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-   -   A downside of not having an Anti-aliasing filter? (https://e-group.uk.net/forum/showthread.php?t=50697)

Ross the fiddler 3rd June 2019 12:25 PM

A downside of not having an Anti-aliasing filter?
 
2 Attachment(s)
I was feeling a little chuffed over my landscaping efforts at the side of our house & took some progress photos today, but was surprised to see this rainbow striped effect on the sides of the timber stair stringers. The timber has been milled with grooves ('Rougher Headed' finish) which I think has created the effect along with the camera not having an anti-aliasing filter.

These two photos are small crops of the images.
With the striped moire pattern Attachment 4958

And no effects on this Attachment 4959

Any further explanations & discussion welcome.

*chr

Growltiger 3rd June 2019 01:21 PM

Re: A downside of not having an Anti-aliasing filter?
 
Quote:

Originally Posted by Ross the fiddler (Post 482067)
I was feeling a little chuffed over my landscaping efforts at the side of our house & took some progress photos today, but was surprised to see this rainbow striped effect on the sides of the timber stair stringers. The timber has been milled with grooves ('Rougher Headed' finish) which I think has created the effect along with the camera not having an anti-aliasing filter.

These two photos are small crops of the images.
Attachment 4958 Attachment 4959

Any further explanations & discussion welcome.

*chr

I don't see the effect. Are you sure the effect is in the photo itself, and not a result of moire on your monitor. The way to tell is to zoom in to 400% and see if the rainbow effect is still there (=in photo) or has vanished (=on the monitor).

Ross the fiddler 3rd June 2019 02:13 PM

Re: A downside of not having an Anti-aliasing filter?
 
1 Attachment(s)
Quote:

Originally Posted by Growltiger (Post 482068)
I don't see the effect. Are you sure the effect is in the photo itself, and not a result of moire on your monitor. The way to tell is to zoom in to 400% and see if the rainbow effect is still there (=in photo) or has vanished (=on the monitor).

No, it's not a monitor thing or zooming in etc. I cropped tighter & upsized the image here (to 8000 on the long side) before reducing for this display.
Attachment 4960

Growltiger 3rd June 2019 02:33 PM

Re: A downside of not having an Anti-aliasing filter?
 
Quote:

Originally Posted by Ross the fiddler (Post 482069)
No, it's not a monitor thing or zooming in etc. I cropped tighter & upsized the image here (to 8000 on the long side) before reducing for this display.
Attachment 4960

I see what you mean now.


May I suggest you take the photo again, exactly the same, but using Hires mode. During my hires testing I deliberately took a photo of a severe moire subject. When I then used Hires mode the moire completely vanished.

Ross the fiddler 3rd June 2019 02:41 PM

Re: A downside of not having an Anti-aliasing filter?
 
Quote:

Originally Posted by Growltiger (Post 482070)
I see what you mean now.


May I suggest you take the photo again, exactly the same, but using Hires mode. During my hires testing I deliberately took a photo of a severe moire subject. When I then used Hires mode the moire completely vanished.

Thanks. I might have to wait a couple of days for the sun to shine again, but a nice thought using the HiRes though. I’ll show the full image as well next time too (I’m in bed now browsing on my iPad).

*chr

Beagletorque 3rd June 2019 03:22 PM

Re: A downside of not having an Anti-aliasing filter?
 
I get the same effect on feather detail. Very annoying!

You can see it on the left wing flight feather.

https://a4.pbase.com/o12/24/841924/1...XI.Woody2n.jpg

Ross the fiddler 3rd June 2019 09:45 PM

Re: A downside of not having an Anti-aliasing filter?
 
Quote:

Originally Posted by Beagletorque (Post 482073)
I get the same effect on feather detail. Very annoying!

You can see it on the left wing flight feather.

https://a4.pbase.com/o12/24/841924/1...XI.Woody2n.jpg

Thanks. Yes, I've had it before in the finer detail of the feathers, but I was surprised how much it showed in this instance.

Would be correct in thinking a sensor of higher pixel count be less prone to this effect?

Otto 4th June 2019 07:53 AM

Re: A downside of not having an Anti-aliasing filter?
 
Affinity Photo has an FFT Denoise filter which claims to be able to remove Moiré patterns but I've not tried it myself.

Bengeo 4th June 2019 08:01 AM

Re: A downside of not having an Anti-aliasing filter?
 
Photoshop Camera Raw and Lightroom have moire reduction in the Adjustment Brush tool.

Beagletorque 4th June 2019 08:15 AM

Re: A downside of not having an Anti-aliasing filter?
 
Quote:

Originally Posted by Ross the fiddler (Post 482104)
Thanks. Yes, I've had it before in the finer detail of the feathers, but I was surprised how much it showed in this instance.

Would be correct in thinking a sensor of higher pixel count be less prone to this effect?


I think it would be the other way around?

Growltiger 4th June 2019 09:53 AM

Re: A downside of not having an Anti-aliasing filter?
 
Quote:

Originally Posted by Ross the fiddler (Post 482104)
Would be correct in thinking a sensor of higher pixel count be less prone to this effect?

Yes you would. If you have enough resolution your camera will fully resolve the moiré area. That is why hires mode can eliminate it.

In the case of the bird (assuming this photo was cropped) a longer focal length lens would give you more pixels on the feathers, and that would help. Or get closer to the bird.

Many programs have tools to help remove moiré, although some simply blur it away, not what you want. Google will give you lots of ways to do it in Photoshop, the simplest of which it to use the slider in ACR or Lightroom.

There are several ways moiré can arise.
1. Two patterns in the area being photographed, one in front of the other.
2. One pattern in the area being photographed, the sensor pixels are the second pattern.
3. One pattern in the photo being viewed, and the second pattern on the viewing device (the camera LCD or viewfinder, or a monitor).

Growltiger 4th June 2019 09:55 AM

Re: A downside of not having an Anti-aliasing filter?
 
Quote:

Originally Posted by Beagletorque (Post 482120)
I think it would be the other way around?

That can be true, provided the lower resolution blurs out the detail so the moiré disappears. But this may not be what you want.

wornish 4th June 2019 12:03 PM

Re: A downside of not having an Anti-aliasing filter?
 
I just tried the Lightroom adjustment brush with the moire reduction tool on the bird image and I cant get it to work on the area of feathers.

Is it actually Moire as I thought that showed as coloured patterns?

Isn't it simply showing a diffraction pattern, which cant be fixed easily. Might be completely wrong though.

Ross the fiddler 4th June 2019 02:20 PM

Re: A downside of not having an Anti-aliasing filter?
 
All food for thought, so thank you all. I'm going to try & recreate the incidence of it on that same subject & see if I can do a HiRes shot with it as well, just to satisfy my curiosity etc. & then I'll post the results here again. I've just had a small play with Moire adjustment in Capture One & it gets rid of the colour red & green in the stripes & minimises the shading of the Moire effect, so a bit more experimenting may help. I'm off to bed now so will come back with more tomorrow sometime (in between paying work I'm supposed to be doing).

*chr

Petrochemist 5th June 2019 09:26 AM

Re: A downside of not having an Anti-aliasing filter?
 
Quote:

Originally Posted by wornish (Post 482147)
I just tried the Lightroom adjustment brush with the moire reduction tool on the bird image and I cant get it to work on the area of feathers.

Is it actually Moire as I thought that showed as coloured patterns?

Isn't it simply showing a diffraction pattern, which cant be fixed easily. Might be completely wrong though.



I suppose with cameras it will often produce coloured patterns (due to the bayer matrix) but most of the occurrences I've seen direct have certainly been monochrome.


This sort of issue is precisely why camera manufacturers put the AA filter in for so many years. It surprises me the effect is as difficult to notice as it is! I've just sent a camera off for an IR conversion which will remove the AA filter as well, so I might have to look out for things like this now...


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