Film testing with a densitometer; Am I doing this right?

[Phillip P. Dimor]

I've never tried running any film tests before, up until now.
I ordered a fair amount of 120 arista.edu/foma 400 and have struggled to get decent results. We have a densitometer at work so I figured I mine as well learn how to do this while I have the chance..

I rated the foma 400 at 400, and took several exposures
A - meter reading
B - blank
C - -5 stops
D - -4 stops
E - -3 stops
F - -2 stops

Now, I set the densitometer to Transmission\Visual (right, right?)
Frame A 0.82 meter
Frame B 0.33 blank
Frame C 0.33 -5
Frame D 0.34 -4
Frame E 0.37 -3
Frame F 0.47 -2

The guide that I am following states that;
"Take a reading of the blank frame (exposure b)
Take readings of all other frames; the frame with 0.10 - 0.15 more density than the blank frame (b) is the speed frame.

If test frame c is the speed frame then your true speed is 2x the test speed.
If test frame d is the speed frame then your true speed is equal to the test speed.
If test frame e is the speed frame then your true speed is ½ the test speed
If test frame f is the speed frame then your true speed is ¼ the test speed"

So frame F would be the speed frame and my true speed would be 125?
I mean.. That's kinda low? Any tips, help or advice would be greatly appreciated..

 

[Claire Senft]

Firstly, your results will change somewhat with development. For the degree of development that you have used approximately 160 would be your film speed.

Go outside and find a scene that has a bright white in the lit area and has a difference of about 2.5 to 2.75 stops of difference between lit and unlit areas using an incident meter with the done pointed at the camera. Set your meter to a speed of 320 and take a shadow reading...in deciding a exposure which should be shoadow based inflate your film speed by a factor of 2.

A difference of 2.5-2.75 is what I ordinarily experience when taking photos that are not backlit with an unobscured sun.

Give this film the same development that you used in your test. Print your negative using whichever you prefer to be your standard a #2 or #3 grade or #2-#3filter or no filter.

If the print has the aount of contrast that you like you are good to go for that type of lighting. If not then if the contrast is too low try a film speed of 200 and redo you test. If the contrast is too high redo your test using a speed of 125.

When you have this dialed in then choose a situation with say 1.5 difference between lit and unlit areas inflating your previous film speed by 1/3 stop and developing for 1.2x as long as previously used. Get this dialed in and you now know how to handle a normal and low contrast scene. Then do the same thing with a scene that has 3.5- 4 stop difference by reducing your normal deveopment by 1/3 and using a 1/2 stop lower film speed.

If you are not going to change your development due to lighting differencesthen use your original film speed and development for all of your work.

 

[smieglitz]

... So frame F would be the speed frame and my true speed would be 125?
I mean.. That's kinda low? Any tips, help or advice would be greatly appreciated..

The EI based on what you have said above would be 100, not 125, and yes that is low. But, it is not surprising.

Your numbers look low to me overall. Your indicated meter reading (IMR) is giving you a net density of .49 (.82-.33 fbf) which is low for the IMR middle gray and high for a frame at an adjusted -2 stops from the IMR. I try to get my zone V net density value to be around .65-.70 when the -4 stop exposure gives 0.15 or so above film-base-fog density. So, I suspect your good exposure index might well be EI 100 and that you are perhaps overdeveloping your film a bit.

Did you perchance shoot a frame at +2 stops over the IMR? If that one read ~0.98 - 1.03 gross density, I'd say you were in the ballpark with both exposure and development if EI 100 is correct.

Shoot another test roll at EI 100 and do the IMR frame as well as the +2 frame and check the numbers again. It actually wouldn't hurt to set the EI 100 and do the entire range of exposures from -5 to +5. That might make the results easier to interpret in terms of both exposure and development.

Joe

 

[Phillip P. Dimor]

Should I be subtracting base+fog from the readings?
I'll shoot another roll at 100 and throw in a +2..
My normal development for this film is D76 1:1.
It is possible that my EI is 100 and I should cut back on the development time?
I'm also using a condenser enlarger, do you reduce or expand the time to compensate?

Sorry about being so full of questions and thank you for the replies!

 

[j-fr]

Should I be subtracting base+fog from the readings?
I'll shoot another roll at 100 and throw in a +2..
My normal development for this film is D76 1:1.
It is possible that my EI is 100 and I should cut back on the development time?
I'm also using a condenser enlarger, do you reduce or expand the time to compensate?

Sorry about being so full of questions and thank you for the replies!

Yes, always subtract b+f from your reading. You don't print b+f, so it is only what's above b+f that's of interest.

If you print with a condenser enlarger, your frame A - the meter reading - should measure about 0.65. That's a good negative denity for middle grey.

If you're looking for a good normal contrast, try these 3 test exposures:

A: meter reading, resulting neg. den. should be around 0.65.
B: meter reading + 3, resulting neg. den. should be around 1.15 - 1.20
C: meter reading - 3, resulting neg. den. should be around 0.15 - 0.20

My guess is that to achieve this, you should use the film at EI of app. 50 % of the ISO speed.

Good luck! j-fr

 

[gainer]

First get a good negative and print. Then use the densitometer to see what made it so. Now you have a predicting tool. The negative may be of a pictorial scene or of a step density wedgw, as long as you know what you want the print to look like.

Photography is an open loop process. There is no feedback until after you have seen the result.