Film testing for personal E.I.

Is Barry Thronton's method of film testing using paper exposures the best

method for establishing a personal E.I.? Is there another as good but without

the darkroom procedure for those without an enlarger. Thanks

What I did ages ago was shoot a bracket in third stops two stop over the suggested exposure and two stops under. I filled about 1/2 the frame with an evenly lit 18% grey card, then just look for the best neg.

You could avoid the enlarger requirement by doing contact prints.

You would just need a controlled repeatable light source then.

This method of exposing the paper is intended to avoid the need for

a densitometer. I think that is your other choice.

The other way if you are minus a densitometer is to use a spotmeter as described in BTZS. I have done this - but without all the faffing about with home made holders: just use a lightbox and a black paper mask with a small hole through which to read the negative. If you do this, I found it is essential to focus on the negative through the hole to get the correct reading and to ensure you take the reading at the same point on the lightbox.

 

I did both tests: one using the print method and one using my spotmeter. Much to my amazement I got the same EI in both tests when I tested Delta 100 (EI=80) and Tmax 100 (EI=100) - whether these are the *correct* same values is another matter... ;-)

 

Also on Barry Thornon's site (www.barry-thornton.co.uk - someone really needs to tell him how irritating that Javascript menu is...) he describes a method of using contact prints to arrive at your personal EI.

 

Cheers,

The standard way is to use a densitometer. Just about every camera club has someone who has one who will help you out.

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The normal methodology is described in Ansel Adams' book <i>The Negative</i>. Another source of method is Fred Picker's <i>Zone VI Workshop</i>. Both of these are broadly recommended.

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Basically, finding your personal EI is a matter of finding the exposure that yields a negative with a Zone I density of about .1 over film base + fog (FB+F). In practice, this is a density that is just barely visable compared to the unexposed film that was under the film rail of the film holder. Development time is usually the development time recommended as a starting point by the film/developer manufacturer.

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After you find your EI, the next step is to find your normal development time. That is, the development time it takes to yield a negative with a Zone VIII density that is around 1.2 - 1.3. The actual value to shoot for depends on the equipment you will use to print (diffusion enlarger, cold light, scanner, etc.). See the books for more details.

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Finally, if the normal development time you find to give you the Zone VIII density you want is appreciably different from the development time you used to get your EI, your EI may no longer be exactly valid. It can move a third of a stop or so, sometimes two thirds, rarely a whole stop. So... iterate, if required.

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It's a pretty painless proceedure designed to give you a personnal EI and normal developement time. It is personnal because you use your meter, lenses, film, developer, and proceedures. You get the EI that fits you. That's why it is important that you, personally, run the tests.

It takes about 15 seconds at the most to find your personal EI using a densitometer (after you've made the exposures and developed the film of course). If you can find a lab in your area that still does wet processing they'll have a densitometer and will either read your five or six exposures for nothing since it's so simple and quick to do, or maybe charge you a little bit for doing it. If you can't find a local wet processing lab you could try Calumet. When Zone VI was still Zone VI they would make densitometer readings for you for a $7 charge. I think Calumet has continued this service since taking over Zone VI but I'm not sure. You could call 1-800-CALUMET and find out. It's so much simpler and accurate to do with a densitometer that it's worth a little trouble to get access to one.

Is Thornton's procedure then simply another way to do the same thing that a

densitometer can acomplish, or has he specified the procedure to tie it into

the papers response, which seems a more proper method. Also, can anyone

tell me why he specifies a film development time of 20% less for his test; This

one I can't understand.

20% less dev time is likely to be closer to your personal dev time than the manufacturer's given time for much the same reason that your EI is fairly unlikely to be the same as the manufacturer's ISO rating. It follows the maxim of developing for the highlights. He also suggests only 10% less for Tmax as a starting time.

 

The problem with the paper method is that it is often difficult to distinguish max-black from as-near-as-dammit-but-not-quite max-black... You could easily be 1/3 of a stop out if your eyes are not as sensitive as they once were (judging from my test strips). It is also difficult to decide what light to use for this test - do you examine the test strips in very bright light or in normal viewing light? Again, this can made a considerable difference to the strip selected as the 1st max-black.

 

However, the densitometer method also has problems as far as I can see: for a start the 0.1 above fb+f is a convention (or possibly a compromise) - more advanced practitioners use different values that suit them and their systems.

 

 

 

Cheers,

In my opinion, the most practical way is that described in Steve

Simmons' book "Using the View Camera." This method relies on

a Zone III placement of shadows and visual assessment of the

photographer's "ideal" Zone III value.

 

Also, stained pyro negatives defy useful measurement by a

densitometer because the stain effectively becomes part of the

overall negative density. (Even Phil Davis, BTZS author, will tell

you this).

 

And besides, what better way to have a "personal EI" than to

base it on your personal preference? After all, it is you who will

decide just how light or dark each zone will be, not some sterile

densitometer measurement. And in my experience it's very

repeatable.

 

Good Luck,

I agree wholeheartedly with David's posting -- what matters in the end is how the values look to you, once they are printed. First though, the enlarger proofing time, ie the minimum exposure to just get pure black in the paper (with an unexposed but developed neg in the carrier). Which "level" of black to take is easy -- just put the test paper where you intend to view the final prints, ie on the wall, or on your bench, or wherever, and look casually (ie don't turn the paper on its end facing the light!) Ask your wife or someone to tell you where the black starts.

 

I spent a lot of time last year testing 3 films for EI and dev times, shooting the side of our house. Door in deep shade under patio = zone 3, cream paint on wall in full sun = zone 8. Very valuable: not only did I learn a lot about zone placement, but I don't need to do test strips for contact prints any more. I just expose for my enlarger proofing time, and from the result I can easily see if a bit of adjustment is necessary for the final print.

 

Spotmeters vary. My Gossen Spotmaster underreads by up to 1.5 stops at low values, possibly because it is UV sensitive, compared with my Minolta. And by using the Minolta to find zone 3, I regularly give up to 2 stops more than I would metering the same scene using a wider-angle reflectance meter. Just some reasons that your EI values may well differ from others'.

So far I have done both the densitometer and print test and neither concurred.

The densitometer test gave me a film speed approx 2 stops slower (new Delta

400) if I was looking for .1 above fb+f (my zone 1 frame was .03 above fb+f)

and in the print test I could tell a slight difference at the zone 1 print from

maximum black with the zone 1.5 frame definetly discernable. Btw, Ilford gives

a manufactuers speed of 500 in Xtol 1:1 @68, 13 minutes.

 

I think the best way to do the test is to find something detailed and expose

from zone .5 ( I have 1/2 stops on my Mamiya lens) up to zone 6....Then print

off max black and pick the range that looks best to me.

 

The one thing that Mr Thornton discusses in his method of printing is the

practice of using multiple exposures in short segments for the test. My

question is, why wouldn't you want to do a real world test of how you normally

print with one longer exposure. There is a increase in print density over the

multiple method, and I can understand what he's saying, but wouldn't use the

multiple exposure method to normally print. Any thoughts.