View Full Version : Film speed testing without a densitometer

David Home
13-Nov-2009, 11:56
Hi all.
I know this subject has been discussed before, but I am hoping to get some more specific comments.

I bid on a X-rite 810 densitometer this week on ebay and it ended up going for $500US.
Oh well, so much for getting a densitometer! I think this is pretty high a price for something I am only going to use occasionally. So I would like to consider the alternatives.

1) Stouffer 4X5 step-wedge from Bostick&Sullivan. Someone mentioned in an older thread using the Souffer on a light box and 'eyeballing' the test negatives to get a close match. Will this get me within 1/3 of a stop? What as the values of the lower steps of the wedge?

2) I have a corrected spot meter from Zone VI which is quite accurate and linear.
Could this be used to meter the negatives on a light table and be accurate enough?

3) Any generous lab staff or serious amateurs in the Toronto area that would let me use their densitometer? I am happy to show my appreciation with beer or butter tarts.

Any other methods please let me know. Thanks for your comments.
Regards, David Home

PS: I just thought that maybe a combination of 1 & 2 might work. This would use the light meter only to make comparative measurements and not demand absolute accuracy....

ronald moravec
13-Nov-2009, 12:24
You can pay someone to read a neg for you. Prolabs should be equiped. Unfortunately I have forgotten the required density reading for i stop above FB+ fog.

For decades I used a standard test target that consists of a color checker or grey card depending, a step wedge, a doll with pleated black skirt and linen white blouse. The print needs to show the pleats clearly and the blouse needs to show detail.

Film speed is detirmined by the fasted speed at which I can get a printable difference in the lowest darkest 2 steps. Development time detirmines if I get grey ( underdeveloped ) or featureless white lacking detail ( over developed) detailed whites.

Add some white and black clothing to the shot.

Remarkably it turns out to be box speed so I must be doing something right. The doll is rendered correctly also.

Keep in mind a 4x5 view camera focused on 8x10 area will have one stop underexposure from bellows extension with a symetrical lens. When you do an outside pic, it will be over exposed unless you compensate. Development time will be the same. 123 and 35 mm have less compensation required.

Less accurate, but go outside and do some white houses and car tires. Tites should be dark, but not as dark as shadows under the car.

My subject is studio strobe lit so it is available day or night, summer or winter and is always the same. It also works for color or digital with the color checker instead of a grey card.

Easy 1/3 stop accuracy.

13-Nov-2009, 12:39
I just use my eyes, and the following method:

Meter for medium grey, with your reference meter. Consider the indicated amount of exposure "zone 5". Make an exposure of a grey card.

Make a series of exposures with one-stop less exposure (zone 4 through -1 exposures).

Develop normally; when you are done, pick the sheet that shows the first hint of visible density compared to clear film. Zone -1 should be clear and zone 0 should be clear and if you have (printable) density on zone 1, your EI is pretty good. Pretty often, it turns out that zone 2 is the first negative that has any printable density on it, so I reduce my EI to 1/2 box speed.

I think zone 1 is supposed to be .1 log D above film base+fog.

13-Nov-2009, 13:37
Try the BTZS approach:

Adjust the light source on your enlarger so that a reflected spot meter reading at ISO 100 reads EV4 on a matboard on the easel.
Place your film on the baseboard and contact print the step wedge on to the sheet film using an exposure time of 0.4 seconds on you enlarger timer.
Process the film. Use multiple sheets, all exposed the same way, and develop for 4, 5.6, 8, 11, and 16 minutes.
Send the film to Fred at the View Camera Store and he will do all of the densitometer testing for ~$50 and give you extensive film information using the BTZS plotter program.

Brian Ellis
13-Nov-2009, 13:46
The reason the x-rite 810 densitometer fetched such a high price is that it's a combination reflection/transmission densitometer. There's very little market for transmission densitometers alone these days because they were mostly used by labs that did film. But there's still a market for reflection densitometers because people who print digitally use them to create profiles and probably do other things.

If you only want a densitometer for film tests, you don't need a combination reflection/transmission densitometer, a transmission alone will do fine and you can get one of those for a whole lot less than $500. I think I sold my Macbeth on ebay for something like $150.

13-Nov-2009, 14:14
A transmission densitometer is also a very simple device to make if you understand the principle of densitometry and can solder. I have an accurate densitometer I made for less than 20 dollars, using a phototransistor and micontroller with LCD display. A simpler form would simply be a battery, phototransistor/photocell, pot, panel ammeter from radioshack, and calculator that can do logs. Extra points if you use a slide rule.

Nathan Potter
13-Nov-2009, 15:24
Phil Davis describes how to use a spot meter with a density wedge as a densitometer in his ever famous book "Beyond the Zone System". To summarize:

If you use a Pentax spot meter find an old 46 mm thread filter of some sort and smash out the glass. Buy an achromat of about 1.790 OD from Edmund Scientific with say about a 5 inch focal length. If lucky you can ram the achromat into the filter ring which then will screw directly into the Pentax front.

Next build a stand that will hold the Pentax directly over a light table with the lens exactly focused on the surface of the light table. When mounted the button needs to be depressed so that you can read the light intensity. I discovered a useful trick in actuating the meter. There is a screw in 1/4-20 thread at the base of the handle which holds a strap. If this is unscrewed the meter won't work - the battery circuit is disabled. The meter is enabled electrically thru the 1/4 -20 screw making connection between the outside metal base on the handle and the internal threads that it screws into. So -- I replace the 1/4-20 strap holder part with a longer brass 1/4-20 machine screw with a wire stub soldered on. Make sure the brass screw doesn't contact the bottom plate - you can wrap a bit of insulating tape around the screw to be sure. Now you can connect an external on/off switch between the brass screw and the bottom plate to actuate the meter as long as the regular button remains pressed. The new switch can be a momentary type that is attached to the stand along with the meter. My light table runs at about 16 EV brightness (164,000 lux) which allows me to measure logD 3.0 at about 5 EV without difficulty.

Some precautions in setting this up though. You want to read only transmitted light so work in a dark room.
Also as mentioned by Davis I cut an aperture on a piece of white cardboard slightly smaller than the width of the Stouffer step so as to see only that particular density on the reference wedge. The aperture also reduces scattered light entering the spot meter so provides increased accuracy. The white surface makes it easier to see where on the negative you are or what step on the wedge you are at.

Operationally you are matching the known density of the wedge to the spot on the negative that you want to measure. You can also do a crude interpolation when the two spots are slightly off and resolve about 1/3 stops. I found it desirable to toggle the meter with the external switch so as to not drain the battery in the spot meter. I would also point out that a calibrated Stouffer wedge is pretty darn linear but the spot meter exhibits a slight discontinuity at some midpoint (I forget just where in the scale). Overall this is makes a pretty effective densitometer as Davis suggests although I've been using such a device in my home darkroom long before Phil suggested it.

Nate Potter, Austin TX.

13-Nov-2009, 17:14
Vuescan has an option to "Toggle Densitometry Display" or something like that if you have a film scanner and Vuescan. After you scan you hold Ctrl and it displays the values as you hover your mouse over areas of the image.

Ken Lee
13-Nov-2009, 17:31
You don't need a densitometer.

Here (http://www.kennethleegallery.com/html/tech/testing.php)'s a brief article that shows you one method. In a nutshell, you try 3 different film speeds, and 3 different developing times.

13-Nov-2009, 19:10
For you "Zone I" test, put the negative over your standard reflected light meter's sensor and look for a 1/3 stop drop. That would be the 0.1 d negative.

If you are using 1.2 d for Zone VIII then then correct negative will give a 3 stop drop when placed over your reflected meter's cell.

In the mean time keep looking for a densitometer. I got 2 for $25 a few years ago.

David Home
13-Nov-2009, 21:37
Thanks for all the comments.
I will keep my eyes open for a transmission only densitometer.
In the meantime I will use my light meter and look for a 1/3 stop drop with the correct negative.
Regards, David

Bjorn Nilsson
14-Nov-2009, 07:44
You don't need a densitometer.

Here (http://www.kenleegallery.com/html/tech/testing.html)'s a brief article that shows you one method. In a nutshell, you try 3 different film speeds, and 3 different developing times.

I'm very much with Ken on this subject. While I own a densitometer, the testing is at best quite tedious. It's also very easy to get caught in an endless testing stage, so that all you do is testing with all the various excuses like, "I'm still not really done with testing that particular combination ...".
So see to that you are getting your negatives close to perfect (where Ken's method is a very good approach) which is much better than most of the classic master pictures had anyhow.


14-Nov-2009, 09:17
There is an excellent article here :
You can test your film without a densitometer. Although I own a densitometer, I prefer using Paul's method. As he states on his article : we exhibit prints, not negatives. IMHO it is the simple way to achieve quickly a first good print.

14-Nov-2009, 10:08
In the DVD book "Finely Focused" there is an article on the Zone I test using a ND filter 0.10, clear film and your enlarger. I have ran the test and checked it against a densitometer and it works.

The DVD info is here http://circleofthesunproductions.com/FinelyFocused.htm

Louie Powell
14-Nov-2009, 10:33
Here's a way to do the film speed test that doesn't require a densitometer.

Film speed is assessed in shadows. Zone I negative density is defined as the density of the film base plus processing fog, plus 0.1.

Run a series of text exposures of a blank, white target. For these exposures, pretend that the target is Zone I - that is, meter the white target, and then give it four stops less exposure so that it records on the film as Zone I. Process normally.

Now, get a small piece of 0.1 neutral density filter. Place the film on a light box, and lay the filter chip on top of the film such that it covers the rebate (unexposed edge of the film), but not the exposed area. Choose the exposure in which the brightness of the exposed area most closely matches the brightness of the rebate plus filter. That exposure represents the proper film speed for your particular combination of film, processing and metering.

If you want to get scientific, you can use a spot meter to compare the brightness of the exposed areas with the brightness of the rebate plus filter chip. My view is that the objective is to find a film speed that results in good shadow detail, and life is too short to make it rocket science.

Incidentally, I've tested many bulk rolls of T-Max 400, and in every case, this test came back with the conclusion that the 'ideal' speed for that film in my Nikon FM-2 and with my processing was in the range of 160-200.

To determine the proper development time, you have to to the test on a Zone VIII exposure. After finding the proper film speed, expose a group of negatives at that speed, and then process them individually, varying the development time in 30 second increments. Set up your enlarger to make a print, and determine the printing exposure required to make the rebate just barely darker than the maximum black that you can achieve on your standard printing paper. Then, holding that exposure time, make a series of test prints of the Zone III negatives. Process them all at once (to assure that they each get exactly the same development). Choose the print where the test exposure is about one Zone darker than blank white paper. The negative from which that print was made was processed at the ideal processing time.

Andre Noble
15-Nov-2009, 13:08
I did one of these tedious film speed tests, but I got caught up in the details, I lost sight of the big picture - and since my articular test still had a subjective component, my film speeds were still inaccurate.

So for now, based on recommendations from people. I consider experts, I am just going to rate all B&W films at 1/2 their box speed. I'm referring to traditional films such as FP4, HP5, Plus X, Pan F, and Tri-X.

Chuck P.
15-Nov-2009, 20:02
While I own a densitometer, the testing is at best quite tedious. It's also very easy to get caught in an endless testing stage.....

I've done testing with and without a densitometer and it's far more tedious without a densitometer than with one, IMO. Being able to determine the optimum film speed along with the characteristic curve with one sheet of film, a step wedge, and a densitometer is a piece of cake. Because of it's simplicity, I would be much more willing to explore various film/developer combinations........in short time to boot.

16-Nov-2009, 00:33
There is an excellent article here :
You can test your film without a densitometer. Although I own a densitometer, I prefer using Paul's method. As he states on his article : we exhibit prints, not negatives. IMHO it is the simple way to achieve quickly a first good print.

Thanks for posting this. I agree that it is an excellent article. It appears so simple that I'm even tempted to try it!