The Great Sensitometer Shootout....

[ic-racer]

I have a number of sensitometers to compare.
Each is a different construction.

EG&G: Xenon flash
Wejex: incandescent lamp
ESECO Speedmaster: green LED
ESECO Speedmaster: blue LED

I'm going to run some step wedges at different development times and see if they all produce curves that can give reasonable information about development time.

The LED sensitometers are frequently available on ebay and I hope to provide some information on the utility of those devices in making control strips for the B&W home darkroom.

Then null hypothesis here is that the color of light and time of exposure will have very little effect on the films response to changes in development times.

[James in GA]

My old toys . Most people just eyeball it. I love how a good meter saves so much time.
And you can't lie to yourself.

[ic-racer]

Two strips of Tri-X 35mm film were exposed using the 4 devices.
The first strip was processed for 5 minutes.
The second strip was processed for 7 minutes.

The the resulting negatives were read with a calibrated Tobias densitometer and plotted in Microsoft Excel. The slope of the straight line portion of the curves was obtained with a linear regression analysis.

[ic-racer]

Exposure on X-axis, Negative Density on Y axis.
Note: Colors of lines change (thank your Bill Gates).

[ic-racer]

Resulting slopes.

[ic-racer]

[ic-racer]

Conclusion:
The color of sensitometer light does not affect Tri-X response to changes in development time.

[michaelbsc]

Conclusion:
The color of sensitometer light does not affect Tri-X response to changes in development time.

Well done, sir!

[gmikol]

This is great. Thanks for taking the time to to do a controlled test.

Knowing that the type of sensitometer doesn't make a real difference, I might abandon my plans to build my own, and see what I can scratch up used.

Could you post the entire curves (toes and shoulders)?

--Greg

[Rafal Lukawiecki]

Thanks, IC. This is very useful, considering my recent barrage of sensitometer-related questions on other threads. I suppose other films should be similar in ignoring the sensitometer light source design, but this is only a hypothesis for now.

Now, I would like either of those, please.