Neodymium help

[robindurant]

Hi

I have just bought a Neodymium Filter as I have a large amount of street light pollution in my area and I experimented last night by attaching it to my Canon 350D /200mm lens and took 20 subs of M31 at 60 secs on iso 1600 to try it out. The result was terrible. Very heavy grain ( multi coloured) and totally un processable. Is it that the filter should not be exposed, or can it not be used this way. I have not tried it in a prime focus way yet, I do hope its better when I do.

Can anyone advise me.

Thanks

[FLO]

Try lowering the iso to 800 and the exposure to 30 secs, I think you will see a significant reduction in noise (grain). The multi-coloured result will be a combination of amp-glow (heat from the cameras power circuits) and bayer-pattern-noise. You should see a reduction in both with these new settings.

Also, the effectiveness of a Neodymium depends on the type/source of the light pollution. This is why some reviews praise it highly and some wonder what all the fuss is about. Where the light pollution matches the wavelengths that the Neodymium is designed to block, the results are outstanding.

<edit> Also, at 30 secs, the 350D performs a clever dark-frame subtraction routine for every exposure (so a 30 secs actually takes 60 secs, 30 for the exposure plus 30 for the dark-frame).

[proflight2000]

I got one of these from FLO and I am one of those people who think it is a godsend. It totally wipes out the yellow dreaded light from abouve the streetlamps, well the two I can see.