Measuring film density

Stephen Ryde · Aug 16, 2019

Hello All

I am curious to know if anyone has or can measure Ilford FP4+ with a densitometer.
I am looking for Film Base + Fog (Zone 0) and .1 above fb + f (Zone I)
I have an Ilford EM10 to measure the difference in the light intensity between my two sample negatives but I don't know what .1 above fb + f looks like using my EM10
Has anyone measured with a densitometer and then with the EM10 that could share there findings with me?

Thank You
Stephen

Bill Burk · Aug 17, 2019

The EM-10 has a usable range to about 2.5 density.

I turned on a 100 watt halogen bulb (don’t trust LED) and walked away until I got a reading of 4 (2 marks). About 6 feet from the bulb.

I read Stouffer scale steps directly over the sensor and got the following:

Step, Density, EM-10
1, 0.04, 4+
2, 0.18, 5
3, 0.34, 6
4, 0.50, 7
5, 0.67, 8
6, 0.81, 10
7, 0.96, 13
8, 1.10, 16
9, 1.25, 20
10, 1.41, 24
11, 1.56, 30
12, 1.71, 40
13, 1.86, 52
14, 1.98, 58
15, 2.15, 70
16, 2.30, 75
17, 2.45, 80

bernard_L · Aug 17, 2019

I have an EM-10. I believe it is meant to "memorize" a given light level, from a known good exposure to another frame, adjusting the aperture to reproduce the same on-board illumination. The construction is unsophisticated, a CdS LDR and a consumer-grade potentiometer. I would not trust it as light-measuring device.

Europan · Aug 17, 2019

I have a comparation densograph that goes up to log 4. You can send me a film, I’ll return it to you together with a graph on paper.

John51 · Aug 17, 2019

Accuracy from one EM10 to another I wouldn't trust but consistency is all we need. If everything is left as is and my EM10 was showing green, it will show green days later.

Bill Burk · Aug 17, 2019

Everyone is right, the EM-10 is a “comparator” so you need something known to compare with.

I would strongly recommend pairing it with a Stouffer scale. Get the green light on under the test negative and then find the Stouffer step closest to the green light.

You will have a “densitometer” that is accurate to 0.15 and this can be adequate for many purposes.

Stephen Ryde · Aug 17, 2019

Thanks for all the feedback

My plan was to use my EM10 to compare the negatives I developed. fb+f and my Zone I tests at shooting FP4 @ 80 iso, 100 iso, 125 iso, and 160 iso I would document the changes in the different light intensity and see if they compare with any numbers that I recieved here.
@Bill Burk The stouffer numbers that you posted Bill may help me a lot
I looked into getting a 21 step wedge from Stouffer but I wanted to try this first. Shipping over the line to Canada is crazy pricing on duty.
I could mail my test to a guy in Missouri and he would put them on a densitometer for me but I like to try playing with what I have available to me first.
Stephen

John51 · Aug 17, 2019

One of the initial tests I did when I got my darkroom running was test for optimum black (blank neg used) at full enlarger height. I set the EM10 to that and lowered the head to only just cover 8x10. Then I dimmed the bulb to match the EM10. Printing times were different.

Stephen Ryde · Aug 17, 2019

@John51 That's discouraging John
Perhaps I will just send my test strip out to get read by a densitometer
Thanks for all your help folks

Stephen

ic-racer · Aug 17, 2019

Do you have a light meter that reads to 1/3 of a stop? Place the film over the sensor. (1/3 stop = 0.1log d)

Bill Burk · Aug 17, 2019

You can measure zero with the lens stopped down and then put your negative in and click f/stops to open the enlarging lens to find how many times 0.3 the density is.

Stephen Ryde · Aug 17, 2019

@ic-racer Yes I do! Place the film over the light meter sensor? Can I do that on my light table and check the EV?

Bill Burk · Aug 17, 2019

John51 said:
One of the initial tests I did when I got my darkroom running was test for optimum black (blank neg used) at full enlarger height. I set the EM10 to that and lowered the head to only just cover 8x10. Then I dimmed the bulb to match the EM10. Printing times were different.

Might have changed the amount of “blue” light when you dimmed the bulb (assuming an incandescent bulb on a dimmer)

Bill Burk · Aug 17, 2019

Segr said:
@ic-racer Yes I do! Place the film over the light meter sensor? Can I do that on my light table and check the EV?

Yes! Every 1/3 stop is 0.1

John51 · Aug 19, 2019

Bill Burk said:
Might have changed the amount of “blue” light when you dimmed the bulb (assuming an incandescent bulb on a dimmer)

That's a likely answer. Original plan was to take a reading, adjust height, dim bulb to give the same time, easy as. It's not a large difference but noticeable. Wouldn't be a problem on my (as yet unused) Durst as it has a sliding barn doors type nd dial.

I could establish the aperture for best IQ at full height and stop down when the head is lowered. Maybe some IQ loss but the smaller the print, the less that matters.

Measuring film density

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