Long exposure NR action

[johnd]

Does anyone know of a Long Exposure Noise Reduction action to remove noise from D70 images?

I'm doing a night photography course and using my D70 as I have a ML-L3 remote I'm using to get long bulb exposures. I know the D70 is not supposed to be the best choice for this, but I haven't got a remote for my D200 and I don't want to hold my finger on the button for 5 minutes (could generate a bit of camera shake). As this is a course we have a heap of students all shooting at the same time while someone paints a tree etc with a torch. On my first shot I had Long Exposure NR turned on which produced a good result. The other students got a bit tired of waiting the extra 5 minutes for the NR to work. So I switched of long exp NR. Now I have a whole pile of images with some lovely red semi circles in top left. I believe this is the D70 long exposure signature.

So to my question, does anyone know of a PSCS2 action that will help in removing the red semi circles? I could attempt to PP manually, but I thought there might be something out there that could help.

Alternatives of course are
1. do it again without other students around and use long exp NR or
2. get a MC36 and do it with D200 (with and without long exp NR).

Thanks
John

[rooboy]

Heh. mine goes purple rather than red, and in the top left corner as well

I reckon your best bet now would be to take a dark frame (i.e. lens cap on & dark cloth over the whole thing) of the same length as the original exposure. Use the same ISO settings as well. In an ideal world you'd do this at the same temperature as the original shot to simulate the sensor heating up, but I don't know how important that would be.

You'd then do some clever fiddling with layers to subtract the noise from the original shot - this is all the camera does with its long exposre NR. I'm not PS savvy enough to explain it myself, I'm sure someone would be able to give you the details though.

[johnd]

Thanks for the suggestion Patrick. Yeah it probably is a purple/red colour. Rather than muck around, I'll go do the shot again. Without a group with me this time so I can use long exposure NR without annoying anyone.
Cheers
John