I have read a couple brief descriptions of this technique - first doing a test strip with the high contrast filter to find the time that gives acceptable dark values, then exposing a sheet for this amount and subsequently doing a test strip on it using the lowest contrast filter to find the time that gives the desired detail in the light areas. How commonly used is this technique? Does it work for all types of negatives, or is it to be avoided with some (eg low contrast or high contrast images)?

-- jeff thompson (thompson.jeffrey@mayo.edu), April 05, 1998

Answers

I'm not sure what technique you are referring to. If you mean using different contrasts in different areas of the print, then yes, it is incredibly useful for those negs that need it. These negs would have areas of different contrast, where the detail from the neg cannot satisfactorily be printed any other way.

However, some people suggest that giving the SAME part of a negative two exposures (one of high contrast, one of low) can be of benefit, and that this is somehow different to printing that area with the appropriate intermediate contrast. This theory sounds like rubbish to me.

-- Alan Gibson (gibson.al@mail.dec.com), April 06, 1998.

You can split the exposure as you describe. You get the same result as a single intermediate contrast exposure. My main objection to the technique is the need to change filtration without moving the enlarger head, so the second exposure isn't shifted. Even with the height adjust clamped tight I wouldn't trust it no matter how gingerly I turned the filter knobs on my dichroic enlarger.

Even without split filtering I find test strips to be tedious. I make a single best guess exposure on 1x1" tabs of paper placed in a shadow area, a highlight area and an important midtone, like part of a face. I put paper clips on the easel while the enlarger is on focus to facilitate placement of the paper tabs while the enlarger is off. Then I develop and fix the tabs. Then based on past experience I visually estimate what adjustments to make. Typical small changes: 1/4 stop overall exposure, 10 magenta, 20 yellow. Adding magenta mostly lightens highlights, adding yellow mostly lightens shadows. My normal print filtration ranges from 0-30 magenta (approx. #2-#3 grade). I normally don't use yellow so I control shadows with overall exposure and highlights with magenta.

-- Tim Brown (brownt@ase.com), April 06, 1998.

Split contrast printing

Hello Jeff, I've been thinking about the same and made some tests and I think you are right. It seems as you could get a different exposure curve with a low and a high grade filter than with one medium, just as you described. I tried the method with a 4"x5" negative taken in Lappland last week with backlit new snow and a forrest in the background; a very difficult situation. I also tried two differrent papers, Ilford Multigrade IV RC and FB. They also seem to bit a bit different. Unfortunately you have not so far got any good answers to your question. I certainly hope someone with sufficient theoretical knowledge to comment on this!

-- Martin Glader (martin.glader@mesvac.fi), April 08, 1998.

Ok,

first up, I have very little experience in printing (just a beginner), so take all of the following with a large grain of salt.

But, it seems to me, from a theoretical standpoint, that summing a low-contrast exposure and a high-contrast exposure _won't_ give you the equivalent of a mid-constrast exposure.

If I understand correctly, a high constrast print will give you greyscale tones in a narrower exposure band than a low contrast print. (ie: dark tones will print max black earlier than they would in a low contrast print. Similarly for light tones/white), thus when you sum them, only that narrower band will affect the low contrast exposure.

The end result of this would be a resulting print density curve (or whatever you want to call it) that resembles the low-contrast curve at each end (towards highlights and shadows), but looks like a high-contrast curve at the mid-tones. Similar to a film having an extended toe and shoulder.

does this hold water? Duncan

-- Duncan McRae (duncanm@zip.com.au), April 08, 1998.

Duncan I think that you are probably quite right about split filter printing being different from using medium grades. I was about to start experimenting with it to try and quantify it's affects to see if it possible to approximate the zone system. It is very impractical to use the zone system with 35mm unless you are taking the same subject on the whole roll. The idea would be to try and expose and develop for a full tonal range and then carry out expansion and contraction by split filter printing. I'm not sure if it's feasible but perhaps worth a try. Whaddya think?

-- Andy Laycock (agl@intergate.bc.ca), April 08, 1998.

My approach is to start by making a soft contrast, grade 1 or so, test strip, and then a full print. A lot of photographers use this approach, the soft contrast gives a good feel for the information in the negative. I then make a test at what I feel will be the final print contrast. The contrast I choose is a best guess, and is normally pretty close to where I think the print should end up. I then make a print at this contrast setting.

Now I have 2 prints to look at, side by side. I may decide that the low values overall in the higher contrast print are to low in value, too dark, and will decide to first try a split exposure. For a split overall exposure I will generally start at 50% soft contrast, first, followed by an exposure of 50%, for the contrast of the harder print. This lets me see the effect on both the high and low values of a split contrast exposure.

After putting this print between the other two, I can decide on the changes in local contrast I want to make, or maybe re-do the percentage of hard and soft contrast for another test.

Typically I use harder contrast for burning and lower contrast when I dodge during the initial exposure, although for high values sometimes a lower contrast works welll for a burn. Only practice and experimentation will tell you what works and what doesn't.

Your best bet is to try some different tests yourself, and see what the results are, any change you make is going to be evident, and splitting contrasts DOES have a different effect that printing at a single contrast. This isn't theory, I have done it and seen the results for myself, but it is hard to explain just how it looks in a print. Invest a few sheets of paper and a few hours, and I think you will be surprised at the changes you can make in a print, just be sure to keep notes as you go, so you know where you have been.

For a real test, with a new material or technique, I use full sheets of paper for my test strips. It cost more, but a full sheet gives you much more information than a strip or square of paper, and information is what you are after, isn't it? You might try and see if this approach doesn't work for you. Good luck.

-- Marv Thompson (mthompson@clinton.net), April 08, 1998.

Well hear is my 2 cents worth. I know some master photographers that use the split filter aproach to printing so it is obviously a valid method. Its apeal is in getting a good contrast that will reproduce the whole negative without being to flat. This is an improvement over a large amount of the printing that I have seen. My problem with it is that getting the correct contrast is only the first step in a fine print and using 2 filters for varying amounts you really don't know where you are on the contrast scale, which might help in making subtle local adjustments. I have done 2 printing workshops with John Sexton and he stresses over and over that you don't know if you have gone far enough unless you have gone too far. This is a good reason to start with a good low contrast test print and gradually increase contrast until you go too far, any short cut is possibly a waste of time if you really don't know what the negative is capable of. As far as 2 filters giving a different characteristic curve than a single filter it just isn't so. Phil Davis wrote an excellent article comparing split filters with a dichroic head and found that he could duplicate anything the split filters could do with a single filter setting a color head. There is no magic that occurs using a high and low contrast filter. That doesn't mean that it might not be necessary to use different contrasts on different areas of a print or burn using different filters, just that you are not doing anything that couldn't be done using traditional methods. I am not saying don't use the split filter approach, as I stated earlier, there a many very good printers that do. There just isn't the big benifit that there might appear to be on the surface.

-- Jeff White (zonie@computer-concepts.com), April 09, 1998.

Since reading the original note, and writing my reply, I have been reading "The Variable Contrast Printing Manual" by Steve Anchell, 1997, Focal Press. He talks about split printing.

I haven't tried it yet, but definitely will. I don't quite follow the explanation in the book, so what follows is my interpretation. It might be wrong; feel free to correct me.

It involves giving two exposures to the whole print (one with a high contrast filter, the other with low), rather than one exposure with an intermediate filter. It doesn't do anything to the print that can't be done with a single exposure. But it does offer a different mechanism for you, the printer, a method that sounds simpler, and offers finer control, than the single exposure method.

The way it works is like this. Photographic paper has a characteristic curve. This is a plot of log-exposure versus density. When printing conventionally, you have two controls. Firstly, you can vary the exposure, which changes the position on the curve. Secondly, you can use a different filter, which changes the slope of the curve. But when you evaluate the print, what do you look at? The highlights (which you might want just off white) and the shadows (which you might want just off black). Split printing gets you straight there.

Different procedures are possible. One is:

1. Choose an aperture for the enlarging lens.

2. With the soft filter, make a test strip of a highlight area. Process, and choose the correct exposure for the highlights.

3. Take a sheet for another test strip. Choose a shadow area. Expose this whole strip through the soft filter, for the time you found in (2). Leave the test strip on the easel.

4. Replace the soft filter with the hard filter. Make a test strip, thus combining the varying hard exposures with a constant soft exposure. Process, and choose the correct exposure for the shadows.

5. Make the final print by exposing through the hard filter for the time in (4), and then exposing through the soft filter for the time in (2).

How does this work? When you expose through a hard filter, a greater exposure will affect the shadows more than the highlights. Exposing through a soft filter effects both the highlights and the shadows, but the change in the highlights is more obvious.

One disadvantage that occurs to me is that dodging and burning are more complicated. In theory, you could extend the procedure by calculating what exposure through what filter is required, given your times in steps (2) and (4) above. The final print made with this exposure and filter should be identical to the one you made in step (5). Being a single exposure, dodging and burning would be simpler. However, this calculation would be difficult to establish, and would only be valid for one enlarger.

-- Alan Gibson (gibson.al@mail.dec.com), April 09, 1998.

Split contrast printing

The advantage of split contrast printing is that you may EXACTLY match the contrast of the print to the contrast of the neagative. However, to do this you MUST use a VC cold light head that can provide EXCLUSIVELY green output and EXCLUSIVELY blue output. That means you must be able to turn off the unwanted color; simply turning it all the way down still allows some light though. This is why I discourage B&W printers from using dichroic heads. Besides the yellowish color temperature of the incadescent bulb, the filters do not go to the extremes required for split VC printing. The Zone VI VC head is the only one designed from the ground up for modern VC papers.

If you have the proper tools, here's what to do:

1. Make a test strip using the GREEN light only on a FULL SHEET of paper. Find the highlight area that prints Zone VIII correctly. (That is the first stripe of fully textured highlight area.) Write down the time required. It helps to print in 3 second bursts and count the stripes to find the right time.

2. Place another full sheet in the easel and expose it with the GREEN light for the time arrived at above. TURN OFF THE GREEN LIGHT. DO NOT REMOVER THE PAPER. Make another test strip with the BLUE light only. Find the stripe where D-Max is reached, the FIRST STRIPE where the black area is as dark as it gets. Write the time down.

3. Make your pilot print by combing the proper seperate exposures on one sheet of paper.

The advantage is that you can burn in light areas, like the sky, with the green light without affecting the higher contrast areas. Likewise, you can intensify certain shadow areas without affecting the highlights. THIS WILL WORK ONLY WITH THE ZONE VI VC HEAD OR ONE WITH THE SAME CAPABILITIES. Also, the paper is very important. Ilford MG IV is particularly excellent. Some VC papers' emulsions are not as finely tuned to the different colors of light and may have overlapping spectral response.

Hope this is useful.

-- Michael D Fraser (mdfraser@earthlink.net), April 09, 1998.

Thanks to all who have shed some light on this area (pardon the pun). It's great to be able to get a wide range of input on a question from experienced photographers. Not that it always totally clears things up.... I wonder if others have had success with split contrast printing without using the Zone VI VC head.

-- jeff thompson (thompson.jeffrey@mayo.edu), April 12, 1998.

Split contrast printing

To make a difference worth all the agrivation, split contrast printing must be done with a light source that produces very narrow spectrum of green and blue seperately. There may be other cold light heads that have two seperate grids and are able to be switched completely off. With the Zone VI (and maybe others) two grid lamp, the green grid will affect only the low contrast emulsion, and the blue will affect only the high contrast emulsion. Filters cannot restrict the bandwidth of light enough to do split printing. They will affect both emulsions to some degree. This is why those who use dicro heads believe that there is no value to split contrast printing.

-- Michael D Fraser (mdfraser@earthlink.net), April 14, 1998.

I know this thread is over a year old, but perhaps someone is eagerly awaiting the news...

Yes, split grade printing DOES work with a single grid lamp. I have a DeVere 54 with cold light, and the Multigrade filters, used below the lens on a wire frame, enable me to do split grade printing. I am quite prepared to believe that it works even better with a two grid lamp.

The great thing about split grade printing, which I hadn't appreciated before getting it to work for myself, is that it enables me to control the density of the highlights and shadows almost independantly of each other. Put it another way, dodging and burning now effect not only the print density, but also the print contrast.

I am now completely sold on the benefits of SG printing, for those negatives that benefit from different contrasts in different areas.

-- Alan Gibson (Alan.Gibson@technologist.com), May 27, 1999.

I have used split contrast printing for years and talked with numerous photographers and all seem to have their own philosophy and approach. I do not use split contrast to acheive an intermediate "grade" of contrast for a print, but usually to alter the local contrast of some part of the print. This can happen even when combining overall exposures. If the first exposure is through a low contrast filter, two things happen. Some different grey values will come in and also in effect the paper is pre-flashed, so to speak, causing the effect of an exposure through a high contrast filter to react differentyly than if done on unexposed paper. Generally speaking split contrast is most useful to me when I need a good clean highlight or a deeper black in the print and just changing the contrast around doesn't seem to get there. I used to get a similar effect using water bath development with graded papers.

-- Les Warren (eyeseales@netscape.net), September 23, 1999.

I'm happy to see that Alan Gibson has given in over a period of a year, because my experience is also that printing with a #2 filter often gives a less crisp image-impression as a whole than a combination of a #1 and a #3 filter. Of course you have to find out how long you expose with #3 in proportion to #1.

-- Lot (lotw@wxs.nl), September 23, 1999.

I use split filter printing because it works. It takes awhile to get the hang of it but in the end if you investigate it thoroughly you will print no other way. It doesn't so much give an intermediate grade but two different grades on the same paper. I can harden and sharpen the blacks and still have very subtle highlights on the same paper. Phil Davis can do anything. Just ask him. He just can't make a nice photograph. Don't just try it once. Experiment with it. And you'll see it works great. James

-- James (James_mickelson@hotmail.com), September 24, 1999.