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-   -   Redrock adaptor owners can you help (http://www.dvinfo.net/forum/alternative-imaging-methods/146226-redrock-adaptor-owners-can-you-help.html)

Martin Amada March 19th, 2009 11:42 PM

Redrock adaptor owners can you help
 
I built a cine-adaptor from Redrock's DIY kit for use with my Z1U. It works fairly well.

I've been using a cheap achromat and now I'm thinking about getting their 72 mm dia achromatic diopter to get a better image. I'm trying to find out how far I'm going to need to put the ground glass from the new achromat to achieve focus, but I can''t seem to get an answer from their support.

I believe my rig approximates the production model, so I'm hoping a Redrock (non flip) production model owner can give me this distance to within a few millimeters, my measuring it in their rig.

Thanks.

Martin

Ted Ramasola March 20th, 2009 08:42 AM

Martin,

Put the distance at 69mm measured from surface of gg (facing the achromat) up to the achromat rim.

This assumes you are getting the achromat from either cinevate or redrock. They have the same power. (the original versions or M2 and brevis.)

Ted

P.S. The weaker the power of the achromat, the farther the distance.

Martin Amada March 20th, 2009 09:17 AM

Hey Ted,

Funny, after getting vague answers from the manufucturers I started thinking about who might be able to help with this, and you were one of the people I thought of!

Have you used either of these with your DIY rig and would you recommend one over the other?

BTW, someone at Cinevate support told me focal length of their achromat was 20 cms. That seems very long to me! What do you suppose that was about?!

Martin

Bob Hart March 20th, 2009 10:20 AM

Martin.


The 8" or approx 200mm sounds about right for a flip adaptor with an approx 4+ achromatic dioptre.

The Brevis and SGPro were originally made as non-flip adaptors. It might be worth enquiring if they still have any of their more powerful achromatic dioptres for non-flip adaptors in stock or where they sourced them.

Ted Ramasola March 20th, 2009 05:58 PM

Martin,

Bob is correct. He actually provided me the chart for diopter power and the equivalent distances from the GG.

Correct me Bob if I'm wrong, it went like;
Power - Distance frm GG

3+ - Approx 10 in. - this may vignette.

4+ - Approx 8 in.

7+ - Approx 5 in.

10+ - Approx 3 in.

In my development, I used the Indian made which wasn't good.

The Cinevate (pre flip) similar to the Redrock (pre-flip) - ok but not optimal for my camera.

The SGPRO - very good for my set up.

I think when adapter makers incorporated a flip module they when for lower power achromats since the flip "shortens" the overall length because the path is bent to a "Z" pattern. if your straighten the Z to a straight line its gonna be a long set up.

Hope this helps.


Ted


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