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 Post subject: Image Interpolation
PostPosted: Wed Oct 10, 2007 11:43 am 
I was looking at the Leica M8 review the other day and realised that the interpolated images from the M8 didn't show a large drop in quality. So I was bored the other day and decided to try it with my D80.

This was the original image:

Image

This was taken at 1/60s, f/5.6 and ISO100.

This is a 100% crop of the original:

Image

I then used Photoshop to resize to 5600x3749, which is about 21mp, using the bicubic interpolation method. I then used 80% unsharp mask like they did on dpreview. Since the resizing and sharpening was bound to make any noise more obvious, I put the interpolated image in Noise Ninja to try and remove it.

This is the result:

Image

I realise that 21mp is kinda pushing it but then again this was just meant to be an experiment. I was wondering what you guys thought about the quality of the resulting image. Any comments, tips or criticisms?


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 Post subject:
PostPosted: Wed Oct 10, 2007 6:01 pm 
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Hmm Graham, nice try.
But I think you have overdone it. See at the small silver ring that goes around the lens: It's much more prominent and contrasty than before. The lettering is also sharper than before. So perhaps you could experiment with a little less sharpening, which would also help noise-wise.

Question is, what did you want to show? That there is not much to be gained resolution-wise from a 21MP-sensor? I'm not sure...
Also, if you're into some resolution-shoot out, you should perhaps use a more finely detailed pic as a test-object :?

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Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews, My Pictures, My Photography Blog
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 Post subject:
PostPosted: Wed Oct 10, 2007 8:25 pm 
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It's an interesting test you've done there Graham, and illustrates how interpolation can avoid jaggies on big prints - BUT as Thomas says, it won't resolve new details which were never captured, so the trick to catch it out (if that's what you want to do!) is to photograph very fine detail such as the converging lines on a resolution chart, and see what happens...


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 Post subject:
PostPosted: Thu Oct 11, 2007 1:58 am 
Thanks for the comments guys. I was just wondering how far the image could be enlarged before that was a huge drop in image quality and whether it was useful at all if for example I really needed to print big.

Thomas, I tried using less sharpening like it suggested and it does help the final image looks more natural.

Seeing that the image is only marginally sharper than viewing the original at 200% without showing any extra detail I would say it isn't really useful although there are supposed to be specialised software such as Genuine Fractals and Photozoom that seem to give much better results. Perhaps I'll give those a try in the future.


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 Post subject:
PostPosted: Thu Oct 11, 2007 3:01 am 
Just curious what sort of sized prints are you ment to be able to get out of a 10MP image?


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 Post subject:
PostPosted: Thu Oct 11, 2007 3:12 am 
Depends on the resolution you are printing at. You get 12.9x8.6 inches if you print at 300dpi.


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 Post subject:
PostPosted: Fri Oct 12, 2007 5:14 am 
I have found if I nail everything meaning exposure, focus ect....

I can get excelent quality 12 x 18 prints even from 6 megpixel 10D.

thats going down to 170dpi, so I belive same print size from a 10 meg camera would be round 220 dpi.

Dave


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