Drop-in Holder / Filter Necessary?

I have a 600 F4 non/IS lens with the glass drop-in filter.

I was wondering if the glass is necessary?

The reason I ask is, I'm from the side that doesn't believe in putting
an extra layer of glass (ie a UV filter) on my other L glass.

So what's the purpose of just having a glass filter in that slot? Obviously
its not to protect the lens. If I remove it and just leave the holder in
do I risk any foreign objects getting down inside the barrel and screwing
things up down the road?

Anyone have any thoughts on this?

Thanks
Doug

Quote:

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Originally Posted by Doug West

I have a 600 F4 non/IS lens with the glass drop-in filter.

I was wondering if the glass is necessary?

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The glass filter changes the focal point a small amount. Without the filter you may not be able to get infinity focus, but you can try it and see. As long as the filter is clean, it should not harm image quality. If you do decide to take the filter out, use gloves (like those thin plastic gloves or thing cotton gloves) to avoid getting any finger prints on the glass, and try not to touch the glass surface even with gloves.

Roger