Purple glow in corners

[dean_godfrey]

I have been trying to take photos of star trails at night and I keep getting getting a purple glow in the upper corners. I

have tryed two lens(50 Prime and a 35-70) both get the same result. I am using a D80 with a tripod. I am using the

manual setting on the camera.Can any one help me with what i am doing wrong?<div></div>

[phule]

Are you covering the viewfinder when taking the shot?

 

Assuming so, I'd say this is the result of the sensor being heated up over time (likely by other components

inside the camera). This is just one of those things that make digital different than film. Each camera model

is different and will show build-up in different areas and at different rates.

 

One solution would be to take many shorter exposures and stack them using stacking software.

[dean_godfrey]

I did not cover the view finder, i didnt think it would make a difference. I would leave the shutter open for about 30 minutes and that glow would be there.

[leicaglow]

Rob's answer is a pretty good guess. That's why pro cameras have viewfinder blinds so light doesn't bounce around the chamber from the eyepiece. It could be a sensor artifact, but possibly refracted light from another light source that was off at an angle and didn't look visually that bright.

[hultstrom1]

That looks very much like sensor overheating looks on the old Canon 1D. There it was a problem already after more than five seconds, and it was one of its major problems. The best way to get rid of it is to use a dark field image and deduct the noise. You can probably turn on a noise reduction function in the camera, I haven't used much Nikon, but it is such a new camera. The alternative is to take another similar exposure with the lenscap on and stack the images in photoshop or similar software.

 

I do not think it is light leaking in through the view finder, that behaves more like flare with a general reduction in contrast.

 

Yours,

 

Michael<div></div>

[iancoxleigh]

It is amp noise.

 

Thom Hogan discusses the issues with amp noise in the D80 in his review of the camera here: http://www.bythom.com/d80review.htm

[bobatkins]

Probably sensor noise.

 

Try a similar exposure in total darkness with the lens cap on and the viewfinder covered. I'm 99% sure you'll see the same pattern. You might be then able to use it to subtract from your real image to even out the background.

[rivi]

It is what is mentioned in the post before, but technicaly spoken it is dark current. Thet is an electric charge that the sensor accumulates with time even without light. depending on the sensor, it might be much stronger on the places where the readout amplifiers are, like in this case. Only way to get rid is to take a dark exposure under the same conditions, i.e. usually right after/before the normal exposure, as the dark current depends on temperature, and to subtract that dark from the subject exposure. This has ro be done in RAW format., hwever. Mabe the cam offers this as a menu option.

[Two23]

Amp noise. I get it in my D80 when making an exposure over 2 minutes. I either shoot the image wide and then simply crop off the top, or clone it out.

 

 

Kent in SD

[stacie_thompson]

http://www.danheller.com/star-trails.html

[15sunrises]

Definitely sensor noise. Not sure if the D80 internal noise reduction, it might be hidden in one of the deeper menus. Looks like there was also some movement during the exposure, most visible in the Jupiter trail.

 

Not sure how you shot this one either, but for trails I'd suggest using no internal sharpening in the camera and shooting RAW. Internal sharpening sometimes leads to jaggy trails.