Re: [APML]: New Photos & Comparison

[Chuck Vaughn <aa6g@aa6g.org>]

Steve Bell wrote:

> I thought to myself, then what does he
> think is making such a big difference? But then I realized that you
> meant those words in reference to how any one film behaves, within
> itself, between a 75 and a 95 min exposure. I imagine you *are*
> attributing the differences to the decreased reciprocity failure of your
> high vac TP compared to Lumicon's TP. But then again, assuming that
> Lumicon does low vac (do they?), maybe if they just hypered until 0.6D,
> you would have gotten the same results with their film.

Actually I was thinking their method compared to my method. That does
encompass several variables; vacuum, base fog level and pure H2 compared
to forming gas. I only pointed out reciprocity failure because I felt it
was insignificant for 75 mins compared to 90 mins on TP. In other words 
the response of both films are rather flat over that short period of time
and should not be considered when comparing the two photos. Significant 
increases in reciprocity failure for TP are typically measured in hours.

Lumicon does use low vacuum and their film usually runs around 0.3D when
developed in D19 for 10 minutes.

I think the difference is increased base fog. Brad Wallis' controlled tests 
show TP to reach maximum sensitivity at around 0.6D - 0.7D base fog. High
vacuum hypering allows the film to be hypered faster, thus accumulating
less fog due to heat. When you combine that with increasing the hypering
to a 0.6D base fog the film is at its most sensitive. I think the only
further improvement would a switch to pure H2 from forming gas.
 
> These images do show one bad trait of TP, that is, its tendency to block
> up. The second photo using the high vac TP doesn't show as much high
> resolution details in those areas where it's starting to block up as
> compared to the first photo. Such is life with TP.

It's probably more the way I scanned them. I might be able to optimize the
scans for the dense areas. The film is not blocked up - that happens only
on very bright objects - but it is hard to scan the dense areas and maintain
the faint parts too.

Chuck  <aa6g@aa6g.org>