Anartia jatrophae, butterfly

Images of undisturbed subjects in their natural environment. All subject types.

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Rui_Santos
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Anartia jatrophae, butterfly

Post by Rui_Santos »

Anartia jatrophae

Fuji HS25


ImageAnartia jatrophae by Rui Oliveira Santos, no Flickr

Balok
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Post by Balok »

I like this fellow - nice colors and angles.
Quaecumque vera

Lou Jost
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Post by Lou Jost »

A beautiful clean image, very nice. There's a little bit of banding in the green background, I am not sure if this is due to my monitor or the image.

rjlittlefield
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Post by rjlittlefield »

Agreed, the image is very nice.
There's a little bit of banding in the green background, I am not sure if this is due to my monitor or the image.
Photoshop levels adjustment shows that there are clearly some bright/dark swirly bands (like contour lines on a map, showing hills). In a focus-stacked image, bands like that are often due to slight variations in exposure from one image to another. But in a single shot like this one, I'm not sure what would cause it. I notice that the image file length is significantly shorter than this forum allows -- only 142 Kbytes versus 300 Kbytes allowed. But I would expect JPEG compression artifacts to be blocky, not smooth like these bands appear to be.

Bottom line, I don't have a good idea what is causing the banding.

--Rik

Lou Jost
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Post by Lou Jost »

Those kinds of bands in smooth transitions (often seen in skies, for examples) are usually caused by gamut problems. If the image was made in a very large color space like ProPhoto, then the 256 levels for each primary color have to cover a wide area in color space, and the gaps between successively higher steps (say, from Green = 157 to Green = 158) will correspond to big differences in perceived colors.

rjlittlefield
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Post by rjlittlefield »

Lou Jost wrote:Those kinds of bands in smooth transitions (often seen in skies, for examples) are usually caused by gamut problems.
Gamut problems can cause big steps in what should be a continuous ramp. The big steps appear when an 8-bit image in a wide gamut like ProPhoto gets converted to a narrower gamut like sRGB. For example, a ProPhoto ramp of a certain bright green color, when converted to sRGB, no longer has any pixels where R=64 or R=66; the values just go as R=63, 65, or 67.

But the bands that I'm looking at here are different. These are alternating bright/dark bands, with cyclic variation and no big steps. For example in the upper right corner of the image, in the area around x=740,y=60, along a 45 degree transect from upper right to lower left, the G component varies cyclically over a range from 115 to 118, taking on all possible values in that range. I think this is not consistent with a gamut problem.

It would be interesting to know whether the bands appear in images that were uploaded to Flickr, or if they only appear in the images that Flickr produced for serving back.

--Rik

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Post by ChrisR »

I can't see anything of the banding on my monitor, unless I do drastic things with Photoshop levels.
The same appllies to Rui's other Flickr images, even at 12MP .
I don't see them on others' images, even trying hard.

Perhaps I need a better monitor. Or perhaps I don't.?
Chris R

Lou Jost
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Post by Lou Jost »

A wide-gamut monitor (like mine) can indeed be part of the problem.

For me, the wide gamut is worth the side-effects. I need accurate colors, especially in the green end of the spectrum, which is where ordinary monitors fall down. When analyzing aerial images of forests, my monitor really shines, while common laptop monitors are horrible. When my colleagues visit me they are always shocked at the difference between their laptops and my monitor, side by side with the same forest image.

rjlittlefield
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Post by rjlittlefield »

For me, using inexpensive Dell and Samsung monitors, the banding is visible but not obvious. I had not noticed it until Lou pointed it out. Now that I do see it, I find it intellectually interesting but not artistically annoying.

--Rik

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Post by rjlittlefield »

Lou Jost wrote:If the image was made in a very large color space like ProPhoto, then the 256 levels for each primary color have to cover a wide area in color space, and the gaps between successively higher steps (say, from Green = 157 to Green = 158) will correspond to big differences in perceived colors.
A wide-gamut monitor (like mine) can indeed be part of the problem.
I agree with both of these. But I think only the second one applies here. The image as posted is already sRGB (as reported by Photoshop CC when given the URL to download directly), and I don't see any of the characteristic big steps that I would expect if it were suffering from the first problem.

--Rik

Lou Jost
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Post by Lou Jost »

I'm using an ASUS ProArt wide gamut monitor. Maybe it is the reason that the banding is obvious to me. But as far as I can recall, this is the first time I have noticed banding on an image in this forum, and I've looked at nearly every image that has been posted here since I joined. So I suspect there is also something about this image that exacerbates the problem. In any case the image is beautiful.

Lou Jost
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Post by Lou Jost »

I also have a high-end Eizo wide-gamut monitor, and I just looked at this image on it. The banding is also conspicuous on that monitor.

ChrisR
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Post by ChrisR »

In any case the image is beautiful.
It is. Rui's stream is worth looking at.:)

Do you see banding on this:?
http://photomacrography.net/forum/viewtopic.php?t=32588
Chris R

Lou Jost
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Post by Lou Jost »

Yes but much less conspicuously than on the butterfly background.

Lou Jost
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Post by Lou Jost »

I now looked at a blown-up crop of the bee, and it has features that suggest heavy sharpening. Perhaps the sharpening algorithm is making the bands?

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