Agfa Copex Rapid / SPUR DSX: reciprocity failure data?

[GLS]

Hi all. I have tried in vain to find reciprocity failure correction data for this film. I have searched google as well as these forums with no luck, and the only "data sheet" on the film I can find (https://www.freestylephoto.biz/pdf/product_pdfs/agfa/Copex_Rapid.pdf) is not worthy of the name.

I know it's a long shot, but has anyone ever found this correction data, or generated it themselves? I have thus far been fudging it by applying the correction for Pan F, but I dislike relying on approximations.

Thanks.

 

[David Lyga]

You know, the easiest and most accurate way to determine this is by test. Simply get a lens that you trust the apertures of, then, wide open, shoot at 1 sec, then closed all the way down (assume six stops here) shoot at one minute. If the densities are the same, then continue: shoot wide open at one minute, than, closed all the way down, shoot at one hour which is six stops more than one minute.

With 'wasting' about one foot of film, you have your answer and can make appropriate adjustments. Of course, the items you shoot will have to be lighted with the appropriate intensities in order to get negatives that will offer useful information.

My 'hunch' for this microfilm is that the reciprocity failure would be about one stop between one second and one minute, no more, maybe less. - David Lyga

 

[AgX]

In hindsight I do not even remember seeing reciprocity charts for Agfa consumer films in their data sheets. And this is a microfilm, thus intended for a sector where there are no reciprocity issues to be expected. Something like that rather should be offered by firms who offer such film with a respective developer for pictorial use. .

 

[GLS]

And this is a microfilm, thus intended for a sector where there are no reciprocity issues to be expected. Something like that rather should be offered by firms who offer such film with a respective developer for pictorial use. .

I suspected this is probably why it can't be found. I use SPUR's Dokuspeed SL-N to develop the film, but there is nothing in the data sheet for that developer regarding reciprocity failure. [edit: INCORRECT: see later post]

You know, the easiest and most accurate way to determine this is by test. Simply get a lens that you trust the apertures of, then, wide open, shoot at 1 sec, then closed all the way down (assume six stops here) shoot at one minute. If the densities are the same, then continue: shoot wide open at one minute, than, closed all the way down, shoot at one hour which is six stops more than one minute.

Thanks for the reply. The thing is, I don't own a densitometer (as I utilise a hybrid workflow), so doing this accurately would not be possible.

 

[David Lyga]

But, in essence, DOING this ACCURATELY IS POSSIBLE my dear bloke. All you need do is work this with the mind, as I had said, rather than with the usage of the almighty densitometer. Entirely, visually, you will see the density difference on that negative, be it a striking difference or one merely pedestrian. The film tells all. - David Lyga

 

[GLS]

Well now I feel very foolish. I looked again at the Dokuspeed SL-N data sheet and there is in fact one line with the data. It is a little sparse, but nonetheless there:

"Reciprocity failure: 1 second +1/2 stop, 10 seconds +1 stop, 1/10000 second +1/3 stop"

I don't know how I missed this. Probably because I was preoccupied trying to find graphs or tables

 

[AgX]

Welcome to the club...