EI Film Index

I

Ian-Barber

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I keep stumbling on articles about the importance of calculating your own EI index. Now I can see the benefits of this but can it be done without a densitometer and an enlarger and darkroom ?.

Also, do you personally do it and have you found it to be beneficial ?
 
Hardly seems worth a post to say this but - from memory, there's a chapter/section in Steve Simmons book on doing this without benefit of densitometer. Just get the perfect exposure for the film rebate to print black and see where everything else falls (or use a sheet of developed but unexposed film). Provided you don't increase the base plus fog by overdevelopment etc. this should be fine.
 
I did read the section in Steve Simmons book but he talks about using an enlarger and wet printing so I am guessing that the only way you can work out your own EI is by using this method.
 
Ian, there are a couple of different ways to determine personal EI without a densitometer: 1) somewhere...I have some instructions for doing this, but you need a piece of properly exposed film to compare to. If I can find the instructions, I'd be happy to make a copy and e-mail to you. But, what to do about the comparative piece of film? Do you know anybody who has done this testing and saved the film?, or 2) spend a bit of money and send the film to Fred Newman of viewcamerastore.com. You may not even have to send film if the film you're shooting is something he has in stock. He will send you a complete BTZS analysis. Check it out on his website, if interested.

Let me know if you'd like me to send along the instructions I have.
 
Do I have this wrong somewhere...

Isn't calculating an EI based on a particular type of film / developer and your own situation (water temp, developing methods etc)
 
I would say yes to that however other areas such as metering techniques and shutters speeds on a particular lens could be off the mark, its not just development that can cause the exposure index to be off, because of all these variables that can change I do not think its possible to get a perfect EI
 
Add in the aperture markings as well - Ansel Adams found it necessary to calibrate his lenses to correct for inaccurate markings at small stops.

You should be able to use Steve Simmons' method with contact prints, but there is going to be a potential difference if you're scanning. Look at the characteristic curves for almost any black and white film, and you'll see that the curve doesn't flatten out but seems to go on rising forever. It won't, but the makers stop showing what happens at about density 3.0. My understanding is that the reason is that for darkroom printing, that's the top of the scale that you can usefully use - printing papers have relatively small ranges.

Now look at the specs for a scanner like the Epson V700/740/800 etc and you'll see that they quote a DMax of 4.0 that they can scan. And if you look at the pdf datasheet for Kodachrome, you'll find that that starts at around 4.0. For current films, TMax keeps going up, and Kodak track the figures beyond the 3.0 mark.

This implies that if your scanner can extract the data from the darker portions, you'll automatically be recording a greater SBR than you could print in the darkroom. And since the point of setting your own EI and development regime is to control the SBR that's recorded in the area up to 3.0, when the 3.0 limit is relaxed you'll get a wider range. Put another way, expose for the shadows, and you may well find that the highlights will be OK anyway if you're scanning.
 
Ian-Barber said:
Do I have this wrong somewhere...

Isn't calculating an EI based on a particular type of film / developer and your own situation (water temp, developing methods etc)
Click to expand...

I don't mean to disagree with Martin, but EI has little to do with development as long as you're development time is something in the normal range. You do have to choose a film, but your personal EI is directly related to your meter (not all read the same or are even set to give the same middle gray value; for example, some meters read Zone V at about 18% reflectance, while others are set to 36% reflectance), camera flare, lens flare, shutter and aperture inconsistencies, and probably a couple other things I'm forgetting.

Where development plays into EI is when doing N- development. Generally, EI drops as development is reduced. Therefore, ardent Zone practitioners have tested for all these parameters and will adjust EI on-the-fly if reduced development is anticipated.

Personally, I wouldn't attempt EI testing using any scanner; just a whole gamut of other variables involved. If you want to take an empirical approach, I'd suggest the following:

1. Set your lens focus to infinity and place a black card (I use mount board) in an even, consistent light source. I place mine on the shady side of the house on a clear blue sky (no cloud) day. The message here is that you don't want the light changing on you as you expose film.

2. Set your meter, ISO dial, or whatever to the manufacturer's speed rating, then take a meter reading of the black card (make sure you're in line with the lens and at camera position, if using a spot meter; otherwise, you'll have to move the camera close enough to fill the frame with the black card.

3. Based on the meter reading from #2 (this will be Zone V), reduce exposure by 4 stops, thereby exposing for Zone I. I would strongly recommend setting shutter speed on one value and varying aperture for the remaining exposures. You'll be opening/closing the aperture a stop or two over/under so make sure you have the aperture range to complete the test. For example, if you had a 2.8 lens on the camera you wouldn't start at f/4.

4. Make exposure at meter reading, then make additional exposures opening/closing the aperture 1/2 stop until all exposures cover a range of 1 stop over (in general, film is rarely faster than the manufacturer states) to 2 stops under.

5. Develop the film using your chosen developer and normal development time; stop, fix, wash, etc, as normal.

6. When the film is dry, you're looking for that exposure that provides a very slight amount of density when compared to the unexposed film edge. This is much easier to see with LF film vs 35mm. If you want, I think I have a sheet of film showing what I'm talking about and I can try to take a picture of it with my phone and post here.

Doing this little bit of testing will get you pretty darn close...close enough that you could adjust your EI as experience dictates.
 
Very well explained Stephen, the penny is now starting to drop. Time to start looking at some data sheets I think
 
Thanks Alan, again, i am finding this interesting and will conduct this test if only to satisfy my curiosity
 
Kodak published a series of paperback books in the '90s that included one or two about black and white film. One of them, called 'Advanced Black and White Photography', gave a method for determining EI using a Kodak Projection Print Scale. This is a flexible plastic disc that is divided up into segments, each darker than the one next to it. It is used for making test print exposures, but can also be used to compare negative densities. The book is part of the Kodak Workshop Series, and can be found on the websites of the usual secondhand booksellers like Amazon. I've found these guides to be quite useful, but if you decide to get a copy, be wary of paying over the odds. The books cost no more than £15 new, and should be pretty cheap now.
Alex
 
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