Determining EI... did I mess up?

[evan_parker]

I took a series of photographs of an evenly lit gray card, placed at

Zone I throughout a series of EI settings on my camera using Ilford

HP5+ (which is rated ISO 400). When I developed the film, though, I

found that the first frame that had perceptible density to it was the

Zone I exposure at 800! I was told that people very rarely end up

having a higher EI than ISO when determining personal film speed...

 

Anyone have any suggestions on what I may have done wrong?

[al_kaplan1]

Perhaps you should try bracketing sets of exposures of actual picture taking situations. You'll spend very little time in real life taking pictures of grey cards. I like good shadow detail so I'd favor the most exposure I can get by with without losing highlight seperation. Were you metering off the card or taking incident readings? Sometimes they don't agree, and with a real life 3 dimensional subject you might need a couple stops more or less exposure.

[ken_miller4]

Keep in mind that *everything* comes into play when determining EI. Did you use the meter on the camera, or a hand held meter? Some hand held meters will read differently than others. It's been pointed out tht meteres from Japan read about a stop different from European meters, so that could be one issue right there.

 

What it really boils down to is this: when you use the EI that *you* determine, with *your* equipment, do the negatives look good? In other words, do you have good Zone III shadow detail? Once you've determined that, adjust your development to get the highlights where you want them.

 

Don't worry too much about the technical aspects of determining EI. Lather, rinse, repeat until you get great smelling, shiny negatives :-)

 

Cheers!

 

-klm.

[galitsos]

Developing Efke 100 4x5'' with a certain proccess I took E.I. of 160 which is 2/3 more of the manufacturer price. You took one stop more. I don't think that is necessarily wrong. Some developers at certain cirquimstances can alter seriously the E.I.

[severi_salminen]

Al: "Perhaps you should try bracketing sets of exposures of actual picture taking situations. You'll spend very little time in real life taking pictures of grey cards."

 

The point in calibration with gray card is that the photographer can control the picture taking process. A controlled test is the only way to actually find out how to expose and develop to get certain density range -> how to "convert" a subject brightness range to certain print value range. Bracketing is fine, but one ends up NOT understanding the process but simply spending more film because of wrong and random exposures. Well, of course I'm exaggerating, but a careful calibrating minimizes all the randomness involved.

 

"Were you metering off the card or taking incident readings? Sometimes they don't agree, and with a real life 3 dimensional subject you might need a couple stops more or less exposure."

 

I don't even understand how Evan could have placed the card on Zone I with incident meter?? Most likely he is using a reflective meter, otherwise it is pretty hard to use Zone System. And what does 3D have to do with this? A gray card is equally 3 dimensional as a tree or your neighbour's nose.

 

To Evan: Could you describe the whole process: how did you setup the camera, card and lighting, how did you meter (what camera/meter), how did you develop and in what developer, how did you print and how did you examine the results. 800 is totally possible but usually the result is a bit lower EI than ISO rating, like you said.

[tim_curry]

Evan,

 

I think you may have done a proper test, but more information would be helpful. I did a film test recently with a white/black subject. Used a north facing white stucco wall and a black poster board (close to black, but not pure black). Used a spot meter to determine zone 1-8 on the white wall (texture) and the black poster board to see where it fell as zones became brighter (sort of a double check and contrast range as well).

 

After development, I first determined a pure black exposure time for film base plus fog density of unexposed film on my paper with my enlarger and my chemistry (unexposed edges of the film must be black on a proof sheet, or there is no valid test). Next started comparing a test strip of known values (Stouffer step wedge) to my film results and notes. Once I had a film speed, the highlight values were determined with a step wedge and development times for a good contrasty shot with whites and chromes (motorcycle in full sun).

 

Results were Efke25 @ asa12 in PMK Pyro 7:00 @ 70f (thanks to Ed for his input). Please note, PMK will typically reduce film speed by a stop so it would be better if we knew your complete process a bit better.

[lwg]

I don't use the first frame with "perceptible density" as my EI. I get better results choosing a frame with a zone I density of .1 above above film base + fog. his gets the image out of the toe area of the film and gives me much better results. Generally this is about a full stop slower than where I first see some density. Try treating the first "perceptible density" as Zone 0.

 

I would try using a speed of 320 or 400 from the sounds of your test.

[don_karon1]

I agree with Larry. The first perceptible density is not necessarily Zone I. I have some calibration tests where the first evident density measured out to be 0.03. The target for Zone I is 0.10, quite a bit higher.

[severi_salminen]

"I agree with Larry. The first perceptible density is not necessarily Zone I. I have some calibration tests where the first evident density measured out to be 0.03. The target for Zone I is 0.10, quite a bit higher."

 

As Adams said: "...I consider the negative density obtained from a Zone I exposure the lowest _useful_ density...". Basically this means that placing (the center of) Zone I at 0.1 one can be certain that it really is the center point of that zone (capable of recording even a bit lower densities and detail) and that we are not too far away from the straight line portion. Placing the Zone I at 0.03 could mean that even Zone III is at toe region and there would be little separation in shadow values and that basically nothing will be recorded below that value.

 

But again, the nice thing is that every one can "invent" their own zone system which satisfies the photographer's needs.

[m0002a]

As already mentioned, the best way is to measure the negative density to determine which frame has about .10 over B+F. However, a test using the first perceptible change in density does work, but it <b>must be applied to the print, not the negative.</b></p>

 

To do this test, print through the film edge to determine the minimum printing time to achieve maximum black. If you use 35mm film, this can be done by printing some sprocket holes, and using the minimum print time where there is no difference is print density between the hole and film base (both being equally black). Be sure that your prints are completely dried (and toned if you normally tone prints) when determining minimum printing time for maximum black of the film edge.</p>

 

Then use the same printing time for the film speed test exposures and determine which print has the first �perceptible change in density� over the maximum black print. But don�t get carried away in looking for the extremely �slight� difference, it should be the first one that is obviously lighter in tone than maximum black.

[ramiro_aceves]

Hello,

 

You should tell us what film, developer,dilution, agitation, development time you used. If you overdeveloped the film too much you get also an increase in the low values. The old sentence "expose for the shadows and develop for the highlights" is ok in general, but development time also affects the shadows(although less than the highlights) ( I have many densitometer graphs that show that). Also certain developers are good for gainning true speed. In your case EI800 seems too much speed gain.

 

For me, HP5 is rated around 280 in ID11 1:1 9 minutes, 5 inversions/minute

 

But no problem, if your meter is a bit mistuned now you now that EI800 works for you. That is the reason of the EI test. I have learnt that the important things are the results and not the numbers. EI800 is your number, EI280 is my number, but our results are ok.

 

 

Just my too cents.

Ramiro.

[ramiro_aceves]

Sorry Evan,

 

I did not read your posting carefully. As others said, the first perceptible density on the film IS NOT 0.1 over fog. In my testing experience, the first shade of gray on the film is usually Zone 0. Our target Zone I is considerably darker and should be 0.1 over base and fog.

 

Ramiro

[kenneth_bruno]

Greetings Evan,

I shoot HP5+ (35mm) at 800. I too found Zone I density at this EI (to my surprise) and have found the prints to have better tonal qualities than when shot at EI 400. I then found a 'real' outdoor situation with a variety of tones and still found EI 800 to produce the best negatives and prints. There are one or two other posts where this subject came up.

I use Rodinal at 1:25

Regards,

Ken.

[wolfgang_am]

Just browsed photo.net forum because I had the same question. My investigations gave me as well 800 ASA.

I did my exposure series based on measuring a grey card with a Linasix 3 and a Minolta auto-spot 1 which I calibrated myself. For calibration I used a luxmeter, which is my basis from now on, and adjusted the metering according the table on the reverse side of the Lunasix meter (which conforms to other internet sources). So assuming the meters are right at least with my processing (did it in D-76 stock, 7.5 minutes) I have 800 ASA on HP5+