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> Dever 507 dichro head multigrade |
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#1
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Dever 507 dichro head multigrade
Hi all,
My dichro head is running out of control using filters for multigrade. With two filter method i get exposing times of aprox 30 sec. using grade 2. Going down to grade 1 it takes 10 times more and I don't really think that's ok. Now I use multigrade filters below the lense. Do filters age? What do so think can I do?
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"I’m not interested in a Walt Disney view of the world, I’m interested in the reality of it." Joe Cornish |
#2
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Filters definitely do degrade Martin.
I wasn't getting the full range of tones in recent work, so invested in a new set of Ilford's MG filters recently. A full new set was too expensive for me, and as I rarely use 1/2 grade filters, I bought the student selection of just full grades from Ilford directly, as shops wanted me to order about a minimum of 100 sets! They only cost me about £10. I substituted the new filters, after trimming them to size, into the holders easily and am looking at trying them out soon. But, looking at the old ones and the new ones next to each other, there's a very big difference in colour and density. So as I said, yes filters do degrade and I can only imagine that the ones in dichro heads do the same, unless anyone knows otherwise? Terry S |
#3
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Bulbs also "degrade" leading to much longer exposure times. I know this because my Durst Multigraph measures and calculates the exposure taking into account the "aging" of the lamp.
In all honesty, the factors you're describing, I would have thought it was more due to a weaker light source. The filters would have a greater impact on contrast rather than the exposure surely?
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MartyNL “Reaching a creative state of mind thru positive action is considered preferable to waiting for inspiration.” - Minor White, 1950 |
#4
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Quote:
Martin, I think the suggestion regarding the lamp may be a better route to explore as lamps do lose power and change colour temperature over time. However the time difference is larger than I would expect from just that. Have you checked the filters are moving correctly in the head and the cyan is not coming into play thus adding neutral density? Have you also checked the pins on the lamp base and in the holder as you get a build up of corrosion which can have an intermittent effect but that is unlikely to affect one grade and not others? They are both worth checking and cleaning though. Bill Last edited by Bill; 13th June 2020 at 02:39 PM. Reason: Additional information. |
#5
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Martin I would agree with Bill about dichroic filters so yes there is something else at fault. It may be possible that as you turn the Y and M dials the filters are not being moved properly or are sticking. It might be worth checking. The check is simple. Just turn each dial and see if the colour on a white easel changes as you do it.
Really Bill has covered everything. Best of luck finding the problem and solving it Mike Mike |
#6
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Only other thing not covered that I can think of is to check the dichroic filters for dust.
As others have said, dichroic filters do not fade. They use a series of stacked coatings to generate interference effects to pass the required colour and reflect the unwanted ones. Both the way they are made and the fact that they reflect rather than absorb the unwanted light (including the heat) makes them almost unfadeable (if that were a real word!) in normal use as long as the coatings are intact and are not physically damaged. I imagine there are exceptions to this rule if they are badly made and the coatings have separated or similar, but I think the general rule holds true. Last edited by Bob; 13th June 2020 at 04:29 PM. |
#7
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It sounds like a bulb issue, rather than the filters. Do the bulbs have a mirrored reflector, or are there mirrors, or other glass elements in the light path? It would be worth checking the condition of the bulbs, and all parts the light passes through, or bounces off, to make sure they have not deteriorated. Some diffuser heads use a lining of white polystyrene foam which can also cause issues when it ages.
Alex. Sent from my iPhone using Tapatalk Pro |
#8
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Quote:
But since the original question post and then my reply along with others, I have done quite a bit of reading about dichro heads and filters. Apparently they are not susceptible to fading like the under lens focusing. So that told me!! Anyway, as I asked for info from people more knowledgeable than myself about the subject, comments have been forthcoming and the poster of the OP should now be a lot more informed. Note to self: Only post replies to things that you actually know something about and not make assumptions!! Terry S |
#9
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That's one of the things which makes this forum so special, Terry, the absence of trolls. Long may it stay this way!
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MartyNL “Reaching a creative state of mind thru positive action is considered preferable to waiting for inspiration.” - Minor White, 1950 |
#10
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I'm not sure if all DeVere colour heads are the same - but I have a Mk4 504.
When I lift up the panel in order to change the bulb, I can see the dichroic filters and if I adjust the YMC dials I can see each one moving in turn. Check yours are individually moving freely and one is not dragging the others along for the ride, so to speak. The effect of adding the other filters in to the mix is to act an a neutral density filter. It is only a 60 second job is you can lower the head to be able to peer in to the bulb chamber. Martin |
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