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Olympus OM-D E-M1 The first Micro Four Thirds camera that offers phase detect focusing so you can use Four Thirds DSLR lenses normally as well a Micro Four Thirds lenses.

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  #16  
Old 30th October 2017
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Re: Interference Fringes?

Yep, it's moiré. Lightroom and similar tools can usually get rid of it.
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Old 30th October 2017
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Re: Interference Fringes?

I have got a jpg of the relevant part of the relevant part of the image, unprocessed apart from conversion to jpg:

http://e-group.uk.net/gallery/upload...92226-Edit.jpg


Your further comments will be appreciated. . .
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Old 31st October 2017
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Re: Interference Fringes?

Quote:
Originally Posted by wornish View Post
Can you put them on dropbox and share the link ?

or if you have a Flickr account you could post them there.

You can actually post images to the gallery here with sizes greater than 800px long edge as long as the overall image size doesn't exceed 500Mb.

Even a 2000px long edge would help diagnose the issue.



If you cant do the above I can pm you my email address, and then you can use the site below to send the image to my email address.

https://wetransfer.com

let me know.

Its interesting to try and find the cause.
PM sent, please send your e-mail address
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Old 31st October 2017
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Re: Interference Fringes?

Thanks Peter for sending the full size images.

I have looked at the "wave" picture and it is certainly Moiré that is causing the issue.

I loaded it into PS and followed the first half of the steps explained here.

https://photographylife.com/how-to-r...e-in-photoshop

The improvement after this first stage is amazing so I didn't bother going to the second.

Here is a cropped version. I have not done any processing so the image is still as shared.

[IMG][/IMG]



and here is the shed

[IMG][/IMG]
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Re: Interference Fringes?

Dave,

Many thanks for that, never having tackled Moire before, I had no idea where to start.

I have PS CS2 and LR5.7, I think that this is beyond the capability of PS CS2, but I can certainly try, as explained in the link, with LR.

I am teetering on the brink of moving to Adobe CC, which will certainly improve my PS.

Thanks again,
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Old 31st October 2017
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Re: Interference Fringes?

Quote:
Originally Posted by Graham_of_Rainham View Post
I think this is Diffraction in much the same way you get coloured bands reflected from a CD. The light reflected off the corrugated panel or the light passing through the railings is defracted by virtue of the distance that they are viewed from.

https://www.olympus-lifescience.com/...r/diffraction/

"In optics, the Fraunhofer diffraction equation is used to model the diffraction of waves when the diffraction pattern is viewed at a long distance from the diffracting object, and also when it is viewed at the focal plane of an imaging lens"


My physics classes always said diffraction required an aperture on a similar order as the wavelength of the wave to be significant. CDs are of that sort of scale while fence railings are billions of times bigger.


Moire on the other hand just need repeating transmitting & obscuring patens (either with different spacing or imperfectly lined up). It's easily generated by two overlaid meshes. I've seen it most often with patterns in the mm to cm size range, but can generate one just with a fine mesh in front of a TV screen.
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Re: Interference Fringes?

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Originally Posted by Pjphoto59 View Post
Dave,

Many thanks for that, never having tackled Moire before, I had no idea where to start.

I have PS CS2 and LR5.7, I think that this is beyond the capability of PS CS2, but I can certainly try, as explained in the link, with LR.

I am teetering on the brink of moving to Adobe CC, which will certainly improve my PS.

Thanks again,
If CS2 can do adjustment layers then your good to go. Lightroom cant do layers so won't work unfortunately.

Affinity Photo does have layers and could be used as well.
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Last edited by wornish; 31st October 2017 at 02:12 PM. Reason: correction
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Re: Interference Fringes?

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Originally Posted by wornish View Post
If CS2 can do adjustment layers then your good to go. Lightroom cant do layers so won't work unfortunately.

Affinity Photo does have layers and could be used as well.
Dave, Your handy link to PhotographyLife had an internal link, showing hoe to do it in LR4

https://photographylife.com/how-to-r...e-in-lightroom

Although it does say that PS is better. I do have layers in PS CS2
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Old 31st October 2017
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Re: Interference Fringes?

Quote:
Originally Posted by Petrochemist View Post
My physics classes always said diffraction required an aperture on a similar order as the wavelength of the wave to be significant. CDs are of that sort of scale while fence railings are billions of times bigger.


Moire on the other hand just need repeating transmitting & obscuring patens (either with different spacing or imperfectly lined up). It's easily generated by two overlaid meshes. I've seen it most often with patterns in the mm to cm size range, but can generate one just with a fine mesh in front of a TV screen.
Moire fringes as you say are typically seen from overlapping lines, such as you see on Bridges with railings over roads etc.. The colour banding comes from the different angle of reflection of each wavelength of light off the corrugated surface. At a distance the light through the railings appears to act as though it has passed through a small gap and again separates into the colour bands as seen.
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Re: Interference Fringes?

Quote:
Originally Posted by Petrochemist View Post
My physics classes always said diffraction required an aperture on a similar order as the wavelength of the wave to be significant. CDs are of that sort of scale while fence railings are billions of times bigger.


Moire on the other hand just need repeating transmitting & obscuring patens (either with different spacing or imperfectly lined up). It's easily generated by two overlaid meshes. I've seen it most often with patterns in the mm to cm size range, but can generate one just with a fine mesh in front of a TV screen.
I do not have much need to do simple mathematics these days, but I just tried calculating the pitch of the shed corrugations in pixels on the image.

Tell me if I am wrong, but I did it this way:

The data for the shed were as follows:

a. Distance to the camera = 2200 m.
b. Lens focal length = 0.140m.
c. Sensor width = 0.0173m.
d. Sensor half width = 0.0087 m.
e. Pitch of shed corrugations = 0.076 m.
f. Half width of shed =x m.



By similar triangles, f/a = d/b, so x= (2200 *0.0087)/0.14 = 136.71 m.

Number of corrugations in half width = 136.71/0.076 = 1799.

The image, corrected for tilt is 4443 pixels wide. So the ratio of pixels to corrugations is 2221/1799 = 1.23.

So, if I have it right, the corrugations are at a pitch of 1.23 pixels. Should certainly produce interference
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Re: Interference Fringes?

Quote:
Originally Posted by Pjphoto59 View Post



So, if I have it right, the corrugations are at a pitch of 1.23 pixels. Should certainly produce interference

I've not checked your maths, but the reasoning all makes sense till the last sentence.
Have a quick look at https://en.wikipedia.org/wiki/Interf...ve_propagation) and you'll see interference is a wave effect that depends on the wavelength. It has nothing to do with the pixels which are considerably larger than the wavelength of light 400 to 700nm.


Moire https://en.wikipedia.org/wiki/Moir%C3%A9_pattern on the other hand would apply to thing similar in size to the pixel. Despite Wikipedia referring to it (foolishly IMO) as large scale interference patterns it's not down to interference of the light waves, just being an interference like effect. It down to parts of one repeating pattern being regularly reinforced by another and is dependent on the pattern spacing rather than light itself. Interference has long had a specific meaning in optics so other words should be chosen when that's not what's going on.
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  #27  
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Re: Interference Fringes?

Quote:
Originally Posted by Petrochemist View Post
I've not checked your maths, but the reasoning all makes sense till the last sentence.
Have a quick look at https://en.wikipedia.org/wiki/Interf...ve_propagation) and you'll see interference is a wave effect that depends on the wavelength. It has nothing to do with the pixels which are considerably larger than the wavelength of light 400 to 700nm.


Moire https://en.wikipedia.org/wiki/Moir%C3%A9_pattern on the other hand would apply to thing similar in size to the pixel. Despite Wikipedia referring to it (foolishly IMO) as large scale interference patterns it's not down to interference of the light waves, just being an interference like effect. It down to parts of one repeating pattern being regularly reinforced by another and is dependent on the pattern spacing rather than light itself. Interference has long had a specific meaning in optics so other words should be chosen when that's not what's going on.
Mike,

At last, I am getting somewhere, now I think I understand the difference between interference and Moire!

More importantly, thanks to Dave, I have a possible route for removing it in PP.
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