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Color & B&W Densitometers
Peter wrote:
On Mar 2, 6:07 pm, jay wrote: Hi all I want to buy a used color & B&W Densitometer that will work in both the transmission & reflected mode @ a fairly low price. (Say $400) I've visited X- Rites web site, & leave w/ my head spinning. I have the impression that some are for continuous film or print reading, some are automated for use w/ dies & inks that have little to do w/ photography, & some are for digital photography uses, & they all cost thousands new. In order to have any idea what to buy, I need the specs & / or advertising data when they were new. But I have no idea of anything. I usually don't get this confused about a technology. But this is amazing. I've looked (on line) @ several Besslers, but some appear to have vacuum tubes. I don't think vacuum tubes are made anymore. But I don't know how to tell which are solid state from looking on line. I went to Wikipedia & really wasn't able to find out much. Does any one have a recommendation how I might sort all this info our & find some solid data on possible candidates for my search. Or actual recommendations would be appreciated, but not expected. BWT where has this group gone? Where ever, I suppose that's where I should post this. Thanks, JD There is a lot to know about densitometers. My guess is that looking around and talking to various sources would be good advice. They appear on eBay. In various countries there are photo flea markets or camera shows. Sometimes they appear there. I found an old Kodak densitometer for about $20 and played with it. At the time I thought I wanted a better one. In the end I got a very full featured modern densitometer for about $50 (a real bargain). For most of what I do, the Kodak has shown itself to be just fine. I'm not sure what you are doing, but my impression is that you can spend a whole lot of money and not necessarily get much more. Even the basic little ilford one works pretty good for me. I've used it for when I have changed the filtration but wanted to keep the same exposure (used it to adjust the f-stop after a filtration change) and never had a problem. Those can be had for almost nothing on fleabay. I'm not sure what the OP is wanting one to do for them? Stephanie |
#3
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Color & B&W Densitometers
Some enlarging meters are also very good B&W densitometers:
http://www.darkroomautomation.com/em.htm If you are enlarging the negatives then the proper place to read the density is at the enlarger's easel. It gives you the effective density in your equipment - taking into account flare and calier effects. If you are doing zone system calibration then what you want is the EI and development time that gives perfect prints on #2 paper in your enlarger, not some arbitrary set of densities. You also need to find the total exposure to the paper that results in almost not white and almost but not quite totally black. The difference in exposure in stops between these points is equal to the difference in negative density you want for spanning Zone I to Zone IX. -- Nicholas O. Lindan Cleveland Engineering Design, LLC Cleveland, Ohio 44121 |
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Color & B&W Densitometers
Nicholas O. Lindan wrote:
Some enlarging meters are also very good B&W densitometers: http://www.darkroomautomation.com/em.htm If you are enlarging the negatives then the proper place to read the density is at the enlarger's easel. It gives you the effective density in your equipment - taking into account flare and calier effects. If you are doing zone system calibration then what you want is the EI and development time that gives perfect prints on #2 paper in your enlarger, not some arbitrary set of densities. You also need to find the total exposure to the paper that results in almost not white and almost but not quite totally black. The difference in exposure in stops between these points is equal to the difference in negative density you want for spanning Zone I to Zone IX. -- Nicholas O. Lindan Cleveland Engineering Design, LLC Cleveland, Ohio 44121 Absolutely, any enlarger timer that gives an exposure time can be used as a densitometer or to measure negative contrast too, an example with my free softwa http://www.bonavolta.ch/hobby/en/photo/darktools.htm Which will be enough for the majority of printers, at least with silver gelatin. Said that, the use is not exactly the same and some densitometers offer features that are generally not available in enlarger meters, like reflection or UV densities measurement which are useful in other processes. Claudio Bonavolta http://www.bonavolta.ch --- news://freenews.netfront.net/ - complaints: --- |
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Color & B&W Densitometers
Claudio Bonavolta wrote:
Nicholas O. Lindan wrote: Some enlarging meters are also very good B&W densitometers: http://www.darkroomautomation.com/em.htm If you are enlarging the negatives then the proper place to read the density is at the enlarger's easel. It gives you the effective density in your equipment - taking into account flare and calier effects. If you are doing zone system calibration then what you want is the EI and development time that gives perfect prints on #2 paper in your enlarger, not some arbitrary set of densities. You also need to find the total exposure to the paper that results in almost not white and almost but not quite totally black. The difference in exposure in stops between these points is equal to the difference in negative density you want for spanning Zone I to Zone IX. -- Nicholas O. Lindan Cleveland Engineering Design, LLC Cleveland, Ohio 44121 Absolutely, any enlarger timer that gives an exposure time can be used as a densitometer or to measure negative contrast too, an example with my free softwa http://www.bonavolta.ch/hobby/en/photo/darktools.htm Which will be enough for the majority of printers, at least with silver gelatin. Said that, the use is not exactly the same and some densitometers offer features that are generally not available in enlarger meters, like reflection or UV densities measurement which are useful in other processes. Claudio Bonavolta http://www.bonavolta.ch --- news://freenews.netfront.net/ - complaints: --- Also, with using an enlarger will not give the same values as a densitometer. Most densitometers are single diffuse instruments. A few may be specular or double diffuse. But you know what you have. Now if you are working for just yourself, and will not compare your readings with anyone else, this may actually be better than with a real densitometer. But if you agree with Ansel Adams, and try to get a net density from Zone I of your negatives to be 0.1, you probably will not know that using an enlarger. You would need a calibrated step wedge to calibrate the enlarger "meter" and it would drift around a lot.. My densitometer has a beam splitter in it that sends half the light direct to a photodetector and the other half through the negative under test to another photodetector. The signals are routed through a differential amplifier. This compensates for changes in temperature, changes in line voltage, differences from one light source to another, aging of the light source, ... . Typically, enlargers have none of this. -- .~. Jean-David Beyer Registered Linux User 85642. /V\ PGP-Key: 9A2FC99A Registered Machine 241939. /( )\ Shrewsbury, New Jersey http://counter.li.org ^^-^^ 09:20:01 up 45 days, 10:40, 3 users, load average: 4.62, 4.45, 4.41 |
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Color & B&W Densitometers
"Jean-David Beyer" wrote
But if you agree with Ansel Adams, and try to get a net density from Zone I of your negatives to be 0.1 There is nothing sacred about that 0.1 OD number - that's just the number AA found for his film, development technique, preferred paper, enlarger and densitometer. If one is trying to fit the film to the paper - AA's original intent with the ZS - then there will a different number as one isn't using the same paper, not to mention film, developers and all the rest and one's criteria for an 'ideal' print will be different. It is equally possible the right number for one's own process will be 0.05 or 0.20 - it is going to vary enormously with the toe response of the film, the shoulder response of the paper and how much shadow contrast - how far up the shoulder and down the toe - one considers best. As ZS speed testing invariably ends up with an EI that is roughly 1/2 of the ISO value it can be seen that AA liked more shadow detail than the ISO standard assumes. With modern films, and their capacity for overexposure, most photographers agree with AA and rate their film at 1/2 the ISO speed - even if they have never gone near the ZS. At very low densities the readings from a bench densitometer and an easel densitometer (AKA DA enlarging meter or one of the old Eseco meters) will be identical. You would need a calibrated step wedge to calibrate the enlarger "meter" Er, I sell the meters to folks who make step tablets - they use them for calibrating the tablets. and it would drift around a lot. Zilch. Nada. If you have the right meter... You need a reasonably stable light source in the enlarger - a standard incandescent source and a ferro voltage regulator provides very steady light after everything warms up. My densitometer has a beam splitter in it that sends half the light direct to a photodetector ... I have been designing spectrophotometers for clinical chemistry for 30 years now. They measure to 0.00003 OD absolute with no drift. ... This compensates for changes in temperature Put a wratten ND filter in the light path and you can use the density readings for telling the temperature - the filter's OD changes with temperature. -- Nicholas O. Lindan, Cleveland, Ohio Darkroom Automation: F-Stop Timers, Enlarging Meters http://www.darkroomautomation.com/da-main.htm n o lindan at ix dot netcom dot com |
#7
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Color & B&W Densitometers
Nicholas O. Lindan wrote:
"Jean-David Beyer" wrote We seem to be talking at cross purposes. But if you agree with Ansel Adams, and try to get a net density from Zone I of your negatives to be 0.1 There is nothing sacred about that 0.1 OD number - that's just the number AA found for his film, development technique, preferred paper, enlarger and densitometer. I know. That is why I said "if". I actually aim at a net density of 0.25 to 0.3 for Zone I in my work. If one is trying to fit the film to the paper - AA's original intent with the ZS - then there will a different number as one isn't using the same paper, not to mention film, developers and all the rest and one's criteria for an 'ideal' print will be different. True. It is equally possible the right number for one's own process will be 0.05 or 0.20 - it is going to vary enormously with the toe response of the film, the shoulder response of the paper and how much shadow contrast - how far up the shoulder and down the toe - one considers best. As ZS speed testing invariably ends up with an EI that is roughly 1/2 of the ISO value it can be seen that AA liked more shadow detail than the ISO standard assumes. With modern films, and their capacity for overexposure, most photographers agree with AA and rate their film at 1/2 the ISO speed - even if they have never gone near the ZS. Yes. Another reason to use more density for Zone I in the negative is because modern papers are capable of much greater density (e.g., 2.2) than older papers (e.g., 1.7). But if you expose enough to get that density in the darkest areas, all the higher zones are too dark, and if you develop more to get Zone V to match (more or less) the 18% gray card, the contrast is too high. Hence, expose more. At very low densities the readings from a bench densitometer and an easel densitometer (AKA DA enlarging meter or one of the old Eseco meters) will be identical. Maybe so. I was thinking of those who rely on their enlarger's light source as being stable, producing sinigle-diffuse illumination, etc. Maybe you get that with a cold light head (though they drift a lot, even the Zone VI stabilized ones). You would need a calibrated step wedge to calibrate the enlarger "meter" Er, I sell the meters to folks who make step tablets - they use them for calibrating the tablets. I cannot argue with what you do. If using an enlarger to calibrate those step tablets were satisfatory, they would not be using your meters. and it would drift around a lot. Zilch. Nada. If you have the right meter... You need a reasonably stable light source in the enlarger - a standard incandescent source and a ferro voltage regulator provides very steady light after everything warms up. I used to have the use of an old Macbeth densitometer, one with vacuum tubes in it. It drifted all the time, even after 30 minutes of warm-up. I had to calibrate it for each measurement. The one I bought (TD-901) seems all solid state and is stable in less than a minute (after the bulb warms up). The old one may have been a TD-101 something like that. Analog readout. My densitometer has a beam splitter in it that sends half the light direct to a photodetector ... I have been designing spectrophotometers for clinical chemistry for 30 years now. They measure to 0.00003 OD absolute with no drift. Of course, the requirements for clinical (and research) chemistry are much more strict that for routine photographic use. ... This compensates for changes in temperature Put a wratten ND filter in the light path and you can use the density readings for telling the temperature - the filter's OD changes with temperature. Back when I got my Macbeth densitometer, it seemed easier than all the things I would have to do to make an enlarger and an enlarging meter do the job. -- .~. Jean-David Beyer Registered Linux User 85642. /V\ PGP-Key: 9A2FC99A Registered Machine 241939. /( )\ Shrewsbury, New Jersey http://counter.li.org ^^-^^ 08:20:01 up 46 days, 9:40, 3 users, load average: 4.39, 4.43, 4.53 |
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