What is Exposure Index

[Sirius Glass]

God originally created light in exactly eight zones of gray. But then Super-XX film came along and somebody thought they detected twelve zones. But then Ansel Adam's discovered that if you simply developed Super-XX for less time, you got back to eight zones, which made Minor White happy because he had already founded a religion which only allows eight zones to be contemplated while sitting crosslegged on a bamboo floormat. Kodak taught a different religion entirely, based on a curved universe.

 

[Sirius Glass]

Although I always shoot at box speed, I may expose at variation to this.

+1

 

[tomfrh]

I have always used the box speed. Some cut the ISO by 1/3, 1/2. or 2/3 f/stop to get a denser negative or because they think that they will get more shadow detail. I suspect that many do it because:

1. They do not know how to meter correctly and regularly take light readings of the sky.
2. Their light meters, cameras or lenses need a CLA.
3. They think they are smarter than the film manufacturer.
4. They love to test and would rather test than actually take photographs.
5. Some are Zonistas.
6. They are compensating for not knowing what they are doing. Related to #1 though #4.

I often shoot velvia 50 at 40, simply because I find that a better baseline for my tastes.

To me it's simply like how much salt to put in a recipe. The cookbook might say 1 teaspoon, but if that's coming out a bit salty or a bit bland for your tastes, then throw in a bit more or a bit less next time!

 

[Sirius Glass]

Lowering the speed of Velvia 50 to 40 will increase the color saturation.

 

[Bill Burk]

Lowering the speed of Velvia 50 to 40 will increase the contrast.

It will make your slides look brighter with the projector on "Low" which might, in the long run, be better for the slides.

 

[markbarendt]

It will make your slides look brighter with the projector on "Low" which might, in the long run, be better for the slides.

Good thought.

 

[markbarendt]

Lowering the speed of Velvia 50 to 40 will increase the contrast.

This I don't get.

I'd expect subjects to move right but not more contrast, please explain.

 

[Sirius Glass]

Please see my edit.

 

[MattKing]

Lowering the speed of Velvia 50 to 40 will increase the color saturation.

If you are referring to metering, I think you have this reversed.

If you meter at 40, you will end up giving the film more exposure, and the transparencies will be lighter.

 

[Sirius Glass]

You are right. I started to respond to your PM and typed "When I got my first 35mm camera I took it to the New York World's Fair every day for several weeks. I learned that if I under exposed the Ektachrome and Kodachrome the colors were more intense. I need to reedit my post." Under exposing slide film by 1/4 to 1/2 f/stop will increase saturation. The danger is that, at least back then if one under exposed by 1 f/stop the slide would start getting too dark.

 

[Arklatexian]

I agree! Sirius' list is a hoot.

We could ad to it ad infinitum - invite 'em - the Illuminati to add more light to 'em.

The only "real" reason to test for EI is to find out if shutter speeds, apertures, exposure meters, enlarger timers, i.e. any variable from shooting to printing the finished print are accurate. I am comforted that everyone in APUG,except me,. can regularly send all their equipment to be CLAed or overhauled regularly (once a year maybe), or maybe we are just too lazy to test each variable (and that includes me). Testing also helps to keep from working more or less blind while in the darkroom. As they say, this is only my opinion, based on what I have read by Ansel Adams, Fred Picker and others, because it makes sense to me, and I may be wrong but, I fear, not any more than some of what I've read tonight. Now does this make me one of the illuminati(whatever that is)?............Regards!

 

[tomfrh]

exposing slide film by 1/4 to 1/2 f/stop will increase saturation. The danger is that, at least back then if one under exposed by 1 f/stop the slide would start getting too dark.

yes, this is my expeirnece, underexposing by a third or a half a stop results in a darker slide that looks more saturated.

In general I find RVP50 too dark when set to box speed, so I set the camera to 40 and use that as the metering baseline.

 

[Bill Burk]

The only "real" reason to test for EI is to find out... Now does this make me one of the illuminati(whatever that is)?............Regards!

oldtimermetoo,

I like to keep my variables broken out where practical.

For example, I'd rather not have my EI include shutter timing. I went to some effort to test the shutter speeds of a camera only to have the mainspring break while I was at the departure gate at the airport (See my picture StoneNYC taken on that trip). I bent the tail of the spring and put it back in operation, but it wasn't accurate anymore. I might not have known what to do if my EI included shutter speeds. But since my EI was intended for theoretically perfect shutters, I just "ignored" the shutter speed markings and estimated shutter speeds by ear.

But I've got no problem with your approach. I appreciate the traditional Zone System approach (which effectively includes "everything" as if it were a closed-loop system) because following the footsteps of the masters makes great adventures for storytelling.

And for me, much of the pleasure of photography is the storytelling.

 

[michaelorr]

My takeaway as one still in learning mode is Ralph W. Lambrecht a couple pages back has the right bottom line on the subject. In addition the developer/dilution choice has some bearing on whether the ISO is achievable. The film cutsheet shows what the film speeds go with what developer/dilution. Massive development chart also has good info, to decide what to set for EI on meter. It was my takeaway from a thread started only a few days ago (placing shadows on zone iv) on the same subject, where summarizing Michael Barendt and Bill Burk's comments come down to understanding what contrast level you are aiming for, and good understanding of what you are metering to get the shadow detail you are looking for. Those guys have it together, and have development charts for contrast index (CI) to prove it. Their final prints speak to their excellence. And Ralph W. Lambrecht wrote the book... And to couple this discussion with a thread started just today, one film one developer, I use only use HP5 for 8x10 because of the speed and the desire to shoot much smaller f/ and I use FP4 in the 4x5, the only films I develop. I settled on using Perceptol as my default personal choice for most developing, if I am able to use a liter of stock up as a single shot in BTZS tubes. If I only have a few sheets to develop and I don't have a compelling reason to use perceptol, I will use DDX, for reasons I don't know other than it is easy to work with for me and my lab conditions. Point is, I will be preparing the development curves for HP5 and FP4 developed with perceptol diluted 1:2 using my development process, temp, as my default. For developing in DDX, if I feel that the negative will be produced that I desire, I will just guestimate from the DDX and film cutsheets. Again my many thanks to Bill, Michael, Ralph and many others who chime in and help us who come to APUG for this very reason - their time is theirs not ours and they are contributing greatly to so many more with their time. There have been at least 4 threads in the past week on these related topics that they all have helped out on.

 

[michaelorr]

I do wish to ask if PE is still reading this thread - I looked up that reference you posted. I have an old Weston meter that is in ASA, recently calibrated, and maybe one or two Pentax bodies that say ASA. So, my read is that I need to derate by one stop the ASA setting relative to the film ISO to compensate for the meter readings of these devices?

 

[Stephen Benskin]

I do wish to ask if PE is still reading this thread - I looked up that reference you posted. I have an old Weston meter that is in ASA, recently calibrated, and maybe one or two Pentax bodies that say ASA. So, my read is that I need to derate by one stop the ASA setting relative to the film ISO to compensate for the meter readings of these devices?

No. It was the testing methodology of B&W film that changed, not the meters. The same meter needs to be able to represent B&W negative, color negative, and color reversal film. From C.N. Nelson's Safety Factors in Camera Exposure, "There are no plans for reducing the safety factor by means of a change in the calibration formula or exposure meters because there are too many meters in existence with the present calibration and because the meters are also used for color film for which no change in exposure level or film rating is required or desired."

 

[michaelorr]

much appreciated, Stephen!

 

[Photo Engineer]

I do wish to ask if PE is still reading this thread - I looked up that reference you posted. I have an old Weston meter that is in ASA, recently calibrated, and maybe one or two Pentax bodies that say ASA. So, my read is that I need to derate by one stop the ASA setting relative to the film ISO to compensate for the meter readings of these devices?

I'm still here!

EI and ASA are so close that there is very little difference. Derating negative films by about 1/3 stop or a tad more in any reference system will insure the maximum count of good pictures on any given shoot due to the inherent characteristics of neg-pos systems, and the curve shape of average films. This is shown in both Haist and in Mees (revised edition) or Mees and James.

PE

 

[Sirius Glass]

I do wish to ask if PE is still reading this thread - I looked up that reference you posted. I have an old Weston meter that is in ASA, recently calibrated, and maybe one or two Pentax bodies that say ASA. So, my read is that I need to derate by one stop the ASA setting relative to the film ISO to compensate for the meter readings of these devices?

No. They will work properly when set it ASA is set to the ISO speed. ASA was renamed ISO for all practical [and impractical] purposes.

 

[pdeeh]

EI and ASA are so close that there is very little difference.

Is that a typo for "ISO and ASA are so close there is very little difference." ?

 

[Sirius Glass]

There is a difference, but so small that it does not matter that is why PE said that and I said:

No. They will work properly when set it ASA is set to the ISO speed. ASA was renamed ISO for all practical [and impractical] purposes.

 

[Photo Engineer]

Is that a typo for "ISO and ASA are so close there is very little difference." ?

See here: http://www.imatest.com/docs/sensitivity_ei/

and here: https://en.wikipedia.org/wiki/Film_speed#Digital_camera_ISO_speed_and_exposure_index

You will find that ISO and EI are different aspects of the same thing.

PE

 

[Xmas]

HP3 used to be 200 ASA then magically it changed to 400 ASA, if you liked your negatives the way they were, you changed your wet Trousers.

 

[OptiKen]

No. They will work properly when set it ASA is set to the ISO speed. ASA was renamed ISO for all practical [and impractical] purposes.

The AMERICAN STANDARD ORIGANZATION was changed to the INTERNATIONAL STANDARD ORIGANZATION

 

[Stephen Benskin]

The AMERICAN STANDARD ORIGANZATION was changed to the INTERNATIONAL STANDARD ORIGANZATION

Just to nit-pick. It's actually The American Standards Association and The International Organization of Standardization. ASA later became ANSI (American National Standards Institute). ANSI and ISO are not the same organization. The international standard for the determination of b&w negative film speed was adopted which is why the film speed prefix of ASA was changed to ISO.