[MF3D.FORUM:930] MF Projection

[Richard Twichell <rmt@xxxxxxxxxxxxxxx>]

Paul said and Tom replied:

> > Not to be combative, but a lot of people use them with the
> > white side forward and the back in black (often for projection
> > reasons, presumably).
> 
> I'd like to know why. I have seen it done but it makes no sense to me.
> Absorption of IR and light by the black surface will contribute to
> heating the mount and the slide. White on the projection side makes the
> mount more visible on the screen.

Uh, I think you are in agreement here.  If I read Paul right, he is
referring to a mount in a viewer - white "forward", toward the viewee,
black "in back".


Tom quotes me and continues:

> > Edmund recommends condensers 1 1/2 times the diagonal of
> > the chip.
> 
> I might challenge this. Where does Edmund's say this?

I will check this - the Edmund's cat. is at work...

> Lenses do not have to be round. You can chop off the overlapping parts.

True...I've seen it done with Ektagraphics...I'm not brave enough to try
this with Rollei or Buhl lenses in metal barrels so will leave the
chopping technique to you!

> What is the chip size (width and height and diagonal) and the center to
> center spacing?

Spicer MF mounts:

chip width: 50mm
chip height:  50mm
chip diagonal: 69mm
center to center:  62mm

I have no problem with heat with the Rollei projectors I'm using  -
there is one piece of HAG between the condensers, with provision for a
2nd which is recommended with a 500 watt bulb.  I omit this because the
polarizer is added just behind the slide. I tried the polarizer in the
spot for the 2nd HAG and it cooked in a hurry!

Dick Twichell