two-pass sharpening

FocalBlade specific discussions

two-pass sharpening

Postby Hessu » Fri Nov 07, 2003 10:28 am

Harald, congratulation to the brilliant plug-in!
I'm using FocalBlade now for some weeks and find it very useful.
Only sometimes I have the feeling when I print big prints from big files, the maximum 400 % sharpening is not enough.
My Canon 10D gets from CaptureOne RAW converter very soft files and I have seen discussions on some places of two pass sharpening. Also the low noise level enables much more sharpening than in my earlier smaller format cameras. First (mild) sharpening after RAW conversion and second as last step depending on the use of the photo (screen, print etc).
Have you made such thoughts and what could be the settings in version 1.01 for a "presharpening", which doesn't make the edges oversvinging? Or should I use some sharpening in C1 conversion (simple USM)?
If you follow this further, perhaps a third button could be useful (Pre, Screen, Print) for the automatic settings.

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Postby HaraldHeim » Fri Nov 07, 2003 2:13 pm

Here is a passage from the FocalBlade manual:

Sharpening Twice


Two or three very weak sharpening applications, won't reduce the image quality, nevertheless sharpening twice doesn't work better. You don't have so much control of the effect and it needs more time. When sharpening twice the risk to add too strong halos is larger. So better apply FocalBlade as the last step with appropriate settings.

Some people still prefer to sharpen photos right after they scanned them or transferred them from their camera. Doing that lets you remove the low pass filtering (blurring) - that was applied by the scanner or camera - to see the quality of the photo more clearly. Nevertheless you also have to sharpen the photo again at final print size. In such a case it is recommended to apply a very light sharpening at the beginning, e.g. by using a "Very Fine Details" setting or low radius of 0.2 to 0.5 pixel. Additionally you should better use "Light Textured" setting or low surface sharpen value for both sharpening steps to avoid too much noise in the surface areas.

If you need a stronger sharpening than 400%, you can also use the DeBlur Pro mode which allows up to 1000%. Of course you can also sharpen twice instead.

I know from personal experience that the 10D shots are quite blurred. I personally set the in-camera sharpening of the 10D to +2 for JPEG shots, which is the maximum value, but still produces an unsharp image. The 10D in-camera sharpening is very good compared to most other digital cameras.

Of course if you shoot RAW, you can't use in-camera sharpening. If you do an strong contrast adjustment in your RAW conversion tool it may be good to apply a pre-sharpening. However, it only makes sense if the software applies the sharpening before it does the contrast adjustment. If your RAW image doesn't need a strong contrast adjustment, you can also apply the pre-sharpening with FocalBlade or simply don't do any pre-sharpening.

I'll think about a Pre button. But I also have a seperate deblur plugin in mind which may be better suited for that task.

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