Reciprocity Timer 1.0

[StoneNYC]

OH, PS I'll use those times I guess and then report back...

[BradS]

Also found this...

"Efke IR 820 film shows significant reciprocity failure but the following corrections worked well:

1 second metered, give1.5 seconds
2 seconds metered, give 3.5 seconds
4 seconds metered, give 8 seconds
8 seconds metered, give 24 seconds
15 seconds metered, give 1 minute
30 seconds metered, give 3 minutes
more then 30 secs, give up."

Tc = Tm * log(Tm) / log(2) ; where Tm is the time indicated by your meter reading and Tc is the Time corrected for reciprocity failure.

[Boinzo]

Thanks Brad.
That equation is a pretty common one and certainly approximates the times Stone lists well - under 4 seconds.
If we can confirm the 1.5 and 3.5 second exposure times I can work it in.

1 0
2 2
4 8
8 24
15 59
30 148
60 355

Tc = Tm * log(Tm) / log(2) ; where Tm is the time indicated by your meter reading and Tc is the Time corrected for reciprocity failure.

[StoneNYC]

Thanks Brad.
That equation is a pretty common one and certainly approximates the times Stone lists well - under 4 seconds.
If we can confirm the 1.5 and 3.5 second exposure times I can work it in.

10
22
48
824
1559
30148
60355

It will be some time before I can test, the film is coming from another country.

There IS a test roll coming to me, but not sure I have enough frames to cover my own testing as well as this, will definitely use 2 sheets for this if it's just the 1.5 and 3.5.

I'll add details when I have them.

[Lachlan 717]

Is the IR film in date? If not, given IR film's propensity to lose sensitivity/speed, these times will be rendered moot by degrees, depending on how old the film is.

[Boinzo]

Hmmm. Very good point Lachlan...

Is the IR film in date? If not, given IR film's propensity to lose sensitivity/speed, these times will be rendered moot by degrees, depending on how old the film is.

[Jac@stafford.net]

[...] And reciprocity of such a film that is mostly IR is hard to meter in the first place since not many own an IR spectrum metering device.

Many years ago someone wrote a good article on how to convert a Weston light meter to read into the IR and UV. I think it was Ed Scott who prepared this chart. Certainly there aren't many functioning Westons left, but surfing our the source might be useful since the Weston is inexpensive.

I don't understand why they didn't include a reciprocity chart...

Perhaps because they don't want to be responsible for the metering/estimation errors of their customers.
.

[StoneNYC]

Is the IR film in date? If not, given IR film's propensity to lose sensitivity/speed, these times will be rendered moot by degrees, depending on how old the film is.

No, none of it is in date... For anyone... Neither is Technical Pan, but it's listed in the app

I'll let you guys know, it will be a month before I have results though

[Kirk Gittings]

I don't now about IR but if the Tech Pan is frozen it will act the same today or 10 years from now exactly how it did when new.

[StoneNYC]

I don't now about IR but if the Tech Pan is frozen it will act the same today or 10 years from now exactly how it did when new.

IR is purported to have really bad keeping qualities but from what I've seen those are exaggerated.

I agree, it will surely be worse than Tech Pan in keeping long term, but it's dated I think 2013 or 2012 expiry so I'm not THAT worried.