Time Temperature compensation factors

[steve_nicholls2]

Recently on one of the lists someone posted a simple chart for calculating times and temperatures using easy to understand maths.

It was something like time * or / by [factor] for a temperature decrease or increase. I had the chart but stored it somewhere safe. Tragic isn't it getting old.

If anyone has a copy of this could they re-post it or send it direct to me

 

<p>

 

Thanks Steve.

[john_hicks]

Can you run a DOS application? If so, I have a spiffy little program that can do what you want and even spit out a time/temp chart to the printer. Let me know and I'll send it to you.

[jimvanson]

Go two thirds down this page

http://www.ilford.com/html/us_english/bw.html

for Ilfords PDF Temperature Conversion Chart

jim

[john_stockdale]

I've looked at charts and times over the years and it seems that there is not a universal set of multipliers for all developer + film combinations. You can see this on, say, the Agfa data sheets where the graphs of dev times for various films show different gradients as a function of temperature, even for the same developer. I have an equation that I worked out from Kodak charts for HC-110. My dev time at 20C was 6 minutes for Tri-X, and the time d for different temperatures t (deg C) is:

59.4*e^(-.1146t)

This can be programmed into a spreadsheet or a sci calculator.

Unfortunately you need to make an equation for each film + dev combo, based on the published charts for the exponent AND your individual time at a known temperature for the multiplier (59.4 in my case). But I only used one film + one developer in those days.

Hope this is helpful

[sean_yates]

Did you mean this"

 

<p>

 

 

"I never claimed to be the cripiest fry in the basket, but I could

NEVER understand why Ilford instructions packaged with developer and

tech sheets have the same goofy TIME/TEMP conversion chart/graph.

 

<p>

 

Blamed thing is useless IMHO - too small and vague - leaves you

guessing. Why can't they just publish T&T like Kodak does in their

B&W Darkroom Dataguide - i.e. Tri-X Pro at iso 320 in D-76 1:1 @ 65

68 70 72 & 75 degrees or whatever?

 

<p>

 

Then I came across a conversion method in Aaron Sussmans book from

the late 60's "Amatuer Photographers Handbook".

 

<p>

 

You take the given time at ANY given temperature for whatever

combination you've got and can calculate the given time at any other

given temperature fairly quickly and certainly with a finer degree of

precision than with the aformentioned graph.

 

<p>

 

I know this may seem hypocritcal coming from a guy who develops by

inspection and "eyeballs" exposures with an incident meter but I find

it re-assuring to have something that seems at least a bit less of a

SWAG than the chart.

 

<p>

 

It goes like this:

 

<p>

 

"Given the developing time at 68 degrees, you convert to the time at

any other temperature by multiplying the given time by the desired

temperature factor T. To convert from the time at any temperature

other than 68 degrees, to any other temperature, you divide the time

of the given temperature by its own factor and then multiply by the

factor of the desired temperature."

 

<p>

 

Here's the chart:

 

<p>

 

Temp in Farenheit followed by factor

 

<p>

 

64 deg factor 1.23 65 1.16 66 1.10 67 1.05 68 1.00 69 .95 70 .90

71 .85 72 .81 73 .78 74 .75 75 .72 76 .69 77 .66

 

<p>

 

This is on page 382 of the edition I have. Hopefully the times and

factors will line up when I "send" this to the forum. FWIW Sussman

has all kinds of neat info in his book. It would definatley behoove

us to look over old photo manuals at yardsales, library used book

sales, etc. etc. etc. My copy came with an enlarger my wife bought me

a while back."

[nigel_smith2]

Just to make it international and line up... (hope this works!!)<P>

<Table border=2 cellspacing=0 cellpadding=2>

<TR VALIGN="bottom">

<TD BGCOLOR=#CCFFFF ALIGN="left">Fahrenheit</TD>

<TD>64.00</TD>

<TD>65.00</TD>

<TD>66.00</TD>

<TD>67.00</TD>

<TD>68.00</TD>

<TD>69.00</TD>

<TD>70.00</TD>

<TD>71.00</TD>

<TD>72.00</TD>

<TD>73.00</TD>

<TD>74.00</TD>

<TD>75.00</TD>

<TD>76.00</TD>

<TD>77.00</TD>

</TR>

<TR VALIGN="bottom">

<TD BGCOLOR=#CCFFFF ALIGN="left">Celsius</TD>

<TD>17.78</TD>

<TD>18.33</TD>

<TD>18.89</TD>

<TD>19.44</TD>

<TD>20.00</TD>

<TD>20.56</TD>

<TD>21.11</TD>

<TD>21.67</TD>

<TD>22.22</TD>

<TD>22.78</TD>

<TD>23.33</TD>

<TD>23.89</TD>

<TD>24.44</TD>

<TD>25.00</TD>

</TR>

<TR VALIGN="bottom">

<TD BGCOLOR=#99CCFF ALIGN="left">Factor</TD>

<TD>1.23</TD>

<TD>1.16</TD>

<TD>1.10</TD>

<TD>1.05</TD>

<TD>1.00</TD>

<TD>0.95</TD>

<TD>0.90</TD>

<TD>0.85</TD>

<TD>0.81</TD>

<TD>0.78</TD>

<TD>0.75</TD>

<TD>0.72</TD>

<TD>0.69</TD>

<TD>0.66</TD>

</TR>

</Table>

[nigel_smith2]

and 2 seconds after posting that I thought of a slight

alteration...<P>

<Table border=2 cellspacing=0 cellpadding=2>

<TR VALIGN="bottom">

<TD BGCOLOR=#CCFFFF ALIGN="left">Fahrenheit</TD>

<TD>64.00</TD>

<TD>65.00</TD>

<TD>66.00</TD>

<TD>67.00</TD>

<TD BGCOLOR=lightyellow>68.00</TD>

<TD>69.00</TD>

<TD>70.00</TD>

<TD>71.00</TD>

<TD>72.00</TD>

<TD>73.00</TD>

<TD>74.00</TD>

<TD>75.00</TD>

<TD>76.00</TD>

<TD>77.00</TD>

</TR>

<TR VALIGN="bottom">

<TD BGCOLOR=#CCFFFF ALIGN="left">Celsius</TD>

<TD>17.78</TD>

<TD>18.33</TD>

<TD>18.89</TD>

<TD>19.44</TD>

<TD BGCOLOR=lightyellow>20.00</TD>

<TD>20.56</TD>

<TD>21.11</TD>

<TD>21.67</TD>

<TD>22.22</TD>

<TD>22.78</TD>

<TD>23.33</TD>

<TD>23.89</TD>

<TD>24.44</TD>

<TD>25.00</TD>

</TR>

<TR VALIGN="bottom">

<TD BGCOLOR=#99CCFF ALIGN="left">Factor</TD>

<TD>1.23</TD>

<TD>1.16</TD>

<TD>1.10</TD>

<TD>1.05</TD>

<TD BGCOLOR=lightyellow>1.00</TD>

<TD>0.95</TD>

<TD>0.90</TD>

<TD>0.85</TD>

<TD>0.81</TD>

<TD>0.78</TD>

<TD>0.75</TD>

<TD>0.72</TD>

<TD>0.69</TD>

<TD>0.66</TD>

</TR>

</Table>