Support our Sponsors, they keep FADU free:   AG Photographic   The Imaging Warehouse   Process Supplies   RH Designs   Second-hand Darkroom Supplies  

Notices

Go Back   Film and Darkroom User > Equipment > Darkroom

  ***   Click here for the FADU 2015/2014 Yearbooks   ***

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 24th March 2021, 11:19 PM
John King John King is offline
Friend
 
Join Date: Nov 2012
Location: County Durham
Posts: 3,318
Default Colour Printing Filtration Differences

I have two colour enlargers. One is an LPL 7700 and the other an LPL 6700 which you would reasonably think they were pretty similar. Both have colour heads and apart from the physical size they are pretty similar. The LPL6700 was donated by my son when he moved to live in Holland. The 7700 is mine from long standing.

The normal filtration I use on the 7700 is around 65Y 62.5M, give or take a few units either way.

I tried the 6700 tonight and set the same 'normal' filtration on the 6700 which resulted gave horrendously deep cyan tinted images. A reduction of 35 units in yellow and 40 units in magenta were needed to get even close to decent print. To get a perfect one there was a little more playing about and tweaking needed.

Two similar enlargers from the same maker, both with apparently the same 'Kodak Unit' filtration so why the extreme difference in the filtration needed. Both bulbs are new and the same transformer unit used.

Don't get me wrong, I can live with the reduced filtration - it makes for shorter exposures, I am just curious why there should be such a big difference.

I quite like the 6700 over the 7700, it is easier to focus and doesn't have the physical mass that the 7700 has, so it may become my main darkroom tool.

Last edited by John King; 24th March 2021 at 11:23 PM.
Reply With Quote
  #2  
Old 25th March 2021, 07:14 AM
GoodOldNorm's Avatar
GoodOldNorm GoodOldNorm is offline
Friend
 
Join Date: Oct 2009
Location: Lincolnshire UK
Posts: 1,227
Default

The filters can degrade from a lot of use so unless both enlargers were brand new I would not be surprised at some difference between filters.
__________________
"Tea is surely the king of all drinks. It helps against the cold, it helps against the heat,against discomfort and sickness, against weariness and weakness". Heinrich Harrer.
Reply With Quote
  #3  
Old 25th March 2021, 08:36 AM
Keith Haithwa Keith Haithwa is offline
Friend
 
Join Date: Feb 2017
Location: Yorkshire
Posts: 76
Default

John, I had a similar problem comparing the same two enlargers a few years ago so I decided to take a screwdriver and physically check the dichroic filter operating mechanism and 'bingo', all was revealed.
The mechanism was horribly gummed up with dried grease and sometimes the filters would move into the light path, other times they would only partially move and occasionally they wouldn't move at all. I would suggest you check your enlarger for this same fault.
As I understand it (and I may be mis-remembering), dichroic filters are made by depositing inert metal oxides on heat resisting glass and as such are not subject to fading by either heat (they reflect most of the heat back and therefore run much cooler) or light.
Reply With Quote
  #4  
Old 25th March 2021, 09:20 AM
John King John King is offline
Friend
 
Join Date: Nov 2012
Location: County Durham
Posts: 3,318
Default

Quote:
Originally Posted by GoodOldNorm View Post
The filters can degrade from a lot of use so unless both enlargers were brand new I would not be surprised at some difference between filters.
No so Norm. "Dichroic filter are incredibly stable and will not degrade for many years".

Not my words but repeated from book written by someone from Kodak, The 7700 head is newer than the 6700 so that should be the other way around if they had faded. They are not like multigrade filters which are coated plastic. The different colours are embedded in glass so will not fade. Very much like stained glass in church windows where the colour is created when the glass is made.

I have had them stick before but with mine it was the runners jumping out of the guide and once replaced all was fully functional again.
Reply With Quote
  #5  
Old 26th March 2021, 07:35 AM
GoodOldNorm's Avatar
GoodOldNorm GoodOldNorm is offline
Friend
 
Join Date: Oct 2009
Location: Lincolnshire UK
Posts: 1,227
Default

Quote:
Originally Posted by John King View Post
No so Norm. "Dichroic filter are incredibly stable and will not degrade for many years".

Not my words but repeated from book written by someone from Kodak, The 7700 head is newer than the 6700 so that should be the other way around if they had faded. They are not like multigrade filters which are coated plastic. The different colours are embedded in glass so will not fade. Very much like stained glass in church windows where the colour is created when the glass is made.

I have had them stick before but with mine it was the runners jumping out of the guide and once replaced all was fully functional again.
Good to know John, pleased you got it sorted.
__________________
"Tea is surely the king of all drinks. It helps against the cold, it helps against the heat,against discomfort and sickness, against weariness and weakness". Heinrich Harrer.
Reply With Quote
  #6  
Old 26th March 2021, 09:07 AM
John King John King is offline
Friend
 
Join Date: Nov 2012
Location: County Durham
Posts: 3,318
Default Filters

Sorry I haven't got it sorted, this was a while back when it jumped the guide. The filters on both are moving very smoothly and sweetly. Set at zero there is just plain white light, set at max filtration the colours darken as expected. The white light lever functions OK as well.

I have spoken to others who print colour using an LPL7700 and the filtration they use is about the same as myself. The 6700 is the one with the massive difference. Oddly enough, it works and works well and with less filtration the exposures are a good bit shorter.
Reply With Quote
  #7  
Old 26th March 2021, 09:54 AM
Keith Haithwa Keith Haithwa is offline
Friend
 
Join Date: Feb 2017
Location: Yorkshire
Posts: 76
Default

Quote:
Originally Posted by John King View Post
......The filters on both are moving very smoothly and sweetly. Set at zero there is just plain white light, set at max filtration the colours darken as expected. The white light lever functions OK as well.
With respect John you need to do a visual check on the filter mechanism itself, turning the setting dial does not give an accurate 'feel' as to how much the filters are actually moving, neither does the light on the baseboard.

The degree of filtration per colour is determined by how much of the filter is inserted into the light path and as I mentioned earlier I found mine to be intermittent due to gummy grease. I only do B&W printing and I'm sure that even minor variations here will be exacerbated when printing colour.

If you can be assured that the filters really are moving correctly then you have a proper mystery on your hands as by your words all the other variables are ok.
Reply With Quote
  #8  
Old 26th March 2021, 10:20 AM
GoodOldNorm's Avatar
GoodOldNorm GoodOldNorm is offline
Friend
 
Join Date: Oct 2009
Location: Lincolnshire UK
Posts: 1,227
Default

Quote:
Originally Posted by John King View Post
Sorry I haven't got it sorted, this was a while back when it jumped the guide. The filters on both are moving very smoothly and sweetly. Set at zero there is just plain white light, set at max filtration the colours darken as expected. The white light lever functions OK as well.

I have spoken to others who print colour using an LPL7700 and the filtration they use is about the same as myself. The 6700 is the one with the massive difference. Oddly enough, it works and works well and with less filtration the exposures are a good bit shorter.
have you tried switching bulbs from one to the other to check if the bulb is making the difference?
__________________
"Tea is surely the king of all drinks. It helps against the cold, it helps against the heat,against discomfort and sickness, against weariness and weakness". Heinrich Harrer.
Reply With Quote
  #9  
Old 26th March 2021, 10:57 AM
John King John King is offline
Friend
 
Join Date: Nov 2012
Location: County Durham
Posts: 3,318
Default

In the first post I said the bulbs are both new (within a few hours use of each other) and to make that amount of difference the colour of the raw light from the bulb would have to visible.

I have had the top cover off and inspected the filter movement and there was nothing different between all three colour filters. They all went right to the end of the travel vertically. From zero to 170 units and back again. There was no hesitation in movement both up or down. Even the grease on the cams that adjust the filters was fine. The springs that return the filters to the correct position were all intact and move normally

The only thing wrong that I found was the white light lever where it pushes onto the spindle, the plastic was cracked, but this has now been repaired. In any case it was still working but a bit wobbly! I did drop one of the tiny screws that hold the outer housing in place, but I am sure I will have one in my workshop from a piece of electrical circuit board that will fit.

I tried to call Rodney Bates the owner of Firstcall Photographic yesterday to get his take on the issue but he is away until Monday. Firstcall are the importers of LPL enlargers so he should know what may be causing the difference in filtration or will know someone that does.
Reply With Quote
  #10  
Old 26th March 2021, 05:37 PM
John King John King is offline
Friend
 
Join Date: Nov 2012
Location: County Durham
Posts: 3,318
Default The plot thickens

As I said I opened the lamp-house this morning and all appeared to be fine with the filters and gears working as they should.

This afternoon I went to do some colour printing but before I started, out of curiosity I compared the two enlargers side by side. With no negative in the carriers with no units dialed in, the colour was white from both heads. I turned the 6700 cyan dial up to 60 units and checked the colour density. I then did the same with the 7700 and the dial had to move to around 125 units before the visual density appeared equal. Like wise with the Yellow and the Magenta dials they were only about half or a little bit more when compared to the 7700. When all were checked at full setting, i.e. 170 units they all looked to be the same.
Reply With Quote
Reply
Support our Sponsors, they keep FADU free:   AG Photographic   The Imaging Warehouse   Process Supplies   RH Designs   Second-hand Darkroom Supplies  

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
'Simma Dot' Colour Printing help set pentaxpete Sale or Wanted 2 16th March 2021 01:06 PM
Colour Printing John King Colour printing techniques 9 11th October 2020 10:27 AM
Judging colour filtration John King Colour printing techniques 14 30th March 2017 08:52 AM
Colour Casts when printing CambsIan Colour printing techniques 26 9th January 2013 08:55 AM
RA4 Colour Printing pentaxpete Colour printing techniques 7 8th September 2009 07:49 PM


All times are GMT. The time now is 03:04 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.