Switch to English Language Passer en langue franÁaise Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,589   Posts: 1,545,938   Online: 1205
      
Page 4 of 4 FirstFirst 1234
Results 31 to 40 of 40
  1. #31

    Join Date
    Mar 2007
    Shooter
    Medium Format
    Posts
    123
    Rob, yes you are right I hadn't digested before I started my post; sorry.
    Tom, if your voltage is all over the place, and if you can actually see these changes in your light output they will be massive, you might as well throw the analyser in a skip. Between exposures the light temperature of the enlarger bulb will vary massively and the filtration dialed in from any test or analysis will be worthless. Sort your supply out first.

  2. #32
    Mick Fagan's Avatar
    Join Date
    Sep 2005
    Location
    Melbourne Australia
    Shooter
    Multi Format
    Posts
    2,841
    Images
    29
    Wow! What a lively discussion this is turning out to be. Firstly I must explain that whilst I have worked in a professional photographic lab, Iím not actually trained in things photographic, Iíve just learnt on the job, so to speak.

    Iíve had a bit of a think about this subject, I have been processing my own personal colour prints in my own darkroom since 1988, prior to that I did Cibachromes in the old 8x10Ē drum on the kitchen sink, plus a long forgotten Agfa colour process, that lasted about 4 years before it died.

    I have been, like most of you, on a continual learning curve, sometimes a reasonably expensive learning curve. Iíll set the scene, regarding what I know about some colour analysers.

    There isnít any electronic analyser that can give you correct colour, before you tell it what the correct colour is!

    In a nutshell, this is one of the major obstacles encountered by people new to colour printing. A person new to colour printing doesnít know what is correct, so they purchase an analyser to tell them what is correct, only to learn that they have to tell a machine something they donít know, so that it can work!

    There are quite a few different types of colour analysers I have used, with the exception of one type, all require you to analyse each colour channel one by one. This is quite doable, but trust me it can be tiring, as well as time consuming. The exception to the rule is the Original Jobo Color Star colour analyser.

    This analyser measures all three colours at the same time; I believe it is able to do this because it has three separate analysers working at once. The Color Star is so called because there is a star of coloured LEDís with two sliding levers allowing you to calibrate the analyser to a light temperature reading in literally 10 seconds. I believe the later 1000 Ė 2000 and 3000 Color Star analysers, work in the same manner. I donít know this, as I have never required any more colour analysing power.

    I have used quite a few different things to obtain reasonably easy colour printing, some were a help, and some were really helpful. Things finally started to come together after a telephone call one very late winter night to Bob Mitchell in the USA, this was 1996. The late Bob Mitchell was quite a darkroom guru, inventor, and photographer and also wrote quite a few very informative articles for Photo Techniques magazine, usually about colour printing.

    Bob had invented another useful gizmo; he called it a, ďColorbratorĒ. The Colorbrator is not a colour analyser. Rather, it is simply an accurate means for calibrating your analyser Ė hence the name: COLORBRATOR.

    IĎm not sure if the Colorbrator is still available, but if they are, get one. Basically it is an instruction booklet, with an actual colour corrected colour print stuck to the front cover.

    Included in the kit:- a special colour test negative, which will produce a trial print, which will display an organised array of 49 colours, an image D-Max display of 16 grey values and a special segment for skin colour.

    You also get a Neutral Comparator, which is a piece of grey card with a small hole at one end. By superimposing the comparator over your test print colour array, you can easily find a correct grey. The actual piece of colour array, which produced the perfect grey on your colour paper, is the piece that you tell your analyser is a grey you wish to produce.

    The Wallace Expo/Disc is a calibrated light filter diffuser, designed originally to turn your, in camera reflected light meter, into an accurate incident light meter, it does this perfectly. The accuracy of the Expo/Disc can be shown by the data sheet, which came with my 52mm Expo/Disc. The sheet tells me that the transmission, which is supposed to be 18% Ī 1/6 stop, had a deviation of 0.77 from these parameters, quite accurate for a cheap mass-produced item. The deviation of the colour transmission on my filter is:- .00 R .00 G .01 B which is basically nothing. It really is as true a grey, as you will get, for colour calibration.

    After a re-think for the less experienced colour printing fraternity out there, and especially for Tom, as he is the original person I responded to, this perhaps, may be a more clear set of steps of how to get quite reasonable, but extremely repeatable, colour printing accuracy.

    First and foremost, only use one type of colour negative film, develop it consistently, or get a lab that is consistent. Select one type and brand of paper, which means Fuji or Kodak. Select one type of paper chemistry. My personal experience with colour negative papers in my own home darkroom with Agfa, Fuji and Kodak papers regarding consistency, is that Kodak is the most consistent manufacturer out there.

    Assuming you either donít or cannot obtain a Colorbrator, you have to get a correct colour balance for your system somehow. I shot pictures with a Kodak colour chart and grey scale from one of the Kodak colour printing books in the scene. I selected a clear sunny day with the exposures taken either mid morning or mid afternoon. The reasoning for the time the shots were taken is to allow light to fall on my models clothing. Early in the morning or late in the evening the light travels through quite a lot of atmosphere and the colour temperature of this light, isnít what daylight colour films are balanced for. The angle of late morning, midday, to early afternoon light, doesnít allow the enough light to fall on my models clothing for me to get a reasonably good colour rendition in the darkroom.

    Take one or two frames of your model, then slide your Expo/Disc onto the lens, point the camera half to the sun and half to the blue sky. Have the camera on automatic everything, fire the shutter. I use aperture priority on my Nikon F3HP camera here. Take some more pictures of your model, this will ensure that your grey negative is in this section of frames. Develop the film.

    Next, take any of the frames with your model (or whatever) place it in the enlarger and somehow get a correct 8x10Ē colour print. View your print(s) under various types of light, tungsten, fluorescent and daylight. You will find that the print(s) that look quite good under all types of light are probably correct, or about correct, regarding colour balance. If you are happy with your print, then you are almost there.

    Set your enlarger filtration and timer, to what produced your perfect print. Which may have been 10 seconds at f8. Next do a colour contact of your roll of film, be that 135 or 120 using your exact same settings. You may find you have to pull or push 1/8 of a stop as this is a contact, not a projected print. So, to pull 1/8 of a stop expose at 9.2 seconds @ f8 or to push 1/8 of a stop, expose at 10.8 seconds @ f8. Once you have this contact sheet, you will be able to see subtle density differences between frames, this is a great help to the home darkroom worker.

    You should now have a very, very good enlargement of a single frame, plus a better than usual colour contact sheet, of your roll of film.

    Next, without changing any filtration, place the Expo/Disc negative into the enlarger and turn it on, place the analyser probe directly under the centre of the projected beam, open the enlarger lens so the maximum amount of light is projected. Turn all darkroom lights off, switch on the (in my case) Color Star analyser and slide the levers until all coloured LED lights are off. This has told the analyser the correct colour, note the settings. On my analyser I also have an exposure (density) setting. Close up the enlarger lens to the correct f stop, which in this case has been f8, slide the density lever until the time of 10 seconds shows, note that setting also.

    The next thing, is to test your system. Take a fresh roll of film, go out into the wild world and bang a few frames off. However, every time you have a new light situation, take a frame with the Expo/Disc attached in the middle of the session.

    Develop the film, then hit the printing department. First up, compose one of your images as you would like, then replace that negative with the Expo/Disc negative, slide the analyser probe directly under the centre of the projected beam, turn the enlarger on.

    Now, you should open the enlarging lens to allow the maximum amount of light to hit the probe. Ensure that the analyser settings are correct, you did didnít you? Turn all lights off, turn the analyser on, now adjust the enlarger settings until all the analyser lights are off, you have correct colour. Next, set the enlarger lens f stop to f8 and check the density reading on the analyser. This density reading could be anything from 5 seconds to 10 seconds or more. You have a few options regarding exposure. You can open the aperture, adjust the exposure, or add or subtract neutral density in your enlarger head, to arrive at a suitable time. Any of these should work without any problems. You could also print at what time the analyser suggested, this could be 8.4 seconds or 11.8 seconds or anything inbetween or outside this set of imaginary times. I have found very little to no colour changes apparent to my naked eye, when changing exposure times willy nilly, in a colour negative darkroom procedure

    Anyway, now you can whack in your award winning negative, focus, expose, develop, then sip on a mug of hot chocolate, whilst you are viewing a near perfect, first go, colour print!

    Mick.

    Ps:- Hopefully this works, it's Friday night after work and I sat down and did this in word in one hit, if it doesn't make sense, give me a hoy.

  3. #33
    Mick Fagan's Avatar
    Join Date
    Sep 2005
    Location
    Melbourne Australia
    Shooter
    Multi Format
    Posts
    2,841
    Images
    29
    Iíve just come in from a darkroom session and thought of a few things.

    Colour casts can be a devil of a thing to correct, even for experienced operators, I read this somewhere and copied it; it hangs in my darkroom, which is why I have just thought of it.

    If you have a cool cast, assume itís a blue cast, if a green print results from the correction, the original error was cyan, so filter out cyan.

    If you have a warm cast, assume itís a magenta cast, if a yellow print happens, the original cast was red, so filter out red.

    If you have a magenta cast, add magenta to make the print more green.

    If you have a yellow cast, add yellow to make the print more blue.

    If you have a cyan cast, remove magenta and yellow in equal amounts to make the print more red.

    If you have a blue cast, remove yellow to make the print more yellow.

    If you have a red cast, add magenta and yellow in equal amounts to make the print more cyan.

    If you have a green cast, remove magenta to make the print more magenta.

    Those are the basic colour corrections one makes for colour printing with colour negative printing.

    There is one other not so well known colour cast, blue blacks!

    If you have sort of good colour overall, but it doesnít look quite right, especially in the blacks, figure out how much paper your RA4 colour developer has processed, or how old it is.

    Old and/or exhausted RA4 developer will give you a blue-black colour in what should be black. By blue black, I mean that the blacks seem to have a bluish, or cold element in them, even when the print is viewed under tungsten light. Drop the developer bath, do another print, see what you get.

    Colour viewing filters are not an absolute necessity, but they really do help to ascertain to the trained and untrained eye, what kind of cast you have. Most people assume you require a colour corrected light source to arrive at the correct colour, or see what the correct colour should be. Well, basically and for absolute technical purposes, this could be true, I donít know, but it isnít an absolute.

    I have successfully arrived at a correct colour by some interesting methods. The best and cheapest one I know,is especially relevant when printing in daytime. I walk outside and use the sun as my light source, it is amazingly colour corrected for daylight temperature, would you believe. Doesnít work too well on cloudy days, but thems the breaks. If your print is going to be viewed under tungsten lights, colour correct it under tungsten lights, same goes for fluorescent lighting.

    How to use print viewing filters, this is my method. Assume we have a print with a known green cast, lying on the table under a kitchen fluorescent light. You view it and can see the slight cast in the white highlights, now you take a magenta viewing filter and quickly (with a flick of the wrist) place it between the print and your eye(s) then remove it before 2 seconds have passed.

    Do this flicking bit a few times and you will start to understand how at first your eye(s) see the correction, from green to white, then the correction disappears as your brain pulls in itís own automatic white balance system. You have to cheat your brain by only viewing the print through the filter for a very small amount of time, otherwise you cannot see what you are trying to see.

    When I used to use drum, or rotary processing, I used twice the amount of chemicals required to cover the paper. After processing, I dropped Ĺ the used developer and replaced with fresh, this was my technique to ensure I never exhausted the, sometimes-miniscule amounts of developer solution often used in rotary processing.

    Quite a few rotary, or drum colour print workers, use a pre-wash to get the paper ready to accept developer by doing a pre-wash, prior to developing. If your intention is to get a stabilised drum and paper temperature, because of your environment, that is probably a good idea. If the idea behind this, is for better processing technique, Iím not convinced it is really required. Having seen and used quite a few colour paper processing machines, from mini-labs through to 6í6Ē wide behemoths, I can say, I have never seen one where the paper is pre-washed to ensure better processing.

    That said, you can process your sensitive materials any way you wish, if it works, keep doing it, donít change, be consistent.

    Hope this helps a bit.

    Mick.

  4. #34
    Ed Sukach's Avatar
    Join Date
    Nov 2002
    Location
    Ipswich, Massachusetts, USA
    Shooter
    Medium Format
    Posts
    4,520
    Images
    26
    Quote Originally Posted by rob champagne View Post
    Unless the colorstar 3000 has built in recognition of 18% grey, ...
    For all intents and puroposes ... It DOES recognize a "middle" gray - (no, not precisely 18% - but cloe enough).
    Carpe erratum!!

    Ed Sukach, FFP.

  5. #35
    Ed Sukach's Avatar
    Join Date
    Nov 2002
    Location
    Ipswich, Massachusetts, USA
    Shooter
    Medium Format
    Posts
    4,520
    Images
    26
    I'm using a Nova tank system which seems far less precise than what I imagine a roller transport machine achieves.
    The usual C-41 ... or for that matter, E-6... Color processing is *FAR* less sensitive than "folklore" has it. I've made my share of "interesting diversions" , and MOST have very little adverse effect on the finished product.

    I may plug the Colorstar 3000 into the voltage stabalizer that came with my DeVere enlarger. The standard mains supply voltage when tested was around 250V with little load, and visibly drops (i.e. lights get dimmer) when an instant water heater or other heavy load is turned on.
    ???? Certainly, that would be of interest, but in the .... 14? ... 15? years that I've been using the Colorstar, I've never found the need for a stabilized power supply.

    I happen to have three (3) of these puppies. The uniformity of color balancing information is remarkable - VERY close, using all three. One, the eariliest model, will indicate an "overall" exposure of ~ one stop less. I suppose I could attempt a "correction" by fussing with the internal calibration ... but so far, the motivation to do so has not had anything like the required strength.

    Let me know if you can see any difference using a regulated power supply.
    Carpe erratum!!

    Ed Sukach, FFP.

  6. #36

    Join Date
    Mar 2007
    Shooter
    Medium Format
    Posts
    123
    as I posted earlier, I use a colorline not a colorstar but that does not require a stabilized supply. neither did my colorstar 1000 which languishes in a cupboard since I got the colorline. The later circuitry of the colorline is much more sensitive and accurate than the old 1000 but I have read that the later colorstars are more accurate than Jobo's german built colorlines, I don't know!
    The main point is that you need a stabilized supply to the enlarger. If this water heater is dipping your lights visibly then you could really do with a new supply to the enlarger, You are asking a lot of the stabilizing circuitry and they only compensate within still quite wide (for colour work) tolerances.
    Mick, thank you for your long and considered post. I do not feel the need to stick to one film or even one paper. The film issue is compensated for by using either grey tone calibration of the analyser or skin tones. I find there is always one thing in the picture that you must have right. Grey tarmac/asphalt road surfaces for instance look crazy with colour casts and skin tone of brides and models just have to be right. If you have a channel on the analyser set for these colours then the film you use is immaterial. The colour palette of the image will still vary from film to film but the analysed colours will be the same. I must keep stressing to those new to colour analysis, the analyser is giving you a filtration to give you a resulting colour on your print not measuring the colour of your negative. If the channel on your colorstar is set to London Bus red. then you could have a black and white negative in the enlarger. It would still zero on the filtration needed to make the print red.

  7. #37

    Join Date
    Mar 2007
    Shooter
    Medium Format
    Posts
    123
    Forgot to say. You do need to have a different channel for each paper but not each film.

  8. #38

    Join Date
    Sep 2002
    Location
    127.0.0.1
    Shooter
    Multi Format
    Posts
    604
    I apologize to the board for reviving this very old thread, but it is chock full of precisely the kind of information I need to get my Colorstar 3000 working with my Beseler Universal 45 light source on my 45 MXT enlarger.

    I'm going to try my hand at RA-4 printing again. I've finally got my Fujimoto CP-31 (plus washer/dryer unit and replenisher) up and running nicely, although I haven't tested it with color chemistry and prints yet. I thought I would do that today, but I ran into a problem. I bought a used Jobo Colorstar 3000, 8 channel version. I didn't get the calibration negatives with it. I did get a photocopy of the manual. I thought it was going to be easy to use it until I got to the part in the manual about calibrating it and programming the channels. EEK!

    Mick Fagin said it perfectly a few posts back:

    Quote Originally Posted by Mick Fagan View Post
    There isn’t any electronic analyser that can give you correct colour, before you tell it what the correct colour is!

    In a nutshell, this is one of the major obstacles encountered by people new to colour printing. A person new to colour printing doesn’t know what is correct, so they purchase an analyser to tell them what is correct, only to learn that they have to tell a machine something they don’t know, so that it can work!
    On top of that, the only paper I have to test with is some very old mostly unused (one is unopened) 100 sheet boxes of Kodak Supra III (N), Ultra III (F), and Portra III (E). It's not dated and I don't recall when I bought it, but it was a long time ago, so I'm sure it's no longer any good. Still, I figured it would be useful to let me work out the whole process of color printing, at least the mechanics, and to work out any kinks with my CP-31. Any calibration I might manage to achieve with this old paper will be useless, but I wanted to try.

    I guess I'll be shooting a gray card tomorrow, although after reading this whole thread, I'm not sure if I need it or not.
    Last edited by SkipA; 07-29-2012 at 11:34 PM. Click to view previous post history.

  9. #39

    Join Date
    May 2005
    Location
    Daventry, Northamptonshire, England
    Shooter
    35mm
    Posts
    6,974
    Calibration on a grey card neg as set out by the instructions is pretty well foolproof but I agree it isn't an easy read or a quick process. I found an article by Frances Schultz on the Colourstar 3000 useful.The link may be here on APUG or try a google if not.

    Calibrating on what is old paper may be fine if you have a lot of it but if you have to switch to Fuji paper then you'll have to re-calibrate again. Fuji paper in my experience requires quite different filtration from Kodak.

    Take your time, do not expect to be turning out a lot of prints in the first few sessions and enjoy the learning experience.

    Best of luck and enjoy yourself

    pentaxuser

  10. #40
    bvy
    bvy is online now

    Join Date
    Jul 2009
    Location
    Pittsburgh
    Shooter
    Multi Format
    Posts
    874
    Images
    36
    Isn't there one of these devices that is "self calibrating"?

Page 4 of 4 FirstFirst 1234


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  ó   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin