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Question

When heavily blurring an image I get unwanted ghosting or artifacting. Please help.

Forum|Forum|8 years ago
August 31, 2017
2 replies
463 views

When heavily blurring an image I get unwanted ghosting or artifacting. That looks like stepped ghosted outlines of the areas with varying saturation and/or darkness/lightness. I've had this occur using all the blur options available (except Average). And my best results so far have been using the Field blur in the Blur Gallery. This is a cutout of an image where the problem is quite apparent. Anyone know what I'm doing wrong? I am working on documents which are 300ppi at various sizes.

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Trevor.Dennis

Community Expert

I am wondering if we could have had a better idea of what is going on if we'd seen more of the image, and we knew what settings you are using? Is this being done on a full layer, or are there any selections active?

I am also wondering what zoom ratio your screen shot was taken at? It appears to have large clumpy noise, which suggests a high zoom ratio. Show us a screen shot showing the entire workspace with the layers panel and maybe the history panels visible, and pasted here at full res.

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Ⓜ️ MadisonAuthor

Participating Frequently

Thank you for the timely response. I am going to attempt the plan of action suggested by c.pfaffenbichler. If that doesn't get the intended results I will update my post to include a more robust description including the specific things you requested.

Thanks again.

D Fosse

Community Expert

Unless you have a 10-bit capable monitor/video card (very few do), you will always see some banding on screen. An 8-bit display system only has 256 discrete steps from black to white.

If that 8-bit banding is very irregular, there is an additional problem. A low quality panel or a faulty monitor profile will make it worse. The most common cause, however, is calibration tables in the video card. Do as much as possible in the monitor's OSD controls, so that video card adjustments are kept to a minimum.

In short, any banding you see in a 16-bit file is in your display system.

c.pfaffenbichler

Community Expert

Anyone know what I'm doing wrong?

Good to see someone not trying to blame anybody else right away when a problem arises.

But you probably have just stumbled on the limitations of working on 8bit images.

I would recommend two steps to try to alleviate the issue:

• Work in 16bit. You would have to redo the blurring unless it has been applied as Smart Filters anyway.

• Add Noise after the blurring. This could be done as a (Smart) Filter or with a Pattern Layer or Pattern Overlay of the appropriate noise set to Blend Mode Linear Light (and possibly reduced opacity).

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Ⓜ️ MadisonAuthor

Participating Frequently

Thanks for the quick response. As a first step I usually assume user error .

I just got on the computer for today, but I will try as you suggest.

My only concern is that I usually add noise/patterns,etc to the image before I apply the blur. Usually this is to add additional color or elements to the image, because my goal is a very smooth blur and in many cases my intended product is blurred to the point that the original image (unless already known) is basically unrecognizable as its source.

Thank you for taking time to reply. I will update here if this is a successful plan of action.

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