Personal film speed w/o densitometer.......and Pyrocat HD

[Doug Bennett]

After several years of serious shooting, I've never done a film speed test. I do not have access to a densitometer. Up 'til now, I've typically pulled one stop, reduced dev by 30%, and gotten decent results. However, I want to give testing a try.

Today, under an even gray overcast sky, I exposed a roll of Classic 400 roll film at 4 different speeds: 400, 320, 250, and 160. I exposed 3 frames at each speed: as metered (i.e. zone 5), -4 stops (zone 1), and +3 stops (zone 8).

Most of the articles I've read say that, after processing the film, I want to look for a zone 1 frame that has "slightly more tone" than the clear leader. Could I not use my light meter to help with this? If I meter through the clear leader (i.e. film base and fog), then look for a zone 1 frame that is 1 stop more dense, am I on the right track?

Pyrocat HD: I plan to take the Formualry PMK times for Tri-X (14 min.) and HP-5 (13 min.) and call it 13.5 minutes for Classic 400. Then, knock off about 20% for Pyrocat HD.

 

[Canuck]

I do mine the simple way. When doing a contact sheet for testing, I give the contact just enough exposure to just barely see the edge of the film on the paper. YMMV, but at this point, the contact sheet will now give me a better idea on what my personal EI is. I just look for the shot that looks the best for density and range of tones. The setting on that frame will say choose me for your EI!

If the density looks good but contrast is too low or high, you can switch grades or better yet, for me anyways, adjust the film development time up (bump up contrast) or down (lower contrast) to get the 'look' you want. Cheers.

 

[etriplett]

Try out this (there was a url link here which no longer exists) in the apug article section. It talks about testing with your light meter. Cheers.

 

[Doug Bennett]

Hmm.... on the test roll, exposed as noted above, I have no density at all on any of the zone 1 frames.

 

[noseoil]

Doug, this is why I use a step wedge for film tests. One shot gets you film speed and development information. Easier to see these relationships on one sheet of paper after it is printed.

 

[Doug Bennett]

Doug, this is why I use a step wedge for film tests. One shot gets you film speed and development information. Easier to see these relationships on one sheet of paper after it is printed.

I'm all ears; tell me more.

 

[smieglitz]

...Most of the articles I've read say that, after processing the film, I want to look for a zone 1 frame that has "slightly more tone" than the clear leader. Could I not use my light meter to help with this? If I meter through the clear leader (i.e. film base and fog), then look for a zone 1 frame that is 1 stop more dense, am I on the right track?...

Doug,

This sounds to me like you would be looking at a density more like zone II 1/2 since any density blocking a full stop above fbf would have a density of 0.30 more. Your film speed should be based on achieving about 1/3 stop or 0.10-0.15 above fbf.

A very useful thing to acquire for doing film tests without a densitometer is a Kodak wratten #96 0.10 neutral density gelatin filter. That gives you a visual comparator that you can simply lay over the film base (e.g., an intentionally unexposed blank frame) and check against an adjacent exposed frame for the standard 0.10 density above fbf upon which film speeds are generally based. IIRC, Henry Horenstein's book on black and white photography also describes a simple 35mm film speed test based on using such a filter.

The filter although not inexpensive is a very good investment and is a lot cheaper than a transmission densitometer. Should you decide to pick up a densitometer in the future, the ND filter can also be used to calibrate the low end of the instrument.

Joe

 

[Doug Bennett]

Doug,

This sounds to me like you would be looking at a density more like zone II 1/2 since any density blocking a full stop above fbf would have a density of 0.30 more. Your film speed should be based on achieving about 1/3 stop or 0.10-0.15 above fbf.

Joe,

First of all, I thought Zone 1 was one stop above fbf, not 1/3 stop. Am I wrong here?

What I was calling Zone 1 was exposed at -4 stops from "as metered", or Zone 5.

I work in the theatrical lighting industry. We have .1 ND filters in stock. I didn't know it was the same ".1". Duh.

 

[lee]

point 10 above fb+f should be the same. in my feeble head

lee\c

 

[smieglitz]

Joe,

First of all, I thought Zone 1 was one stop above fbf, not 1/3 stop. Am I wrong here?

What I was calling Zone 1 was exposed at -4 stops from "as metered", or Zone 5.

I work in the theatrical lighting industry. We have .1 ND filters in stock. I didn't know it was the same ".1". Duh.

Doug,

The density response of a film to a set exposure (i.e., a stop) is not linear over the range of the film. You are correct that -5 stops exposure is one stop less exposure than -4 stops, but that doesn't mean the densities will correspond neatly. Density is the log of opacity (which is the reciprocal of transmission) so that a density of 0.30 represents an increase in opacity of one stop or a cut in transmission of 50% of the previous value.

Given a set increase in exposure by one stop (and standard development) the densities of corresponding zone exposures might be something like:


zone 00 ( -6 stops from indicated meter reading) = fbf or 0.00 net density
zone 0 ( -5 stops from indicated meter reading) = 0.02 net density above fbf
zone I ( -4 stops from indicated meter reading) = 0.10 to 0.15 above fbf
zone II ( -3 stops from indicated meter reading) = 0.25 above fbf
zone III ( -2 stops from indicated meter reading) = 0.35 above fbf
zone IV ( -1 stop from indicated meter reading) = 0.55 above fbf
zone V (indicated meter reading) = 0.70 above fbf
zone VI (+1 stop from indicated meter reading) = 0.85 above fbf
zone VII (+2 stops from indicated meter reading) = 1.00 above fbf
zone VIII (+3 stops from indicated meter reading) = 1.20 above fbf
zone IX (+4 stops from indicated meter reading) = 1.40 above fbf
zone X (+5 stops from indicated meter reading) = 1.50 above fbf

Now these target density values will vary with the type of film used, developer, type of enlarger, paper type, camera format, etc., as well as which zone system text you read so they are not set in stone and others will give you different values. But, the point is that a constant one stop exposure change (input) ranges from about 45% to 65% increase in the resultant density change (output) and the rate of that change isn't constant. If it were a perfect 1:1 relationship between exposure and density (input to output), zone X would have a 3.00 net density value. Also, the rate of density change in the midtones is typically greater than that of the shadow and highlight zones.

(Also, if you use a pyro based developer the stain adds to the effective zone densities for ultraviolet sensitive print processes, but that is another tale...)

Check a standard zone system book for more detail on the above. (Ansel Adams' "The Negative" is the cornerstone text.)

Trust me though, your zone I exposure (-4 stops from the indicated meter reading) should produce a density value above fbf of ~ 0.10 for medium & large format films, and ~ 0.15 for 35mm film.

Joe

 

[smieglitz]

... Could I not use my light meter to help with this? If I meter through the clear leader (i.e. film base and fog), then look for a zone 1 frame that is 1 stop more dense, am I on the right track?

Doug,

After all my long-winded replies I forgot to mention that yes, you can probably use a good spot meter to read the frame densities and get you in the ballpark. You need to be careful of flare and target +1/3 stop (= 0.10 density) above the blank fbf frame to determine the proper - 4 stop exposure and film speed.

(And BTW, "I think we're all Bozos on this bus.")

Joe

 

[Doug Bennett]

Thanks for the information, Joe. I don't have a spot meter, but my Sekonic is accurate, and if I'm careful to meter a constant light source, it should work.

Why I didn't build any density in any of the -4 frames (even at ISO 160) is still a mystery.

I gave the Classic 400 a 5 minute presoak, but when I dumped the developer, it had picked up a noticeable blue color. Could this be a contributing factor?

(And BTW, Joe, "Everything You Know Is Wrong").

 

[sanking]

Why I didn't build any density in any of the -4 frames (even at ISO 160) is still a mystery.

I hate to mention this, but are you sure that you mixed both Stock Solutin A and Stock B to make the working solution? If you did not, the result would be no density as all as both parts are necessary to make the working solution.

Several people have reported early death of Pyrocat-HD stock solutions in the past, only to later discover that they failed to add one of the stock solutions in mixing the working solution. You would be amazed to hear how often this happens, but I must admit that I have done it myself more than once.

Sandy

 

[Doug Bennett]

I hate to mention this, but are you sure that you mixed both Stock Solutin A and Stock B to make the working solution? If you did not, the result would be no density as all as both parts are necessary to make the working solution.

Several people have reported early death of Pyrocat-HD stock solutions in the past, only to later discover that they failed to add one of the stock solutions in mixing the working solution. You would be amazed to hear how often this happens, but I must admit that I have done it myself more than once.

Sandy

I don't think so, Sandy. I developed what looks to be normal-ish density in the zone 5 and zone 8 frames.

 

[sanking]

I don't think so, Sandy. I developed what looks to be normal-ish density in the zone 5 and zone 8 frames.

Doug,

Sorry, I misunderstood the report of your original test. I though you were saying that you got no density at all on the negatives. My mistake for not reading closer.

Sandy

 

[Canuck]

An article in The Black & White Enthusiast called "Taking Control" by Andrew Smallman. He discusses exposure and graduation and how to determine a personal EI using an exposure meter to help plot a E/D curve. Sounds like what you guys are all doing at the moment

 

[noseoil]

Doug, you have the correct method of testing, just try it again.

I use a white wall in full sun for 35mm testing. Don't use low enough numbers on speed and aperture to get into reciprocity trouble with any film, stay below 1/2 second if possible. This is one cause for bad low numbers, at times around a second, all bets are off.

Take the first shot at zone V. If you are at zone V, subtract 4 stops to get to zone I. If you are at zone V, add III stops to get to zone VIII. If you vary your speeds accordingly, there should be something there on the bottom.

My mention of a step wedge is what I use with 4x5 film testing. It won't fit in a 35mm camera too well. tim

 

[Doug Bennett]

Thanks, Tim. I was shooting the test with my Minolta Autocord 6x6, and did indeed stay at 1/30 or above. It's a mystery, but I'll have another go at it. I may first test with a film/dev combo that I'm already fairly successful with. HP5/HC-110 dil H probably. For all of my playing with films and developers, I have a hard time beating that combo.