Densitometer advice

ParkerSmithPhoto · Apr 24, 2016

I am thinking about picking up a densitometer for my film calibration. Any advice on a good value that will read RGB as well as regular readings? I would also appreciate any "beware of" advice. Don't want to waste my money on a POS. Thanks in advance.

Luis-F-S · Apr 24, 2016

I'd get an X-Rite 301. It's the only B&W film enlarger that X-Rite still sells and supports. The Macbeth color densitometers are getting quite old and IMHO could be a PIA to get repaired. In the 301's try to get one with the single red switch on the right side with the On/Off switch on the back. Those are the more recent units since this densitometer has been made for over 40 years! L

RPC · Apr 24, 2016

I have a X-Rite 810 and it is a great little unit. It does visual, and RGB for both transmission and reflection readings, and HD-LD calculations for you (for use with control strips).

Mr Bill · Apr 24, 2016

Hi, I haven't used one for a half dozen years or so, but over the years, I've used dozens of Macbeth, and later Xrite machines at the place where I worked.

I agree that the older Macbeths might be repair headaches, but can't say for sure. I'd personally try to avoid the oldest using PMTs (they have a removable round filter turret facing front). I'm just presuming that the electronics are really old tech, but not much real basis for this. I do know that older units had a row of pots in the back (inside); these were interactive adjustments for the machine's linearity; if someone has randomly tweaked any of these... well good luck!

My preference would be something like an xrite 810, which reads R, G, B, and V(isual) all simultaneously. But I think replacement lamps may be costly, so make sure it all works first. You'll need instructions to calibrate it, as well as the test plaques. Since it does both transmission and reflection, you need both plaques.

Those would be my preferences, maybe not the best choice, but the ones I'm most familiar with. The Xrite 810 was one of the workhorses of the earlier days of one-hour minilabs. Id really say that operating condition is probably the most important thing, as well as having calibration plaques. I wouldn't want to pay too much, knowing that in the event of failure it may not be worth trying to repair. Best of luck.

Chan Tran · Apr 24, 2016

The PMT is the most sensitive device but it drifts a lot so re-calibration is needed often. They also recommend not to power down when not in use.

Bill Burk · Apr 24, 2016

I think ParkerSmithPhoto just got a densitometer I recommended...

Now to see if it is all I say it is...

It takes advantage of a sensitive receptor that exactly matches human visual response.

ic-racer · Apr 24, 2016

A while back I was still able to get parts for my older model Tobias transmission denstometer from Tobias. Don't know if that is still the case.

Diapositivo · Apr 25, 2016

I've very recently discovered that if you have a good scanner you can use it as a densitometre using software as VueScan and probably Silverfast.
I still have to do it, but using calibration target slides such as those sold by Fuji, Kodak or Wolf Faust, and knowing the density of each patch, you can make a graph reporting the real density and observed density. Then you can use your scanner as a densitometre.

An example which I found on the internet

RalphLambrecht · Apr 25, 2016

ParkerSmithPhoto said:
I am thinking about picking up a densitometer for my film calibration. Any advice on a good value that will read RGB as well as regular readings? I would also appreciate any "beware of" advice. Don't want to waste my money on a POS. Thanks in advance.

I got a Heiland densitometer and love it.It comes with a long cable so I can read densities on large prints.In 20 years, it never needed an adjustment or maintenance.perfect equipment; made in Germany.

davedm · Apr 25, 2016

[OT]

Questions to X-rite Owners (810, 811, 820)

How do you calibrate color transmission (if you do it at all)? X-rite no longer sells transmission calibration film. However they do sell a reflection plaque.
The problem is that with 811, you have to calibrate transmission first before you calibrate reflection according to an x-rite support article.

Of course one can calibrate with stouffer wedge for visual but then your RGB will not be in calibration.

To OP
I would second Louise's suggestion for an X-rite 301 or similar which is supported by MFG. The key is to find in used condition for a good price.

Mr Bill · Apr 25, 2016

davedm said:
Questions to X-rite Owners (810, 811, 820)

How do you calibrate color transmission (if you do it at all)? X-rite no longer sells transmission calibration film. However they do sell a reflection plaque.
The problem is that with 811, you have to calibrate transmission first before you calibrate reflection according to an x-rite support article.

Of course one can calibrate with stouffer wedge for visual but then your RGB will not be in calibration.

Dave, going from memory on the 810...

Transmission and reflection modes are independent - if you only want to use one mode it is not necessary to calibrate the other.

To calibrate film (transmission) mode, it will probably suffice to use a piece of b&w (stouffer wedge?) film with a known "visual density," then set each of the colors, individually, to the same density value. (The procedure is to set each of the aim values into the densitometer memory, then read the reference film when prompted.) (Note that "zero" is first set with a "blank" reading.) The factory calibration plaques come with the proper r, g, and b values, but they are only very slightly different, on the order of a percent or two (rough guess) of the density value. Or, if you know someone with a color densitometer, ask them to read your reference strip, then use those individual color densities as your aims.

ParkerSmithPhoto · Apr 27, 2016

Bill Burk said:
I think ParkerSmithPhoto just got a densitometer I recommended...

Now to see if it is all I say it is...

Well if it isn't I know who to blame!

What kind of bulb does this thing use? Expecting delivery on Tuesday.

Bill Burk · Apr 28, 2016

Use S-11 clear bulb it says on the bottom...

ParkerSmithPhoto · Apr 28, 2016

Bill Burk said:
Use S-11 clear bulb it says on the bottom...

Readily available. Any idea on the wattage?

DREW WILEY · Apr 28, 2016

wattage? .... depends on the intensity of the lightning strike and length of the kite string.

ParkerSmithPhoto · Apr 28, 2016

DREW WILEY said:
wattage? .... depends on the intensity of the lightning strike and length of the kite string.

Thanks, Mr. Franklin.

Bill Burk · Apr 28, 2016

I picked up a couple to try from my local hardware store.

25 watts was too bright and too hot.

10 watts was just about right. It measured about a stop lower in intensity than the original, but the design of the densitometer doesn't depend on the actual intensity.

Mr Bill · Apr 28, 2016

Bill Burk said:
I picked up a couple to try from my local hardware store.

Bill, all of the transmission densitometers I've ever worked with directly, prior to the automated strip readers, used internal optics to project an image of the lamp filament into the measuring aperture. This relies on having a specific filament shape that has to be aligned properly when the lamp is replaced. Whenever we had a densitometer that kept jumping out of calibration, it was almost always due to a lamp with a damaged filament; the aperture was only partially filled (with the image), and using the densitometer caused the filament image to jiggle; periodically settling into different positions.

I'm guessing that some random bulb is not going to be right? Assuming that your densitometer works on the same principle. Anyway, it's something to be aware of as a possible issue.

DREW WILEY · Apr 28, 2016

My wisecrack was appropriate. To be consistent, bulbs for this kind of usage were supposed to be broken in, or run for a specified period until they
reached a plateau of output before being sold. Then, toward the end of their lifespan, once that specific level of efficiency drifted, you replaced them.
The same applied to early spectrophotometers. The bulbs had to come from an exact source. Of course, the color temp of the bulb is also related to voltage fluctuations, so ideally needs some kind of voltage stabilizer too. Kinda like needing a crank to start your Model T engine. I'll stick with my modern X-Rite. They make all kinds of neat stuff. My wife once used a trade-secret X-Rite colorimeter for designer vaccine quality control. This kind of medical prototyping product typically cost about $40,000 per ml to make! The X-Rite machine cost 6 million dollars and was used in small lab with a timed bank vault door on it. So next time you complain about having to drop a few hundred for a decent used darkroom densitometer....

Chan Tran · Apr 28, 2016

You can use a piece of film with known density of about 3.0. The exact value isn't important but you must know exactly what value the film is. That's all. You need some other densities to check.

Bill Burk · Apr 28, 2016

One of the most important things to look for in a densitometer...

Is the shipping.

Bill Burk · Apr 28, 2016

Mr Bill said:
Bill, all of the transmission densitometers I've ever worked with directly, prior to the automated strip readers, used internal optics to project an image of the lamp filament into the measuring aperture. This relies on having a specific filament shape that has to be aligned properly when the lamp is replaced. Whenever we had a densitometer that kept jumping out of calibration, it was almost always due to a lamp with a damaged filament; the aperture was only partially filled (with the image), and using the densitometer caused the filament image to jiggle; periodically settling into different positions.

I'm guessing that some random bulb is not going to be right? Assuming that your densitometer works on the same principle. Anyway, it's something to be aware of as a possible issue.

Hi Mr Bill,

I've got a Macbeth that uses a tiny halogen bulb with a small flat coiled filament that I just happen to be able to pick up at the hardware store. That densitometer is sensitive to exactly where you position that bulb. When you get it just right, you can really see it is in the right spot.

But this particular one doesn't work on the same principle, you guessed it. The book that came with mine is dated 1940.

Anyway for hoots, I read a calibrated step wedge with the original bulb and changed the bulb to the 10 watt hardware store bulb. The standard deviation of my reading differences from calibrated strip is 0.0376 with the original bulb and 0.0348 with the new bulb.

If I throw out two lowest and four highest readings where the greatest deviations occur, I get standard deviation of 0.022 with the original bulb and 0.019 with the new bulb.

That's what my gut was telling me, that I'm within a couple points on average. For a primitive device, getting readings within a couple points is acceptable to me.

Now I could work on the tip regarding shape of the filament and making sure it falls in the place where it is supposed to be. I can see there is some shadow movement as I twirl the knob. I'm sure that's throwing off readings on the extremes of the scale.

Bill Burk · Apr 28, 2016

For fun I put the 25 watt hardware store bulb in.

About the same results. Standard deviation of 0.0332 over the full range, and kicking out the extremes 0.0214.

It's based on the principle of the law of inverse squares. The light bulb travels on a pair of electric wire loops that bring it its current. It travels back and forth, kind of like the station indicator needle of an old school tuner. And you read the density off the linear scale.

The light itself travels two paths to your eye. From the back of the bulb to a mirror up to a piece of opal glass, up to another mirror and then along about a 15 inch tube past a lens and a piece of glass to a semisilver mirror. The semisilver mirror... of all things... is pointing down.

The other path from the front of the bulb hits a mirror pointing up to a piece of opal glass where you put the sample being read.

The really cool part is called the field mirror. It's a mirror pointing up to your eye, which has a hole in its silver.

The hole shows the piece of the film you are measuring while the field mirror is reflecting up to your eye the light from the back side of the bulb that had been directed down to it.

You turn the dial, like changing the station on that old tuner, until the spot matches the surroundings.

Bill Burk · Apr 29, 2016

Here's what it looks like on the inside...

And here's looking at a sample.

Hopefully ParkerSmithPhoto got a better field mirror than I did.

ParkerSmithPhoto · Apr 29, 2016

Bill Burk said:
If I throw out two lowest and four highest readings where the greatest deviations occur, I get standard deviation of 0.022 with the original bulb and 0.019 with the new bulb.

How are you able to pull such precise numbers from that scale? If I'm within a few hundredths I'm sure it will be more than adequate for my needs.

Might need to to send me a scan of that booklet. Looks pretty cool.

Densitometer advice

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