Rear gel filters - Sigma 12-24

Good morning all,

I havee recently bought a Sigma 12-24. due to the bulging front element of the lens it does not accept screw in filters (although it is possible to screw them into the lens protector but results in viginetting).

The lens has the ability to take rear gel filters which I would like to make use of for a ND filter for longer exposures.

Unfortunately I haven't a clue where to get these; is there any body able to point me in the right direction please? I have read that I may need to buy larger sheets and cut them down; does anyone know where to get these?

I have read about some very clever people adapting existing filter systems to attach to the fornt of the lens but I think these solutions may be a bit expensive for me.

As ever if anyone has any suggestions they would be most appreciated.

Thanks

Ross

There may be a very simple and cheap solution ?

Depending upon how much the 'bulge' is, it may be possible to screw in an 'up-size' filter adaptor to move the filter holder further away from the 'bulge' ?

i.e. if the filter ring is 52mm dia you could screw in a 52 to 58mm or 62mm adaptor, or pro-rata.

These adaptors are very cheap off e-bay suppliers.

Just a thought ?

Peter

Gel filters were manufactured by Kodak but they may well have been made by others as well. They come in 4 inch squares. Dont be tempted to use lighting filters because they are optically very imperfect. You can pick up gels on ebay but take care since gelatin dissolves in water so rain will destroy them, they are also incredibly fragile so once they have been in and out once they should probaby be discarded.