Creative photography

[wazungy]

I have wondered over the years why I sometimes get blue fringe when I look very closely at a landscape photo that shows the thinner branches or leaves (twigs, pine needles etc.) against a sky background.
If against a blue sky, the area around the twigs, pine needles or even between the spaces of closely spaced broad leaves is darker blue than the surrounding sky. I have seen this effect on both my Canon A-40 and canon A620 on clear sky and slightly cloudy sky (white thin cloud).

Is it something to do with the way the sensor records thin or narrow objects against a certain color background?

Is it some case of chromatic error? The A620 is rather good at bright objects on a dark background. I have seen little chromatic errors with this camera normally.
Is there a documented reason for this?

Thank you for any info or advice.

Waz

[bdery]

Hi and welcome!

Do you have sample pictures to show us? Normally, chromatic aberration is visible as a purple band at the border of very contrasty areas. Blue is not generally associated with CA, but it still might be the case here.

Does the image look good, apart from that fringe? Are the colors well balanced?

It could be a JPEG compression artifact too. Have you tried different compression settings? (image quality levels)

[ShutterbugGail]

Hi Waz,

It would be helpful to answer bderys questions. In the mean time, let me approach this from a different perspective.

The vast majority of consumer digital cameras I'm familiar with have fringing when taking photos like you describe but if I don't have a choice I expose for the sky. There will be little or no fringing but the overall image will be underexposed. I correct exposure in photo editing software. I rarely have purple (blue) fringing however this technique may not work well for those who don't like to edit images.

[wazungy]

Yes, I have a sample photo that shows the effect rather well.

How do I attach it to the message?

Waz

[ShutterbugGail]

How do I attach it to the message?

Here's info about How to Insert an Image:

http://www.digicamhelp.com/cgi-bin/yabb/YaBB.cgi?board=errors;action=display;num=1089641725

You'll need to have the photo uploaded to a server. Many people use photo hosting sites such as Flickr (www.flickr.com).

Related reading: Photo hosting

http://www.digicamhelp.com/what-is-photo-hosting/index.htm

[wazungy]

I uploaded the shot to webshots.

try:
http://cards.webshots.com/invite/pickup/113200421dlxD/album/529500341pkvtGa

There are two images, looking up through the branches.

I have no idea if this link will allow multiple views.
Download if you have to.

Thanks,

Waz

[bdery]

I looked at the images, and even though the resolution is very low even at full-size, the darker blue surrounding the branches strikes me as a JPEG compression artifact. I could be totally wrong about this, of course, and seeing the full-size images could tell us more, but it doesn't look like chromatic abberation, mainly because it's all around the branches, while CA normally dominates on one side (it's a focus problem caused by the fact that the lenses are spherical for the most part).

Are you shooting at the best compression setting possible? (FINE or SUPERFINE in general). This could be it. Or maybe you're not shooting at the maximum resolution, and that's what is causing that effect. I really get the feeling that it's caused by the compression.

[wazungy]

Thanks Shutterbug and bdery.

I usually shoot at maximum res super fine.  The tree you saw were images  cropped from a much larger image just as they came out of the camera (no photoshop or other manipulation).
It is unfortunate that the camera only saves as jpeg. I agree that the effect does not look like chromatic abberation.  It may be a compression artifact but why only on branches against a blue or hazy -blue sky? The compression algorithm should not favour any one color over another. It might be that the sky is mostly close to saturated blue channel but less so with red and green that causes the effect. But then this by itself would mean that the effect would be seen on many digital camera shots of trees and sky where the sky is almost saturated blue (many landscapes I imagine).
Perhaps I should look for this effect on any grid type foreground on a solid color background. I think an experiment is brewwing...hmmmm.

Anyhow, I thought this would be the place to find out if this is a common effect or not.
I gather it is not seen on "higher end" D-SLR's then?
Or has any other reader seen this and with what camera under what conditions?

Thanks again,

Waz

[bdery]

Try to sort through your other files, and look for a contrasty area.  Maybe you'll see the same effect repeated there. Or maybe your saturation, contrast and sharpness settings are off.

I don't think it's completely common, at least I have never noticed it with both my Nikon SQ and my Canon S2. It's clear that a DSLR will, in general, deliver better pictures. However, in bright daylight the differences are marginal, the most dramatic differences are seen in low light.

Good luck with your experimentations.