8mm Forum: Scope lens advice needed ...

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Posted by Mike Peckham (Member # 16) on November 10, 2004, 02:43 PM:

I'm having a bit of difficulty setting up my scope lens in such a way that I don't get vignetting at the corners. I'm starting to wonder whether or not it will be possible with my lens or if I should perhaps be investing in a different make and type [Frown]

.

I'm using the F1:1,1 lens on the GS and have a swing away bracket mounted on the front, in that I have a Sankor 16F Anamorphic lens. I'm wondering in part if the problem is with the distance between the two lenses. When I used to use this set up on the Sankyo 800 with a free standing lens holder I was able to get the base of the Anamorphic to slot right into the projector lens and didn't seem to get a problem with vignetting.

I just don't seem to be able to get a clean edge to the frame and an even light across the image area and into the corners.

Any advice would be gratefully received.

Mike [Smile]

Posted by Tim Christian (Member # 48) on November 10, 2004, 03:24 PM:

Vignetting in a scope lens is determined by two main factors: projection lens focal length and projector lens to anamorphic spacing. Even a spacing of 2 mm will cause vignetting in marginal cases. With a Proskar 16B, with focal lengths down to 15 mm, there is no vignetting at spacings of 1-2 mm. On the other hand, the smaller 16C starts to vignette at focal lengths below about 20 mm.

It is just the same with cameras.

Posted by Tony Milman (Member # 7) on November 10, 2004, 04:34 PM:

Mike,

I am using a Kowa 16Z (I think!) and unless my eyesight is as bad as I thnk I don't seem to get this- why not bring it along to the next get together of the lightwater 6 (hundred)?

Posted by Kevin Faulkner (Member # 6) on November 13, 2004, 05:47 AM:

The Scope lens for super 8 needs to have quite a large rear element. The Kowa 8Z has just this and I think is a rebadged version of the 16D. I suspect the rear element, from your description Mike, is a little on the small side especially as it was designed for 16mm.

I think Mike, that if you were to zoom the image to its smallest size then this uneveness would disapear. If it does then its down to the reason above.

Kev.

Posted by John Cook (Member # 203) on November 13, 2004, 11:01 PM:

Kevin,

I've been thinking of acquiring a scope lens, if you could only purchase one lens and had limited funding would the Kowa 8Z be your choice to mate to a GS1200 with a F1.1 lens? If not what would be your lens of choice?

Regards, John

Posted by Kevin Faulkner (Member # 6) on November 14, 2004, 05:39 AM:

Hi John,
Yes the Kowa 8Z is an excellent choice of Scope Lens. I have one which I use on both my GS1200 Xenon and also my Elmo 16CL. It has a large rear element which is what's required for super 8 when projecting at the short distances that most of us do and at the magnification required for super 8.
Be wary of using some of the 16mm scope lenses as the rear element will be a bit too small and you wont be able to get it close enough to your prime lens to stop vignetting.

Kev.

Posted by Mike Peckham (Member # 16) on November 16, 2004, 02:11 PM:

Thanks for the advice chaps, I tried holding the lens just in front of the projector lens with as little gap as possible and that seemed to improve things but clearly this is the wrong lens to be using for 8mm. I shall now be on the look out for a Kowa 8Z and a new bracket.

This all started after seeing John Clanceys scope set up in his living room, I had no idea that super 8 could look so good in cinemascope, made me realise that I wasn't getting the full benifit [as it were]. [Wink]

Mike

Posted by John Clancy (Member # 49) on November 17, 2004, 01:57 AM:

I also get pretty good results from the cheapie lens Walton were selling years ago. I think it's an Iscomorphot Iscorama and was designed specifically for Super 8. These can be picked up for as little as £25 whereas the Kowa is generally at least £80.

I use the Iscomorphot for 35mm now. Has a bit of vignetting but it saves having to move the Kowa over to a different machine every time I want to watch a 'Scope film. I'm not saying it's as good as the Kowa but it certainly gives good results and represents good value.

Get one with the original box Mike. You'll love it - a scantilly clad girlie on a beach.

Posted by Paul Adsett (Member # 25) on November 17, 2004, 05:41 PM:

John , you're forgetting that with Mike, nothing can compete with Rexette the stripper!

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