Determining a B&W Film's Real Speed

[Colin Corneau]

I've noticed it's common for experienced LF shooters to expose film at speeds other than what it's listed at - Ilford HP5+ @ 200, for example.

Why is this so, and how can someone starting out figure out a film in this way?

Would I be wise to get to know a film by shooting/developing it at its listed speed first and then experimenting, or is this alternate EI listing immutable?

Thanks for any help

[Nick_3536]

Different developers provide different speeds. You might like more/less contrast.

Your shutter/meter maybe off.

You may like a different look then the offical standard.

The whole point of an EI is it's personal.

I'd suggest a copy of Adam's book. The negative explains things from one view point.

[Bruce Watson]

The listed ISO rating on film is the films response to a well defined set of test conditions in a lab. This is good information to have, but it doesn't define what will work for us individually, with our equipment, our exposure techniques, our developers, processing techniques, etc., etc., etc.

This difference between the ISO rating and what actually works for individual photographers has been a frustration since the early days. Guys like Ansel Adams and Fred Archer developed the Zone System in the 1940s to try to make sense of it. Part of what they did was to explain what was happening, and how to make tests to define your personal exposure index (PEI, or EI), and how to make tests to determine your normal development time (which almost always differs from the times the developer/film manufacturers list on their data sheets).

Many people think the Zone System is fairly complex, especially those who are new to it. There have been many attempts to simplify it over time. The late Fred Picker did a good job with his Zone VI Workshop book. Many people love the BTZS methods. And there are lots more out there.

The thing that all have in common though is testing to find your personal EI and your personal development times. This in turn just codifies what photographers where doing anyway -- expose for the shadows and develop for the highlights. You set your EI so that with your exposure technique you capture enough shadow detail for your needs. You set your development times so that you don't blow out your highlights. That's it in a nut shell.

[Bruce Barlow]

Nick, beg to differ, but it isn't personal, or at least I don't think it should be. You want enough exposure to give you shadow detail while still using the range of the film. Too low an EI and your shadows are denser than they need to be. Too high and there's nothing on the negative. Get the exposure right, then get the development time right, and you have full-range, easily printable negatives that make the most of the materials you choose to use.

The "standard" (ouch, not really, but what many folks use), is "enough exposure to yield a Zone I density of .1 above film base plus fog." Zone I, a deep shadow, means not much negative density. Once you have tested for your own personal film speed, you're off to the races. So I guess it is personal, but with some method behind the madness.

You can do a simple test to find the "right" EI for you, your camera, any film and any developer. At the risk of self promotion, visit my web site where you can get a kit with instructions and materials to do the test, repeatable ad nauseum (testing isn't my favorite thing to do).

Fellow-Bruce, beg to differ. The Zone System need not be complex at all, even though many have made it so. Exposure ought to be mechanical - formed of simple habits and repeatable every time to yield reliable results. Set development times eliminate the need to complex calculations and adjustments in the field. Proofing for minimum exposure to get max black thru clear film sets another standard from which we need not vary. Testing for EI and development time may take a day, most of which is spent waiting for things to dry. Picker, as wacky as some may think him (me included), got it right.

[steve simmons]

You should probably do your own testing rather than just shoot and hope. This is a good exercise and will show you just how the low and high values respond to increases and decreaes in exposure and development.

There are many ways to test. Some use BTZS, others use Picker's method (described in his book The Zone VI Workshop and in an article in the Free Articles section of the View Camera web site) while others might refer to the newer version of Adams's The Negative. Bruce Barlow also has a workbook for film testing. However you proceed you will get to very much the same place.

I strongly encourage doing your own testing. What someone else does with a different supply of water and different agitation (even if you think it is the same) won't really help you, just give you a false sense of knowledge and security.

steve simmons

[Turner Reich]

In Ansel Adams book "Examples" he stated that before light meters and other reliable equipment he "BRACKETED", I shouted because it's a dirty word in some circles.

I would suggest that you bracket your exposures until you have determined the "personal" EI. By personal, I mean an Exposure Index for you, determined for your lenses, cameras, shutters, light meters, chemical, etc., all of the factors that influence the exposure and development of the negative that will yield the kind of photograph you are expecting.

This is personal ownership of the way a film will react to your variables. They won't work for someone else, unless they have adjusted some of their variables to compensate for the that speed or index.

Give bracketing a try, make one exposure based on what you think is going to work, then under expose by one frame and over expose by one frame. That will give you the opportunity to see what is happening in visual terms.

When you give a try to printing you will soon see what works. Then you will start to see what the development does, and will soon adjust that. After that your will need to fine tune your personal EI to compensate for the development.

Use the same film, developer, camera and lens for the initial testing, then make changes based on new lenses etc..

If you follow this and don't jump around with changes you will soon be up and running, be consistent with agitation and dilutions. Make sure the shutter is working properly, have a CLA if it needs it.

Good Luck

[Ted Harris]

Bracketed a bad word? Hmmmm. I've done all the testing. I have my personal film/developer speed/time/temperature combos all worked out. I will still bracket most of the time, especially when its a money shot.

[Colin Corneau]

Thank you, this is all (slowly) starting to make sense.

My big problem right now is I don't have a dependable, reliable way to develop my negs -- I'm still wading through the different options out there, although I do know I want some sort of daylight loading tank-type of system (Nikkor, Jobo, etc.)
These seem to offer the easiest method for consistency in development (apart from things like temperature and agitation consistency, of course)

So, a big crash course here that's still in progress.

[Kevin Crisp]

Buy three trays and a thermometer and you have a dependable, reliable way to develop negatives. I second the recommendation to get a copy of the Zone VI Workshop.

[Peter De Smidt]

Just a quick comment, .1 above film base plus fog should be considered a minimum value for Zone I, especially with large format film. While it does depend on the film, exposing a little more get give significantly better shadow separation. The only way to know for sure, though, is to try it yourself.