Cokin P Filter System - What am I missing?

Zillah

For college this year I've decided to do a project with infrared photography. I got my hands on a Cokin P filter and a mount with adapter for my shiney new Sigma 17-70. Everything slots into place nicely, but there's one thing wrong that I just can't get my head around.

There are 3 slots in the filter mount, but even the one closest to the lens leaves a few milimetres of space for unfiltered light to pour in. This works when you're shooting from a dark location, but outside I'm getting really visible reflections of the lens on the inside of the filter.

Now, I could solve this by putting a ring of masking tape around the filter to block the light...but I can't believe thats what they intended. What am I missing about how this mounting system works?

DaireQuinlan

I was actually wondering this myself the other day, I want to get that pack of Ilford SFX and included cokin IR filter to play around with, but all the cokin filter holders I saw seemed to have the same thing you were talking about, the filter was at a remove from the lens, and there was a gap between them. I guess if the filter was big enough it wouldn't matter overly much, maybe its just the angle you're looking at the filter at ?

rymus

I dont think youre missing anything really.. same with my cokin set, there's a small gap. It's the design of the filter holder that leaves a small gap between the slot in filter and the front of the lens. Better than having the filter pressed right up against the lens I would imagine, wouldnt like to have to replace a scratched filter every few months.

Zillah

rymus wrote: »

I dont think youre missing anything really.. same with my cokin set, there's a small gap. It's the design of the filter holder that leaves a small gap between the slot in filter and the front of the lens. Better than having the filter pressed right up against the lens I would imagine, wouldnt like to have to replace a scratched filter every few months.

But, it makes it entirely usless where there is any ambient light. I can fix it with a bit of masking tape, but it doesn't make sense that they'd choose a mounting system that requires jury rigging to fulfil its basic purpose.

rymus

prepare for some major sticky filterage...

I didnt even know you could get IR cokin filters. Presumably for that very reason, that they'd leak light. I've only ever really found it an issue when taking wide shots.. Anything from 10-14mm can cause a massive pain in the cornholio

DaireQuinlan

Yeah, its this one here ...
http://www.7dayshop.com/catalog/product_info.php?products_id=102935

The filter is designed specially for that Ilford SFX film, which is 'sortof' infrared, so I guess its a 'sortof' IR filter :rolleyes:

LiNgWiStIkZ

My Cokin IF filter got somehow scratched:eek:

Zillah

The mounting system is Cokin, the filter itself is a Wratten I think. Point is, the filter is a square piece and slots into place perfectly. There is no filter that can be installed in this mount that will not suffer from the half centimetre gap.

Fenster

This is your friend

I'm also very happy to answer any questions on IR photography or processing.