm)
Exposure time: 0.0020 s (1/500)
Aperture : f/4.5
ISO equiv. : 80
Exposure bias: -0.33
Whitebalance : Auto
Metering Mode: matrix
Exposure : program (auto)

Workflow: interpolated the pic from 5 MP to 10 MP using Krita (in B-Spline mode) then sharpening with Gimp (setting 35). OS: Linux (Kanotix)

Comments on how to improve my lacking cam skills are welcome!

Downsampled to 1024x768 (makes a nice wallpaper):

[squirl033]

unfortunately, the process of downsizing/resampling to 1024x768 negates anything you did by interpolating up to 10MP, because you've just turned your 10MP image into a less-than-1MP image and lost most of what you added in. the only real proof of how good a picture looks after interpolation is to either display it at full size (not practical on most PC monitors) or to print it as a poster-size enlargement. if you can make a nice, clear 16x20 or larger print from that 10MP file, then your interpolation process is good. if it comes out fuzzy or pixelated, then you need to revise your workflow a bit, or use a different sampling algorithm.

one trick i've heard is helpful wheninterpolating to a larger file size is to do it in stages, never upsizing more than 10% per step. i can't say for sure if that works better than doing it in one jump, but i have tried upsizing a 5MP file to about 7.5MP using that method, and it made a very commendable 16x20 print.

[pdx_doug]

I am curious as to why you chose to interpolate up to 10MB. Coming from a digital printing background, interpolation or upsampling never seemed to give me any more real detail, although it did help make the resulting pixelization a little less dramatic.

[shutterbuggy]

squirl033 wrote:

unfortunately, the process of downsizing/resampling to 1024x768 negates anything you did by interpolating up to 10MP, because you've just turned your 10MP image into a less-than-1MP image and lost most of what you added in.

I downsampled the 1024x768 pic from the original pic. At first I saved the out-of-camera JPG to TIFF, then interpolated to 10 MP and saved it to JPG, at quality 92 in Gimp!
The 1024x768 pic stems from the TIFF originated from the original JPG.

I tried interpolating in steps with the outcome being bad.

[shutterbuggy]

pdx_doug wrote:

I am curious as to why you chose to interpolate up to 10MB. Coming from a digital printing background, interpolation or upsampling never seemed to give me any more real detail, although it did help make the resulting pixelization a little less dramatic.

It comes in handy if you want to have a huge image.

[David C]

It's quite a good photo - which could probably even look better with some post-processing (eg for architectural shots = a touch of unsharp mask, both for sharpening and local contrast enhancement; making sure all the horizontal and vertical edges are squared up; a bit of a saturation boost; some selective lighting to draw the eye into the frame; etc)

Though it's a bit of a pity that the modern path lights look out of place against this building! :roll:

With the upsizing, the 10% increments only applies to methods such as bicubic or bilinear (where it does make quite an improvement). With better algorithms like splines, Lanczosor Mitchell - then it should be all in one go...