A funny line in my image

I am new'ish using ND filters... and when i have been doing LONG exposures (anything over 10 seconds) I am getting an artifact across the image!

See the below image and you can see it. Is this some thing to do with the filters? It does it if I use either Cokin or screw in filetrs. When I use no filter I don't get any issues.

Thanks,
Ian

There are some very bright, burnt-out areas. I wonder whether one of them is causing problems, perhaps internal reflections within the camera itself or even overloading the sensor's electronics. Do you still get an artefact with an ND filter if there are no very bright spots?

Steve

I'll give a test and get back with the results.

What ND filters/holder are you using ?

If you are using something like the Lee system, rather than a screw-in filter you need to be covering the area where the holder meets the front of the lens during the exposure. A baseball cap or piece of cloth or even your hand will do.

Using too small a square/oblong filter can cause problems as well as light is being reflected from the filter edges.

Can you post an image of your set-up

Is it due to light getting in through the viewfinder?
It might be that if the viewfinder isn't covered.

I was using 82mm Pig Iron ND1000 scew on filter and Cokin P Series.

It would seem this could be the case as it also does it with a screw-in filter. Although when I did along exposure without covering the viewfinder, the light leakage was more evenly spread across the image, giving a more 'mushy' effect. I guess the difference might be around how well the mirror edges are sealed when it is up to expose the sensor, and in Spad's case the leak is around one edge.
Worth a try - to simply hold something dark in front of the viewfinder eye-piece when putting the ND filter on.

Update!

I have been out for a quick play earlier today....

It seems to be the mirrors leaking light. I put a cover ove the eyepiece and that has sorted it!

Thanks for all your advice and help.

Glad that sorted it!

Good to hear!