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. ~m [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 base >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 with >your material... From that point, its easy to calculate the necessary >exposure adjustment. > >Regards, >Loris. > >-----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.
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