On Mar 2, 4:29 pm, David Nebenzahl <nob...@[EMAIL PROTECTED]
> wrote:
> On 3/2/2008 11:39 AM jch spake thus:
>
> > David Nebenzahl wrote:
>
> >> Like LF cameras, used enlargers are now going very cheaply, either
> >> locally available or on a certain little web auction site. (If you're
in
> >> an area served by Craigslist, check there.)
>
> >> A 4x5 enlarger doesn't take up that much more room than your present
one.
>
> > Fair enough. Have you any recommendations for enlargers? I have
> > _never_ looked at MF or LF enlargers. Are they mainly condenser
types,
> > or the diffusion types? For example, the condenser in the Durst is
> > already pretty massive and heavy. I shall also have to design the
> > enlarger base surface for multiple enlarger mounts.
>
> The usual: Omega (D2), Beseler, etc. Shoot: I just saw a Beseler 4x5
> enlarger, at the Oakland Museum White Elephant sale, going for about $25
> (no lens, but otherwise looked complete). These are all condenser types.
>
> In the event that you need parts (which is likely, since many enlargers
> will come without needed parts, like negative carriers, lensboards,
> etc.), you can find these on that small little on-line auction site.
> Likewise, lenses (including really good ones, like Componons, Nikkors
> and Rodenstocks) are going for cheap.
>
> Hint: get the next-size-up lens for your format if you don't need to
> make big enlargements; for instance, get a 165 mm instead of a 135 mm
> lens for 4x5. This will give you better corner-to-corner sharpness.
>
> Older enlargers, like the Elwoods (mostly found in 5x7 size like mine)
> are diffusion types.
>
> The baseboards are a little larger than your Durst, but not by much.
The Elwood lamp is a strange mixture. Its not really diffusing
because it concentrates the light using a polished parabolic
reflector. The lamp itself is diffuse, a large size opal lamp, so the
source is not specular. In addition, there is a rough, sandblasted,
ground glass light equalizer to even out the center to edge
illumination. This glass has surface which is nearly clear at the
edges and becomes progressively more diffuse toward the center. I am
not sure how this compares with the sort of partially diffusing
condenser lamphouse found on enlargers such as the Omega, but its
probably similar.
There are enlargers with true diffusion sources. Most cold light
sources are very diffuse as are most color head types which have light
integrator boxes, essentially diffusers.
Few enlargers have truly specular sources. A few point source
lamps were supplied for special purposes such as making very large
prints or printing from microfilm where the highest possible
resolution and edge sharpness is necessary. For the most part these
sources are impractical for general use because they exaggerate flaws
in the film so much.
Practical lamphouses vary about one paper grade overall for
black and white film with silver images. The amount of variation in
effective density with the relative diffusion of the light source
depends on the particle size of the image. Coarse grain silver images
have the most and dye images have the least. This is known as Callier
effect. For color films and chromogenic B&W films the effect is nearly
nil.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@[EMAIL PROTECTED]
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