White halo/fringe problem

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ray rozema

ray rozema

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Hello

I'm hoping for some advice. Sometimes I have a white halo/fringe on some of the edges of a typically a bright/white subject that is well lit. Shooting Nikon D850, F 4 ,600 mm, with 1.4 x TC. F stop is mid range , thus diffraction should not be the cause. The subject (bird) is tack sharp so it shouldn't be due to camera motion or subject motion. The halo is present before post processing thus not due to oversharpening.
Two questions: What is the cause? How can it be avoided?

Thankyou
Ray
 
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ray rozema said:
Two questions: What is the cause? How can it be avoided?
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Some sample images as Warren mentioned would help a lot.

But are these shot as raw files or are they jpegs where some sharpening has been applied in camera? Also do these happen to be backlit images where a bright halo is expected(think hair light used all the time in movies)?
 
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Attached is an example. ( Hope I have the correct file type and size) The only processing was to change image size for the forum. Nikon D850, 600 mm with 1.4 TC, F14, 1/8000, EV-1, ISO 800. Spot metering. Picture Control set to neutral. To answer DRwyoming questions: They are shot as raw files . I have not taken backlit images.

Thanks for your help

White Halo Effect.jpg
You can only see EXIF info for this image if you are logged in.
 
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Ray, I have opened your image in Lightroom and in Capture One Pro. There is not much feather detail on my computer but that may be related to resizing for export to the web, but in Capture One Pro my computer says the whites around the bird's head and upper shoulder are quite blown. The tree look well exposed, but I suspect the bird is overexposed. It could also be that he is a long way away? His eye is not quite sharp. I am not being critical of your shot, so please don't think me rude, and things are always disrupted when the internet resizes them.
I
 
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Looks overexposed to me, at least the egret. That being the case, sensor bloom is the likely culprit which comes from the overexposed areas bleeding into the pixels next to them creating a halo effect. This was very common back in the early days of video cams to the point I used to have nd filters for shooting in daylight just to knock the exposure down to a point the sensor could handle.
As to how to avoid it, expose for the highlights and bring up the shadows in post if needed. In situations like this, I'd probably go -1.6 to -2.0 exp comp.
 
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Just noticed your data says f14. If this is correct you could also have diffraction effects. No need to go beyond f8 with that combo unless your subject is very close and/or you need extra DOF. I also wouldn't be surprized if some atmospherics are at work.
 
I don't really see halos as much as overexposure. You might have the latitude in your raw file to selectively pull the very bright areas down while keeping the branches just so. Be worth a try.

You said spot metering and -1 compensation, so something went wrong, if you metered the white bird it should have pulled the white down, unless you metered the darker bark or water by mistake which would pull the exposure up. Was it fully manual exposure, or maybe auto iso? Does the exposure lock if you recompose or does it continue to adjust when you move the camera? Trying to think of ways the exposure might have gotten too high.

Matrix metering works well in this situation as well. And maybe turn on blinkies so you catch those overexposed patches.
 
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Good points It was aperture priority. I have since changed to Manual with auto ISO. I meant to spot meter the bird but I might have recomposed slightly and did not lock exposure

Thanks again I have learned a lot.
 
ray rozema said:
Good points It was aperture priority. I have since changed to Manual with auto ISO. I meant to spot meter the bird but I might have recomposed slightly and did not lock exposure

Thanks again I have learned a lot.
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Just keep in mind that manual with auto iso is also an automatic mode. You could call it 'aperture and shutter priority' since it automatically adjusts iso but lets you choose the f stop and shutter speed. So in this case with the spot meter reading the dark water or tree stump it wouldn't help without a healthy dose of negative exposure compensation and/or exposure lock.
 
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