Re: [APML] Zenitar 16mm f/2.8

I appreciate everyone's feedback.

At first, I thought something was wrong with the lens.

Now all I need are some transparent haze free nights to try it out.

Thanks again.

Chris

----------------------------------
Chris Cook
Astronomical & Nightscape Photography
www.abmedia.com/astro

-----Original Message-----
From: Kirk Carbo <kcarbo@lobosservices.com>
To: 'Discussion of Film Astrophotography' <astro-photo@seds.org>
Date: Thursday, June 26, 2003 8:55 AM
Subject: RE: [APML] Zenitar 16mm f/2.8

I agree with Robert. I have a 300 mm f2.8 Tokina lense and it has a filter slot in the back of the lense. The lense is supplied with a filter holder and a clear lense. I called Tokina and asked what the clear filter was for. They told me that the lense was designed with a filter element and the clear filter should be inserted when another filter is not used.

Kirk Carbo

-----Original Message-----
From: Robert Reeves [mailto:reeves10@swbell.net]
Sent: Wednesday, June 25, 2003 7:28 PM
To: Discussion of Film Astrophotography
Subject: Re: [APML] Zenitar 16mm f/2.8

Hi Dominic -

Do you know why this is? Isn't just a clear filter. Since it's needed for the lens to reach focus at infinity, it seems to me that it's acting more like a corrector of some sort?

Weird...

Chris

----------------------------------
Chris Cook
Astronomical & Nightscape Photography
www.abmedia.com/astro

Hi Chris !

Yes you should have this filter or the other colored filter to have the focus at infinity. You can make the test visualy in daylight , you'll see that you should have the clear filter for a good focus !

Let us know when you'll have an astrophoto with this lens that I find verry useful.

Clear skies !

Dominic

It would seem to me that the clear "filter" is needed for this reason... (If I'm wrong, chime in) All filters slightly shift the focus point. The degree of shift is dependent on the thickness of the filter. The fisheyes have colored filters built into them because you can't put a filter over the outside of the lens like you do on a "normal" lens. Thus when the colored filters are not being used, something has to take their place in the optical path because it is designed from the ground up assuming that one of these filters will be in the light path, either a colored one or the clear one for "no filter".

Robert Reeves                      reeves10@swbell.net
520 Rittiman Rd.                   www.robertreeves.com
San Antonio, Texas 78209    210-828-9036
USA                                     29.484 98.440 200 meters
_______________________________________________
Astro-Photo mailing list
Astro-Photo@seds.org
http://seds.org/mailman/listinfo/astro-photo