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11-17-2017, 06:49 PM - 1 Like   #1
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Are these striations actually on the feathers?

Photographed a Kookaburra on my back fence here in Brisbane. Some of the shots show striations on the feathers. Are these a photography/processing artefact or are they really there?

The processed shot. K-3 + DA* 60-250/F4 @ 250mm FL, 1/125s, f/5.6, ISO320:



At first I thought this might be some FPN. But look at two consecutive DNGs from the shoot.




The first is a bit OOF, but that's not important here. Compare Region "A" in both shots and then look at Region "B".
  1. The 1st raw shot was tilted 2.5˚ compared to the 2nd. To me, the striation also appear tilted in "A" in shot 1 compared to shot2.
  2. There appears to be a slight curve in the striations in A.
  3. The tilt in "B" is different from "A", and the banding frequency may be different too.

These 3 points make me think it's not some harmonically-related FPN.


Perhaps it's a demosaicing artefact in the raw developer?

I normally use Silkypix Developer Studio v6. So I tried RawRherapee 5.2 using the AMaZE demosaic method. The arefacts were still visible. In RT you can switch off demosaicing completely. I did this, but it's still there:



So I don't think it's developer-related.


Perhaps it's an artefact from aliasing?
The K-3 has no AA filter and I did not have the pixel-oscillating option turned on. There is aliasing visible at 100% on the feathers - From Silkypix:




RT's AMaZe probably handles this aliasing better. I've not done any extra processing in Paintshop Pro X7, so the image will look different:



But I would have thought that striations, if due to aliasing, would be a lot finer/narrower than is visible here.


So, what do you think is going on?


The 29MB DNG of the 2nd, sharper shot is available for download here if you want to examine it further:

https://dl.dropboxusercontent.com/s/epdoehcjw9aotsa/K3_62311.DNG


Dan.


Last edited by dosdan; 11-30-2017 at 01:27 AM.
11-17-2017, 07:15 PM   #2
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Great image!

The light and dark striations on the brown portion of the feather look natural. They chevon naturally at the center of the feather, are present even in OOF areas, and aren't affected by imperfections in the feather.

The colored striation in the white tips of the feather look like classic aliasing artifacts.
11-17-2017, 07:19 PM   #3
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BTW, two other heavily processed shots. I was feeding dog food to 2 of the 3 magpies that come to visit me a number of times each day, and this kookaburra decide to muscle in.

1/125s, f/5.6, ISO640 (it was early in the morning), 250mm FL.


1/320s, f/4, ISO800, 250mm FL.



--------------------------------------------------------------------------------------------


Here's a short video clip of 2 kookaburras' on my back fence, shot with a Panasonic HC-V770 camcorder. I picked it up in a hurry so as not to miss this. I was shooting standing, unsupported. The excerpt starts at 11x and zooms to 16x, so while I have OIS activated, it was only partially successful. Unfortunately, the kookaburras here were only chuckling, not full-on belly laughing.

https://dl.dropboxusercontent.com/s/yt0obk6irm8zd8o/Laughing%20Jackass.mp4


--------------------------------------------------------------------------------------------


Recently had a holiday at Cooroy Country Cottages.

COOROY COUNTRY COTTAGES

Here's an excerpt from a video of magpies & kookaburras eating dog food at the homestead. The proprietor feeds them after 4pm every day.

Taken with a Panasonic HC-V750. While I normally shoot using Full HD 60p 50MP MP4, on this trip I decided to use Full HD 60p 28Mbps AVCHD for a change.

The 1st clip was shot with AF, but this resulted in the focus always being on the palms in the rear. (It started on the palms without any birds - when the birds arrived, the focus didn't change to the foreground.) So for the 2nd clip, shown here, I switched to MF and focused on the rim of the feed bowl.

Also, I was recording 5.1 audio in the 1st clip. Since there was the noise of kids swimming behind the camera and a caged bird inside the house, I switched to Stereo mode with zooming mic in the 2nd clip.

It had been drizzling and it was overcast. This made the birds a little more hesitant to come feed, so I set the camera shooting on a tripod and walked some distance away. This was a bit of a pity as I should have come back and framed a little wider/higher.

Also, because of the late-afternoon, overcast conditions, I'm fairly sure I shot with backlight compensation.

As usual, I find the output, straight from my HC-V750, lacking in contrast. So I've used the NewBlue ST Video Tuneup plugin that comes with Vegas Pro 12 to give it a bit more punch. Original on Left; Processed on Right:




A funny thing happened. I was playing the OOF Clip 1, searching for the sound of a distant kookaburra "laugh" that I could mix in to the audio track of Clip 2 to provide a bit more atmosphere. I was playing the clip fairly loudly in my computer room here in Brisbane. One of the local magpies, which I'm feeding, was nearby. He got excited, bobbing his head, and ran along the top of the fence in front of my open window looking for the source of the new magpie calls he could hear.

https://www.facebook.com/dosdan/videos/1587938641244686/

Dan.

Last edited by dosdan; 11-18-2017 at 01:25 PM.
11-17-2017, 07:22 PM   #4
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QuoteOriginally posted by dosdan Quote
Are these striations actually on the feathers?
I don't know about the striations but its a very nice photo of the Kookaburra

11-17-2017, 07:31 PM   #5
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QuoteOriginally posted by dosdan Quote
Some of the shots show striations on the feathers. Are these a photography/processing artefact or are they really there?

The K-3 has no AA filter and I did not have the pixel-oscillating option turned on. There is aliasing visible at 100% on the feathers.

So, what do you think is going on?
Dan,
This is moire effect from the feather pattern with no AA filter on the K-3. Depending on the monitor viewing magnification and post-processing, it will be more or less visible.
11-18-2017, 03:19 AM   #6
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QuoteOriginally posted by Alex645 Quote
Dan,
This is moire effect from the feather pattern with no AA filter on the K-3. Depending on the monitor viewing magnification and post-processing, it will be more or less visible.
I'm not so sure about that. My father used to raise pigeons and I would sometimes help him banding them. That sort of coloration striations is very common in darker colored birds It is very subtle and you need to be close up to see it.

It's like that with black cats. They actually have tabby stripes but you can't see the stripes unless the lighting is just right.
11-18-2017, 06:34 AM   #7
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With some species, there can be minor variations in feather growth, showing up as lighter or darker bands, if the adults have had intermittent problems feeding the young. Were these first year birds ? If so, that may have been a contributory cause, and may disappear with the next moult.

11-18-2017, 11:53 AM - 1 Like   #8
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QuoteOriginally posted by 35mmfilmfan Quote
Were these first year birds ? If so, that may have been a contributory cause, and may disappear with the next moult.
This is a wild bird, so I don't know.

What I've done is switch the K-3's AA filter emulator on. If the kookaburra comes again I'll see if I can get another side-on shot of this spot.

Dan.
11-18-2017, 11:53 AM   #9
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They look natural and are seen in many species. As 35mmfilmfan says, these may be due to variations in nutrition intake during feather growth.
11-18-2017, 12:13 PM   #10
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QuoteOriginally posted by Alex645 Quote
This is moire effect from the feather pattern with no AA filter on the K-3
Alex, thinking on it a bit more, if these striations were moiré-related, they shouldn't be visible in the shot that was slightly OOF. As I understand it, for moiré to be visible you need a very sharp image. That's how the AA-filter emulator works: it slightly blurs the image by oscillating the sensor with a radus of either 0.5 or 1 pixel-pitch. But the OOF blurring looks a lot more than that in that particular image.

Dan.

---------- Post added 19-11-17 at 05:34 ----------

QuoteOriginally posted by pete-tarmigan Quote
these may be due to variations in nutrition intake during feather growth.
Any ornithologists in this forum? It would be interesting to know the growth rate of the feathers so I could try to work out the time-span between the stripe-inducing events.

Dan.

Last edited by dosdan; 11-18-2017 at 01:36 PM.
11-18-2017, 02:11 PM   #11
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QuoteOriginally posted by dosdan Quote
Any ornithologists in this forum?
Pete-tarmigan is really the fellow to listen to....
11-18-2017, 07:29 PM   #12
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I posed this question in the Photography sub-forum of Whirlpool Broadband News. Tekno provided this link which discusses hidden patterns caused by biochemical changes which requires x-ray analysis to be seen. But they look like the patterns I saw at "B".

Hidden feather patterns tell the story of birds

That article references another article that discusses visible bars:

Growth Bars in Feathers on JSTOR

Quoting from p.486:

"These bars are most commonly seen in the wing and tail feathers"

and

"The visibility of growth bars varies greatly among birds, from nothing to very marked"

see also p.314 Ptilochronology: Feather Growth Bars as Indicators of Nutritional Status on JSTOR

And if you do a search on Ptilochronology it brings up images that look like the pattern at "A" too.

Dan.
11-19-2017, 12:57 PM - 2 Likes   #13
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Here's a shot I took yesterday. No striations were visible, but it was cloudy. I think I'll need full sunshine to be sure. AA filter Simulator set to "1". It's 4123x3216 so you can pan around it to inspect the detail. The head & body's good, but the tail's soft. IMHO, SilkyPix Developer Studio Pro 6 has done a decent job here in the balancing act between maintaining detail & controlling noise.


Pentax K-3 + DA* 60-250 @ 250mm FL. 1/125s (handheld with IBIS), f/6.3, ISO400 + 1/2 Stop boost in PP.



I was sitting down on the concrete slab, but if I'd laid down I would of got a more pleasing background.


Dan.

Last edited by dosdan; 11-19-2017 at 01:10 PM.
11-19-2017, 01:22 PM   #14
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I didn't know about the striations in bird feathers....so now I'm thinking, it may be a combination of both. The pattern is on the feathers, but with an AA filter, any moire effect caused by the pattern is eliminated.

For sure, it would be great to see with better or identical light to your first posted images.
11-20-2017, 05:45 AM - 1 Like   #15
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QuoteOriginally posted by dosdan Quote
Any ornithologists in this forum? It would be interesting to know the growth rate of the feathers so I could try to work out the time-span between the stripe-inducing events.

Dan.
I'm an ornithologist. The growth rate is dependent on the individual's nutritional intake at the time of feather growth, as the papers linked by dosdan state, rather than a cycle set by the seasons like the growth rings on a tree. Nutritional intake is in turn dependent on food availability, which may be variable due to weather or cycles in population size of the food item.
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