Re: [APML] Hutech IDAS LPS Filter Question

["GARY HATFIELD" <Starmangmh@msn.com>]

Title: Message

Thanks Ulrich.  Do you know of a LPS filter the WILL work with a 55mm lens?

 

Gary

----- Original Message -----

From: Ulrich C. Beinert

To: 'Discussion of Film Astrophotography'

Sent: Friday, April 01, 2005 11:54 AM

Subject: RE: [APML] Hutech IDAS LPS Filter Question

Hi Gary,

 

yes, that means the filter won't work well with a 55mm lens. I have tried it, and what happens outside a central circle that has a diameter of about half the frame is that the filter no longer blocks the correct wavelengths because the angle of incidence isn't correct. Everything in that range becomes horribly colorful, and because different wavelengths are blocked, the filter no longer has the light-pollution-suppression-effect. I don't think I have the photo anymore, and even if I did, I don't have a film scanner I can use. But I would agree that anything less than 105mm doesn't make sense if you want to use an IDAS filter.

 

Regards,

Ulrich

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