U of S | Mailing List Archive | alt-photo-process-l | Re: Density Base OHP and Stouffer

Re: Density Base OHP and Stouffer

It's interesting that the UV densities read on a UV densitometer are about
double of what my scanner estimated using visible light, I honestly didn't
think they were that much. Clearly I'd be better off just working with step
wedges rather than the scanner at this point of calibration. On a positive
and thankful note it also means the error I thought was insignificant has
now bumped my exposure up an additional minute-and-a-bit based on my initial
calculations. Still relatively small but definitely worthwhile rooting out
at the beginning. Thanks all.


[p.s. FYI, My initial exposure was 10 minutes (600 seconds). To compensate
for the additional density of the OHP I converted the .08 density difference
to a per cent (+~27%). So, 600 seconds of exposure plus 27% yields an
additional 162 seconds or 2:42. So my total exposure adjusts to 12:42
minutes. Pretty close to what I'd eyeballed (~14 minutes) , but it's nice to
know the math supports and even betters this.]

----- Original Message ----- 
From: "Sandy King" <sanking@clemson.edu>
To: <alt-photo-process-l@usask.ca>
Sent: Friday, November 24, 2006 9:17 AM
Subject: RE: Density Base OHP and Stouffer

My measurement with a densitometer in UV mode gives the following.

Stouffer 21-step tablet, Step 1 = 0.10
Stouffer 31-step tablet, Step 1 = 0.10
Pictorico base, 0.18
Crystal Clear (PhotoWarehouse) base, 0.06

Sandy King

At 3:48 PM +0200 11/24/06, Loris Medici wrote:
>I don't have a densitometer too but I clearly remember people reporting
>density of Pictorico as something like log 0.15, and most graphics films -
>like the ones that Stouffer use - base density is something like 0.05.
>Therefore there should be around 1/3 stop (0.15 - 0.05 = log 0.10) STP
>difference between the two. I use Photowarehouse Ulfrafine Crystal Clear
>transparency and I think its base density is something like 0.10 (0.05 less
>than Pictorico) and this is completely consistent with the facts: a) My
>printing times w/ Ultrafine are faster than w/ Pictorico b) When I put the
>transparency material over the Stouffer step tablet (31-steps) so that half
>of the tablet is covered (that way I can see the density difference between
>the Stouffer tablet alone and Stouffer tablet + inket substrate - I think
>this is covered in Mark's book, IIRC that was a trick that Sam Wang
>suggested) I get exactly 1 step difference between the two. Just use the
>trick mentioned in (b) and you'll see how many steps difference you get
>your material... From that point, its easy to calculate the necessary
>exposure adjustment.
>-----Original Message-----
>From: Michael Koch-Schulte [mailto:mkochsch@shaw.ca]
>Sent: 24 Kaszm 2006 Cuma 05:39
>To: alt-photo-process-l@sask.usask.ca
>Subject: Density Base OHP and Stouffer
>I don't own an actual densitometer. My scanner coupled with VueScan puts
>Pictorico OHP at either LogE of 0.08 or 0.10 and it puts my Stouffer
>tablet's Step 1 (clear base) at between 0.04 and 0.06. Does this sound
>close? Do most people use 0.04 or 0.05 (or something else) when calculating
>the printing time between the two? 0.05 is a bit more convenient because
>it's 1/6 of a stop. The resulting error is rather small but I'm just
>wondering. Thx.