Infra Red Filter Problem

[tesarver]

For a while I have been using a B+W 092 IR screw filter on the EF-M 22mm lens. I have been getting good results with this filter, but since it only fits the EF-M 22mm Lens, I bought a Cokin A.007 89B IR Filter as I have a ring adapters that will fit 43mm and 52mm. When The Cokin Filter Arrived, the 1st thing I noticed was that it blocks almost all visible light compared to the B+W IR Filter. When I tested the Cokin with the EF-M 22mm I got some strange results. So I tested the Cokin with the EF-M 18-55mm and got the same results.

Now the other thing I noticed was that you need to focus prior to putting the Cokin Filter on as that lens will not focus with the filter on. Anyway here are the results from the same scene:

This Image was taken w/EF-M 22mm w/B+W 092 IR Filter:


Now here is the what it looks like w/EF-M 18-55mm w/Cokin A.007 89B IR Filter:


As you can see with the Cokin Filter there are 2 bright circles on the bottom left hand corner of the image. Same problem w/the EF-22mm Lens. So my question is what is causing those bright circles?

Also note that the sun was behind me.

Thanks

Tom

[S_J_P]

Re: Infra Red Filter Problem

It looks just like light-leak to me Tom, I suffered exactly the same phenomenon when using Cokin (square) filters. After trying various fixes, none of which worked satisfactorily, I bought screw-in filters and reducing-rings.

It seems that the long IR (or ND) exposures exacerbate the small amount of light-leak around the Cokin holder, resulting in internal reflections.

[tesarver]

Re: Infra Red Filter Problem

Thanks Steve for clarifying that issue for me.

Tom

[tesarver]

Re: Infra Red Filter Problem

Based on your advice Steve, I have a hood for the Cokin Holder. What I did was go upstairs and pulled a pair of black socks from my drawer. I cut off the foot part of the sock and used that to cover the hood, IR Filter and the Lens, doubling the sock over the set-up. Here are the results:

There are using the EF-M 22mm w/Cokin A.007 89B Filter.

The exposure time for this image was 10 sec



The Exposure time for this image was 30 sec



I was pretty pleased with the results of both of this images, and there appears to be no more light leaks on the image.

Tom

[S_J_P]

Re: Infra Red Filter Problem

I should have tried a sock like you Tom! Your ingenious use of footwear could have saved me me cost of the screw-in filters

The images are looking good

[tesarver]

Re: Infra Red Filter Problem

Thanks Steve

[Muscat]

Re: Infra Red Filter Problem

Look is good Tom

[tesarver]

Re: Infra Red Filter Problem

Thanks Ian

[pelliott1954]

Re: Infra Red Filter Problem

Haa, good trick with the socks Tom, both images look good to me.

Regards Paul

[tesarver]

Re: Infra Red Filter Problem

Thanks Paul.

[colin C]

Re: Infra Red Filter Problem

Socks heh? Stinky ............ but effective!

[tesarver]

Re: Infra Red Filter Problem

Thanks Colin

[Montana 5]

Re: Infra Red Filter Problem

I saw the Black Sock listed on the info for the picture in the other post Tom, I thought no it can't be, must be some gadget those IR togs use anyway top marks for improvisation and great that it solved the problem. Like both of these by the way.

Doug.

[tesarver]

Re: Infra Red Filter Problem

Thanks Doug

[2Beers]

Re: Infra Red Filter Problem

Great Images Tom and ingenious solution to a problem