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  #1  
Old 20th November 2019, 10:37 AM
John King John King is offline
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Default Last one -I think

I do believe that I have just bought the very last available bulb, brand new and in it's protective casing for a Duka50 colour safelight. (Sodium Vapour)I am not saying how much I paid for it, but it was WELLunder the last advertised price for a new one which was listed around at £180 or so. It was cheaper than a good used, working replacement complete DUKA with a bulb that had unknown usage.

With my old bulb I had noticed that the time needed by the bulb to gain maximum brightness had increased significantly, nor was it as bright as it had been when the max brightness had been eventually attained.

Add to that I was not 100% certain the light given out was still safe to use with Colour RA4 paper. as I had a degree of fogging in the highlights which had only just started to appear despite the lamp being in the same position as it had been for years. Not bad though for a bit of electronic kit 35 years old.
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Old 20th November 2019, 10:58 AM
Lostlabours Lostlabours is offline
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John, that sounds expensive.

I've bought 2 colour safe lights in the last 2 or 3 years, both Kodak Beehive housings and less than £5 each, a Wratten 10 and a 10H. These use 15w bulbs and there are LED equivalents.

Of course I have other Wratten filters I can use with them as well like an OC (same as Ilford 902) for MG paper.

Ian
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Old 20th November 2019, 10:59 AM
Anon01 Anon01 is offline
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Surely a new safelight ???
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Old 20th November 2019, 11:58 AM
John King John King is offline
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No these safelights are purely designed for colour printing and because they are using a Sodium Vapour bulb the colour paper is 'blind' to that wavelength of light and you can work in relatively high levels - enough for me to read print if I really need to.

Yes I can use my beehive safelight but they are no good whatsoever for colour printing. Oddly enough they are not recommended for Multigrade paper so they also supply a red filter to go over the light window so MG can be used. They really were the Rolls Royce of safelights

No Cannik new DUKA safelights are no longer made.

Last edited by John King; 20th November 2019 at 12:03 PM.
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Old 20th November 2019, 12:39 PM
Lostlabours Lostlabours is offline
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John, the Wratten 10 and 10H safe-light filters are for Ektacolor papers. I use them for indirect illumination, or rather direct illumination of my darkroom stop clock when processing in my Nova tank.

I had a large Kodak sodium vapour lamp red safe-light a few years ago and ended up rewiring it switching it to two tungsten bulbs and a dimmers switch.

Are there no alternative (cheaper) Sodium vapour lamp bulbs the DUKA50 could use ?

Ian
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Old 20th November 2019, 04:40 PM
Mike O'Pray Mike O'Pray is offline
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Most on Photrio seem to use a Thompson Sodium Safelight which sounds as if it should use the same kind of light but there is the problem of voltage and possibly fitting plus import duties etc .

However given the price and scarcity of the bulb for the DUKA I have often wondered if the bulbs are the same. None of the users of the Thompson Safelight seem to comment on the price of the bulb so I assume that in the U.S. both price and scarcity is much less of a problem or may not even be a problem at all

Mike
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Old 20th November 2019, 05:00 PM
John King John King is offline
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Default Sodium Vapour lamps

Quote:
Originally Posted by Lostlabours View Post
John, the Wratten 10 and 10H safe-light filters are for Ektacolor papers. I use them for indirect illumination, or rather direct illumination of my darkroom stop clock when processing in my Nova tank.

I had a large Kodak sodium vapour lamp red safe-light a few years ago and ended up rewiring it switching it to two tungsten bulbs and a dimmers switch.

Are there no alternative (cheaper) Sodium vapour lamp bulbs the DUKA50 could use ?

Ian
No, not as far as I can tell, the shape is important because the plug in socket is quite a tight fit as well. Plus it is a completely unique base fitting with nothing else like it. Made by Osram to a specification designed by Kaiser. No one else made them.

I am quite happy with this bulb, actually it is not that expensive compared to what it was when they were readily available. If this one lasts as long as the original, that will see me out.

(Have you seen the prices of bulbs used in digital projectors? they have a far shorter life and can cost up to £200 each!!!)

I am used to it and prefer to use something with a good track record and if I know an exposure is going to be a long one, I can reduce the light emitting from the lamp by adjusting an internal baffle.
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Old 20th November 2019, 05:37 PM
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Bob Bob is offline
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If the lampholder has a special base type then it should be possible to replace it with a standard type given sufficient quantities or gaffer tape, string and Araldite... Any low pressure sodium discharge lamp should emit on the same wavelength so hacking a lower-cost replacement should be simply a matter of changing the lamp holder (he said...).

However, there may be something special about that Duka lamp as the unit also has a red filter for B&W - but checking their spectrum online, low-pressure sodium lamps do not emit anything detectable down there... Odd.


[Edit: I just counted the number of "should"s - that's not inspiring confidence even in me... ]

Last edited by Bob; 20th November 2019 at 05:54 PM.
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Old 20th November 2019, 06:48 PM
John King John King is offline
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Nor me either. Anyway I have the replacement on the way and it should arrive in the morning.

Some things I can do a 'bodge' and live with it, but given the cost of colour paper and chemicals I would rather have the correct equipment. Apparently it does run quite hot so gaffa tape string and araldite may not quite meet the needs.

My biggest problem will be actually removing it from the wall at the back of the darkroom because it is actually quite inaccessible. Put there because it gives good shadow less reflected light onto the other end of the workbench (away from the enlarger). Even with a set of step ladders it is quite a stretch.
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Old 21st November 2019, 04:02 PM
John King John King is offline
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Default New Bulb

I arrived today and it is nothing like I anticipated. The base has 9 quite long pins each slightly offset so the bulb can only go in one way. The glass part of the bulb is about 4" long by about 3/4 inch wide and perfectly parallel all the way from base to the top.

The actual bulb itself is in a separate glass envelope inside the outer one and appears to have a translucent copper coloured coating on the inside. The filament, if you can call it that, is like no other filament I have seen and appears to go into and out of three separate glass 'blobs' inside the envelope

You have to partially dismantle the lamp holder to fit the bulb and to do so the plastic frosted outer cover on the case front must come off. The baffle lever has to be disconnected. and the cylindrical baffle which shrouds the fixed internal baffle has to be pulled off the support. It is fun trying to get it back in the right place!!! NOT!

Attached to the outer edge of the lamp shell (on the inside) is what looks like a ballast resistor connected by wire to the base of the lamp case.

When tested, it warmed up noticeably quicker than the old one and with the baffles completely open it was also quite a bit brighter as well.

I doubt very much if there is anything else even vaguely similar in construction that could work or be adapted to do so which will account for it's high price.
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