kirk_keyes

"Measuring the zero point is straightforward."

Glad to hear that.

"Measuring the high point is what I'm unclear about - when it says "START MEAS. (FILM)", what film do you use? The film base of the film you're measuring or the XRite calibration transparency?"

You use whatever "film" you are going to use for the calibration standard. But this "film" is not just film base.

Look in the manual and find the section on transmission calibration. Follow the button sequence in the manual and get to the set up page for the standards. There should be values already stored in the densitometer so you can't just go and use any old piece of film for calibration. You will need to change the preprogrammed, stored values for the calibration to work.

So what you need is a piece of film which you know the density of already. If that is an X-rite calibration standard, a Stouffer or Kodak step wedge with known densities, or even a film that someone read for you - they are all going to work. (Althought the X-rite on is nice because it has the values for Vis/R/G/B as I mentioned above. If you use something that only has a visual density, you could use that to calibrate the visual channel value.)

Think back to your high school geometery class - what you are trying to do is make a calibration by "plotting" two points, the zero point and the high (FILM) point. These to points make a line if you graph them on paper. To make a good calibration curve, you need to choose these two points so that they bound the range of densities that you wish to measure. The X-rite standard uses a density of about 3.0 - that's large enough that it does not exceed the working range of the densitometer and it's high enough that it is greater than the range of densities that you will want to measure.

If you zeroed on no film, and then calibrated the high point with your film base, this could work for a narrower range of densities, say 0.00 to 0.15 or so, as long as you programmed the densitometer to know what the actual densities for the high point film are. You will not get accurate readings when you get a ways away from your high calibration point doing it this way.

"If its the latter and my film base has a different color cast than that of the reference film, is that going to mess up my density measurements?"

The color cast of the films are immaterial. That's the beauty of using a color densitometer - it can see the color casts and then tell you just what the amount is. (This is based on the bandwidth of the filters used in the densitometer, of course. Since we are using filteres that follow an ANSI/ISO standard (Status M) that allows us to make good comparisons with others that are using Status M filters as well, and pretty close comparisons to others using Status A filters.)

That X-rite film I keep mentioning is just a piece of black and white film that has had the density values for Vis/R/G/B measured on each step. Think about this - a densitometer is calibrated with the B&W film of known density. You then can measure C-41 film, E-6 film, or B&W film with that densitometer. The color cast of the B&W film is usually pretty insignificant compared to the color films. But the densitometer can tell you the absolute density values for all 3 types with just the one calibration.

I guess the short answer is that any color cast in the calibration film and/or film base is taken into account by the density values of the calibration standard.

As I said above, you need to get a suitable calibration standard and then program the values of the calibration standard into the densitometer. Once that is done, then the color casts can be accurately measured.

"Trust me, it would require a LOT of ND filters, and so much stuff surrounding the flash head that I would stand a good chance of overheating it."

I bet he meant to suggest that you put a single ND filter on the camera lens...

Well, since you mentioned me by name, Peter, I guess I'll give your questions a shot.

Question 1) First, I suggest you check out these standards from X-Rite

http://www.xrite.com/product_overview.aspx?ID=24&Industry=1&Segment=12&Action=Accessories

3 Step Certified Wedge (Transmission), Part Nr. 319-68, $41

3-Step Calibration Plaque (Reflection), Part Nr. 302-12, $71

You can buy online from X-Rite which makes it really convienent.

I bought a set of 319-68 and 302-12 for my Noritsu DM-201, and even though these are made by X-Rite, they work just fine.

Before you do the calibration, you need to go into the set up menu and adjust the settings that are stored into the DM-201 for the calibration points. The instrument uses a two point calibration. For transmission mode, there is only one point that is stored since the other point is a "zero" point that doesn't use any calibration film and the values are always going to be 0.00 Optical Density. With the X-rite standard I mentioned above, your high cal point density will be about 3.00 density.

So to calibrate you set the instrument in trans or abs mode - and then absolute, not relative. Then as you see, for transmission, you measure the zero point - do it with no film under the sensor. Then you take the calibration film and make a second reading for the high point. Assuming you made good readings of each point, the densitometer will then be calibrated.

I always go back and read the zero point, and then all the steps on the X-rite cal standard after doing the calibration to verify that I made an acceptable calibration. (The other points on the film are about 0.25, 1.25, and 3.75 OD.)

You may notice that the X-rite cal film lists some acceptance criteria for different density ranges - I think it says for densities from 0.00 - 3.00 you should get readings that are +/- 0.02. For 3.00-3.5 it was +/- 1%, 3.5 and up +/- 3%.

So after I do a calibration, if the zero point (no film) doesn't read back 0.00 for all 4 measuremnts (R,G,B, and Vis) then I recalibrate. For the other values of the cal film, if they are within the criteria listed on the film, I go ahead and measure densities. That means the 0.25, the 1.25, and the 3.00 steps are all within 0.02, and often 0.01 of the value stated on the film. The 3.75 point is usually within 0.05 (1.3%).

You should not use film base (B&W, color neg, or transparency) to make the zero point reading. That will shift that calibration point upwards and screw up your calibration.

You may be able to tweak a calibration curve by putting in "biased" values in for the Hi val point. But I would not worry too much about the absolute accuracy of your readings. If you are within 0.02 of the cal standard check points, that should be sufficient. If you get 0.07 for a 0.06, that should be (and is) perfectly acceptable. 0.07 is the "a correct value" as it is within the range of values 0.06 +/- 0.02.

You need to remember that not only is there some uncertainty in the calibration of densities, but any instrument also has an uncertainty in making measurements. I think the Noritsu manual lists an accuracy of 0.02 for readings in the lower density ranges. Just keep that in mind.

Both the reflection and transmission X-rite standards have Vis and RBG values. Until you get standards that have all 4 values, you can just calibrate the DM-201 for the Vis values that you have if you want. If your current film is fairly neutral in color, you could just assign the Vis value to the RGB cal values in the instrument and then get approximate values. But if you are concerned about 0.01 differences in density, I highly suggest that you get one of the X-rite calibration films.

Question 2) I have not played with any of that stuff. I think there are two reasons you probably don't see any E-6 films mentioned. First - I suspect that Noritsu made this densitometer to support their line of C processing equipement. And second - the DM-201 does not have the "proper" filters as specified by ANSI/ISO for making transmission density reading for direct viewing materials. The DM-201 has Status M filters which are for neg films and papers and Status A filters are designated for use with transparency films. I have the specs somewhere that list the differences in the filters, but I think the bottom line is that the Status A filters transmit a narrower range of wavelegths than the Status M. The central peak of the two sets are very similar though.

I suspect that you will not have much difference between these two sets of filters for B&W work. For transparencies, I suspect the Status M will work acceptably for what I imagine most of your uses to be.

Question 3) Don't know - do you have more questions?

Kirk - www.keyesphoto.com

I've got 2 DM-201s and they are just fine for B&W use. They are designed to do transmission and reflection, and they have Status M filters for use with color neg materials.

My favorite thing about the DM-201 is that it displays Red, Green, Blue, and Visable reading all at the same time. Not changing channels. That makes it very fast to use. I've been playing with staining developers, and you can read all 4 channels very quickly with this machine.

The first DM-201 I bought, I payed about $900 in 1999. I got a backup one about 2 months ago - it only cost $100. Quite a good deal on a machine this nice.

I suggest getting a transmission and reflection calibration standard from X-rite. You can get both for a bit over $100. After calibration, both machines read back the calibration standard to within 0.02 Density immediately afterward and only drift +/- 0.01 for days or weeks after. (For the calibration range of 0.00 to 3.00. For the 3.75 calibration point, they are about 0.05 accurate, which is well within the specs for this machine.)

As far as your plotting goes, I would just leave the B+F density in your graphs, as it affects printing time. The slight purple color gets accounted for when you work with the total density, so leave it in.

I have made a PDF of the operation manual for this densitometer - if you want one, send me an email.

Kirk

I think this would work. Neat idea. You may need to play with the volume of developer to make sure you get enough to ensure even development. Use your fastest rotation speed, to make sure the developer gets spinned up into the center part of your tubes using a smaller volume of liquid. But if you get enough liquid to fill the tank to near the center post, then this should work at either speed.

Evenly fog a sheet of film, load it in, and take it for a spin. Let us know what you get!

Kirk - www.keyesphoto.com

Andy wrote: "Take two 4" telescopes (100mm aperture). One is an f/10, one is an f/4. The f/10 scope will have a FL of 1000mm, the f/4 will have a FL of 400mm. The f/10 will have a lot more magnification, but since it has the same physical aperture (100mm) as the f/4 scope, they will resolve and expose stars identically."

This has to do with sources of light that are considered to be "point sources".

Another way to think about this, from a camera viewpoint, is that the larger that effective aperature of a lens is the brighter it will record the stars. A normal lens for 35, a 50 mm, at f/2.8 lens has an aperature of 17.9 mm, while a normal lens for 4x5, a 150 mm, at f/5.6 has an aperature of 26.8mm. The 150 mm lens at 5.6 on the 4x5 will record stars brighter than the 50 mm lens on the 35 at f/2.8.

Of course the lens at f/2.8 will record detail in the landscape faster than the lens at f/5.6, so there is a trade off here.

Kirk - www.keyesphoto.com

PhotoCraft has an E-6 Refrema Dip'n'Dunk processor. They are at 320 SW Stark, Portland. 503-225-0515

I believe they have a 2 1/2 hour turn on E-6.

This invite extends to any other Portland area people as well.

Kirk

Ron - I'm in SE Portland and use 4x5 too. Myself and about 4 other guys that shoot mostly large format have been getting together at the Lucky Lab Pub in inner SE Portland once a month for the last few years to talk photography and share photos.

It's an informal group, if you're interested send me an email at kirk@keyesphoto.com and I can give you more detail.

Kirk

I have to say that I fully agree with Ryuji on the issue of premanence vs. fixing speed. I'm much more interested in the print lasting 100 years, than my having fixed it in less time.

Bill wrote: "Needless to say, when speaking of clearing time tests here, we are presumably referring to best possible results with fresh fixer."

And don't you think that someone trying to show the fastest results will also pick a film that clears the fastest, and not go looking for the one film that takes the longest?

Ultimately, I really don't care which is faster. Especially when we are talking seconds....

I use a two bath fixing procedure that is sufficiently long to fix the film with a nearly used first bath and then fix with a second bath for an equal amount of time. Takes me twice as long to fix, but I have great confidence that my procedure will produce lasting results.

Bill - I hope you'll get your formulation tested for permanance, perhaps you could talk Wilhelm into helping here?

And also, I hope you'll make safety and handling instructions for the TT class of fixers clear on the packaging. While most people may think that thiocyanate is the big safety concern, as you originally did in the thread of yore, I would say that the thiourea is a much bigger hazard here. I know many people use it for sepia toning, but I'm not sure that most people know that it has a pretty high hazard risk.

Many MSDSs list thiourea with a "Health Rating: 3 - Severe (Cancer Causing)" and state "Lab Protective Equip: GOGGLES; LAB COAT; PROPER GLOVES". But they also include the info "WARNING! [...] POSSIBLE CANCER HAZARD. MAY CAUSE CANCER BASED ON ANIMAL DATA. Risk of cancer depends on duration and level of exposure." (Taken from the JT Baker web site: http://www.jtbaker.com/msds/englishhtml/t3107.htm )

Just let people know they need to use more personal protective equipment and take extra care than they would for standard fixers.

Kirk

HI Bill,

Perhaps you are not testing the same film as Clayton did to come up with that claim? As you know, different films have different fixing times.

Exact same position? The answer is no, it will be slightly different.

The orbit of the earth is not perfectly round so the shadows when traced over a year's time will form an uneven figure-8 pattern. This shape is called an annalemma - see this website for a nice, short description:

http://www.twigsdigs.com/sundials/office/

Kirk - www.keyesphoto.com

Tom - read the following page - http://www.scantips.com/no72dpi.html and then continue on to the home page - http://www.scantips.com/

This web site will tell all that Jeff was asking about. It's a really good resource.

Go to www.phototechmag.com and look for the back issues that have articles by Bertram W. Miller (Millar?). He wrote a series of articles in the early 90s that I seem to remember covered this sort of approach.

You will need to figure out the response of the paper to exposure - make a print with a step wedge and then make some measurements of it with your densitometer.

I think Miller even had a computer program to help with this, put I'm not sure if it is around now, or even would run on modern computers...

Kirk

Yes, it's racked out pretty far. I think the sliding track on top of the focusing rack is fully extended and then the focusing track is out a bit as well.

But it does work. One thing to remember is that you can mount the Technika on the tripod with the mount point located in the front door/bed, instead of the regular mount on the body of the camera. '

Another thing to think about is getting a 360 mm Nikon telephoto, it should focus about where a 270 mm lens does. Probably wieghs more than a 355/f9 G-Claron, and it should be a lot less than a 360 mm f/5.6 anything.

And does anyone know if you can use the Nikon tele at 500 mm on a Technika?

Donald - most of this has already been invented - it's a tray with a slosher film holder and all you have to do is add a light tight lid.

Kirk - www.keyesphoto.com

I'm afraid I don't have the CMW - but I do have a Fujinon 125/5.6 W. I love it. See http://www.keyesphoto.com/Kdkgearinfo_Lenses.html

It's small, light, and I think the 125 mm fills the gap between 90 and 150 mm much better than the more common 135 mm lens. And this Fujinon also has almost the same film coverage as a Schneider Symmar-S 135 mm, which I had before and replaced with this lens.

Kirk - www.keyesphoto.com

"However, I've seen many references to silver as a bactericide, which would seem to make it inadvisable to put silver-bearing chemicals into a septic tank."

Yes, that IS true. It's ionic silver, compounds like silver nitrate that will release ionic silver when dissolved in water.

But silver is a very reactive compound when released into the environment. It will form very insoluble precipitates with chloride, and especially sulfide, as well as bind up with some of the larger organic compounds that can be found in the water column. Once it reacts with these compounds, it is few difficult to get if back into the ionic form.

Now I don't mean to say that there is no concern about silver in the environment, but it does appear that science is currently rethinking much old notions of the environmental fate of silver in the last dacade or so.

"Tank was completely full with developer."

Try leaving a little room for air in the tank next time. THis will help move the liquid around when you agitate. It is much harder to get good movement of the liquid in a completely full tank than it is in a partially full tank, or even a nearly full tank.

Donald wrote: "If you note, silver and cadmium are in the same column in the periodic table -- and cadmium is one of the most toxic of metals, worse even than mercury. Silver has some similar properties, but is less toxic (as is usually the case with the lighter elements in the same column)."

Also note that oxygen and sulfur are in the same column on the Periodic Table. The Periodic Table is not much help in telling us about toxicity.

And actually, silver and cadmium are NOT in the same column - silver is in IB between copper and gold, and cadmium is in IIB between zinc and mercury. At least in the version of the Periodic Table I like...

That second link that Roger mentioned is here:

http://www.inchem.org/documents/cicads/cicads/cicad44.htm#6.0

I found it very good, and it comes from a reputable source, the World Health Organization. A lot of material to digest, but very good.

Well, that does look uneven!

You say that agitation was to specification - and what specification was that?

I think your dust issue is just coincidence.

Don't give up the the WD2D+ yet - there are lots of people that use this with no problems.