[pure-silver] Re: New color head "discoveries"
- From: "Ole Tjugen" <oftjugen@xxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Fri, 14 Jan 2005 22:34:09 +0100
Again the cheap little EM-10 is a great tool: It gives consistent readings
all the way from 200M to no filter to 200Y to 60D on my Meopta Colour
head, and also gives consistent readings when I use the other enlarger
with blue and green hand-held filters. With any filter or combination, a
reading of 85 gives near paperwhite at 10 seconds exposure on Ilford MG.
Ole Tjugen
On Fri, 14 Jan 2005 15:39:45 -0800, Dave Valvo <dvalvo@xxxxxxxxxxxxxxxx>
wrote:
> Bob, if you use the PC filters, either Ilfords or Kodaks, they are
> balanced
> for exposure so as one changes from -1 to 3.5 (filter label) there is no
> need to change exposure. When changing to 4 and up simply increase
> exposure
> by one stop.
>
> But when someone uses dichroics ..there is only one M filter and one Y
> filter. To go from 10M to 100M more filter is added to the light path
> which
> reduces energy and requires more exposure. This is called a subtractive
> system. Ilford made an MG 500 head enlarger that is additive. Blue and
> Green light is used and by pushing PC buttons on the controller the
> computer
> adjusts the light output to balance exposure between the two lamps so
> paper
> exposure remains constant.
>
> What I hear you saying is you have calibrated your subtractive enlarger
> so
> that you always have equal exposure by balancing the amount of Y against
> the
> amount of M required. Unfortunately M is a much denser filter and to
> make
> this system work you will limit yourself to a small range in the lower to
> center of the LER range. Then as your bulb ages you will need to
> recalibrate.
>
> Dave
>
>
>
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