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Bill, 70's military B&W
14-Sep-2012, 19:22
I just acquired a Macbeth TD 929, it came with nothing but the power cord. It seems to work, but I do not know anything about it. Do I need a specific negative to calibrate it?
I picked it up for almost nothing only because I read about folks using them to evaluate their negatives. I'm a Newbie and hope to use this machine to help me with some tests as I set up my darkroom and get started.
Any help would be appreciated.
Bill

C. D. Keth
14-Sep-2012, 20:26
Here's a manual (http://webpages.charter.net/craigclu/900series.pdf). That should get you started.

Bill, 70's military B&W
15-Sep-2012, 06:00
Chris, thanks for the manual, I read it front to back. It says that I must have a "instrument calibration reference", then at the end of the manual it lists parts, but does not offer the instrument calibration reference as being for sale.
I assume (yes assume) that without something to calibrate the unit it is worthless. Any suggestions? I know I can call the company, and I will next week.
How will having this machine help me in the pursuit of the perfect negative. I've never seen one in operation.
I know that in a lot of the books they talk about doing test strips until you do not see a difference in the blacks, then you have found the minimum time to reach maximum black.
Would the TD 929 help there?
Where else would it help me?
Bill

ic-racer
15-Sep-2012, 06:35
In terms of transmission density calibration, you can get a calibrated step wedge from Stouffer. Once you get the wedge you can use a step around 2.5 log d as the target for the calibration procedure. The wedge should come with a sheet indicating the exact value.

Kevin J. Kolosky
15-Sep-2012, 08:32
Chris, thanks for the manual, I read it front to back. It says that I must have a "instrument calibration reference", then at the end of the manual it lists parts, but does not offer the instrument calibration reference as being for sale.
I assume (yes assume) that without something to calibrate the unit it is worthless. Any suggestions? I know I can call the company, and I will next week.
How will having this machine help me in the pursuit of the perfect negative. I've never seen one in operation.
I know that in a lot of the books they talk about doing test strips until you do not see a difference in the blacks, then you have found the minimum time to reach maximum black.
Would the TD 929 help there?
Where else would it help me?
Bill

My MacBeth is a TD903 so I am somewhat familiar with them. And I use a Stouffer Wedge to calibrate my each time I use it. Zero it first, then calibrate, then use.

The basic zone system test from most authors requires you to find your personal film speed. this involves finding zone 1 on your negative. And zone 1 has usually been defined by most authors as .10 (using a logarithmic scale) above film base plus fog (to make a discerable difference from pure black on a print).
So what you are first going to want to do is make yourself a negative that is "film base plus fog". And you are going to take your new (to you anyway) densitometer and measure its density in log units.
Then you are going to want to make a few negatives at different exposures around zone 1 (keeping track of the film speed for each exposure) and develop them normally. You are then going to measure each one and then subtract the density of that film base plus fog negative, watching for one that is about .10 above film base plus fog. When you find one, check to see what ASA or film speed that one was. Most authors will then tell you to use that film speed for that film.

That will get you started.

I highly suggest going on to Fleabay (ebay) and purchasing a copy of either Ansel Adams "The Negative" or Fred Picker's "Zone VI Workshop". I think for a beginner I would suggest the Zone VI Workshop. Read that book cover to cover a few times before you then buy Ansel's book. You will then be well on your way.

And if you are really really interested, I can highly recommend two books from Kodak. One is called "The Basic Photographic Sensitometry Workbook" (pub. Z-22-ED), and the other is called "Practical Densitometry" (pub. E-59). I have read my copies of those two books so many times they are starting to get worn out.

Bill, 70's military B&W
15-Sep-2012, 14:36
Ic-racer and Kevin,
Thanks, I'm in over my head on this one but, I'll keep reading and trying. I'll get a Stouffer Wedge and calibrate each time. I was hoping that this would help me in setting up my tests, for my own film speed and possibly in the future judging a negative. Like I said I got it for almost nothing, so I want to put it to good use.

I am right now plowing thru "Way Beyond Monochrome" wow what a fantastic book. It may also have a section on density, haven't gotten there yet.
Fascinating book, right away I was blown away by the concept of using f/stops of time instead of 3-6-9-12 seconds when making a test strip. Makes sense, like a light bulb just came on right above my head!
Bill

Bill Burk
15-Sep-2012, 15:02
Bill,

A "calibrated" Stouffer Wedge is more expensive than one that isn't calibrated. You could buy the "uncalibrated" one and send it to someone on this forum who has a trusted densitometer. What they mean by calibrated is that someone went to the trouble to read off all the values and mark them down. Someone here could do that for you.

I'd recommend using the Stouffer Wedge for testing. Put it in contact with film and expose the film (like making a contact print), you get better tests when you better control the time and light. Then you develop the film and read the different patches with your densitometer. The results can go into a spreadsheet that Ralph Lambrecht provides.

The better you control the variables, the more reliable your test results. Don't expect results so reliable that nobody can debate the outcome. But you will immediately see how development time affects contrast and you will get a sense of how film speed works.

Bill, 70's military B&W
15-Sep-2012, 17:48
Bill,
Thanks for the reply,
2 questions
Can I get the Stouffer Wedge at B&H? Or does it come from some other supplier?
You were kind enough to answer and seem to know a lot about it, could you calibrate the Stouffer Wedge for me? I'd really appreciate it.
I'd order it and have it sent to your house.
Ralph Lambrecht, is he a member of the Forum, or is that spreadsheet a commercial item?
I found a section on densitometers in 'Way Beyond Monochrome' but I have not had a chance to read it yet. I will!
Thanks,
Bill

ic-racer
15-Sep-2012, 19:13
If you are going to go to the trouble to buy a step wedge I'd just get the calibrated one. It is only about $16.

If you are on a budget ask someone to send you a clip of fogged film around log 2.0 to 3.0 that has been measured on a calibrated meter. That would be almost free; you only need a single density patch to calibrate your densitometer.

Kevin J. Kolosky
15-Sep-2012, 22:21
My Macbeth has been pretty reliable. I can calibrate an uncalibrated wedge for you if you don't want to spend the money on the calibrated one. I don't know what a calibrated wedge costs nowadays as I purchased mine many years ago, and also have the calibration wedge from macbeth that came with the densitometer.

Another thing that a densitometer is good for is to use it to check on your negative expansions and contractions. So say you want to find out the development time to expand zone VII to Zone VIII you can expose some film to Zone VII and then develop for different times and measure the film density to see which one is now zone VIII. And of course you could also expose some negs to zone VIII and develop them less than normal (but different times of course) and see which one is now a zone VII density.

Bill Burk
15-Sep-2012, 22:35
I thought they were higher than $16 for calibrated, but if that's all, then Bill, you should splurge on it. You can get it anywhere it's available. My densitometer isn't calibrated. I'm sure it's "good" because I get readings that are within .02 of old readings I took on my Stouffer Scale from college, but that's not a good reference standard. Kevin's a better bet. Ralph is a regular on APUG he has the spreadsheet on his website.

Bill, 70's military B&W
16-Sep-2012, 06:39
Thanks everyone, I really appreciate all the help! I definitely spend the $16 and get a calibrated wedge.
I assume you get it at B&H? Is there a specific one I'll need. A little bit of knowledge is a dangerous thing.
I read the densitometer section in Way Beyond Monochrome last night and it did not help! Hopefully Fred Pickers book will do a better job, and I also hope the wedge will come with instructions. Another thing, I need to get this darkroom/supplies finished and then play with the thing.
Then the questions will really start.

Steve Sherman
16-Sep-2012, 08:03
Here's a manual (http://webpages.charter.net/craigclu/900series.pdf). That should get you started.

Hello Chris,

Seems the link you posted for PDF does not contain info on an older TD 901 model which I have. Any chance you know of a link which would provide info on that unit.

Many thanks in advance, Steve Sherman

ic-racer
16-Sep-2012, 08:42
Thanks everyone, I really appreciate all the help! I definitely spend the $16 and get a calibrated wedge.
I assume you get it at B&H? Is there a specific one I'll need. A little bit of knowledge is a dangerous thing.
I read the densitometer section in Way Beyond Monochrome last night and it did not help! Hopefully Fred Pickers book will do a better job, and I also hope the wedge will come with instructions. Another thing, I need to get this darkroom/supplies finished and then play with the thing.
Then the questions will really start.

From the Stouffer website:

T2115C 21 Step Transmission Guide 1/2" x 5" Calibrated $16.55

Phone order in: 574-252-5772

Fax order in: 574-252-5776

Email order to: dbittner@stouffer.net

Order with Visa or MasterCard, COD, or prepay.

Kevin J. Kolosky
16-Sep-2012, 10:29
"I read the densitometer section in Way Beyond Monochrome last night and it did not help!"

Well, then as a starter, what your densitometer is doing is looking at the light that is shining on the sensor and measuring that amount of light. And then, when you place something on it that blocks some of the light its making a comparison and a computation and giving you a number expressed in log units.

So, the light coming through is transmitted light, and the measurement of that light is transmittance. If there is no blockage you have 100 % transmittance.

Density then is basically the opposite of transmittance measured in log units. D=Log 1/t where D is density, T is transmittance and log is the logarithm of a number.

If you recall from Algebra class, log is really nothing more than basically an exponent used to raise a number to describe some other number. So, for example, if you are using base 10 and you want find the log of 100 it would be 2, or 10 to the second power. Log 1000 would be 3, and log 10,000 would be 4. So the log of a number between say log 0 and log 1 would be a number between 0 and 1.

If you have 100 % transmittance what would your density be. well D=log 1/T here T=1.00 so D=log 1/1 or D=Log 1 and the log of 1 equals 0, which has to be correct because if you are transmitting 100 % of the light then you have no density.

What is really interesting is that if you change your transmittance by 1/2 or double it (both supposedly 1 stop) you change your density by .30 on the straight line portion of the curve. But on the lower end of the curve and the higher end of the curve you do not get .30 density difference when you change the exposure by a stop. They say you have less separation at these levels, and the separation is not linear. You would need a calculus determination (derivative) to find the slope of the non straight line portions of the curve.

Again, I would highly suggest you get ahold of the Basic Sensitometry Workbook by Kodak.

ic-racer
16-Sep-2012, 13:54
In terms of instructions for using the step wedge, there will be none with the wedge.

You will be using it to calibrate you densitometer, and the instructions for that are in the manual.

The Fred Picker book should take you through making a zone 1 exposure to get your Exposure Index. You will use the densitometer to determine which zone 1 exposure had the appropriate density (0.1 on your calibrated densitometer). This measurement will not be affected much by development.

If you have questions about development time for your film you can contact print the step wedge on film and make H&D curves on graph paper and calculate the gamma, looking for around 0.7 when developed properly. Or you can shoot some zone VII frames and measure them with the densitometer (looking for about 1.25 when developed properly).