Is a Janpol enlarger lens capable of getting the filtration for RA-4 direct positive?

arnoud bakker

Member
Joined
Jan 10, 2019
Messages
40
Location
netherlands
Format
Multi Format
hello all,
I was wondering if a Janpol color enlarger lens was capable to filtrate light, so it can be useful for the RA-4 direct positive process?
anybody? best regards! Arnoud Bakker.
 

koraks

Moderator
Moderator
Joined
Nov 29, 2018
Messages
22,764
Location
Europe
Format
Multi Format
I understand (but have not used) the Janpol lens to be a lens with an integrated and adjustable dichroic filter stack intended for color negative enlargement. As such, it can be expected to perform the same or similar as a regular dichroic enlarger head. I understand that only two filters can be used at the same time, but this should be OK since you technically never need all three anyway. Looking at the filter adjustment range, I'd expect you have enough filter room for this particular purpose. You may experience some benefit from adding a blank piece of orange-masked C41 film to the light path to bring the filter corrections closer to what the RA4 paper expects.
 

MattKing

Moderator
Moderator
Joined
Apr 24, 2005
Messages
52,890
Location
Delta, BC Canada
Format
Medium Format
IIRC, one of the reasons that almost all dichroic colour heads include a cyan filter adjustment is that with Cibachrome/Ilfochrome and Kodak R (print from slide) prints, sometimes it was advantageous/necessary to use that cyan filtration.
So your question is a good one.
I don't know whether @koraks suggestion will help, or hurt .
 
OP
OP

arnoud bakker

Member
Joined
Jan 10, 2019
Messages
40
Location
netherlands
Format
Multi Format
it is just an 20 euro guess... and worth trying..
guess I'll change the 80 mm lens parts for 150mm (or more )
everything to make it simply work outside.. and..... it does not have to be perfect..
 

brbo

Member
Joined
Dec 28, 2011
Messages
2,101
Location
EU
Format
Multi Format
That's the spirit!

If it works (no additional filtering needed and the filtering part of the Janpol color lens can be fitted to other lenses that can cover LF) it will simplify direct RA-4 considerably.
 
OP
OP

arnoud bakker

Member
Joined
Jan 10, 2019
Messages
40
Location
netherlands
Format
Multi Format
I just placed a bid on eBay, and sooner or later there will be a Janpol
I do have paper, although the inventation is nice and I'll drop by soon!
 
You must log in or register to reply here.
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…