Unsharp Mask when the image is big, how?

[planetrobert]

Hi,

I always like to do a little unsharp mask before posting web-ready images, just to sharpen up the "in focus" areas a bit more, but how do you see the results of the unsharp mask tool when the image you are looking at fills the screen yet is only at 16% full pixel size?

If I shrink the image down to 640 x 420 then I can see the whole image at actual pixel view and do an unsharp mask action and see the results instantly, but if I perform unsharp mask on an original huge size image, I see nothing happening.

Any ideas?

 

[Peltigera]

Change the DPI setting to a large number then the image will fit your screen. After you have sharpened, change the DPI back to the level you want. Changing DPI does not change the resolution of the picture, just the display, unlike changing the total pixels to 640 x 420 does.

 

[L Gebhardt]

You should export a copy of the file at the final size for the web. Then do your sharpening on the smaller file.

 

[Pioneer]

I rarely sharpen until I am about to print. Actually, I guess it would be more accurate to say that I never sharpen an image until it is set for printing. I don't even bother before that. Once I have my image set for print size and resolution it is usually a lot easier to evaluate the results of my sharpening. And since it is the last thing I do the sharpening has been optimized for the print.

 

[planetrobert]

Right, but say I want to make a 12 x 18 inch print, I can't see that image at 300 dpi on my screen in such a way that performing an unsharp mask function delivers a visible change in the image. So I will test out Peltigera's idea about making it a large DPI setting I guess.

 

[L Gebhardt]

Right, but say I want to make a 12 x 18 inch print, I can't see that image at 300 dpi on my screen in such a way that performing an unsharp mask function delivers a visible change in the image. So I will test out Peltigera's idea about making it a large DPI setting I guess.

In that case resize the image to 12x18 at 300ppi, so 3600x5400 pixels. Then do your unsharp masking and look at the image at 100% (actual pixels). The strength of the filter will depend on the type of paper and the printer. For glossy paper you want less strength than for a matte paper since the matte papers bleed a bit more. The only true way to tell if it's sharpened correctly is to print a small section and see. I usually find that the image has to just start looking over sharpened on the screen at 100% before the results are noticeable on a glossy inkjet print. For matte it starts to look kind of ugly on screen before it's really showing on the print.

You shouldn't see much change at any magnification less than 100%. You would also do well to stop thinking about images in terms of DPI, except when printing. DPI is meaningless on the screen. I bring this up since you mention 300dpi on your screen, which isn't possible on most monitors (retina display iPhones pass this, but the retina display Mac Books do not). So I sense you are falling it the misunderstanding that I've seen so many others have. peltigera's advice isn't going to help you, as changing the DPI without changing the pixel dimensions will not look different on the screen.

 

[pschwart]

Right, but say I want to make a 12 x 18 inch print, I can't see that image at 300 dpi on my screen in such a way that performing an unsharp mask function delivers a visible change in the image. So I will test out Peltigera's idea about making it a large DPI setting I guess.

- always check your sharpening at 100% magnification
- the image doesn't need to all fit on the screen -- hold down the space bar
and mouse all around the image to check sharpening and see if
spotting/cleanup is required
- as others have commented, optimal sharpening for print output will probably
require sharpening beyond what looks best screen viewing

 

[planetrobert]

I will try out these techniques and post an update. Thank you.

BTW, do I need to reply like this as a courtesy or is that just annoying since it sends a link to everyone again?

 

[L Gebhardt]

I will try out these techniques and post an update. Thank you.

BTW, do I need to reply like this as a courtesy or is that just annoying since it sends a link to everyone again?

I see it as a courtesy to post back. Other's may see it as annoying, but you need to subscribe to the thread to get notices. So if it annoys people they don't need to subscribe.