Zoom Blur

[Marpel]

I find, at least on my computer, that Zoom Blur with a larger Blur % takes considerable time to complete (upwards of 20 + minutes). This results, of course, in a long wait to see the outcome.

In an attempt to reduce the wait time to preview and compare variations in Blur %, I have tried downsizing the image as well as cropping the immediate area around where the + is placed. It appears the reduced size of the image has a significant impact on the time it takes, however these extra steps are onerous and it still sometimes takes up to 8-ish minutes.

Anyone have any suggestions on any other quicker method to preview/compare the effects of a change in the parameters of this tool?

Marv

[jsachs]

There are some faster methods, but not as accurate. Maybe some day I will experiment with speeding it up.

Increasing the step size also makes it a lot faster while still giving you some idea what the final result will look like.

[davidh]

Why not giving it its own preview window like some other blur (and sharpen) methos have.

[tomczak]

You can already get a similar effect as a dedicated preview window for this particular transformation, and almost just as fast, if you insert a Resize Transformation just before the Zoom Blur. Resample the image significantly there (say to 25%) - the smaller output will be used by Zoom Blur which will let you preview the effects much faster.

Once you're happy, bypass the Resample (right-click on the white circle in Resample, which will turn it off, but not take the focus from the Zoom Blur preview window) and wait...

If, instead of trying to preview the whole image, you would like to see what the Zoom Blur does to a full-size fragment of your image, replace the Resample with Crop and do the same thing.

p.s. With Crop alone, you can actually combine cropping and thus zooming on an area you like and downsampling the image in one go - you don't need a separate resize if you change your mind as to what you want to see in 'preview'. Just crop (or not crop) as you like and toggle resize checkbox on and off.

So inserting Crop rather than resize, is probably the best way to go.

[Marpel]

Thanks for the replies.

I actually don't have much of an issue with waiting for the final Zoom Blur results with the chosen settings, it's just the time taken to see some samples of various settings that I'd prefer not to do. However, as tomczak pointed out, I will likely add a resize or crop step in the workflow.

And another question:

I have two images, one of some clouds, the other of a building with a steeple. I have composited the clouds into the building image. I then ran Zoom Blur with the origin + placed at the tip of the steeple. Results are OK, but I don't like how one part of the building roof adds to the blur (gives a large darker halo in the clouds along the roof line.

In hopes of doing the same settings on just the cloud image, then compositing that result around the building, I tried "Reload Last Settings" but all I could get was the same Blur % and not the same placement of the origin; the + was at the center of the image. I'd rather not just eyeball the same origin location between images so is this the way it is supposed to work?

Marv

[jsachs]

I tried this here and it restored the center location OK. Bear in mind that Reload Last Settings reloads the last setting that ran to completion after clicking OK.

[Marpel]

Jonathan,

Thanks for the response.

I just tried it again (after running it through the first time with clicking OK) and it did not restore the center location, but left it back at the center of the image.

Having said that, as the time went up to 14 minutes, I did not let it run out and just clicked cancel.

So that prompts the question - when you ran it, did the center location + actually move to the location you had initially set it, or does it stay in the center of the image (as it does in my case), but give a result as if the point was where it was initially placed?

I should also mention that, while waiting for a response, I tried the same operation while using the same mask for the composite (don't know why i didn't think of that initially) and it seems to help considerably. Just a little cloning required between the images.

Perhaps I will download the latest update to see if things change.

Marv

[Marpel]

Sorry, I made a bit of a mistake in my most recent post; using a mask did not solve the problem, the halo I mentioned is still present as it appears it still interacted with the building (although it was outside the masked area, which seems weird to me). I inadvertently viewed the wrong image when I made that claim.

Marv

[jsachs]

I tested on a small image and set the step size up so it would complete quickly. I moved the center cross and clicked OK. I then opened the same image and did a Reload Last Settings and it restored the center location and produced the same result as before. I also tried opening a different image and the center point was placed in the same relative location in the new image and all other settings were restored.

The halo is similar to the reason behind Precise Gaussian.

One way to get rid of it is to clone out the steeple with sky before blurring and then composite the steeple back in afterwards.

[Marpel]

Jonathan,

I just downloaded the latest update and tried this again.

When I Reloaded Last Settings, the wait time was much shorter so I let it run. And it produced the result I was looking for.

The thing that confused me was when the Reload Last Settings is clicked, it leaves the center location + in the center of the image, and doesn't move it to the recently set location. I presumed from this that the zoom would originate from the center of the image, but actually it does not.

So, everything works out OK.

Thanks for your patience.

Marv