If so he is wrong. First of all 15 SECONDS is a fixed amount
so would be a variable percentage of developing time. Secondly,
if one assumes a ten minute developing time 15 seconds is 2.5%,
which would not make a significant difference.
In fact, from Kodak data on contrast index vs time I think
even 15% is a bit tight, more like 20% and around 30% to 33% for
cubic grain films. I have no idea what the term "3D" means as
applied to emulsion grains.
On 11/25/2019 11:33 AM, Dana Myers wrote:
On 11/25/2019 11:06 AM, `Richard Knoppow wrote:
I think using a water bath for the tank is a good idea. Even if you fill the tank first and drop the film in (Kodak recommended procedure) there will still be an effect on the temperature of the developer. One procedure, I think from color processing, is to have everything in a water bath.
Oh, it's a good idea, it's a great idea. It's just not convenient for me these days.
BTW, I think the statement that +/- 15 seconds makes a difference probably means +/- 15%.
I think Bob was pretty precise in his wording:
"T-Max Film development time differences of +/- 15 seconds are enough to
make a difference. For 3Ds 25% is an appropriate difference."
Generally, Kodak states that their time/temp charts are for a contrast index suitable for diffusion printing.
J-109 makes no mention of enlarger type, specifying CIs instead. IIRC, Kodak
suggests a CI of ~0.58 for diffusion printing, and the J-109 chart uses CI 0.56
as the nominal dev target. Implication being the expected printing is via
diffusion.
The fact is that B&W photography is very forgiving, you can wander all over the place and still get decent prints but try doing it twice in a row.
Absolutely. Somewhat ironically, when I transitioned from darkroom printing
(almost always with polycontrast paper and a set of filters) to scanning, I quickly
realized how much I'd been compensating for exposure/development variation.
Cheers,
Dana K6JQ
On 11/12/2019 9:04 AM, Robert Shanebrook (Redacted sender makingkodakfilm for DMARC) wrote:Keep it simple:
Use time-and-temperature to control contrast/density. Yes, T-Max Films are more sensitive to time-and-temperature differences than 3D films. T-Max Film development time differences of +/- 15 seconds are enough to make a difference. For 3Ds 25% is an appropriate difference.
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