Canon 17-40L and filter holder

[rafikicat]

I have recently bought a 17-40 lens which has a filter holder at the rear - should I be getting filters to fit into this, rather than put the filters on the front of the lens. I presume the rear filters would be gel, is this correct? Help please.

[etherial]

Well you've got my attention, not sure what you are talking about?

[jjphoto]

I have recently bought a 17-40 lens which has a filter holder at the rear - should I be getting filters to fit into this, rather than put the filters on the front of the lens. I presume the rear filters would be gel, is this correct? Help please.

The rear filters are gels, such as Kodak Wratten gels, that you have to cut to size. I've never used gels in the holder at the rear of the lens but my understanding is that there is a greater tendency for the filters to flare and reduce contrast at the rear element. I believe that’s stated in the instructions with the lens. I only ever use filters using the normal front thread on this lens. Why wouldn’t you?

JJ

[rafikicat]

Mic, I think JJ's answer explains the situation. I've always used filters at the front of lenses too - just wondered why they would put a holder at the back, and if there was any benefit. I've been thinking about an ND graduated filter, but there seems to be a lot of discussion on various brands etc. so I don't know where to start.
Any help on this one?
Thanks.

[rafikicat]

Following on - I've looked at some of the filter related threads and now I'm even more confused. This is my problem - I can carry only a limited amount of camera gear on cross-country day trips, unfortunately I'm past the age where weight is not a problem (I'm in my 70s) and I think a GND filter would be great for snow photos, particularly panoramas, now what is the simplest answer? The Cokin system looks way too complicated.
Thanks in advance - I'm just so glad I found AusPhotography, such a helpful band of people.:D