on 07/16/02 11:21, [EMAIL PROTECTED] shared with me:
>> "Dave" writes:
>>> I've had a question from a co-worker about something that she believes is
>>> called "Seattle Film" - apparently, according to her, it's a film which is
>>> both a negative AND positive film (i.e. is print and chrome capable).
>>
>> Yes, they will sell you both slides and prints from the same film.
>> Doesn't
>> mean that it is one film that does both though, just that they will produce
>> both from it.
>> In fact, last I heard, they had ceased using the movie film and special
>> processing that it required and were now using ordinary (Agfa?) C-41
>> negative film (and even marked it as requiring C-41 process too).
>>
>>> he also stated that it's only available via mail order from the U.S.
>>
>
> Seattle FilmWorks, as noted above, used to do the movie film thing --
> less-known fact is that they would, even then, process ordinary (non-movie,
> not-sold-by-them) colour negative film and return one's negatives with prints
> and slides. They are also not the only lab to provide that service. I don't
> care for the results from Seattle Film Works back when I dealt with them --
> quite a while now -- but they were/are not the only lab to provide that
> service. I've used Dale Labs www.dalelabs.com several times and liked the
> results.
>
> Bottom line is, you can get slides made from negatives ... it's not a matter
> of shooting a special film, it's a matter of dealing with a lab that offers
> that service.
But the slides will be contrasty, with no highlight or shadow detail (at
Seattle Filmworks). Always best to pick your best neg and have a shadow mask
made to sandwich with your negative. This produces a transparency for
display or projection with the best possible gamma.
Some old (non digital) slide copying machines use a semi-silvered, actinic,
or dichroic glass at 45 degrees to the light path, and a second controllable
flash unit to hit the copyfilm with a bit o'light along with the primary to
ultimately cut the normal buildup of contrast in the copy process, be it
negs or slides.
>From the Web:
Gary Reese <[EMAIL PROTECTED]> wrote:
"Contrast control in slide copying can be achieved by pre-flashing
the special slide copying films. That gives a low level fogging
exposure to the shadows in your original slide. The fog exposure plus
slide exposure will help keep the shadows from blacking out. The
technique is covered in books about slide copying. It is akin to
fogging at Zone 1 or Zone II in books about the Zone System. Slide
copies like the Bowens Illumitran have circuitry to pre-flash the emulsion.
"
Pre-flash as a contrast control procedure works exactly as
described. The Bowens slide duplicating machine combines a pre-flash
with a dichroic filter head for precise color balancing. This delicate
color balance shifts from batch to batch of film, with local voltage
fluctuations and the age of the bulb. Its a fussy business. Another
more radical technique is to make a contrast mask of the original slide,
sandwich the two together, and duplicate the stack. The mask is an
under-exposed and under-developed B&W contact "print" of the slide. The
approach serves to bring the highlights to the shadows; the opposite
approach of pre-flashing. This method is useful for extreme contrast
scenes and is also applicable to creating direct positive prints
(Cibas). Both methods compress the total tonal range.
The problem with high reproduction ratios and small lens apertures
is diffraction of light through the diaphram. The light rays no longer
all converge at a point, making precise focus impossible. Too small an
aperture does nothing for DoF and kills the sharpness of the details
over the whole image. Its better to reduce the reproduction ratio for a
given focal length lens and gain DoF that way, or use a shorter focal
length lens, increasing the reproduction ratio and gaining DoF because
less extension is required. That's why a range of macro lenses, from
20mm to 135mm, is needed (at least that's my personal rationalization
<g>). However, it doesn't take too long before DoF is hopelessly small
no matter what you do, so you do your best to arrange your subject angle
to as thin a plane as possible anyway.
John P
JoMac, Pentaxian
"Pentax, Quadraphonic, Betamax, Macintosh"
and above the rest.
k t,
s e n
Living life a w o
almost parallel to, r
yet ever so slightly o u t -------> f
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