Rollei RPX 25 & long exposures

For some time I have used Foma 100 as my go-to long exposure film. It has atrocious reciprocity failure, which I take as an asset; I get two to three stops extra. Its reciprocity failure is well documented and I have a reliable conversion table for long exposure times.

But lately I have run into quality issues (scratches) that led me to consider alternatives. So far I am considering the Rollei RPX 25. It is a slow film, but not very popular and I have not been able to find much about it. From the Rollei range I know (and like!) only the Infrared.

Does anyone have experience with the RPX 25? How it performs in low light / heavy ND filter situations and is there a good table of reciprocity failure values?

Many thanks!

Fire said:

For some time I have used Foma 100 as my go-to long exposure film. It has atrocious reciprocity failure, which I take as an asset; I get two to three stops extra. Its reciprocity failure is well documented and I have a reliable conversion table for long exposure times.

But lately I have run into quality issues (scratches) that led me to consider alternatives. So far I am considering the Rollei RPX 25. It is a slow film, but not very popular and I have not been able to find much about it. From the Rollei range I know (and like!) only the Infrared.

Does anyone have experience with the RPX 25? How it performs in low light / heavy ND filter situations and is there a good table of reciprocity failure values?

Many thanks!

Click to expand...

I have it has in use often but never with so long times that reciprocity failure is of
interest.
The first Rollei RPX 25 / Retro 25 came from Agfa.
They were identical with the Agfa emulsion APX25 !
Than emulsion is every well documented
from Agfa you should get lot of datashieds as pdf from the net.

But never mind the emulsion they are using now is an other one.
Can't say the origin from mind now - but
there are lots of infos about to find simple. Just google!
In Rollei's side should be a pdf with datas shied from download area.
Just google to 10min. sure you find infos.
Sorry to have reciprocity datas not in mind - but it is an emulsion (even the new one) with very smal grain.
But in regard with CMS20,RolleiRetro80s (ISO40) it is not so far away as one could think due to ISO25.

with regards

Oh - sorry my smartphone doubt on my
syntax - but smartphone syntax made
more trouble to understand just one
sentence.
Total different words - hope you can read
it.

- have it had in use
- that emulsion
- is very well documented
- On Rollei's site

with regards

So I got your Info - sorry again - not in mind but in notes.
Your reciprocity is ok between :
1 -1/1000 sek.
AND I have a table of schwarzschild corection - it is a courve you can easyly
find your corections.
Must have it from Rollei but can't find
it there again.
Perhaps download Server is offline or busy.
Well - and it seams to be it comes from
Ilford - if that is correct - I've heart it
different 2 years ago.
You should have no quality problems.
Perhaps they changes production to Ilford within last 2 years.
My Rollei25 I bought 2014 (100ft 135)
and boxes of 5 120 film are as quality from Kodak - NO Problems at all.
Just look to download area at Rollei to
get conversation courves due to
schwarzschild.

Bon Chance

You should be able to find the English translation of the Rollei RPX 25 data sheet here:

http://www.rangefinderforum.com/forums/showthread.php?t=153582

I put an English version of the RPX datasheet on one of my sites, here:

http://www.atwaterkent.info/Images/Datasheet_Rollei RPX 25_aug English_245.pdf

-----

But to the original problem...

Why don't you use Fuji ACROS film?

It requires zero reciprocity correction out to 120 seconds, and
only 1/2 stop from 120 seconds to 1000 seconds.

Developed in Rodinal 1:50 it's absolutely marvelous.

It's the only film I shoot in 35mm, 120, and 4x5.

- Leigh

Thank you for your kind comments.

I have searched for the datasheet on Maco direct (my source for all info Rollei) but it is not listed there - https://www.macodirect.de/en/film/black-white-films/1859/rollei-rpx-25-roll-film-120. The Flickr group for RPX 25 has 83 members (84 after I joined) and so I rather asked here.

I will check the recommended downloads.

As for the Fuji Acros recommendation, I agree that it is a sweet film and pairs nicely with Rodinal. I shoot it in medium format and develop in 1+50 APH09, and can not praise the combination highly enough.

But in my specific situation I do not aim for low reciprocity failure, but high reciprocity failure. I want expositions running in minutes, and when shooting Acros in broad daylight even a ND1000 filter is not enough to take me over a minute. It is rare that a high reciprocity failure would be considered an asset, but it is so in my case.

Fire said:

Thank you for your kind comments.

I have searched for the datasheet on Maco direct (my source for all info Rollei) but it is not listed there - https://www.macodirect.de/en/film/black-white-films/1859/rollei-rpx-25-roll-film-120. The Flickr group for RPX 25 has 83 members (84 after I joined) and so I rather asked here.

I will check the recommended downloads.

As for the Fuji Acros recommendation, I agree that it is a sweet film and pairs nicely with Rodinal. I shoot it in medium format and develop in 1+50 APH09, and can not praise the combination highly enough.

But in my specific situation I do not aim for low reciprocity failure, but high reciprocity failure. I want expositions running in minutes, and when shooting Acros in broad daylight even a ND1000 filter is not enough to take me over a minute. It is rare that a high reciprocity failure would be considered an asset, but it is so in my case.

Click to expand...

You should not use my intention for a special shooting I am planning or already
have under construction.Fire

In my shooting the reciprocity failure is a
help with ND 1000.

But seriously - fire : Good Luck !

I have not used the film yet but a German photographer how had tested it extensively wrote in his review on Aphog that the reciprocity failure was rather high, so I would recommend Acros for your night shots as well.

I suppose I have not been clear about "long exposure" photography I had in mind. Not night shots, but daylight shots with heavy ND filtration. Usually with moving water. In conditions like these a strong reciprocity failure is not a problem, but actually an asset - I want to have my shutter open for as long as possible!

Thus Acros is to be avoided, and an ASA 25 film with significant reciprocity failure looks intriguing.

This is the kind of shots I am after:

I had downloaded the English translation of the Rollei datasheet; thanks for sharing! There are some reciprocity failure data points, but rather unusual - I mean, what sort of exposure time is 10 seconds? Isn't it supposed to be either 8 or 16 seconds:

The points at the chart do not correspond to the quoted times either.

But I took the data points, crunched them in my trusty R Studio and came with an equation that seems to fit them rather nicely.



Now the big question: time to apply all this in practice!

Fire said:

I suppose I have not been clear about "long exposure" photography I had in mind. Not night shots, but daylight shots with heavy ND filtration. Usually with moving water. In conditions like these a strong reciprocity failure is not a problem, but actually an asset - I want to have my shutter open for as long as possible! Thus Acros is to be avoided,and an ASA 25 film with significant reciprocity failure looks intriguing.

This is the kind of shots I am after:

I had downloaded the English translation of the Rollei datasheet; thanks for sharing! There are some reciprocity failure data points, but rather unusual - I mean, what sort of exposure time is 10 seconds? Isn't it supposed to be either 8 or 16 seconds: The points at the chart do not correspond to the quoted times either.

But I took the data points, crunched them in my trusty R Studio and come with an equation that seems to fit them rather nicely.

Now the big question: time to apply all this in practice!

Click to expand...

Glad to see you are planning "water shots" - I need the reciprocity failure because I am much over 1 min.
(Daylight of cause)
Notice Fire : As I see you followed the
recomandation from the datas given at
Rollei's side.
They stated you have to extend the courve to times you need - am I right?
Ok - now we are in concern to
"curve discussion" .
I was no genius in mathematics but
I remember these curve discussions. ..
from school. .....!!
As I know scharzschild you have to add
the time.
In other words : When you have very long
exposure times the sensitivity of your
emulsion goes down in a logaritmic function.
The exposure times you have to add wiĺl
expand more and more.

Hope it is not in wrong direction but it is
quite logical and I have it in mind so to many years.

THAT have nothing to say...hmmm.

So back to photographic practice :
You should have an exposure series.
Like : 50sek./1min./1min10./1min20./
a.s.o.
Back in darkroom you look at results.
At least I would have a look on the
curve to check If your curve is correct.

with regards

I forget to say : If the extention of your
curve is correct you have following
adjustments in time - look to your curve:
You want an exposure of : 2min - ok?
The curve (within adjustments) at 120sec. showes quite clear a messured
time of : 37sek. this is your basis of
aperature setting!
Exposure time to your shot is 2'00"

everything clear fire?

with regards