I have the opportunity to acquire a simle exposure meter, an Ilford EM10, on which correct exposure is achieved by changing aperture. However, I wish to use the lens stopped down optimally 2-3 stops all the time. Is there an easy way to convert to times or is it so crude I might as well stick with test strips?

-- Nigel Craig (Nigel-Craig@btinternet.com), July 01, 2001

Answers

enlarging lens are the same as camera lens when it comes to f stops. just use that as your point of reference. f8 will need twice as much light as 5.6, etc., etc.,etc.

-- Ann C lancy (clancya@mediaone.net), July 01, 2001.

The EM10 is a nice thing to have around but is annoying in that it is calibrated to changes in aperture. I used the following method to recalibrate the instrument for my purposes - may be too much trouble for some, but here goes...

I inserted a step tablet into the negative carrier and read the EM10 readings off at each step at my usual aperture setting. This gave me a smooth S shaped curve (much like a characteristic curve) - given how non linear it is, its not surprising that they calibrate it for one point. I plotted the EM10 reading against the density of each step (so, it actually can function as a cheap, crude densitometer provided your light source does not vary too much). I then printed the test strip. So, at this time, I know what density prints completely black (at this exposure time) and what density is just short of white. If I want any other density to print as black, I just need to adjust my exposure (each 0.3 additional density is equal to one stop). Now when I insert an actual negative into the carrier, I measure the parts I want just short of black and just short of white. I then look at any adjustments that are needed to the time and expose - so, for e.g., suppose at 10 seconds a density of 0.1 on the step wedge printed as total black and the density I want as total black on the negative is actually 0.2, I need 1/3 stop more exposure.

I should also add that I find this a convenient way to get into the ballpark but there are enough subtle decisions that still have to be made that I'm unsure that it is actually a significant advance over the test strip. Also, I looked at it in terms of using it for graded papers - have not looked at spectral sensitivity which might be an important factor when using variable contrast papers etc.

Cheers, DJ.

-- N Dhananjay (ndhanu@umich.edu), July 01, 2001.

Don't fool with a meter as limited as the EM10 unless you're willing to tailor your printing technique to suit its limitations. Get one that lets you vary everything you want to vary while still giving you the info you need to get started. Using the EM10 to print as you want to do apparently means doing your own calculating of times and then making test strips. In fact all metering schemes require making test stips if you want good prints. It's just that the more versatile meters get you to that point quicker and give you more options without your having to do a lot of calculating for yourself. At least that's my experience of enlarging meters.

-- Keith Nichols (knichols1@mindspring.com), July 01, 2001.

I use one and go along with Ann's answer - it works for me. It's just a means to and end though and provides me with a good "ball- park" starting point from which to fine tune the exposure. If I want to do some dodging, etc - I merely double the time and halve the lens opening, and so on. It really shines when making prints of a whole roll of film and making little test strips for each one becomes a pain.

-- Harv Jenkins (hjenkins@prcn.org), July 01, 2001.

You can also look at the site http://unblinkingeye.com/index.html. and get a conversion table for times into stops prepared by Ed. It is in the articles section.

-- Jorge Gasteazoro (jorgegm@worldnet.att.net), July 01, 2001.