On Apr 13, 7:49=A0pm, news*NOSP...@[EMAIL PROTECTED]
(A R)
wrote:
> Peter <w2...@[EMAIL PROTECTED]
> wrote:
> > On Apr 13, 4:55 pm, news*NOSP...@[EMAIL PROTECTED]
(A R)
> > wrote:
> > > Now, I have a pair of spherical condenser lenses but unfortunately I
> > > have no cell to mount them in. A single lens on its own fits snuggly
i=
n
> > > the enlarger head and seems (by eyeball) to give a uniform
illuminatio=
n
> > > across the easel.
>
> > > I know some enlargers use single apsherical lenses but what
> > > advantage/disadvantage do I have using a single spherical lens?
> > > I need more time!
>
> > Broadly, I think the objective of a condenser system is to (i) as you
> > said evenly illuminate the negative, (ii) pass as much of the light
> > through the negative as is practical and (iii) pass it through as
> > nearly colimated as possible.
>
> > With one lens, if the convex side is toward the negative, objective
> > (i) would likely be fulfilled. =A0I have doubts about (ii) and (iii).
>
> But what if the lens was turned flat side towards the negative?
>
> --
>
> I need more time!- Hide quoted text -
>
> - Show quoted text -
It should be evident if you try it.
The extent of the effect depends on the lens and the distance from the
light source and the film. For a distant light source it should the
lens should cause the light to converge. As you bring the light
closer to the lens it willl converge to a lesser degree. Measuring
the focal length and doing a bit of ray tracing with paper and pencil
should clarify the behaviour.
Since you have the lens, you can just try it (small light, dark room
and white piece of paper as a target).
|
