sharpening depends on size of image?

David · 19th December 2004

If my image is 1024 x 768 at 72ppi, I find using an agressive 400, 0.5, 0 in USM works well. But if I do a much larger image dimension at 240ppi say, then even 400, 0.5, 0 looks so mild. I need something much more!

Does it mean the amount to sharpen an image depends on the resolution?

willyfoo · 19th December 2004

Yes... it depends on the amount of details in the image...

Ie.. for a 4MP image of a closeup potrait, my setting may be 120%, 2.0, 3
But for a 4MP image of a group photo, the edge of each face is much smaller, thus less radius... and may turn out to be 90%, 1.0, 3

When the images are reduced, each edge that defines a feature, ie, the line that defines the lips will be defined with less pixels as well, thus radius should also be reduced... for web images the radius is typically about 0.5-0.8.

David · 19th December 2004

Thanks Willy... ic...

I was shooting 8mp on the 20D and converted my images to jpg. Previously I had downsized to a small 1024 x 768 and had no problems with sharpening. At 8mp, the same sharpening wouldn't work at all, almost like no effect. I had to use a much drastic setting like 200, 1.4 (radius), 0.

willyfoo · 2nd January 2005

I suspect a larger radius would yield a more pleasing effect...
Try 120, 2.0, 0 instead and compare the effects...

Shodan99 · 2nd January 2005

I read in some magazines that it is most useful to do USM with the image in Lab colour mode, with the highlight in the lightness channel. I donno if it helps or not...

19th December 2004	#1
David Member Join Date: Mar 2002 Posts: 1,155	sharpening depends on size of image? If my image is 1024 x 768 at 72ppi, I find using an agressive 400, 0.5, 0 in USM works well. But if I do a much larger image dimension at 240ppi say, then even 400, 0.5, 0 looks so mild. I need something much more! Does it mean the amount to sharpen an image depends on the resolution?

19th December 2004	#2
willyfoo Senior Member Join Date: Jan 2002 Location: North Posts: 2,085	Yes... it depends on the amount of details in the image... Ie.. for a 4MP image of a closeup potrait, my setting may be 120%, 2.0, 3 But for a 4MP image of a group photo, the edge of each face is much smaller, thus less radius... and may turn out to be 90%, 1.0, 3 When the images are reduced, each edge that defines a feature, ie, the line that defines the lips will be defined with less pixels as well, thus radius should also be reduced... for web images the radius is typically about 0.5-0.8. __________________ Singapore Wedding Photographer Willy Foo on Twitter & Facebook

2nd January 2005	#4
willyfoo Senior Member Join Date: Jan 2002 Location: North Posts: 2,085	I suspect a larger radius would yield a more pleasing effect... Try 120, 2.0, 0 instead and compare the effects... __________________ Singapore Wedding Photographer Willy Foo on Twitter & Facebook

2nd January 2005	#5
Shodan99 Member Join Date: Nov 2004 Posts: 382	I read in some magazines that it is most useful to do USM with the image in Lab colour mode, with the highlight in the lightness channel. I donno if it helps or not...