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  #1  
Old 17th February 2019, 11:56 AM
longhouselife
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Default Using filters to increase ND

Reading a little in other posts about being able to increase Exposure times through using filters to increase ND.

I have the in-built system of the LPL7700 head, I also have a set of Agfa colour balance Gel (?) filters. In addition to this I have two sets of Ilford Graded filters the 'standard' boxed set and also a 100mm ish square Gel set.

In using:

I could dial in ND on the LPL then use the under lens graded filter holder and filters, or I could with the Leitz Valoy enlarger use the Agfa filters inside the condenser head, under the bulb, and then use the Graded filter holder again under the lens...?

Is there a table of filter combinations to give varying ND grades..?

ie. 45Y45M45C = ND 0.6 or some such value...
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  #2  
Old 17th February 2019, 01:12 PM
mpirie mpirie is offline
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To increase exposure times, the first option has to be stopping down the lens.

I've never seen a comparison chart that says that 45 units of all cyan, magenta and yellow equals a neutral density.

Since Multigrade papers rely on the colour of the exposing light to define the contrast, i would not be surprised if that approach lead to a grade change.

You may be able to get hold of a swatch of colour gels from somewhere like Lee filters which would include an ND set?

Otherwise it'll be suck it and see.

Mike
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  #3  
Old 17th February 2019, 01:51 PM
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MartyNL MartyNL is offline
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What I generally do with my diffuser enlarger, especially with smaller prints is to use a lens for the format next size up. So in the case of 6x7 try using a 105mm lens. As well as an increase in exposure you get some increased distance for extra working space.
In addition, some enlargers have extra white plastic diffusers for x2 or x4 stops which can go directly on top of the mixing box.
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Old 17th February 2019, 01:59 PM
Richard Gould Richard Gould is offline
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As Mike above said, first close down the aperture on the enlarging lens don't be afraid to close it down all the way, and even with Kentmere RC paper which is the fastest around will give you plenty of exposure time, down to 50 or more seconds, the colour balance filters is for colour printing, using a non colour head, I can't help you as to how, for black and white printing you would be better of using the Ilford MG filters, with your LPL you need the set with the pole which shoud have a holder to fit the filters under the lens, the other set is for above the lens in a filter draw in a black and white head,as dialing in ND using the filters in the enlarger, that would be a big nono for using MG or MC paper as the grades are controlled by different colour filters, look at your ilford MG filters and you will see the colour of the filters, the higher the grade the darker the couour, so if you dial in nd then you will throw your grades out.If you really need to use a ND filter, and I can't see any reason to unless your prints are really tiny then I hink the only way would be to get proper ND filters made for cameras and attach them using blu tak to your enlarger lens, you will need to get large ones and they can be expensive, only use your colour head filters to dial in the grades, or leave the enlarger set to white light and use the Ilford filters to change grades,
Richard
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Old 17th February 2019, 04:16 PM
Tony Marlow Tony Marlow is offline
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I have seen reported that dialing in equal values of yellow magenta and cyan you get white light with a lower light value. Using seperate Ilford MG filters should work. A bit of trial and error would give a good indication on how much the three coloured filters would increase exposure.

Tony
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Old 17th February 2019, 08:11 PM
Mike O'Pray Mike O'Pray is offline
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From another site it would appear that 30Y,M and C equals one stop but I'd have thought that the usual number of 30 may be affected by how many units of Y,M and are on the dichroic head?

If there is a filter drawer in which can place filters then if stopping down doesn't give enough exposure along with what MG filters in the drawer then ND filters of a range of stops looks like the simplest idea

I'd be surprised if stopping down plus MG filters to get the right grade doesn't achieve long enough exposure

Mike
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Old 17th February 2019, 08:40 PM
longhouselife
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Thanks for the responses, so far...

The reason I was asking was to see if there was a way of, obviously, increasing exposure times. I have a number of negs (35mm) where when trying to print at 5x7 (smallest paper I have used, so far) or less, and even with the lens stopped down to f/16 I am getting in the region of only 6 - 10 secs even with a G3 - 5 filter in place. Not a lot of time if any really for doing a dodge or a burn...

Now. These are negs that I am attempting to get a print from where I might not really be bothered with in an everyday sense. But for me at this stage in looking at overcoming obstacles to less than ideal resources, it makes sense to explore possibilities for how I might overcome them in the future. Other than aiming for a good neg from the off

Week two of my printing 'adventure' over Time for a break as I head south for a few days. Might even take a image or two instead...
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Old 17th February 2019, 09:00 PM
mpirie mpirie is offline
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Mike may be right that equal amounts of the three colous may result in a neutral reduction in light reaching the paper and you could check by using your light meter on the baseboard. I've never seen a chart, but that doesn't mean they don't exist.

To find out what effect that approach has on contrast grades will be a case of try it and see.

Mike
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  #9  
Old 17th February 2019, 09:38 PM
longhouselife
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So, I just did a quick barnyard test...

Using my Minolta IVf lightmeter set directly under the lens and on the baseboard.

ASA set at 400. (I don't think this will matter, just enough to get a range of stops)

Dialling in:
60 CYM gave me One Stop

120 CYM gave me Two Stops

170 CYM(highest I can set) gave me Three Stops

All done with the lens at a height to give coverage for a 7x5.

Something to play with, anyway. I think tomorrow I will make a base print and then three identical prints with no further filtering other than ND and see what if any differences there may be.

Last edited by longhouselife; 17th February 2019 at 09:43 PM.
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  #10  
Old 18th February 2019, 08:17 AM
John King John King is offline
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I am not sure about the filter idea to get a neutral density...however what I have seen done - and it worked, is for someone to photograph a 37% grey card several times using a 6x6 med format camera. Starting at 2 stops under exposed, then 1 stop under, followed by correct exposure. The next being one stop over....2 stops over....3 stops over I am sure you get the idea. You could even fine tune it by exposing each frame at half stop intervals.

Then place the resulting developed negatives OVER the top of a 35mm neg carrier and this will give you a more or less accurate series of neutral density filters.

The film will have to go over the top of the negative to place it out of focus with the film plane in the carrier. I use an LPL7700 as well and I know from experience that there is enough space to fit a piece of film in above. (I used to do it when I printed colour to be able to get accurate colour balance when I printed a B&W Negative but used an unexposed, but developed piece of colour neg film).
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