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muleyman
Moderator
Posts: 103

Ah, the ever present purple fringing. 

I was out picking up some food tonight. On the way home, I crossed a Great horned owl sitting above a farm field.

I dropped off the food and drove back to the area with my digiscoping gear in hand.

I took some photos and headed home again.

Scope magnification for all these images was 30X

For the first image, whitebalance set to cloudy. ISO at 200 shutter at 1/50.


These last two images I adjusted to... whitebalance set to cloudy, ISO set to 100 and shutter to 1/20.




You may be saying......

I don't see it. There seems to be no purple fringe around anything.

But, if we crop and blow up the image, we see that there is purple fringe around many areas where light is passing through or around areas with highlights.

 

I found this explanation on the internet.

Purple fringing is a phenomenon caused by different wavelengths of light (different colors) bending at different angles when passing through the glass of a lens. When light travels through the lens, it bends so that it can focus sharply on the sensor in the camera. Because each color of light bends differently, each color ends up being focused in a slightly different place.

 

If you have an image that contains fringing, notice that it's usually worse near the edges of the image. This is because the light entering the lens must be bent at a sharper angle than it is near the center of the lens, thereby greatly increasing the chance of fringing.

 

Think about a prism. When white light hits a prism, each wavelength (each color) of light bends at a different angle and exits the prism to land in a different place. This is why the light coming out of the prism spreads out into different visible colors. (If each landed in the same place, the color would be white since all the colors added together form white.)

I seem to always have purple fringing in my images, if this internet explanation is correct, it may be due to my scope having a 95mm objective lens and the image being funneled through the eyepiece and through the camera lens, then onto the sensor.

Small sensor, big dia lens. Lots of light bending.

January 9, 2015 at 8:09 PM Flag Quote & Reply

raphael
Member
Posts: 5

Learning so much from your magnificent posts.



August 23, 2015 at 3:14 PM Flag Quote & Reply

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