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  #21  
Old 29th August 2012, 05:01 PM
Mike O'Pray Mike O'Pray is offline
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Ian I think I can picture the equipment you refer to in my mind's eye. I think I have seen it on e-bay. If I am right this is not the Comask which is all metal and has 4 white hinged lids on one side which will give four 4x5s or 2 x 5x8s with borders and on the other no hinged lids but a black metal border which can be lifted to give a 8x10 with or without borders.

I think you have one where the bits lift out and there are four pieces each side giving eight exposures.

By the way and if this complicates things then just ignore it but it is possible to cover all the colour casts with Y&M only and ignoring C altogether.

If C is kept at 0 then it can be used to increase exposure time by adding C( usually in units of 10). I think each 30 units of C adds the equivalent of a stop. If you need to do this then you need to add the same to Y&M to retain colour balance. So if balance is 40Y and 50M and you need a third of a stop add 10C and 10Y and 10M

Mike
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  #22  
Old 23rd November 2012, 10:26 AM
John King John King is offline
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Default Colour prints.

I have been processing colour prints for over 20 years using the RA4 process and there are several points which have not been brought up which may affect the colour balance. There are NO SET RULES to getting the correct balance. There are so many variables which can effect the end result so everyone will have to find their own preferences.

The enlarger, there are at least 3 different colour filtration values. Some are calibrated in Kodak Units (LPL which I use is one) then there are the Durst Units (Several enlarger makes use these) and then Leitz units used by the last of the Leitz enlargers. They are all different and this will show.

The film developing will also affect the colour balance too as will different makes of film so I try to stick to one make/speed, together with one make of C41 film developer which makes life a lot easier.

The paper you use will also throw up variables, one brand of paper may vary the balance from one box to another, admittedly not by much but enough to upset the colour balance. Not to say different makes will be totally different. I stick to FUJI because they come in separate sheets and not rolls.

The RA4 developer will also give differing results depending on it's age and how diligent you have replenished the bath (Using a deep tank) Using a Jobo or other kit where it is use once and dump will not be affected but then you have to ensure the drum is spotless each time or you will get streaking. Plus there is the possibility of temperiture variation and this will alter things yet again.

The age of the bulb will also make a difference, the older the bulb the warmer the light gets.

The use of Kodak viewing filters are a help but ONLY with Kodak filtration values and Kodak RA4 paper. They are a guide which way you need to alter the filtration with FUJI paper but you don't get the easy calculation factors of how much you need to alter the exposure by.

Assuming you have a set up where the temperatures are constant. Some RA4 devs are room temp (What is that meant to mean?) others 35C then can I suggest you standardise your process to cut down or minimise as many of the variables as possible.

I am not saying that the following is correct for everybody but my exposure/developing/finishing for colour printing using a LPL6700 enlarger with Fuji Superia 200 film is as follows:-

The normal filtration using FUJI Paper is around 20Y 15M (No cyan) This can and does change depending on the ambient light at the time I took the photograph.

Developed in Kodak Ektacolour RA4 developer in a Nova 12x16 deep tank which is replenished with fresh developer at the rate of 100cc's per every 80sq inches of paper developed. In other words 10cc per every 10x8 print. It doesn't seem to matter if you over replenish, just don't under do it.

Develop for 45 secs, stop bath for 30 secs, bleach fix for 45 secs to 1 min. Rinse the print or test strip, and because a wet RA4 print will be 'blueish' I view it under a daylight quality bulb only when it is dry. I use a cheap hair dryer for this purpose. The colour balance can be better assessed if you look at the mid tones rather than the highlights. If the scene happens to contain an area of grey tone this is perfect!

I use a DUKA colour safelight which is angled to give a reflected light off the ceiling (white) from about 8 feet away with the adjuster about half way so this factor has to be taken into account with my method.

If you have a difficult negative and we all do at some time, I cheat a little and make a small inkjet print which I use to compare the RA4 print against.

I have also successfully printed Kodak CN400 black and white film with a filtration of:- no yellow no cyan and 10 magenta. This gives a slightly sepia toned monochrome print.

At the end of every session, I replenish all the baths, replace the lids and then cover the top with cling film. This excludes any air getting to the developer. If the seal is good, when the chemicals cool down there is a partial vacuum formed inside the baths which can be seen when the Cling Film is sucked inwards. I have on occasion over the years used the same replenished bath for 12 months and only changed it when the tar deposits became to much.

The Colour filtration from the various enlargers as I said can be different, I have actually found 4 different scales and these are:-

Enlargers using Durst scales:- Dunco, Durst, Kaiser, Lupo.

Enlargers using Kodak scales:- Beseler, De Vere, Chromega, Fujimoto, IFF, Jobo, LPL, Omega,, Paterson, Simmard.

Enlargers using Agfa Scales:- Agfa, Krokus, Meopta

Enlargers using Leitz: Leitz only


As I said before these are my personal settings and method of working with someone else it will be as different as the Arctic to the Sahara!
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  #23  
Old 23rd November 2012, 07:20 PM
DavidH DavidH is offline
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I hope you don't take offence at this, but does the lever that takes out the filtration on the left hand side of your colour head work correctly? If anything has got a little stiff, it may be that dialing in filtration is something of a lottery.
A fellow Meopta user.
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  #24  
Old 23rd November 2012, 08:17 PM
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Argentum Argentum is offline
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Whilst I've never printed colour I rekon a lot of it is just a lack of experience which will come in time.

Also actually understanding colour theory helps a lot by which I mean knowing that something which is slightly cyan (and being able to recognise it) requires less cyan OR more Y+M. Or something which is slightly red requires more cyan OR less Y+M. Then when its slightly orange what do you do? i.e. you have to instictively know what to add or subtract and understanding colour theory makes that a whole lot easier to know whether you want to use subtractive or additive changes and which colours. Experience will increase your ability to make correct interpretations from a colour cast.

In the mean time get yourself a Colorstar 3000 if you can find one with all its bits, although doing without one might be a lot more frustrating in the short term, it would be a lot more educational in the long term.

p.s. there is a good thread over at apug about colour calibration

http://www.apug.org/forums/forum40/5...libration.html

using one of those gizmos to produce a mid grey neg gives you something to produce a grey print and hence some default filter settings that will be close even if you don't have a colorstar 3000

Last edited by Argentum; 23rd November 2012 at 08:40 PM.
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  #25  
Old 8th January 2013, 06:36 PM
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CambsIan CambsIan is offline
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I have not been in the darkroom for several months and have not yet tried any of the tips that have been given, but rest assured that they have all been read and appreciated.

New Years resolution is to spend more time in the darkroom in 2013, hopefully. Maybe family and work will have other ideas though!

Once again, many thanks to all who have offered advice.

Ian
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  #26  
Old 9th January 2013, 08:40 AM
John King John King is offline
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Quote:
Originally Posted by Jon Butler View Post
If your still seeing the base orange cast you need more filtration try 60/80
to start with and increase until untill it's gone. You then have to fine tune the filtration by using viewing filters.

All normal colour negative films have a orange base.

Don't worry, when you sort out colour printing it's much easer to get good results then trying to produce a fine print in B&W.
J.
Just a point about using viewing filters. If the person is using FUJI paper which is the only one available in cut sizes at the moment the viewing filters will be way out of calibration.
As far as I know only Kodak made viewing filters so they should be used only as a very rough guide to get pointed in the right direction.

I do agree about the ease of getting a good print compared to a fine art B&W
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  #27  
Old 9th January 2013, 08:55 AM
John King John King is offline
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Default Curing colour casts

Rather than using viewing filters which as I said before will be difficult with Fuji paper can I suggest the following:-

Get an easy negative to print, one that has no extreme highlights or really dense shadows or was taken in mixed light sources and print that to perfection - it only has to be a 5x4 size.

Once you have got this print make a permanent note of the filtration then with the same negative make another print but introduce 10 extra units of yellow. Then another with +20 units of yellow and another with +30 units of yellow.

Return the filtration to what it was then repeat the steps using +10 units of magenta then +20 and +30.

Now repeat all the above steps but reduce the units by -10,-20,-30 with each of the two colours and after drying keep them as a reference.

Prints should only be judged when they are dry because as you will have found out they all have a blue cast whilst the emulsion is wet I use a cheap hairdrier to speed this up. They should then only be judged in daylight or under a blue daylight quality bulb.

I have found that looking at an print overall will not give you a good idea of any colour casts, but concentrate on the shadows, the densest part will give the game away straight away. A good neutral blackis what to aim for.
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