From dichroic head to ND filter

Hi guys,

recently I like to print quite small and to keep the exposure times reasonable long I have to stop down the lens quite a lot.

My DeVere504 with a Dichroic head unfortunately does not have an integrated ND filter. However I taught that maybe I could replace the cyan dichroic filter, which anyway is never in use since I print B&W only, with a ND filter! The idea is to get a fully dimmable ND filtration using the cyan knob...

Could be that simple?

Cheers,
Ferru

If your after using a lower output frequently have you thought of fitting a lower powered bulb ?
And keep the currently fitted one safe for if you need to print big .

Using a lower power bulb should work but is not a very flexible solution.
Tonight I check the size of the filter in the head and see if I can find something similar around, I was thinking to use a 5-6 stop reduction filter.

Have you tried throwing all three filters in to see how much neutral density that creates? Another trick to try is using a fogged and processed neg on top of your negative carrier, even better an ND filter if it available.

FerruB said:

Hi guys,

recently I like to print quite small and to keep the exposure times reasonable long I have to stop down the lens quite a lot.

My DeVere504 with a Dichroic head unfortunately does not have an integrated ND filter. However I taught that maybe I could replace the cyan dichroic filter, which anyway is never in use since I print B&W only, with a ND filter! The idea is to get a fully dimmable ND filtration using the cyan knob...

Could be that simple?

Cheers,
Ferru

Click to expand...

It's simpler than that: add 30cc of everything for a stop of ND, 60 for two. That's all there is to it.

FerruB said:

Using a lower power bulb should work but is not a very flexible solution.
Tonight I check the size of the filter in the head and see if I can find something similar around, I was thinking to use a 5-6 stop reduction filter.

Click to expand...

Try what has been suggested by Lachlan Young, assuming that stopping down your lens to a small fstop hasn't worked. If you still need to apply a 5-6 stop reduction filter after all of that then I feel something must be wrong with your set-up. If there isn't then I wonder why I haven't seen many other posts about this problem.

Let us know what effect a small f stop and Lachlan's suggestion results in with respect to exposure times.

pentaxuser

As I understand it, cyan only controls the amount of red light passed to the paper, and has little or no effect since the paper isn't sensitive to red anyway (assuming a B&W paper).
If you want to reduce the light with filtration, you'll need a ND filter.

bdial said:

As I understand it, cyan only controls the amount of red light passed to the paper, and has little or no effect since the paper isn't sensitive to red anyway (assuming a B&W paper).
If you want to reduce the light with filtration, you'll need a ND filter.

Click to expand...

Like the others above say. If you add equal amounts of yellow, magenta and cyan to the basic filter pack you will get neutral density. If your basic filter pack is 20Y & 30M. Dial in 50Y, 60M, and 30 Cyan. Bam, neutral density filtration.

bdial said:

As I understand it, cyan only controls the amount of red light passed to the paper, and has little or no effect since the paper isn't sensitive to red anyway (assuming a B&W paper). If you want to reduce the light with filtration, you'll need a ND filter.

Click to expand...

bdial,

Correct that cyan only affects red light, to which photo paper is not sensitive. That only means, however, that you don't need it in order to create "neutral density" as far as the paper is concerned. Since the paper doesn't see the red anyway, we can create neutral density for the colors the paper does see by dialing in equal amounts of yellow and magenta (this is, in essence, what Ilford does to arrive at their "speed-matched" settings for dichro heads).

#OP: You can dial in equal amounts of yellow and magenta on top of the other filtration you are using to get longer exposure times. 30cc of each is approx. one stop. Say you need 40M to make the print, but the printing time is too fast. Dial in 30Y and 30M more to get 30Y-70M total and you should be really close to the same print at one stop more exposure.

Best,

Doremus

mshchem said:

Like the others above say. If you add equal amounts of yellow, magenta and cyan to the basic filter pack you will get neutral density. If your basic filter pack is 20Y & 30M. Dial in 50Y, 60M, and 30 Cyan. Bam, neutral density filtration.

Click to expand...

The Cyan isn't needed with B&W.

Thank you for the may ideas!

Lachlan Young said:

It's simpler than that: add 30cc of everything for a stop of ND, 60 for two. That's all there is to it.

Click to expand...

This is probably the easiest. Did you find out the equivalence 30cc = 1 stop? Actually, what does CC in filtration the stand for?

The filter in the DeVere 5054 Dichroic head measure 25x25mm,about 15mm in thickness and held in place by two screws. So swapping the cyan filter with a ND filter is in principle feasible and quite easy to do. However, I realized that it will not allow a variable homogeneous ND filtration when the magenta or yellow filtration are in use due to the filter pack design! Only a ND in/out will make sense...it would be easier to explain with a drawing...but in a nutshell is because by inserting partially the ND filter it will first overlap with the (partially inserted) M or Y filter and leave an aperture of un-filtered light entering the mixing box...

At this point I think I will use the C-Y-M superposition system for the moment and maybe later adapt an old ND filter I have around to fit below the enlarger lens...

Cheers,
Ferru

FerruB said:

... Did you find out the equivalence 30cc = 1 stop? Actually, what does CC in filtration the stand for?

Click to expand...

CC means "Color Compensating." The densities are given in a similar logarithmic scale that neutral-density filters use, i.e., 0.3 density equals one stop. For CC filters, the density number is multiplied by 100 for convenience. From the Kodak publication on Camera and Lighting Filters: " In a typical filter designation, CC 30Y represents a "color-compensating filter with a density of 0.30 that is yellow."

FerruB said:

... At this point I think I will use the C-Y-M superposition system for the moment and maybe later adapt an old ND filter I have around to fit below the enlarger lens... Cheers,
Ferru

Click to expand...

Forget the cyan filtration; it's not necessary and you'll be able to see what you're doing a lot better. Just dial in equal amounts of Y and M in addition to what you are already using.

Best,

Doremus

You can also use a piece of metal with holes in it, or some screen.

Do not bother with ND filters with a Dichroic head. Just add equal parts of M, C, Y to make the equivalent of an ND filter.

Doremus Scudder said:

CC means "Color Compensating." The densities are given in a similar logarithmic scale that neutral-density filters use, i.e., 0.3 density equals one stop. For CC filters, the density number is multiplied by 100 for convenience. From the Kodak publication on Camera and Lighting Filters: " In a typical filter designation, CC 30Y represents a "color-compensating filter with a density of 0.30 that is yellow."



Forget the cyan filtration; it's not necessary and you'll be able to see what you're doing a lot better. Just dial in equal amounts of Y and M in addition to what you are already using.

Best,

Doremus

Click to expand...

I am just 2x checking.....so if a print looks good with 30M, but you require some ND, you would add (for example) 30Y and 30M.
Making for a total of :
60M
30Y
Is that correct.?

Colorhead cc's aren't necessarily equivalent to density values. For example, one of my big Durst heads comes with a conversion scale. It's kinda like F versus C temp readings. That's because subtractive YMC filters aren't pure, and allow a bit of white light thru. A minor issue unless you assume 30 cc's do equate to exactly one stop. Aging of filters also has an effect, mostly due to gradual spalling off a the dichroic coatings (if you have an old heavily-used colorhead).

FerruB said:

Thank you for the may ideas!



This is probably the easiest. Did you find out the equivalence 30cc = 1 stop? Actually, what does CC in filtration the stand for?

The filter in the DeVere 5054 Dichroic head measure 25x25mm,about 15mm in thickness and held in place by two screws. So swapping the cyan filter with a ND filter is in principle feasible and quite easy to do. However, I realized that it will not allow a variable homogeneous ND filtration when the magenta or yellow filtration are in use due to the filter pack design! Only a ND in/out will make sense...it would be easier to explain with a drawing...but in a nutshell is because by inserting partially the ND filter it will first overlap with the (partially inserted) M or Y filter and leave an aperture of un-filtered light entering the mixing box...

At this point I think I will use the C-Y-M superposition system for the moment and maybe later adapt an old ND filter I have around to fit below the enlarger lens...

Cheers,
Ferru

Click to expand...

Regarding the amount of filtration, what Doremus said - I may have been off with exactly how much density 30cc's of each colour adds, but it should be enough to get your exposure under control. DeVere's dichroic heads are wonderfully easy to work with in my experience.

That said, I wouldn't go fiddling around with the inside of the dichroic head - if you have a look at how the LPL VCCE system works (to take one example), it really would need a tightly interlocking set of gears & cams to operate the three filters relative to each other.

At that point, you'd have an easier time building an LED head...

CC is also color correcting and CP is color printing. If you have a Durst Head (and some DeVere heads are made by Durst) the color correction is in density units and 30C+30M+30Y equals 30 neutral density (one stop/step) with CP filters it's only approximately correct but probably close enough. I have also cut a piece of aluminum window screen to fit the filter drawer or a piece of Rosco or Lee theatrical gel in the drawer.

darkroommike said:

If you have a Durst Head (and some DeVere heads are made by Durst)

Click to expand...

Other than the Ilford MG600 head, I'm not sure which DeVere heads you're referring to - the regular colour MKIII/IV/V dichroics use Kodak rather than Durst filtration (at least according to the data sheet in Ilford's paper boxes) - either way, the principal is essentially the same.

CMoore said:

I am just 2x checking.....so if a print looks good with 30M, but you require some ND, you would add (for example) 30Y and 30M.
Making for a total of :
60M
30Y
Is that correct.?

Click to expand...

Yes, correct.

And a clarification of density on CC filters. Theoretically, 30CC of all three subtractive colors, yellow, magenta, and cyan, should equal to 0.3 neutral density, or one stop of neutral density. As far as the paper is concerned, cyan is superfluous, so, to the paper, 30 CC each of yellow and magenta should give you roughly one stop exposure difference. If your enlarger light source is too bright, just dial in equal amounts of Y and M and leave it that way, adding more M or Y to that basic package as needed to adjust contrast filtration.

Those who are recommending equal amounts of Y, M and C to achieve neutral density are correct. However, since the paper can't see red light, filtering it out with the cyan filter is simply not needed. Doing so makes the projected image a lot dimmer for our eyes. So, to achieve the same reduction in exposure and keep a brighter viewing image, just use Y and M.

As for metal discs with holes, screens, etc. These work well, but need to be installed at the light source. The Omega Chromega heads have exactly this feature to adjust light intensity; a disc with holes that moves into the light path very close to the bulb and before the light gets to the dichro filters. You could install a screen or disc with holes directly in front of your enlarger bulb and see if that works.

Best,

Doremus

10-4.....Thank You