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FORUMS Canon Cameras, Lenses & Accessories Canon G-series Digital Cameras
Thread started 05 Sep 2002 (Thursday) 01:06
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Loss of Sharpness in Smaller Images

 
jimworth
Mostly Lurking
11 posts
Joined Sep 2002
Sep 05, 2002 01:06 |  #1

I've noticed that whenever I produce smaller images (e.g. 640 x 480 pixels for an eBay listing) from my G2 shots, the sharpness is degraded. I would like to understand why this is. For example if I take a large resolution shot (4 MPixels) and then resize it to 640 x 480 using Paint Shop, it doesn't look as sharp as the original. With both the original and the shrunk image, I'm viewing the image in a 640 x 480 pixel area of the screen.

I've tried shooting at 640 x 480 (small resolution) so that no resizing is necessary and still the shots don't look sharp.

The thing that confuses me is that when I view an image in a 640 x 480 area of my monitor, it doesn't seem like a higher resolution image (e.g. 1280 x 960) can provide any more information to the 640 x 480 pixels that are actually displayed than a low resolution image that is 640 x 480 to begin with. Why does the image captured at higher resolution it look sharper in this situation?




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ken-w
Member
91 posts
Joined Aug 2002
Sep 05, 2002 12:22 |  #2

jimworth wrote:
I've noticed that whenever I produce smaller images (e.g. 640 x 480 pixels for an eBay listing) from my G2 shots, the sharpness is degraded. I would like to understand why this is.

Basically because you're throwing away pixels - image sharpness depends on edges and in a smaller photo there are fewer edges to work with.

With regards to your problem, you should be using the sharpening feature of Paint Shop (which I don't use so I don't know its capabilities). Almost all photos need post camera sharpening, in fact the pro recommendation is to shoot your pictures with in-camera sharpening turned off or set to the lowest setting and then do post process sharpening.

In programs such as Adobe Photoshop and Corel Photopaint the most effective sharpening tool is the "unsharp mask" or "adaptive unsharp" (I have no idea why they call a sharpening tool, "unsharp" - but there you go). I most often use a 3rd party plug-in called "nik Sharpener Pro" but that is overkill for what you want.

Sharpening should be the very last thing you do to the photo and it should only be done once - multiple sharpening only degrades the photo. You should get some pleasing (and sharp) results.

Why does the image captured at higher resolution it look sharper in this situation?

Good question - I have no idea - perhaps it is the way the program shrinks the photo - the original, even when shrunk still contains all the info, whereas the resized image has discarded much of this info in order to shrink the size (i.e. it has remapped all the pixels).

However, if you put the two side by side, and then sharpen the smaller photo (using your unsharp mask or whatever Paint Shop has to offer) it will look sharper than the original.




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Loss of Sharpness in Smaller Images
FORUMS Canon Cameras, Lenses & Accessories Canon G-series Digital Cameras


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