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  #1  
Old 30th April 2020, 12:09 AM
Nat Polton Nat Polton is offline
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Default Wotan Duka 50 Colour Safelight.Instructions.

I have just been reading about Duka 50 safelights being OK for colour printing.
Trouble is a lot of writers leave out the details of using one correctly.
I have a few questions.
Are they left on all the time, or just a few seconds occasionally?
I have also read they need time to warm up to a correct safe light condition. True?
Are they for direct or indirect illumination?
What distance must they be from the light sensitive materials?
Which colour papers are they safe with? Especially Fuji Crystal.
Is there a copy of the makers instructions on line, and if so where?
Anyone that uses one for colour regularly ever found a source of replacement lamp bulbs for them recently?
Cheers All.
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  #2  
Old 30th April 2020, 09:17 AM
John King John King is online now
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Default Duka Safelight

Nat,welcome to colour printing.

I have used a Duka since 1991/2 when I started colour printing and without one I would give up RA4, it makes the job so much easier. You mention a DUKA 50, Don't get me wrong, but I ask because if you have misquoted and you have DUKA 10 they are not suitable for colour.

You will have seen that on the rim there is a scale with a moveable knob underneath and this mechanically controls the level of light that is allowed to be emitted.

The safelight takes about 5-8 mins to warm up and get to the full power so it should be switched on before you start to work and NOT switched off during the session unless you are leaving the room for a break. It is also possible that extra switching on and off will reduce the life of the bulb.(Unconfirmed)

The position of the light is quite important and for best illumination it should be fixed on a wall behind you so you are between the lamp and the enlarger The lamp house needs to be swivelled upwards so it reflects of a preferably white ceiling. This way you are working in your own shadow and less light hits the sensitive surface of the paper but it is enough to work by

My darkroom is about 8 feet across so the distance the light has to travel is around 10 feet but obviously very indirect. I have the sliding output set at 9. It will take you eyes about 2-3 mins to accustom to the reduced light level with the room light off and the safelight on.

Out of preference I use Kodak Endura paper, but have used Fuji with my DUKA at the same settings. Although Fuji is slightly faster than Kodak I have not noticed any significant fogging, so long as the total exposure when the paper is out of the box is kept to no more than 10 seconds. Obviously this does not include the exposure time (Another reason why I work in my own shadow). When you take a sheet of paper out of the box, it is a good move to place the paper face down on the easel until you are standing in front of the enlarger.

There are now no know sources of replacement bulbs anywhere! I bought one as a spare after a long search around a year ago which I think must have been the last one in UK. To be quite honest they are VERY expensive at £90. Are they available anywhere else in the world - I don't know. If the bulb goes, you will have to buy another replacement lamp 2nd hand, unfortunately the old housing will be scrap. (Or kept in case the transformer goes).

As far as I am aware there are no instructions on the web, what I have described here is from personal experience. In fact I cannot remember getting any when I bought my safelight new. If you have not done colour printing before you will have a few disappointments before it eventually 'clicks' and it becomes 2nd nature.

One big hint! after developing and fixing the print, it has to be fully dry before you assess the colour balance as there is a significant colour shift from when it is wet. I use a daylight LED bulb with a colour temperature of 6500degrees Celsius. Even the blue tinted daylight bulbs are still too warm to be fully accurate.

With a Duka you can also print B&W with the setting fully open without fear of fogging B&W paper, even Multigrade.

I have sent you a PM.
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  #3  
Old 30th April 2020, 10:19 AM
alexmuir alexmuir is online now
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I think John has covered all the questions. I am sure I have the original instructions somewhere. I will try to locate them. As far as I recall, they donít say very much.
One point that caught me out early on was the very dim light the unit emits when initially switched on. I thought it wasnít working. Iíve never needed, or tried to source a replacement lamp, but I did buy a second complete unit as a backup. Itís still in storage. The original, bought secondhand, has worked for about 10 years. I only use mine for B&W.
Alex.


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  #4  
Old 30th April 2020, 10:29 AM
Mike O'Pray Mike O'Pray is offline
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Nat, John has covered it very well but there may be some confusion in the difference between the DUKA 10 and 50. I have the 10 and it does colour OK It uses the same sodium bulb which as John has said may be now impossible or almost impossible to source.

In fact there was an earlier thread on this on FADU in 2010 started by Alex Muir. Look for what Alex has titled Kaiser DUKA 50 Safelight
The 10 is an earlier version of the 50

In that earlier post someone mentions a DUKA 5 having only a fluorescent tube and being suitable for B&W only but I cannot comment on the accuracy of this. This might be the one that John is thinking of

John, mine which is the 1O has two sliders on the top of the lamp. It has been some time since I used it but I assume that the slider further from the front and which clicks as you move it, is the one that sets the max intensity via a dimmer system and the smooth sliding front most one sets the cover which at ots lowest setting almost covers the bulb

So in summary the back clicking slider sets an electrical dimmer system so that for instance a setting halfway along sets half power and the smooth slider controls how much of the bulb shows so at 50% power you can set the slider at minimum coverage of the bulb so that min coverage at 50% or set the slider at max coverage which gives you all of the 50% of the power you have set on the dimmer slider

Does the DUKA 50 have both of these slider?

Not strictly relevant to Nat as he is looking at the DUKA 50 but still germain, I feel, to how the DUKA's controls work and not worth starting another thread for

Thanks

Mike
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  #5  
Old 30th April 2020, 10:30 AM
Nat Polton Nat Polton is offline
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Thank you John, you have answered everything very thoroughly.
I did a lot of colour printing, slides and negatives in the nineties then photography stopped abruptly as work changes suddenly upset my daily routine.
Colour for me in those days was all done in the dark until the paper had been loaded into the drum, then on with the lights.
I have bought a second hand 8x10 Nova slot tank and intend using it solely for colour prints. I tried a dry/wet run in the dark and figured I could manage ok . Then I started reading about the Duka 50 and thought that's for me.
Travelling about before lockdown I saw a few, not many, in photography shops. So there appears to be no shortage of viable second hand Duka 50s.
I won't be doing any for a couple of weeks yet as household circumstances have changed. I now have the box bedroom for a darkroom. No running water but permanently blacked out and central heating. Luxury!

Thanks again John
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  #6  
Old 30th April 2020, 10:40 AM
John King John King is online now
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I have just done a web search for an original bulb - Wotan NA10FL and there are seemingly non to be had world wide There are however seemingly plenty to be found second hand on Fleabay, and SDS and Mr Cad.

However when looking for something else, I have found one in my cupboard of forgotten bits and pieces which I had put away years ago when it stopped working. I remember now that this was because a wire on the inside of the removeable outer cover had become detached.

As the bulb has this removable outer cover, I can get to the wire and re-solder it to the point it was originally fixed on. Getting the working bulb out to test it after repair is not the easiest thing to do. The base of this lamp has about 10 pins which will only fit in one way and that is more difficult than you think because they are thin and easily bent.

A job for a wet day I think. Mind you at the moment with the restrictions it doesn't matter what sort of day it is.

Last edited by John King; 30th April 2020 at 10:44 AM.
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  #7  
Old 30th April 2020, 10:56 AM
John King John King is online now
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Default DUKA Dimming

This is a simple mechanical link inside via an arm connected to a cylindrical drum shaped baffle with tall triangular slits. That sits over another slimmer drum with rectangular shaped openings.

Set the lever to full power, i.e. at its brightest. and the triangular openings are fully over the rectangular openings.

Move the lever to the opposite end of the scale and the triangular openings gradually close the light slots, so eventually all light is stopped although it is still switched on.

Mike, like yours, mine has two similar levers but I have never used the lower one so quite honestly I don't know what it's effect would be!

You have set me thinking!
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  #8  
Old 30th April 2020, 11:24 AM
Mike O'Pray Mike O'Pray is offline
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Quote:
Originally Posted by John King View Post
This is a simple mechanical link inside via an arm connected to a cylindrical drum shaped baffle with tall triangular slits. That sits over another slimmer drum with rectangular shaped openings.

Set the lever to full power, i.e. at its brightest. and the triangular openings are fully over the rectangular openings.

Move the lever to the opposite end of the scale and the triangular openings gradually close the light slots, so eventually all light is stopped although it is still switched on.

Mike, like yours, mine has two similar levers but I have never used the lower one so quite honestly I don't know what it's effect would be!

You have set me thinking!
Thanks John So just to be clear the slider you are talking about that you use is the front one that has a kind of a raised portion on it for holding between say thumb and index finger. This one slides smoothly.

My back one is a flat knurled one that clicks as it is moved and gives off a ratchet-like clicking sound

On your DUKA what is this clicking flat slider set at? Incidentally my scale goes from 0 to just of 35. Is yours the same

Thanks

Mike
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  #9  
Old 30th April 2020, 11:28 AM
Nat Polton Nat Polton is offline
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John, Alex and Mike, thank you all.
This is getting very interesting indeed.
Cheers.
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  #10  
Old 30th April 2020, 12:07 PM
John King John King is online now
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Mike. The one at the front (closest to the screen) is the only one with numbers and I have it set at 9 for colour printing. When I do B&W the slider is fully open.

As I said I have never moved (as far as I can remember) the rear slider but have done so just now and it does seem to have a ratchet inside. I am printing this afternoon, so when the light has warmed up I will check to see if it makes any change. You learn something every day.

Watch this space
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