how to evaluate my maximum black test

[bkrystad]

One of my tasks in my new darkroom was to do a maximum black test on my equipment with my current film of choice. Here's the setup:

1) Beseler 23C Series II enlarger w/ condenser head
2) Minolta C.E. Rokkor-X f/2.8 50mm lens
3) Ilford HP5 Plus ASA 400 film
4) Ilford Multigrade IV glossy paper

I set up the enlarger height for 6"x9" enlargments of 35mm film. I put a developed blank frame in the negative carrier and set my timer to 2 seconds. I marked 2cm intervals on a piece of 8x10 paper and had my piece of opaque cardboard ready. I ran the timer 10 times, each time moving he cardboard 2cm over the paper. That's the test.

I've attached (poor) scans of the results, just for an indication. The first is at f/16 and the second is at f/22. At f/16, the interval at which I can't perceive a change in black is between 12 and 14 seconds. At f/22, the interval is clear up to or beyond 22 seconds. Makes sense, given reciprocal exposures.

Now I'm trying to make sense of the results. Here are my conclusions. I would appreciate any comments on my thinking -- from "that's about right" to "that doesn't make any sense at all."

1) This is a fast enlarger lens, that's why I'm getting to maximum black so quickly at f/16. (I did a test at f/11 as well, that went black at around 6 seconds, as you might imagine.) Apertures faster than f/16 are for bigger enlargements with the lens positioned higher (relatively less light reaching the paper).

2) Given the speed at which the paper gets to maximum black at f/16, I'm safe using that f-stop for low contrast negatives. That allows the blacks to get black and the contrast to be higher.

3) I'm safe using f/22 for high contrast negatives, as it allows more midtones to develop before getting to maximum black.

I'm going to be working on multigrade filters next, which of course is more appropriate for manipulating contrast in prints. But I just want to get a sense of how I should be using this test information when I'm making straight test prints. Should I lean toward using f/22 or f/16 as a starting point?

 

[Skeletor]

The chosen aperture has nothing to do with contrast.
There will be no difference beetween a Print with f11 and 10sec and one with f16 and 20sec except for a theoretical difference of sharpness.

 

[Bryce]

Yeah, I'm afraid the test as you've done it is not going to prove useful in real printing. Invariably you will have a filter in the system, and that will control the time for maximum black. So you would have to repeat the test for each grade filter to know where maximum black will come in at a given F/ stop on your enlarger lens. You would have to repeat the entire process for every possible head height, and for each film type.... In other words the max black test isn't useful.
What you are after in real printing is max black at at least one point on the image, as well as pure white somewhere. So having a true black sample on hand will allow you to be certain you have actually achieved black, but realistically you will have to work out an exposure for each negative by trial and error.
It sounds laborious and is, but there isn't a practical way around the problem and test strips make it go fairly quickly. Prior experience with similar negs and lighting and so forth will get you in the ballpark quickly.
Hey, just go print a picture or two!

 

[EmilGil]

If you're using VC papers, check out Paul Butzi's article on calibrating your system.

As for using f/16 or f/22, I would get a ND filter or a less powerful light bulb to be able to use f/5.6-8 instead. Very few enlarger lenses benefit from being stopped down more.

 

[bkrystad]

Thanks for the corrections to my thinking! This is definitely helpful.

I was just using this test to try and understand the interaction among my enlarger, lens, film base and paper. I'll plan to spend most of my time using test strips on the negatives I'm choosing to get better results.

I'll investigate using neutral density filters to allow me to open up the lens.

I guess I was curious why this particular lens was reaching black so quickly. I'm using the PH111A 75w lamp I'm supposed to with this enlarger. Maybe something else in my configuration is adding to this result, but I don't think so. Maybe I just need a slower lens.

 

[Bryce]

I use the same brand of enlarger and my printing times without a ND filter are silly short also. I think I'll try and replace the bulb with LED's when it finally gives out!

 

[JoeV]

If your film's metering, exposure and development methods are consistent, you should be getting negatives whose average density is rather uniform from shot to shot and roll to roll. This means that you needn't have to pretest all possible contrast grades; rather, pretest the grades you will most commonly use (like, in the range of 2-3.5 for instance.) Then do the 'minimum time to maximum black' test just for those grades, with the appropriate filters inline. This will get you ballpark proof print exposure times quickly and easily. From there, you're going to have to do test prints anyways, if you intend on manipulating your images with dodging, burning, split-filtered printing, to create a finely crafted finished print.

~Joe