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I've just started playing with time lapse shots of the night sky. Every shot I have taken I've noted these purple patches of light on the final image. I've used different lenses with and without filters and pointing in different locations. The result is always the same. The final test I did was to leave the lens cap on a time lapse shot. As can be seen from the 1st image below that the light is still there even with the cap on.
I'd like to know if this is possible in the optics in tbe body of the camera or electronic intferance in the camera.
Has anyone else experienced such an effect?

Go to your D70 Menu, the 2nd menu down and switch on Long Exposure Noise Reduction.

Have you set The NR=Off?

Why would you turn off Long Exposure Noise Reduction to off when he's doing time lapse?

imarine wrote:I've just started playing with time lapse shots of the night sky. Every shot I have taken I've noted these purple patches of light on the final image. I've used different lenses with and without filters and pointing in different locations.

Its time exposure, not time lapse!

I have had the same problem, it has nothing to do with noise reduction, its light coming in through the viewfinder. Make sure you have it covered with something completely opaque, or else make sure its dark where you are. By dark, I mean dark as in out in the country with NO lights in view anywhere near you! Dark locations do not exist anywhere near large cities

Gordon

I agree with Gordon - cover the eyepiece

... and an eyepice cover actually came with the D70 provided you didn't throw it out with the packaging (it's a little black rubber thing that fits into the viewfinder).

OK, dumb question alert!!!

I've heard from another location that looooong exposures can suffer from heat affecting the colours produced, and the example I saw (can't remember where I read this) produced some discolouration in the top left corner... Or is this just mis-information???

Dunno, just wanted to ask...

imarine wrote:I've just started playing with time lapse shots of the night sky. Every shot I have taken I've noted these purple patches of light on the final image. I've used different lenses with and without filters and pointing in different locations. The result is always the same. The final test I did was to leave the lens cap on a time lapse shot. As can be seen from the 1st image below that the light is still there even with the cap on.
I'd like to know if this is possible in the optics in tbe body of the camera or electronic intferance in the camera.
Has anyone else experienced such an effect?

Yes this weekend also..... And it was only after a 1hour exposure!!!! That I realised that I had not covered the eye piece.
Also discovered when I got home a very large piece of dust!!!! Thank goodness for PS.

Looks like so-called "amp glow" to me - the heat produced by the electronic components affecting the CCD. You can use your own dark field image to fix this - trouble is the characteristic changes with ambient & camera temperature.

Cheers

Ok, I've re-tested using the eyepiece cover and NR turned on, and lens cover on. I'm still getting the same effect in the top left corner.

Another question, how are you getting more then 30minutes of exposure time? I've read in the manual that the most is 30minutes and when I use the camera in bulb setting with remote it always stops itself automatically after 30minutes.

that is classic case of amp heating next to the CCD, its not light through the viewfinder (though that can cause issues.) It will occur from about 60 seconds onwards. Common problem with CCD's.

You need to run NR on. You need to make sure you let the NR job finishes. If its a 20 min exposure, then you have to wait until "job nr" finishes which will take as loing as the exposure itself.

30 minutes is the maximum for bulb / exposure on a d70.

Mal wrote:

imarine wrote:I've just started playing with time lapse shots of the night sky. Every shot I have taken I've noted these purple patches of light on the final image. I've used different lenses with and without filters and pointing in different locations. The result is always the same. The final test I did was to leave the lens cap on a time lapse shot. As can be seen from the 1st image below that the light is still there even with the cap on.
I'd like to know if this is possible in the optics in tbe body of the camera or electronic intferance in the camera.
Has anyone else experienced such an effect?

Yes this weekend also..... And it was only after a 1hour exposure!!!! That I realised that I had not covered the eye piece.
Also discovered when I got home a very large piece of dust!!!! Thank goodness for PS.

hmm care to share how you got past the 30 minute limit on bulb shots on d70? interested to know. Manual says not possible. Page 83 & Page 107

darb wrote:

Mal wrote:

imarine wrote:I've just started playing with time lapse shots of the night sky. Every shot I have taken I've noted these purple patches of light on the final image. I've used different lenses with and without filters and pointing in different locations. The result is always the same. The final test I did was to leave the lens cap on a time lapse shot. As can be seen from the 1st image below that the light is still there even with the cap on.
I'd like to know if this is possible in the optics in tbe body of the camera or electronic intferance in the camera.
Has anyone else experienced such an effect?

Yes this weekend also..... And it was only after a 1hour exposure!!!! That I realised that I had not covered the eye piece.
Also discovered when I got home a very large piece of dust!!!! Thank goodness for PS.

hmm care to share how you got past the 30 minute limit on bulb shots on d70? interested to know. Manual says not possible. Page 83 & Page 107

Darb I'm guessing 30 minutes for exposure + 30 for NR = 1 hour

ah so a 30 min exposure then well, 1 hour shot i guess you could call it

didnt kill a battery or three did ya ? hehehe

This was the subject of one of the first threads I read through when I happened upon this group. Darb and Greg B I think had some friendly words at the time I believe. The effect that Darb was illustrating is the exact thing on your shot, and the NR fixed it (according to Darb). Atleast I'm pretty sure it was Darb.

nah it was with gstark and it quickly digressed into an argument over pedantic semantics but you get that, dead and buried !

as for the content of the original point to that thread, it was a case of putting your camera in a pitch black room, viewfinder covered to rule it out, doing a long exposure, say 5 minutes, or whatever produces a nice and obvious example of the problem at hand. ... then do the same test again, with NR ON, 5 minutes again (10 mins by time NR finishes.) and bobs your uncle, the purple CCD heating tinges have disappeared.

I always have NR on during time exposures, fact of life with a d70 really. Have never tried doing it in PP though. Be sure to turn NR OFF when youre not doing long exposures, as it slows your frame rate if doing sports etc.

The effective doubling of job time per capture is a bit of a pain, but you get that. Whenever I go camping ill trounce off into the bushes with tripod and camera, set a shot, then walk back to the camp and have a beer with everyone ... though last trip ( http://darb.net/lake-navarino ) I was rather merry and practically couldnt find my camera among the bushes ... freaked out for a bout a minute, then realised I was 50 metres off where I thought I put it

I'll buy a round if the NR doesnt fix it. (he did say he has it on, but didnt fix it, is uspect maybe he's not letting the NR job finish?) ... if not, hmpf got me stumped mate, works for me.