Is this (moiré) normal?

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Hi,

I shot some pictures over the last weekend after being sort of away from the hobby in the last few years.

One particular picture sparked my attention because of this:

9070742760_b9b4e1c23c_z.jpg
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Screenshot from 2013-06-17 20:50:48 by aclix, on Flickr

After noticing this effect I took a few more pictures just to test:


9068441155_8fcf0b8d08_c.jpg
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Screenshot from 2013-06-17 20:39:49 by aclix, on Flickr


9070782082_156b38aa67_c.jpg
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Screenshot from 2013-06-17 20:58:08 by aclix, on Flickr

These were all taken with my D300 with the nikkor 50/1.8 or the 180D/2.8.

It seems that the effect is more noticible on yellow surfaces. I shoot some yellow book covers and the effect was there also, not as pronounced but definitly there, so this is not exclusive of fabrics.

One strange thing that happened, at least for me, is that when I upload the original files to flickr the effect is gone.

9070749604_e5102252c7_c.jpg
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DSC_4717 by aclix, on Flickr

I had to take a screenshot of each picture to show the effect as it is and also as it shows on the D300 screen. On the D300 screen the effect seems even more intense and it seems that sometimes I can notice it a bit looking through the viewfinder.

I have this camera since 2008, and although I haven used it much, I find strange that I can only see this effect now. Is this moire effect or is my camera defective?

regards,

Alex
 

Growltiger

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Yes, it is normal. Moire is a physical effect which can be reduced by an anti-alias filter (which your camera has) but can never be entirely eliminated.

The easiest solution is to wear a different shirt. Those types of material are banned from use by TV presenters for the same reason.

Flickr reduces image quality, that is why the effect went away.
 
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Be careful making a judgement here as although this is a moire pattern it may be a false one created when viewing your images via the monitor. Your images suggest that you are viewing at 19-22% and 159% so...

Question:
Does the moire remain when you view at 100%?

Unless you view your image at 100% on screen it is quite possible that you will see moire under certain conditions - then if you are really unlucky you will try to remove something that is not there and get really frustrated :wink:.

The fact that you had to take screenshots to show the effect and that it is not observable with uploaded images suggests that this is not moire that is actually baked into the file either Jpeg or Raw but a screen induced moire
 
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What Tony said...

If you view images at anything but 100% moire "may" be produced because the image
is being interpolated to accommodate the viewing size... :wink:
 
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Thanks for all the answers. When viewed at 100% the effect is gone. It shows a lot (depending on clothing) on the LCD screen when viewing the picture on the D300 and also on the pc monitor at sizes under 100%. Do you see this very often in your pc monitors or your camera LCD?

Alex
 

Growltiger

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Thanks for all the answers. When viewed at 100% the effect is gone. It shows a lot (depending on clothing) on the LCD screen when viewing the picture on the D300 and also on the pc monitor at sizes under 100%. Do you see this very often in your pc monitors or your camera LCD?

Alex

I sometimes see it on the D300 screen, yes. But I have the D300 centre button configured to zoom to 100% so I have an instant check on focus and moire.
 
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Yep, I see it all the time both on the camera and my monitor depending on what size I'm
viewing at (other than 100%), this is normal...

If you view an image at 100% then 1 pixel from your sensor = 1 pixel on your monitor

If you view an image at 200% then 1 pixel from your sensor = 2 pixels on your monitor

If you view an image at 50% then 2 pixels from your sensor = 1 pixel on your monitor

Changing the resolution of the image to other than 100% can introduce all kinds of weird
patterns/effects, moire is one of the possible patterns/effects...
 
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William,

Think about it?

At 200% then 1 pixel from your sensor = 4 pixels on your monitor.

DG

No...

At the same "aspect ratio":

You don't double the number of pixels by doubling the hight and doubling the width of the area... Doubling the hight
and doubling the width of the area gives you 400% more area and 400% more pixels...

You double the area/pixels by multiplying both the hight and the width by the square root of 2 (1.41421356237)

(Rounded out we'll use 1.4142)

1.4142 pixels x 1.4142 pixels = 1.9999616 pixels = 200% (rounded out)

Another way to explain:

A rectangle with a long side of 20 pixels and a short side of 10 pixels = 20 x 10 = 200 pixels (100%)

20 pixels x 1.4142 = 28.284 pixels... 10 pixels x 1.4142 = 14.142 pixels...

28.284 x 14.142 = 399.99232 pixels = 200% (rounded out) of the original rectangle...

At 200% 1 pixel from your sensor = 2 pixels on your monitor (rounded out)

You could however double either the hight ~or~ the width (one or the other NOT both) to double the
area/pixels but that would also be changing the "aspect Ratio"...
 
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Hi William,

In PS take an image - any image - and increase its size to 200%. The pixel size will double in both directions - height and width.

Now compare its 100% size on screen to the 200% size of the original?

That's where I am coming from.

DG
 
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OK, I see what you're saying... But that's actually a 400% increase in image area/pixel count
no matter what PS chooses to call it... :wink:
 
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Both are correct a 400% increase in image area and 200% enlargement or enlarge by a factor of 2 are the same. You must increase both width and depth of an image equally to maintain the aspect ratio.

In graphics/photographic terms Adobe is IMHO using the correct terminology i.e. 100% is 1:1 regardless of pixels or analogue film (note you cannot have a 100% enlargement, it is just 100%). So a 2x or 200% increase is double the size or pixel numbers in the horizontal and vertical.

In terms of film (some may remember!) taking a 5x4 negative and enlarging by a factor of 2 or 200% will give a 10x8 print or 80 sq inches which is 4 times the original area of 20 inches. So everyone is correct :biggrin:
 
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Then in photography they are using an incorrect term (200%) to describe what in geometry
would be 400%... I can accept that but it is not geometrically/mathematically correct...

In geometry to increase the area of a rectangle by 200% (and keep the same aspect ratio)
you multiply the long and short sides by the square root of 2 (1.4142)... Multiply the sum of
each by each other and that gives you 200% more area... To increase the area by 300%
you use the square root of 3 (1.7320)... For 400% by the square root of 4 (2.0)... Which is,
I guess, what is being done in photography but they seem to "call" it 200%...

I guess early photographers weren't very up on proper geometry/mathamatics... :tongue:
 
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Not really as in photography they are using the terms quite correctly and in a way that is understandable by all photographers i.e. 200%, 400% etc means an enlargement 2x, 4x etc. and refers to the final dimensions of a print in both the horizontal and vertical.

Photographers are not concerned about calculating area of a print as this is fairly meaningless - to them!. Of more importance to the film manufacturers as their costs and sales are usually calculated on a square metres basis.

The important bit is final print size and its relationship to the original either in pixels, inches, centimetres or other.

They would be really confused if you had a lab and asked them to calculate the sizing by using a square root formula :confused::tongue:

Perhaps the plethora of film formats and paper sizes UK, American, etc have helped making this easy for photographers to standardise on this sizing method?
Common film sizes
http://en.wikipedia.org/wiki/Film_format
Common print sizes
http://en.wikipedia.org/wiki/Photo_print_sizes
 
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William,

All of the talk in this thread prior to my post was of 100% VIEW or 200% VIEW.

I know where you are coming from but it is not what was originally spoken of.:smile:

In any editing programme or AV software if you zoom in to 200% then Each original pixel is represented by 4 (interpolated) pixels.

It's the same on a TV - if your image or AV show is 960x540 and you VIEW it full screen (16:9) then each original pixel is represented by 4 new pixels (and it sometimes looks like rubbish).

:smile:

DG
 

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