Sharpening very large prints - is input sharpening a mistake?

[hdomke]

What is the best way to sharpen prints that will be 20-feet wide?
Conventional wisdom says sharpening should be done at multiple steps: input sharpening, creative sharpening (optional) and output sharpening.
Since sharpening enhances edge contrast by creating halos my concern is that those halos will become visible in huge prints.

It would seem to me that sharpening for huge prints is best done as a single-step process just prior to printing.

What do you think?

Do you know of any websites or articles that deal with preparing files for printing at very large sizes?

[Bart_van_der_Wolf]

Since sharpening enhances edge contrast by creating halos my concern is that those halos will become visible in huge prints.

There should be no halos, presuming that the (deconvolution!) sharpening is done well. When that is achieved, then further enlargement cannot enlarge any artifacts either.

It would seem to me that sharpening for huge prints is best done as a single-step process just prior to printing.

What do you think?

1. There is no problem with stepwise sharpening, provided that no artifacts are created in the intermediate process step (which might be hard, depending on software an skills)
2. If artifacts are created by the chosen sharpening approach, then it's better to postpone the sharpening until after the final output resizing.

A lot can be achieved by using good resampling software and good sharpening techniques.

Cheers,
Bart

[hdomke]

Bart,

There should be no halos

I thought that sharpening always enhanced edge contrast (i.e. added halos), but if done properly the halo is imperceptible.

There is no problem with stepwise sharpening, provided that no artifacts are created

If sharpening is enhanced edge contrast, and if there is significant enlargement after sharpening then that enhanced edge contrast might become apparent. In other words the "halo" becomes apparent.

A lot can be achieved by using good resampling software

I always resample my enlargements using bicubic smoother in Photoshop. Since I am talking about printing 20-feet wide here my up sampling is often significant.

My concern is that when you print huge prints that need a lot of resampling that you need to think about sharpening in a different way.

Thoughts? Comments?

Here is a link to some of my installations: click here.

[Bart_van_der_Wolf]

Bart,I thought that sharpening always enhanced edge contrast (i.e. added halos), but if done properly the halo is imperceptible.

Hi Henry,

No, fortunately there are better sharpening possibilities than USM (which does) boost ege contrast). Deconvolution sharpening restores the orignal image's sharpness. However, it is not flawless because some of the information is alrady lost, so it requires a bit of restraint if it creates the basis for further enlagement.

Depending on the tools, sharpening in Photoshop can be best done on a luminosity sharpening layer with a blend-if adjustment that avoids clipping due to oversharpening. It also reduces the risk of halos spoiling the fun. Smart sharpening is using a sort of deconvolution sharpening, but there are better tools for that operation.

I always resample my enlargements using bicubic smoother in Photoshop. Since I am talking about printing 20-feet wide here my up sampling is often significant.

Bicubic smoother is not bad, but there are better methods available. Commercial programs like Qimage or Photozoom Pro are capable of higher quality resampling, and the free ImageMagick command line tools (using the Mitchel Netravali filter settings) in general also produces better results than Bicubic Smoother does.

My concern is that when you print huge prints that need a lot of resampling that you need to think about sharpening in a different way.

I fully agree, hence my suggestions.

Cheers,
Bart

[Schewe]

What is the best way to sharpen prints that will be 20-feet wide?

What image source? What's the output process? You realize unless you have a really huge file size, this is gonna be a question of what you're expectations are...I would still go with the multi-sharpening workflow. The output size isn't really a factor that would change the sharpening workflow, the final output resolution and how you got there would.

So, until you more fully outline your workflow, the image source and the final output, I really can't tell you much. I would suggest taking the image up in size and test various processes and output smaller segments to see results. Just don't expect 20' images to look really nice and tight from up close.

[hdomke]

Jeff,
Thanks for responding. I know you know a lot about sharpening a lot since you wrote "Real World Image Sharpening" (which I have and greatly enjoyed).

You realize unless you have a really huge file size, this is gonna be a question of what you're expectations are...

These are not prints what would survive pixel peeping. I understand that. But I want them to look as good as possible and sharpening is a critical part of that.

So, until you more fully outline your workflow, the image source and the final output, I really can't tell you much.

Okay, lets say I have a high frequency landscape image taken with the P65+ in a single shot using good technique. After RAW processing it is sampled up to 54-inches tall by 240-inches wide and 150 DPI. It is to be printed on canvas with an Epson 11880 using ImagePrint 9 software.

How would you approach sharpening this image?

[Schewe]

Okay, lets say I have a high frequency landscape image taken with the P65+ in a single shot using good technique. After RAW processing it is sampled up to 54-inches tall by 240-inches wide and 150 DPI. It is to be printed on canvas with an Epson 11880 using ImagePrint 9 software.

How would you approach sharpening this image?

I would capture sharpen in ACR/LR with a sub 1 Radius, 40-50 Detail and an Amount that makes the image look "good" at 1:1...I would upsample in Photoshop using Bicubic Smoother to get the output resolution to 360PPI, do some additional creative sharpening prolly running Super Sharpener 1 or 2 from PhotoKit 2, maybe a touch of smoothing if any diagonal edges start chattering. Then I would ad a touch of Photo Grain (also PKS2)...I would just the image at both 100% and at 25% and do whatever tweaks the image needs and then do output sharpening in PKS2 for 360PPI output. I would double check edges and modify the masks to remove any output sharpening that introduces edge artifacts, then print tests to confirm the process.

Then go back and tweak the steps as required...