Heliopan vari ND finetuning to prevent cross hatch vignetting.

[Postmaster]

Darren was asking me this:

Hey Frank, I have a question . My Heliopan has the cross hatch vignette when at MAX ND on wide lenses eg. 17mm . When at 17mm properly exposed shots in full sunlight outside has some vignetting at the corners (not max ND ,because max ND as stated yields the cross hatch "X" which disappears only at 35mm and above). However when zoomed in to about 24mm the vignetting goes away for a properly exposed image in sunlight.

My question to you is does your wide lenses preferable 17mm (or in that region) exhibit these things? I've been using my Heliopan for some months now and only just realized this some weeks ago. So its something that can be missed. Another fellow dvxuser said his had the cross hatch and he exchanged it and the replacement doesn't have it. But i'm not sure what focal length he tested it at (cant get a response from him as yet). I'm weighing whether to send mine back for a replacement.

I wanted to write a step-by-step article about that in my blog, but gonna answer it first here.

The wider the lens, the sooner you get the cross hatch vignetting, because it crawls in from the sides.

Actually I found an easy fix for that.
The Heliopan has a little screw on the side, that not only acts as a stop, but also holds the front glass in position.

1. Take your widest lens, and put the Heliopan on it. Point the camera to the sky.
2. Turn the ND to the max, till it hits the stop (you probably already see the vignetting coming in)
3. Loosen the screw just enough, so that you can twist the front glass.
4. Dial the glass back till the vignetting is gone - make sure the outer ring stays at maximum.
5. Fasten the screw.
6. Wipe off your greasy fingerprints.

Done.

Frank

[jambredz]

wow...thanks for the post Frank. I'm Darren BTW for those who don't know I'll definitely try this out. It would save me some $ and alot of waiting.

[Postmaster]

Welcome

[moldcad]

Frank, are we talking about vignetting as per attached screengrab? If so, I noticed that some users got Heliopan to replace their filters, and the replacements are claimed to be free from this ugly effect - what is a consensus here? Should I complain about mine (only vignettes on wide lenses; the screengrab has been taken from the kit lens at its widest):

[Postmaster]

They behave the same on longer lenses, but you don`t see it, because they are errr... longer.
So yeah, the problem consists mostly on wider glass.

That's why I said, take your widest lens to fix it.

I have no idea if this is a problem with the filter glass per se or just a miss alignment, due to a loose screw.
But my fix worked for me.

Give it a try, there is nothing to loose.

Frank

[moldcad]

Frank - I must have a bad day, or my English is not good enough, but I don't follow your prescription

Could you please re-word it for dumb people like me?

EDIT: I have read your post again carefully, and finally got the idea - by "dial/twist the front glass" you mean exactly that - the glass inside the outer ring - and not the ring itself... Now I'm clear!

What's more - I can understand now how various units may vary in when exactly the vignette starts; early start (long before the end stop) doesn't necessarily mean the filter is "worse" or defective.

[morgan_moore]

I think this always happens if you polarize too much.

Frank is just talking setting the stop so that you are physically restricted from dialling in that much pola??

S

[Postmaster]

When I received my Heliopan it was fine, but after a while, that little setting screw got loose.
So while cleaning the filter, the front glass got twisted and the cross hatch effect showed up on wider lenses.

So my fix is basically for resetting it to "factory presets" - or fine tune it for your widest glass, if you want.

Frank

[Stu Siegal]

Frank, THANKS! This works to perfection, saved me much shipping $ & aggravation. Notes to others: a little gaffers on the side keeps the lens from slipping off it's max setting, and the little screw is very sensitive. It only takes a turn or so to loosen it, and once you're done, don't over-tighten it or you won't be able to freely rotate the filter.

[Postmaster]

Glad I can help.

Frank