Strategy to Achieve a "Tapered-Edge, No-Blur" Circular Area Within a Blurred Image

[PixelPest]

While the OP seeks for a solution for Affinity Designer but Photo is mentioned, would a "depth of field" blur work?

I still don´t get an image by "Tapered-Edge, No Blur" unfortunately.

[lacerto]

The method presented by @JimmyJack is still very useful, to apply more control on how the varying amount of blur is adjusted (even if the seams would require further manual processing).

UPDATE: Note, too, that any Live Blur effect borrowed from Photo (or Photo Personal of Publisher) can be subsequently used and fully edited also in Designer.

[Old Bruce]

On 9/15/2022 at 7:07 AM, Optimalist said:

Imagine an image to which a Gaussian blur has been applied. Now imagine a circular area within this image where this effect is not applied.

I think this discussion has gone far off the rails into the weeds if not the deep woods. I don't think the idea was to blur a circle.

 

[PixelPest]

39 minutes ago, Old Bruce said:

On 9/15/2022 at 4:07 PM, Optimalist said:

Imagine an image to which a Gaussian blur has been applied. Now imagine a circular area within this image where this effect is not applied.

 

Isn´t that exactly what the "Depth of Field Blur" set to Elliptical does? Though not available in Affinity Designer afaik.

[Old Bruce]

13 minutes ago, PixelPest said:

Isn´t that exactly what the "Depth of Field Blur" set to Elliptical does? Though not available in Affinity Designer afaik.

Check the fourth post from Optimalist where he comments on my screenshot, pointing out how the only problem with it was that the edge was distinct. Compare the various multiple pictures of circles with blurs on them to that image. I don't see the relationship between the most recent screenshots of Circles that are blurred and my original screenshot with a circular area un-blurred. Hence I think we have wandered far afield.

I too though of the Depth of Field blur filter but, as you pointed out, we are dealing with Designer, not Photo.

[Optimalist]

Hi Everyone (@Old Bruce@PixelPest@lacerto@thomaso@JimmyJack@David in Яuislip@John Rostron),

Sorry for my absence. Apparently, on my first day on this forum, I went over my allowed number of posts and couldn't reply to anyone anymore.

After downloading a trial version of Affinity Photo, I was able to confirm @thomaso's assertion that applying any kind of gradient to a Gaussian filter does not affect its blur radius (or sigma), but instead merely its opacity. The depth of field effect does change blur radius—but it doesn't use a Gaussian blur. It may be a bokeh blur or something else. In any case, I can't use that kind of blur because it doesn't have the right properties and causes strange overlapping effects. See the image (and .afphoto file) below.

• On the left half of the image is a depth of field effect, with everything out of focus except for the center of the left spiral. Note the darkened areas where the blurs overlap and produce pattern artifacts.
• On the right half of the image is a Gaussian effect. Note that it does not produce any pattern artifacts—just blur.

How they blur differently is most obvious where they're side-by-side, at the center spiral.

This brings me to conclude that none of the tools in the Affinity suite of products produces a Gaussian blur that gradually increases from no blur to a certain level of blur. (I have no idea if any other image editing products do, either.) So it seems that I'll have to resort to the "brute force" method that I described in my original post. It will be a pain to implement, but at least it will look very close to perfect.

Thanks for the ideas, suggestions, and thoughts!

DOF v Gaussian.afphoto

Edited September 16, 2022 by Optimalist

[lacerto]

On 9/17/2022 at 12:35 AM, Optimalist said:

This brings me to conclude that none of the tools in the Affinity suite of products produces a Gaussian blur that gradually increases from no blur to a certain level of blur. (I have no idea if any other image editing products do, either.)

Blur effects are quite popular and varied so there is a good chance that you may find what you are after. One worth a look might be GIMP, and its G'Mic plug-in, which also (partially) operates within Affinity Photo (Windows version only), but for some reason unfortunately not when using specifically the Blur filters (or I at least could not make them work with my test images, which were b/w grayscale and RGB 8-bit pixel layers; in context of Photoshop they work just fine).

But the same filters do work in current version of GIMP (and you can pick the depth of field blur type, in example below "Gaussian" blur is used):

GIMP also has a bunch of blur filters of its own, and one of them is called "Variable Blur", but which I could not apply to make any effect at all with these kinds of black and white images. But they might be useful in some specific situation.

UPDATE: I had another look on the "Variable Blur", and realized now that it works by using a loaded image as a blur mask:

As the feature has additionally an Opacity and Blend mode control, it might help you achieve what you are after. 

 

 

[Old Bruce]

20 hours ago, Optimalist said:

This brings me to conclude that none of the tools in the Affinity suite of products produces a Gaussian blur that gradually increases from no blur to a certain level of blur.

It really depends on the gradient on the mask (or the transparency stops settings Tool's in Designer) of the gradient. You can generate anywhere from Full Effect of Blur all the way to No Effect of Blur anywhere on the subject. Start with Full, go to 40% and then back up to Full.

[thomaso]

17 minutes ago, Old Bruce said:

It really depends on the gradient on the mask (or the transparency stops settings Tool's in Designer) of the gradient.

Are you able to make the masking gradient's transparency changing indeed the blur value?

To me the mask only reduces the opacity of a consistently blurred image rather than a varying blur value. (… as in my impression every mask for every fx, filter or adjustment does, lacking in an option to reduce the applied value rather than its layer opacity.)

[Old Bruce]

30 minutes ago, thomaso said:

Are you able to make the masking gradient's transparency changing indeed the blur value?

Oh, I see. Forty pixel blur going to a twenty pixel blur going to a 10 or 0 pixel blur.

[R C-R]

5 minutes ago, Old Bruce said:

Oh, I see. Forty pixel blur going to a twenty pixel blur going to a 10 or 0 pixel blur.

So can you do that or not?

[Old Bruce]

1 minute ago, R C-R said:

So can you do that or not?

Not sure. I doubt it. I have to admit that I would be hard pressed to come up with need for this. I am quite happy with the results from simply reducing the opacity of the blur through masks and gradients.

[thomaso]

1 hour ago, Old Bruce said:

I have to admit that I would be hard pressed to come up with need for this. I am quite happy with the results from simply reducing the opacity of the blur through masks and gradients.

The missing option to gradient the values of an effect, adjustment or filter becomes obvious at areas of high contrast. Then a masking transparency gradient gets blended with the sharp image below instead of fading the effect's values. For instance:

[Old Bruce]

Your second screenshot is an excellent demonstration. The screen has the same Lines Per Inch (LPI) from top to bottom. As an analogy it would need to have a continuous change from say, 40 to 300 LPI.

I would guess that this improvement or option to have the blur Amount change instead of just its Opacity would be possible to code. Having said that I doubt that I would actually notice if you used it. I can think of images from my pictures where this would be more obvious, dead flowers against a textured wall instead of apples against a smooth wall. The textured wall would be blurred all the way out to the 40 pixels everywhere currently whereas with the proposed method it would be varied from 40 pixels to none. Under the current method I would need to make a mask and edit it somehow to be wider on the left and narrower on the right, The Yellow apple would have a large area around it to be blurred and the red apple would have a very narrow area around it to be blurred.

This is too early in the morning here on the Wet Left Coast and I doubt much of the above is actually coherent, so I'll pause now.