What's your secret for getting the correct gray scale in an enlargment

What I do is start out with a test exposure that gets the light tones (such as skin tones) the way I want them. Then I look at the dark tones. If they're not black enough, I use a higher-contrast filter, and if they're too black, I use a lower-contrast filter.

You almost never need to try every one of them, unless you're searching for a special effect. Depending on how you develop your film and how you like your prints to look, you'll probably find that most of your negatives print with a #1-1/2, a #2, or a #2-1/2. Then, if your print looks too flat, you go up a half-number or a number; if it looks too contrasty, you go down a half-number or a number. Lather, rinse, and repeat.

Actually, if you insist on being terribly analytical about it all, you can measure the density range of the negative: measure the density of the lightest important highlight, and of the darkest important shadow (ones that have detail in them, not absolute black or white.) I've got a "spot mask" for my Minolta light meter that lets me use it for this measurement.

Once you know the exact distance between the highlight and shadow in f/stops, you convert it to log density units (0.3 log d units per f/stop, I think...) With that information in hand, you can consult the spec sheet of your paper and see what contrast filter is recommended for that log density range.

Even after I learned all that, though, I found I got better results by just making a test strip with a #2 filter, then looking at it and deciding whether I needed to go up or down!
 
You can try the two-filter printing methods, using just the highest and lowest filters. Do a test strip at 0 and determine which exposure give you detail (body) in highlights before going grey. Then a second test strip at 5 to determine the least exposure for a good blackin shadows. Then add the two and give 1/2 the total exposure (or stop down the lens one) through the two separate filters. It will average the contrast automatically.
 
Make lots of test strips; start with something in the grade 2 to 3 range, and judge from that whether you will need more or less contrast, or are OK with what you got. jlw's suggestion is also very good, and manual split-grade printing (what Poptart explained) is good for particularly 'difficult' negs.

Roman
 
There's a possibility to measure. Take a densitometer or an equivalent light meter. There you can get the min and max density of the neg in logD. Now you can have a look to a table to see which filter you would need to show the complete range of the neg. This is not the 'ideal' result, but helps to orient.

I use the Kunze clock with light meter (FEM MP104). This one has a densitometer mode. The tables are comming with those light meters, for example:
http://24x30.de/index.php?page=dichte2grad .

Now should one test stripe for the blacks and one for the lights be enough.

/rudi
 
Once you do enough of it, you know just by looking at the negative. It should have a creamy, below-average contrast, which will put it on about a 2-1/2 or 3 - this is close to real world contrast. If your personal choice is to have smoother tonal gradation, develop the neg longer in the future; if you love high-contrast, develop it less. If you don't do your own developing, more exposure will put it on a lower filter, and less exposure will put it on a higher filter.

Ilford Multigrade revolves around Zone VI, or Caucasian skin tone, so as jlw wrote, as you go up or down in filter, that tone will stay the same.

There are other theories, including shadow-based printing and highlight-based printing. I learned the latter. If you start with getting your highlight detail where you want it, when you change filters you'll have to adjust the time somewhat.

Ultimately though, work on getting consistent exposures and a consistent development time. Eventually you'll know at the time of exposure which filter you're going to print it on, and how to develop that neg so you get it.

Rob
 
I'll confess that I'm less scientific in my approach to many people and as Rob says with experience you will be able to get within the ball park simply by looking at the negs. Usually it's a slight boost in contrast rather than decrease I need.

I start off with a straight grade 2 print at F11 and my guesstimated time. From that I can judge the actual time and where I need to dodge/burn if at all. Also if I need to use a higher or lower grade filter.

With more challenging light I find that printing grade 2 for the first third of the exposure time with any dodging/ burning done at this stage. I then Open the aperture 1 stop and throw in a higher grade filter for the remaining time seems to nail the print the way I like it.

As I say not very scientific but it works for me.
 
This is my method and take it for what it is worth.

I establish a minimum exposure for maximum black for each film and paper I use.

I take a sheet of photo paper and expose it to room light then develop it. This gives me my maximum black that that particular paper can achieve. I then develop an un exposed sheet of paper, this gives me my maximum white for this paper. I now have my two end points for comparison of the blackest black and whitest white in a print.

I take a frame of unexposed, but developed film and print a test strip through this negative with a number two filter. When I find a time and f-stop that will just achieve the maximum black for this paper and negative combination as compared to my maximum black end point. I record this f-stop and time, say it is f8 at 9 seconds. I then make a full test print of my negative that I want a print of at this min. time max black exposure. I wait for the print to dry and then compare it to my max black and max white reference prints. If I think it needs more or less contrast, say a 2.5 filter instead of a 2, I will “out flank the print”, that is I will go past what I think it needs say a 3 or 3.5 filter for my next test print. This lets me know if I was close in my guess. I then fine tune from there with dodging, burning, split filter printing etc.

Free advice from me, I hope it didn’t cost too much!!

Wayne
 
All of the advice is excellent and I will only add that ease of printing makes a strong case for consistency in exposure and development. Two photographers in my area (one a working pro and the other teaches the photography courses at the local junior college) are both extremely inconsistent in their exposure and developing techniques and as a consequence burn through a lot of paper and time in the darkroom with printing. The pro shoots IR only and exposes everything at f/8 1/125 regardless of conditions; the instructor knows enough about light conditions that he does not need to use an exposure meter. Both have the most relaxed (I'm being kind) style of film development that I have ever witnessed: no thermometers, approximate measuring of chemicals, inconsistent agitation, close enough timing...The real shame as I see it is the instructor is teaching newcomers to photography and processing his methods; the pro knows both sides and chooses to work as she does. Both produce beautiful work as an end result, but printing their negatives is almost like starting from scratch each time.

Careful work and consistency in exposure and development can eliminate a lot of trial and error in printing. These were the skills that my father passed on to me with his cameras and darkroom, and later in life I came across an excellent reference book (David Vestal's "The Art of Black and White Enlarging") which along with reading Ansel Adam's "The Zone System" have allowed me a greater understanding of proper exposure -- exposing for the results you envision at the time you take the picture as opposed to the "accidental art" that my two friends mentioned above rely upon. Of course I will be the first to admit they also produce real art as opposed to my "snap-shots" but that is in spite of their techniques, not because of it 🙂.

Vestal's book, as the title suggests, is primarily concerned with printing. However, a significant portion of the book has to do with determining the correct for you exposure index for the film you choose to use, as well as the proper development. It is important to note that this is subjective; it is wrong to conclude that Tri-X's true speed is 320 or 200 -- it's true speed is what is right for you after you have done a few controlled exposure and development tests. Once you expose and develop consistently printing becomes much more predictable.
 
Another thing that hasn't been mentioned, is that most fibre based b/w papers "dry down" and look a bit less contrasty, than when they are sitting in the fixing tray. You need to evaluate a few prints dry to get a feel for this, and in general you may find that you need to make your prints a tad too "contrasty" (when viewed wet) to compensate for the "dry down" to achieve the final contrast you wish. Ansel Adams used to quickly dry his test strips in a microwave oven to view them.
 
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