Neutral density with a colour head

[markbau]

I have to make some postcard size prints and I'm finding the exposure times to be ridiculously short, less than 5 seconds which isn't enough for burning and dodging. I can't stop my lens down any more due to diffraction. I'm using Ilford below lens filters. If I added equal amounts of Y, M and C that would extend my exposure times but does anyone see any problems with this?

 

[cowanw]

In the case of Black and White the cyan component is unnecessary and will just make it harder to see your print. A Cyan filter has no effect on Black and White paper. Also I am unconvinced that each of yellow or magenta units is equal in all machines and some observation of your results vis a vis contrast will be in order.

 

[markbau]

In the case of Black and White the cyan component is unnecessary and will just make it harder to see your print. A Cyan filter has no effect on Black and White paper. Also I am unconvinced that each of yellow or magenta units is equal in all machines and some observation of your results vis a vis contrast will be in order.

I realise cyan has no effect on B&W paper, I just want to use all three to increase exposure times. Thinking about it a bit more, maybe I should just use cyan because it has no effect on B&W paper. The thinking behind using all three is that they, in equal amounts, would just add density with the actual contrast filtration being done by the below lens filters.

 

[MattKing]

Use equal increases in all three filters. It will increase your times slightly compared to using equal increases in just the magenta and yellow filters.
But before you do that, I'd suggest re-visiting the possibility of stopping down further.
Diffraction limited resolution concerns are very much related to how much magnification you are working with. At postcard size printing, you may not be able to see or measure the effect.

 

[cowanw]

Barring filter inefficiency the use of cyan is wasted. In a subtractive situation Cyan is a minus red; Take away all the red you like; it's the safe light. Cyan has no effect on exposure times. Test. Use min cyan and max cyan with otherwise white light and find no difference.

 

[Patrick Robert James]

Get an ND filter. If push comes to shove you can use a polarizer.

 

[Sirius Glass]

Equal amounts of Cyan, Yellow and Magenta filters will yield a Neutral Density filter of about the same value. Polarizers are for reflections and glare and therefore will have no value in the darkroom.

 

[btaylor]

Try the equal color adjustments first— see how well they work. I do it sometimes to increase exposure times, particularly with the very fast color papers. It would be quite simple to hang an ND filter above or below the lens too. Perhaps Peter is was thinking about the variable ND’s when he brought up polarizers, as they are essentially 2 ND’s with adjustable orientation to one another.

 

[RPC]

As was said earlier the cyan filter will have no effect on b&w paper. A cyan filter, at least theoretically, will completely pass blue and green (ignoring filter inefficiency), and stop only red, to some degree, to which the paper is not sensitive. The yellow and magenta, which block blue and green, would be all that is necessary for VC paper and yellow only for graded paper. All three would be needed for color.

 

[pentaxuser]

I feel for markbau. He seems to be getting irreconcilable statements here. There has to be right and wrong answer about whether C is needed to balance and/or add ND to both Y and M based on the science of what these filters do to affect ND and thus increase exposure time for B&W paper

I had thought and this is purely based on what I have seen in previous replies on this subject that an equal amount of all three filters( I think 30 units was mentioned ) add about one stop of exposure. So if markbau is getting 5 secs he now gets 10for dodging and burning but the print looks the same..

There would seem to be consensus or close to consensus that Y and M in equal amounts will add ND. It then remains to be seen if adding the same amount of C will make any difference. Can I take it that cowanw and RPC are saying that C does nothing at all to exposure of B&W paper even if it does make the projection look darker. Leave C at zero or make C 100 will have no effect on the resultant print. The paper but not our eyes is blind to C

So presumably the problem with erroneously using C( as RPC and cowanw contend) becomes particularly important if using an analyser in that the print projection will look darker and "fool" the analyser to "recommend" an exposure that will render the print too dark. i.e. 30Y and 30M will, say, double the exposure but produce the right print but 30 C added on will fool the analyser to suggest more than double but this will be a mistake that leads to too dark a print?

Have I got this right?

pentaxuser

 

[Sirius Glass]

Using only Yellow and Magenta will produce something between Grade 0 and Grade 5. If he wants true neutral density he will need equal parts of all three and thus avoid have the contrast change from what he wants.

 

[Mick Fagan]

It works perfectly.

Adding 30 units of each colour will add 1 stop of neutral density; generally.

So, if you are using 0C 70Y 47M with a time of 5 seconds, then adding 1 stop of ND is: 30C 100Y 77M with an approximate time of 10 seconds. You can add another stop by adding another 30 units of each filter, simple as that really.

I've been doing exactly that for decades with my 5x4" DeVere colour enlarger and 5x4" negatives to make postcard prints. Not to mention, the prints from very thin negatives that I have inadvertantley made.

Many Meopta colour enlargers have a ND filter on the side, usually 2 stops, which is a great help, but just adding equal amounts of all three filters is exactly the same thing.

7.5 units is a ¼ of a stop, 15 units is ½ a stop, 30 units is 1 stop of neutral density. This is one of the reasons I use enlarging times in 1/8th of a stop increments, instead of the more usual 1/3 of a stop increments. In some instances, I further refine my "F" stop printing times to 1/16 of a stop.

Mick.

 

[RPC]

The above works with color. Someone please explain how unaltered blue and green with the cyan filter will affect b&w paper.

As for yellow and magenta, increasing the yellow filter will block more blue. Increasing the magenta filter will block more green. Increasing both equally will block the blue and green equally, which is the same effect as closing down the aperture.

 

[Mick Fagan]

The above works with color. Someone please explain how unaltered blue and green with the cyan filter will affect b&w paper.

Exactly the same.

Essentially, neutral density is just a grey filter. Which is why the word, "neutral" is used.

Mick.

 

[John51]

Do you have a longer lens available? Would allow you to raise the enlarger head.

 

[RPC]

Exactly the same.

The same as what? How?

 

[MattKing]

The cyan filter attenuates red light. In a perfect world, with perfect cyan filters, and variable contrast paper that has absolutely no red sensitivity, adjusting the cyan filter would have no effect on exposure.
We don't live in a perfect world.
So I recommend using all three filters, even though the cyan filter should have very little effect.
For panchromatic materials, you need to add equal amounts of magenta, cyan and yellow filtration to reduce exposure.
For non-panchromatic materials, that have no red sensitivity, the effect of adjusting the cyan filter should be very small.
By the way, we are assuming here that the settings on your magenta and yellow (and cyan) filter dials accurately adjust the amount of magenta and yellow (and cyan) filtration in a linear way. If they don't, making equal changes will have an effect on contrast as well.

 

[MattKing]

Do you have a longer lens available? Would allow you to raise the enlarger head.

This actually doesn't make a difference, except in one quite indirect way.
The intensity of the light at the easel (and therefore the exposure) is a function of the magnification, not a function of the distance between the negative and the paper.
A 4"x6" print from a 35mm negative (as an example) will be a 4x magnification no matter whether it is made using a 50mm lens or made using a longer lens, and the exposure won't change.
The one advantage of a longer lens (for this purpose) is that it may offer smaller apertures at the stopped down end - f/32 instead of f/16 or f/22 for example.

 

[cowanw]

I feel for markbau. He seems to be getting irreconcilable statements here. There has to be right and wrong answer about whether C is needed to balance and/or add ND to both Y and M based on the science of what these filters do to affect ND and thus increase exposure time for B&W paper

I had thought and this is purely based on what I have seen in previous replies on this subject that an equal amount of all three filters( I think 30 units was mentioned ) add about one stop of exposure. So if markbau is getting 5 secs he now gets 10for dodging and burning but the print looks the same..

There would seem to be consensus or close to consensus that Y and M in equal amounts will add ND. It then remains to be seen if adding the same amount of C will make any difference. Can I take it that cowanw and RPC are saying that C does nothing at all to exposure of B&W paper even if it does make the projection look darker. Leave C at zero or make C 100 will have no effect on the resultant print. The paper but not our eyes is blind to C

So presumably the problem with erroneously using C( as RPC and cowanw contend) becomes particularly important if using an analyser in that the print projection will look darker and "fool" the analyser to "recommend" an exposure that will render the print too dark. i.e. 30Y and 30M will, say, double the exposure but produce the right print but 30 C added on will fool the analyser to suggest more than double but this will be a mistake that leads to too dark a print?

Have I got this right?

pentaxuser

That's an interesting question and makes me wonder just what it is that analysers measure, But I do know that the Zonemaster does respond to red light as well as blue and green, for example safe lights need to be off. That said I don't think you can ever be sure what a minus stop of Yellow and Magenta would do with analysers without testing. Note that in many enlargers the maximum number for the two filters is different and so the effect is unlikely to be one to one unit by unit.

 

[RPC]

The cyan filter attenuates red light. In a perfect world, with perfect cyan filters, and variable contrast paper that has absolutely no red sensitivity, adjusting the cyan filter would have no effect on exposure.
We don't live in a perfect world.
So I recommend using all three filters, even though the cyan filter should have very little effect.
For panchromatic materials, you need to add equal amounts of magenta, cyan and yellow filtration to reduce exposure.
For non-panchromatic materials, that have no red sensitivity, the effect of adjusting the cyan filter should be very small.
By the way, we are assuming here that the settings on your magenta and yellow (and cyan) filter dials accurately adjust the amount of magenta and yellow (and cyan) filtration in a linear way. If they don't, making equal changes will have an effect on contrast as well.

The inefficiencies of the filters has been acknowledged. They would be small, however, and unpredictable. I would suggest he use only the yellow and magenta for b&w which should do the job and give more precise and predictable control. Any non-linearities of values would probably be small and not show, but he could adjust if needed.

 

[Sirius Glass]

The above works with color. Someone please explain how unaltered blue and green with the cyan filter will affect b&w paper.

As for yellow and magenta, increasing the yellow filter will block more blue. Increasing the magenta filter will block more green. Increasing both equally will block the blue and green equally, which is the same effect as closing down the aperture.

EXCEPT as I stated before, using only Yellow and Magenta filters CHANGE THE CONTRAST. Therefore using only Yellow and Magenta filters do not have the same effect as closing down the aperture. That is exactly as it works, even though you choose to disagree.

Using equal amounts of the three filter produce Gray which is neutral which Yellow and Magenta is not.

 

[RPC]

Even with equal values of yellow and magenta? If I measure an equal drop with filters in green and blue hitting the paper with an analyzer, I and I measure the same change by closing the aperture, I will get different results?

 

[Sirius Glass]

Even if equal values?

Yes

QUOTE="RPC, post: 2191026, member: 15535"]If I measure an equal drop with filters in green and blue hitting the paper with an analyzer, I and I measure the same change by closing the aperture, I will get different results?[/QUOTE]

Yes, again the contrast will change from the contrast you are working to achieve.

 

[RPC]

So how does adding cyan change that? The blue and green would not change except to a very small degree, and the red is irrelevant.

 

[RalphLambrecht]

I have to make some postcard size prints and I'm finding the exposure times to be ridiculously short, less than 5 seconds which isn't enough for burning and dodging. I can't stop my lens down any more due to diffraction. I'm using Ilford below lens filters. If I added equal amounts of Y, M and C that would extend my exposure times but does anyone see any problems with this?

if equal settings indeed create equal filtration.