IR filter for Canon 18-55 lens

[smeech]

Hi all

I have read on various websites that the Hoya IR filter is not great for some Canon EFS lenses. Guess what? I have those lenses.

Does anyone have any ideas which IR filters are good for the 18-55 kit lens and the 55-250 kit lens.

I want to take widefield shots of the night sky.

Thanks all

[Merlin66]

What specifically do you want to do?

The canon DSLR CCD chip has a built in IR filter which stops all the light above 700nm getting to the chip....

[smeech]

I've read it stops 75% of light above that wavelength. Tell me if this is wrong please? Therefore in theory if you allow longer exposures you can capture nebulae? Right? Or have I totally misread this?

I have a 550d and I have read that the IR filter on the sensor isn't quite as good as it was on earlier models - therefore allowing more IR through. Again, please tell me if this is utter tripe?

Thanks

[Merlin66]

I can't comment on the 550D - no data.

On earlier chips and filters (>450D) the chip is still sensitive to far red up to 700nm - which includes the astronomical Ha at 656nm.

The standard filter is about 25% effective at 656nm whereas the modded cameras can be up to 40-50% effeictive at Ha.