Long Exposure hassle

[bradzo66]

Hi all , I really enjoy long exposure and spend many a night wandering , when I first started my 40d would pop and image up almost immeadiatley after finishing the exposure but of late it seems to take the same amount of time to show the image as it did to take it ??? I am well into using manual modes and have been using Tv (shutter priority a bit for these shots but it also happens in the bulb setting . I am wondering if I have changed a setting that is causing this or am I starting to suffer gremlins . Its not a huge deal unless doing lightning or light trails where you are waiting for a certain shot . Thanks in advance .

[kelticsol]

Might be some kind of noise reduction. I might default to running it when your iso is high or some other incident happens with your camera.

[dcclark]

Many cameras have an automatic "long exposure noise reduction" mode, in which -- once the photo is taken -- the camera takes another exposure of the same length, with the shutter closed. This way, if there are any "hot pixels" or sensor amp noise, the "dark frame" will show it. Then the camera subtracts the "dark frame" from the original image, removing the noise. It's likely that this is what your camera is doing -- this usually only kicks in for longer exposures, maybe 1 second or more. There should be a setting to disable it (I turned this off almost immediately -- it's annoying and hard to deal with when doing time-lapse photos).

[mainak_ch]

Long exposure noise reduction, or high ISO noise reduction could be the cause. Ensure they are turned off , and then check.

[bradzo66]

Perfect guys , I had a feeling I had set something that was causing it , a bit over a month ago I read a post here that had mentioned it and I can remember turning it on in the camera settings . Thank you all for yr precise diagnosis , All the best

[markjdos]

On the 40D, check your custom function on the menu (C.Fn II-1: Long-exposure noise reduction). If it is turned ON or to AUTO, then the noise reduction process will take the same amount of time as the exposure. For example, if you shoot a 30 second exposure, it will take about 30 seconds to process the noise reduction. Can be kind of a pain, but I generally find I get better results if I use noise reduction for long exposures.

[bradzo66]

You are very correct about the results being better , sometimes especially when shooting lightning I dont have the time to wait so would probably prefer that it was off but do like the results when doing light trails . Thanks for looking in . All the best .