Re: gloy for tricolor on yupo?

Yves,

A standard step tablet is far more usefull for determining exposures and
exposure scales—because it is a standard.  Because it is standardized, then two
different people can have a meaningful discussion of their outcomes, exposures,
etc.  A digital step tablet is alwalys of unknown value and does not allow
such a discussion or comparison to take place.

One can easily account for the Base + Fog of the standard step tablet and
factor that out when necessary,
Best Wishes,

Mark Nelson
Precision Digital Negatives

In a message dated 3/31/06 5:57:29 AM, gauvreau-yves@sympatico.ca writes:

> Hi,
>
> when I see below that one should use a step tablet to find proper exposure,
> I would suggest a couple of reason to be doubting these measures. First,
> unless the material you use as your negative is exactly the same as for your
> step tablet which is rarely the case, you wouldn't be sure they behave
> exactly the same way mostly because of there (probably) different response
> to UV, if you make digital negatives, then I would suggest making a step
> tablet the same way you intend to make your negative since this way you can
> establish a direct relationship with what you see on screen (pixel values),
> your negative and your print if you are using a scanner of course. Creating
> an adjustment curve using this pixel values instead of densities is
> pratically child play. A traditional step tablet would give you more work to
> establish this same relationship.
>
> Regards
> Yves
>
>
>
> ----- Original Message -----
> From: "Katharine Thayer" <kthayer@pacifier.com>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Friday, March 31, 2006 1:02 AM
> Subject: Re: gloy for tricolor on yupo?
>
>
> >
> > On Mar 30, 2006, at 8:03 PM, Christina Z. Anderson wrote:
> >
> > >
> > >
> > > The 6 minute printing time, given UVBL and 15% dichromate and my
>
> > > workflow gives me a layer that develops in an hour and yet can also
> > > be spray developed without the layer sloughing off. It also
> > > provides a deep enough colored layer.  At 5 minutes it is not bad
> > > either, but the layer of gum is a bit more tenuous and not as
> > > strongly colored--the more exposure, the deeper the gum layer is
> > > and hence the more pigment remains on the paper.  At least, in side
> > > by side step wedges exposed at 1, 2, 3, 4, 5, and 6 minutes this is
> > > the case--the colored layer thickens and therefore deepens with
> > > exposure. If my website ever gets up it'll show this little example.
> >
> >
> > Well, of course, all of this goes without saying:  for each
> > combination of light, dichromate, film, paper,  etc etc there is a
> > "best" exposure,  which  can easily be determined with a step wedge,
> > and which produces the optimal hardening of the gum layer;  anything
> > less than that exposure will result in less than optimal gum
> > hardening.   I would be very surprised if there are any gum printers
> > who don't know that.
> >
> > But my point,  which I wonder if you've missed,   was that this
> > "best" exposure is different for every system of equipment,
> > materials, etc.  It's hardly surprising that your students found that
> > the same exposure worked for them, given that  I would assume that
> > they would be using the same equipment and materials, but surely
> > you're not suggesting that 6 minutes is an optimal exposure in some
> > kind of general and absolute sense.
> >
> > Katharine
> >
>
>
>
Received on Sat Apr 1 04:32:21 2006