Personal EI and Development

marsbars · May 5, 2007

This is probably a simple question but I am new to developing my own film. Actually I am still in the process of getting all I need to do it myself. I have read many places about EI. For the most part I understand that it is the ISO that one comes to for the results that one desires.
Now my question is if for example I am shooting HP5+ and I decide that I want to shoot it an EI of 320. When it comes to development would I still develop it as and ISO 400 film or would I use my new EI?

Peter De Smidt · May 5, 2007

It depends. Your EI is your exposure index. In other words, it's how much exposure you have to give to get shadow tonal separation that you'd like. Once you have that, then you develop to get the highlight contrast that you'd like. Exposure mainly controls shadow separation, and development mainly controls highlight contrast. (There is some linkage)

You can shoot cards, or scenes or whatever. Make a range of exposures such that you expose at an EI 1/4th of box speed to twice box speed. Develop as recommended by the manufacturer. Now make a print using grade 3 paper for 35mm (or grade 2 for larger formats.) What frame gives you the type of shadow detail that you'd like? That's your EI. Now set that eI on your camera and take some pictures of scenes with bright things in them. Develop them as you did before. Now try to print on the Grade 3 (or 2) paper. Do you get the overall look that you'd like? If so, you're good. If the highlights are too dull, try developing for %20 more. If they're too hot develop for %20 less and recheck.

You can make this more complicated, but you don't have to. Most EIs are at about 1/2 the box speed. (ISO is a specific way to determin speed, and it's not real accurate in real world conditions.)

Roger Hicks · May 5, 2007

It's two separate questions.

First, use the EI that give you enough shadow detail and agreeable tonality. Determine this by bracketing the first roll (or two, or three...). Most people find that +1/3, +1/2 or +2/3 stops gives them the shadow detail and tonality they life, i.e. EI 320, 300 or 250 for ISO 400. A few find they are happier with higher speeds than ISO. A lot depends on how you meter: under contrasty conditions you can use higher speeds with spot metering of the shadows (do not waste time with mid-tones) than with broad-area metering.

Second. use the dev. time that gives you negatives you like when printed on grades 2 and 3. Many advocate reducing development compared with the manufacturers' times; a substantial minority gives more.

Quite apart from this, +/- 1/3 stop is more accuracy than is inherent in the system. Err always on the side of overexposure and you will not go far wrong.

Cheers,

Roger

Ryuji · May 5, 2007

You can go as crazy as you want. There is the right way, there are many wrong ways, and there are a couple of simple ways that work most of the time. I stick with the latter until I sense a reason to do otherwise.

That is, take the box speed and cut in half, or take 2/3 stops off. Most (probably all) pictorial b&w negative films have a huge overexposure latitude but very little underexposure latitude. Modern films don't lose resolution and tonality by overexposing a bit, unlike many old emulsions. So the simple solution is obvious. If someone makes a film or developer that doesn't work with this rule and they don't give you any warning on the data sheet, they deserve a phone call.

Adjust the development time so that you get the contrast you want on grade 2 or 3 (pick this one first). I make my negatives to print on multicontrast paper without filtration with well adjusted condenser head.

Chuck_P · May 5, 2007

Keep in mind that the aforementioned "latitude" is not to be considered a safeguard for all exposure variances; relying on the latitude of any film should be a logical move, not an automatic one. It essentially comes into play in overall flat subject brightness ranges. When less of the exposure scale is used, say, three or four zones in the lower to middle portion of the scale, then there is more latitude for "increased" exposure to capture contrast in the upper zones. If the scene is already contrasty, then there is no longer any "huge" latitude for an increase in exposure because much of the scale is already being utilized. Doing so, will, most likely, result in an exposure error with regard to the upper end of the exposure scale. An increase in exposure is one thing and an exposure error is another. I would do some reading and personal research in the "Zone System" or "Beyond the Zone System" techniques of exposure and development; you will learn much in the way of personal EI and how to make it work for you.

Keep on truckin.

Chuck

Ryuji · May 5, 2007

Chuck, what you said is all true, but if you deal with scenes with huge range that you cannot afford to lose, careful metering and/or bracketing are important. Considering the difficulty of metering the scene accurately, I think the small error from the assumption that the true film speed is 1 to 2/3 stop less than the box speed is relatively unimportant. I think it's more important to learn how to use meter in that kind of situation.

Also, some modern films like Acros and T-MAX 100 in some developers don't lose highlight details as easily as old films from the time zone system was devised. So, quite often, longer exposure time and even longer burning-in can solve much of the problems that required more complicated techniques before.

gainer · May 5, 2007

Read the significant shadows of the scene. It is then safe to use Ryuji's approach. If the highlights are so high as to bump the top of the film's latitude, you should be able to tell by reading the highlights. Then you can decide whether it would be better to reduce overall exposure or to reduce development. In either case, you are in for some dodging or burning in the printing because, as any painting artist knows, you cannot have sufficient local contrast otherwise. A scene whose brightness range exceeds that which can be shown on paper is usually composed of two or more scenes such as a room with a large window where the outside scene and the inside scene are seen by the eye's adaptivity. If both scenes are essential to the photograph, you have a problem with the latitude of paper that precedes the latitude of the film. Makes one want to deal only in transparencies.

Maybe I am getting old after all.

gainer · May 5, 2007

You see! While I was cogitating and writing, Ryuji hit the nail squarely.

Ryuji · May 5, 2007

"Expose for shadow" is a general rule that usually works, but when the subject range is so wide that the film is going to "lose" (well, soft clip) both ends, it may not be the best technique to use. In such a situation, you can't get what you want until better film emulsion comes out (ha!) and you just need to find a compromise that you can take. Or, go back to "the right way" and expose for the shadow, note the subject range, and adjust the development time.

I often shoot in the situation where I can't meter shadow because they are too dim. I have the most sensitive meter (goes to -7EV at 100 I think) but I still need many strong street lights before I can measure dark shadow. I can imagine opposite problems as well. I use brackets when I have to, but what if my base exposure is already 20 min in freezing winter?

radiantdarkroom · May 5, 2007

It usually safe to rate a B&W film 1/3-2/3 less sensitive I found. Development depends on Enlarger(diffusion, condenser) to get a nice print a grade 2 or 2.5.
Less development works usually works well with condenser enlargers. I think the development times in instructions are usually for a contrast index that works well in diffusion enlargers. I use a Ilford 500 diffusion head and always get excellent quality prints when I follow these general rules.

Curt · May 6, 2007

. . . then bracket . . .

Even AA admitted he had to bracket.

or get the Zone IV book, Fred Picker and follow his instructions on the setup and testing for EI and developing time. Or The New Zone System manual.

Steve Smith · May 6, 2007

We had quite a long thread on this a few months ago. Since then I have found that generally, I get good results using 1/2 the box speed as my personal EI. i.e. HP5+ at 200.

The exception to this rule is on very bright sunny days with no cloud where there is increased contrast. In this case my EI is the ISO claimed by the film manufacturer. i.e. HP5+ at 400.

So far, my development times in both cases have been the manufacturers recommended time and I get negatives that I like and can print without using any extreme grade settings.

Steve.

Dietmar Wolf · May 6, 2007

Roger said it perfect!

The problem with the advice "halfboxspeed", or similar rule of thumb, is that there are so different ways to measure the light. So its really important, that you learn to measure the light in a repeatable way. Your way.

For example, I nearly never measure the light of the sky. I always measure on the important part of the picture. That is my personal style. Other peolpe measure straight forward, and usually get more light reading than myself.

The shadow (enough exposure) is the most important, because you cannot get shadow through printing, but you can burn the highlights if they are too dense on the negative.

Development: you have to shorten development (10-20%) if you expose more than box speed. This is named "pull development" (opposite to push).

Tony Egan · May 7, 2007

Hi Mars,
Lots of very good responses here. Looking at the development charts on www.digitaltruth... would suggest the following for HP5+ in XTol 1+1;
ISO 200 = 10.25 mins
ISO 400 = 12.00 mins
ISO 800 = 14.25 mins
So, if you were using this developer around 11 mins at EI of ISO 320 would be a start.
As indicated above the variables are many. The difference between 11 and 12mins could be offset by slower or faster shutter speeds on your camera, temperature variations and agitation and diffuser vs condensor enlargers, paper choice etc. etc. If you are new to this and can afford to do it I would do some kind of fine printing course as soon as you can to gain an appreciation of what is possible in a final print and how to get there. Such courses invariably include how to get the right negative first.

I think the phrase "Personal EI" is a bit of a furphy and potentially dangerous for the uninitiated. It's not a personal thing. It will be different depending on what you want the output to be. Maybe "Purpose EI" is a better way to think about it.

Anyway, good luck with getting set up and may you have a long and fruitful journey!

Personal EI and Development

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