Polapan 55 and reciprocity

greenspun.com : LUSENET : Large format photography : One Thread

I have recently tried the Polapan 55 pn. Great film! The problem of getting the right exposure is discussed here in several Q&As. I have had some good results exposing at ISO 32 and only compensating for bellows extension. I normally use a 500w tungsten lamp.

However, when it comes to longer exposures, the outcome varies, and I wonder if anybody can give some ideas about how too compensate the reciprocity? Thanks in advan

-- Einar Faret Saastad (einar.f.saastad@c2i.net), October 07, 2001


It very much depends on what is the results which you wan to achieve, you aim at a good positive 32 ISO is a good speed, if on the other hand you aim at a good negative, I'd rather expose for iso 25 but it depends on your enlarger as well. I'd like to put an extra question to you and the readers, and tha is can you expose for say 100 ISO and thefore develop longer or "warmer" or a combination of the two?, I've read opposite opinions about this and would like some direct experience reports. In some cases I've seen work of photographers where clearly the exposure exceeded the emulsion limits, how do they do that?

-- Andrea Milano (milandro@multiweb.nl), October 07, 2001.


I have successfully used PN 55 at times - it gives a negative with a distinctive tonality that can be useful in making a particular statement about a given motif.

The guidelines for speed and reciprocity I use are from Ansel Adams' book Polaroid Land Photography - no longer in print unfortunately. Tis is what he suggests and it has worked for me:

Suggested ISO = 50

Print ISO = 64

Negative ISO = 20


Metered 16 sec Factor 2X Time 16 sec

Metered 8 sec Factor 2.5X Time 40 sec

Metered 32 sec Factor 3X Time 96 sec

Metered 64 sec Factor 4X Time 256 sec

Expansion and contraction of development is possible within limits but I shall have to get back to you later on that.

Cheers ... WG

-- Walter Glover (walterg@netaus.net.au), October 07, 2001.

Sorry, obviously the table should read:

Metered 8 sec Factor 2X Time 16 sec

Metered 16 sec Factor 2.5X Time 40 sec

A message preview for checking spelling, grammar and typographical errors such as this would be a fine thing on this site.


-- Walter Glover (walterg@netaus.net.au), October 07, 2001.


On the subject of expansion or contraction of the tonal scale of P/N55 through variations in processing time, allow me to quote from the 'Film Characteristics' in Appendix B of Polaroid Land Photography by Ansel Adams:

"Effect of development changes: Essentially none, since the print and negative develop to completion. A very slight decrease of the base-plus-fog density occurred at 60 seconds (development). Insufficient development must be avoided, since it produces discoloration of the negative when it is exposed to light."

Elsewhere on page 47 he says:

"The use of development time changes to control values will have some effect with the print from either of these films (55 & 665). The negative, however, shows very little, if any, response to development time changes, except that a slight reduction in filmbase-plus-fog density will occur if development is extended, to about 60 seconds or more with Type 55.

"Under any circumstances, it is essential that adequate development be given to reduce completely the unexposed and undeveloped silver remaining in the negative. Otherwise, when the print is separated from the negative, silver which is still sensitive to light will be exposed and it may then add density or produce a discoloration in the low values (shadow areas) of the negative."

I hope that this helps with your pursuits.


-- Walter Glover (walterg@netaus.net.au), October 10, 2001.

Moderation questions? read the FAQ