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-   -   Condenser (https://www.dvinfo.net/forum/alternative-imaging-methods/125140-condenser.html)

Rich Hibner July 1st, 2008 05:53 PM

Condenser
 
Hey, how would you know what FL condenser best suits your need?

Oscar Spierenburg July 2nd, 2008 04:51 AM

I've been taking apart old SLR cameras for their condensers. They are very good, even though they aren't made out of glass.
But I haven't found one yet which doesn't have a marker of some kind for the exposure meter.
So far I've used front pieces of telephoto lenses, but for my new adapter I need a rectangular lens. I also read about using the front pieces of binoculars.

Rich Hibner July 2nd, 2008 10:54 AM

Perhaps I didn't make sense. If I have a GG and was getting vignetting and needed a condenser lens what focal length would be suite me? Is it trial and error? PCX or DCX?

Rich Hibner July 4th, 2008 09:54 PM

Just Oscar has input? Common, somebody out there has something else....Bob??? Where are you?

Bob Hart July 5th, 2008 08:19 PM

Sorry gentlemen. I am no use to you on condensers.


You are well ahead of me in this. I have never used them, just getting by with good prime lenses on adaptors to avoid corner/edge brightness issues.

From my short journey inside a Mini35 to remove a fragment off a surface, it seems that whatever they use in there has a very long focal length as to be almost indistinguishable from a flat glass panel if it is not just that. In their breakdown diagram for the PRO35, the optic just behind their groundglass is referred to as a "field lens".

The front face of the front element of their relay lenses is concave, like some of the big Canon HD lenses. Their optical path is engineer designed to task from front to back, compared to the home-builder's traditional approach of mixing and matching existiing available components.

As I understand things from posts here over the years, plano-convex condensers are best employed as matched pairs with each optic positioned very close to the groundglass on either side, plane face towards groundglass.

The mix and match application of a single condenser between the groundglass and the achromatic dioptre may be an illusary rather than real benefit.

Unless the builder takes care to examine if the condensor is not simply reducing the area of groundglass seen by the camera through simple magnification, a stronger dioptre or zooming in might achieve the same with less distortion and aberration.


FOOTNOTE:

Actually on reflection I find that I lie. The first adaptor I built used a reversed telescope eyepiece optic, the unbranded SW5042 50mm 2" for Tascos, which I re-barrelled to fit the 58mm PD150 filter mount. This assembly is an achromat and a separate biconvex element. It was adequate for a very short non-flip adaptor but also a dead-end because of edge distortion. The exit pupil was 44mm. My groundglass coverage was 24mm - just.

This clip was shot on it -

http://www.youtube.com/watch?v=Zxfjt0Y-EXk

.

Igor Babic July 9th, 2008 04:24 AM

Try this
 
On sgpro site you can find condenser and achromat combo for updating older flip units. Try to ask Wayne if he can sell you this for your DIY adapter.

Rich Hibner July 9th, 2008 01:43 PM

Nothing against Wayne, but I'm my objective is to make this without the aide of current 35mm adapters. The condeser would be for his unit and GG and I don't think it would match mine. Plus, you can buy condensers from Surplus Shed, Thorlab and Optsigma..so I wanted to know if there was a condenser with a ceratin focal length I should look at. I don't even know if I need one, so I wanted to get ahead of the game.

Stephen King July 14th, 2008 09:53 AM

PCX focal length
 
I want to mount a PCX lens between my SLR lens and the GG holder (almost abutting the GG holder), but I'm not certain what focal length to buy.

I found a 55 mm coated mounted PCX lens (which would fit nicely into the canon eos tubes) with a focal length of 130mm. They also have a 54mm unmounted with a 92.5mm FL. Plus all other focal lengths, sizes, etc.

HELP

Thanks


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