ASA n/a ???

[thefizz]

I have been looking at the massive development chart on digitaltruth.com and see some film speeds as n/a (not applicable).

Can someone explain how a film speed can not be important when choosing which development time to use.

Regards,
Peter

 

[clogz]

It simply means that at a certain film speed the developer will not give good results. Also, I might be that no data on the combination is available.

Regards

Hans

 

[thefizz]

How is one to know which film speed will work or not?
The chart still gave developing times?

 

[argus]

Peter,

Test for yourself and contribute the data if you get acceptable results. It helps to know the properties of the film and developer you want to use.

I was really surprised not to find times for HP5+ @200 in Rodinal 1+50 on the list before. I tried and tested and sent in the result for 135 and 120 format.

G

 

[thefizz]

Thanks for your views Geert & Hans. I still don't understand why they show a dev time & temperature without any film speed but I agree about testing as some of the info on digitaltruth is a little off.

I hope that's a Leffe beer your having in you profile picture Geert.

 

[P C Headland]

If there is no speed listed, then I'd assume the times are for the film's "box" speed.

 

[srs5694]

The Massive Dev Chart is made up, in part, of user-supplied times. Thus, my guess is that somebody submitted a development time but neglected to mention the film speed.

 

[argus]

BTW, don't forget that development also depends on the method of agitation: by hand (multiple varieties) or in a rotary drum.
In the best case, the times at Digitaltruth are only a starting point for your personal dev. combo.

I hope that's a Leffe beer your having in you profile picture Geert.

It's shaken Rodinal disguised as Leffe

G

 

[Paul Sorensen]

I just had a look at the dev chart and the films I saw with the NA were infrared and ortho films. Here is a quote from Kodak's web site about their infrared film:

Film speed: Normal ISO speed values do not apply. Make trial exposures under typical conditions. With a KODAK WRATTEN Filter No. 25, try a setting of EI 50 (daylight) or EI 125 (tungsten) and bracketed ± 2 stops

I imagine that because of the limited sensitivity of ortho films, that they present a similar problem for metering, but I am not really sure about that. Otherwise, I didn't find any other instances of the NA being listed for the film speed. There were a few where the film speed was listed as ? and I can only assume that was a case where the info that they received was incomplete but they still deemed it useful.

I hope this helps,

Paul.

 

[thefizz]

Thanks Paul, yes it was IR film I was checking but as some times included film speed I thought it strange for some not to. I still think it's pointless providing dev times without film speeds. I have since done a little trial & error and have nailed down a good combination for Maco 820 Aura.

I ended up with dev time of 10 & half minutes in rodinal 1:14 exposing the film at 100ASA and making the necessary exposure adjustments for filters. Next I want to try Rodinal at a more dilute mix.

Peter

 

[BradS]

Thanks for your views Geert & Hans. I still don't understand why they show a dev time & temperature without any film speed but I agree about testing as some of the info on digitaltruth is a little off.

I hope that's a Leffe beer your having in you profile picture Geert.

I assume that this means that who ever supplied the dev times did not supply the information. In this case, I usually assume that they rated the film at box speed or try to cross refereence with other published data (or, ask here ). In anycase, all published dev times should be considered rough starting points which you refine to your own conditions, processing techniques, etc...

 

[thefizz]

I assume that this means that who ever supplied the dev times did not supply the information. In this case, I usually assume that they rated the film at box speed or try to cross refereence with other published data (or, ask here ). In anycase, all published dev times should be considered rough starting points which you refine to your own conditions, processing techniques, etc...

Yes that seems to be the case.

Thanks