# 7 min max shutter open



## CorteOnCamera (Jul 24, 2012)

Hi there
New to this forum. 
I have 7D and have tried to do some star trails but I find that the maximum time the camera will operate with an open shutter is seven mins plus minus seconds. 
Settings: bulb, widest aperture and using remote control TC80N3 locking the on switch. Tried using long setting but my remote controller battery is flat so thought ok to manually control the time. If I go over the seven mins, say 8 mins, then at the end of this time when I turn the switch off on the remote controller the camera's red light on the bottom RH side remains on as if it's still processing the information. I have tried waiting but this seems to be an infinite period I could wait. Tried turning off the camera but it will not allow me. So the only thing I found to do was open the camera's battery compartment which of course deletes the last image. 
Perhaps I'm doing something wrong. I will appreciate any advise on this matter.
I'm currently traveling remote areas and unable to quickly purchase a new battery.
Looking forward to hearing from you.


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## sandymandy (Jul 24, 2012)

I remember when u took a long exposure photo e.g. 5 minutes the camera will take another exposure the same time (5 min) and then combine the two images for noise reduction. maybe thats the prob? turn off noise reduction if u dont wanna wait


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## neuroanatomist (Jul 24, 2012)

You have Long Exposure Noise Reduction enabled. After you take a long exposure, the camera takes a second exposure of equal time with the shutter closed, then subtracts that dark frame from the image to remove thermal noise.


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## Mt Spokane Photography (Jul 24, 2012)

neuroanatomist said:


> You have Long Exposure Noise Reduction enabled. After you take a long exposure, the camera takes a second exposure of equal time with the shutter closed, then subtracts that dark frame from the image to remove thermal noise.


 
+1


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## CorteOnCamera (Jul 24, 2012)

Yes I did have Long exposure noise reduction on Auto. But I wonder why this didn't happen at 6 mins or less?
Anyway I will try this again with that function disabled and see if that was the problem. If it works but the result is far too noisy I will try patience and watch the clock.
Thanks for the replies. And I will let you know the result.


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## neuroanatomist (Jul 24, 2012)

CorteOnCamera said:


> Yes I did have Long exposure noise reduction on Auto. But I wonder why this didn't happen at 6 mins or less?



Disable = off
Enable = on for all exposures >1 s
Auto = on for all exposures >1 s if the camera thinks there's sufficient noise


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## Wideopen (Aug 7, 2012)

neuroanatomist said:


> You have Long Exposure Noise Reduction enabled. After you take a long exposure, the camera takes a second exposure of equal time with the shutter closed, then subtracts that dark frame from the image to remove thermal noise.



+2


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