Mounting filter gel between the film rails

[thefsb]

with kodak hie gone i'm looking for alternatives. a lot of folk think wratten 88a is a good match for the efke and rollei ir films. not much chance finding a 39 mm screw in filter that color so i've been thinking about fitting a gel between the film rails, i.e. between the film and the shutter on a bessa r or r4. b+w makes a 89b filter in 39 mm, but ... one nice thing about between the film rails is that it would work with my 15 mm heliar as well as my 25 mm snapshot.

anyone had any success doing this?

or how about mounting gel behind the lens? there's space available, it seems, but i can't think of an elegant mechanical solution.

[sepiareverb]

How much space behind the lens? A well fitted Schneider type lenscap might work- cut out the bulk of the cap, use the 'ring' that's left to hold the gel?

First idea.

[thefsb]

Originally Posted by sepiareverb

How much space behind the lens?

i took a look yesterday and didn't measure but in the region of 10 mm from lens base to shutter mechanism.

Originally Posted by sepiareverb

A well fitted Schneider type lenscap might work- cut out the bulk of the cap, use the 'ring' that's left to hold the gel?

sounds interesting. can you point me to info on a "Schneider type lenscap"?

[Bryce]

Mounting the filter between the lens and the film will affect focus distance. With a longer lens and a thin gel this might not be a problem but the 15mm would almost certainly give trouble.
For most lenses, you can buy a larger than necessary filter and mount with a step up ring. The 15mm will be harder...

[rbiemer]

What about something like this:
http://www.adorama.com/LEGSP.html
Not in stock right now at Adorama but I have seen variations of these around. Worth looking further for maybe?
Rob

[thefsb]

Originally Posted by rbiemer

What about something like this:
http://www.adorama.com/LEGSP.html

that's certainly an option. and about the simplest. couple of disadvantages, though. the holder and gel will be quite a big part of the scene in the viewfinder (and look funny on such a nice wee compact camera). and (if i understand things correctly) a planar filter in front of a very wide angle lens adds fall-off at the corners. putting it behind the lens or between the film rails neatly solves both problems.

one of the nice things about using rfs for ir is that you don't have to look through a near opaque viewfinder.

[spyder2000]

Don't try to mount your gel between the film rails. Dirt or dust on the gel will be in focus on the film. Mount your filter up front. I really like the lenscap idea but if you use the gel holder, your gels will remain a standard size and useable on other lenses. When Kodak stopped distributing them, they got really expensive.

[thefsb]

Originally Posted by Bryce

Mounting the filter between the lens and the film will affect focus distance. With a longer lens and a thin gel this might not be a problem but the 15mm would almost certainly give trouble.

i had another look inside with the 15 mm mounted and at closest focus i think there's still enough space.

Originally Posted by Bryce

For most lenses, you can buy a larger than necessary filter and mount with a step up ring. The 15mm will be harder...

or use a gel holder. should work for both.

[sepiareverb]

Originally Posted by spyder2000

Don't try to mount your gel between the film rails. Dirt or dust on the gel will be in focus on the film. Mount your filter up front. I really like the lenscap idea but if you use the gel holder, your gels will remain a standard size and useable on other lenses. When Kodak stopped distributing them, they got really expensive.

Dust will basically contact print on the film if the gel is at the film plane. Dust shouldn't be as much of a problem at the rear of the lens though. Here are the Schneider caps at B&H- they are in manufacturers part number order, so don't relate to size much.
http://www.bhphotovideo.com/bnh/cont...ring+not+found

[Ronald M]

Only polyester can go between the rails. Gels scratch far to easily.

Cut a circle to fit a clear 39mm filter and tak the gel in place behind the glass. I have some I have been using 5 or years that way. Store in a hard filter case.

A bit of tape or dab of rubber cement will do no damage.

[sepiareverb]

Originally Posted by Ronald M

...Cut a circle to fit a clear 39mm filter and tak the gel in place behind the glass...

Now there is the simple, elegant solution.

[thefsb]

Originally Posted by sepiareverb

Now there is the simple, elegant solution.

at one level, yes. but my freehand circle-cutting scissor skills aren't exactly top notch. any suggestions how to simplify that nerve-racking challenge?

[rbiemer]

I note some light fall off with my CV21 occasionally (with or with out filters) and think it likely the wider 15 would show this more.
And the CV 77mm adaptor is probably no more elegant than a gel holder on the front of the 15. And 77mm IR filters are pretty pricey, too!
For 39 or 77 mm IR filters, you could look at these folks:
http://www.filterfind.net/helio.htm?46,76
You'll see the "special effects/infrared" button.
Good hunting!
Rob

Originally Posted by thefsb

that's certainly an option. and about the simplest. couple of disadvantages, though. the holder and gel will be quite a big part of the scene in the viewfinder (and look funny on such a nice wee compact camera). and (if i understand things correctly) a planar filter in front of a very wide angle lens adds fall-off at the corners. putting it behind the lens or between the film rails neatly solves both problems.

one of the nice things about using rfs for ir is that you don't have to look through a near opaque viewfinder.

[thefsb]

heliopan web site says they offer a 715 nm filter in 39 mm screw mount, which is equivalent to wratten 88a. does anyone know where to buy them in the us?

[thefsb]

Originally Posted by thefsb

heliopan web site says they offer a 715 nm filter in 39 mm screw mount, which is equivalent to wratten 88a. does anyone know where to buy them in the us?

i found a vendor. if you're interested, it's a place called cambridge world. if you don't know this place, check out the web site http://www.cambridgeworld.com/ -- they have a deep selection of unusual stuff. and i had a nice conversation about places in central scotland while i placed an order for the rg715 39 mm.

so i'll try out the rollei film and (perhaps the efke too) with my 25 mm snapshot, maybe even the 35 mm color, and worry about the 15 mm lens later after i see the results.

[ddutchison]

Originally Posted by thefsb

...my freehand circle-cutting scissor skills aren't exactly top notch. any suggestions how to simplify that nerve-racking challenge?

I use gels this way too.

Take a slip of clean paper twice the size of the gel, fold it in half, and draw a circle on it by tracing around the threaded end of the filter it's to go behind.

Sandwich the gel in the paper, then cut along the circle, just inside the line. Slightly smaller is ok, slightly bigger will be a pain.

I don't see why you couldn't a cut a gel to fit inside the 15mm Helliar's lens shade - held in place by a couple of bits of double-sided tape. I'd leave a little tab on the circle and fold it up to facilitate installation and removal.