Legacy SCREEN (Dainippon) DM-300 Densitometer Help

[ludwighagelstein]

Hi everyone,

This is my first post here - seeking help. I´m a photographer and recently bought an old but working Dainippon Screen DM-300 Densitometer, but sadly there is no manual to be found in the vast expanse of the internet and Screen themselves couldn't find one either - I asked there first. Now, in a last resort I figured that if someone had a manual for the device or worked with one once they´d probably read it here of all places, so here we go...

I´m grateful for any input!
Thanks in advance,

Ludwig

 

[maxon]

Never used a DM300 myself but since you're not in the printing business I can give you some hints. Like many other similar instruments, this one appears to have a light source probably a small light bulb powered with stabilized voltage, designed to produce an output as constant as possible. Now if you managed to power it on, whenever you close the instrument down with an exposed film in between it will measure the light being transmitted i.e. transmission mode and display it as neutral density value ND. It should have a zero button on it, you first take a blank measurement (no film) and press the zero to, well, zero the instrument, then you insert the material and take a second reading. The device is supposed to read ND in 0 to 5 range, to measure imagesetter films and help one decide how black is the black on film. The second function - be it a switch or button - is for reading raster dot percentages. It merely reads the light in transmission mode and report the value as dot percentage : you put an unexposed/transparent film in-between, take a reading and zero-ing, then do the actual measurement on the region of interest. It may or may not need a 100 percent calibration before the actual reading, some densitometers need to set a zero, then set a full black tone ; once it knows the two limits it can read anything in-between with moderate accuracy. That's all there is know really, you shouldn't need a manual for this. Fairly simple. Hope it helps.

 

[ludwighagelstein]

Thanks a lot for you very detailed answer. I failed to mention in my OP that I do know the very basics of densitometry. The device works and displays the densities in transmission mode. It has indeed a zero button (white) which zeroes the densitometer without any film under the aperture. After zeroing, and with film inserted it gives me the Base+Fog reading with a clear piece of film. However, when I press the black button next to the white button that zeroes the densitometer, nothing happens. Thus I wanted to read what the button is supposed to do. Also, a useful information would be what the Dmax the device can read is, and wether there are multiple aperture inserts apart from the current 3mm aperture. I wouldnt have a problem making a say 1mm aperture to take a narrower reading, but my question is if it would falsify the reading or diminish the sensitivity. Anyways, thanks a lot!

Never used a DM300 myself but since you're not in the printing business I can give you some hints. Like many other similar instruments, this one appears to have a light source probably a small light bulb powered with stabilized voltage, designed to produce an output as constant as possible. Now if you managed to power it on, whenever you close the instrument down with an exposed film in between it will measure the light being transmitted i.e. transmission mode and display it as neutral density value ND. It should have a zero button on it, you first take a blank measurement (no film) and press the zero to, well, zero the instrument, then you insert the material and take a second reading. The device is supposed to read ND in 0 to 5 range, to measure imagesetter films and help one decide how black is the black on film. The second function - be it a switch or button - is for reading raster dot percentages. It merely reads the light in transmission mode and report the value as dot percentage : you put an unexposed/transparent film in-between, take a reading and zero-ing, then do the actual measurement on the region of interest. It may or may not need a 100 percent calibration before the actual reading, some densitometers need to set a zero, then set a full black tone ; once it knows the two limits it can read anything in-between with moderate accuracy. That's all there is know really, you shouldn't need a manual for this. Fairly simple. Hope it helps

 

[maxon]

You have a pair of density buttons (and another pair for percentage) in reflective and transmission mode.
In reflective mode - small light table removed - try to zero the percentage reading on unexposed paper using the black button.
Dmax is usually 4.5 or 5 ND i.e. rapid access or high contrast film depending on densitometer manufacturer or model. I've seen ancient densitometers unable to measure densities above 3.
Aperture cannot be replaced unless it is a threaded insert or other obvious way to remove easily. I assume the photodiode inside is calibrated for a specific amount of light i.e. original aperture.
For reflective mode you should look for a second light source near the sensor.

 

[ludwighagelstein]

both modes work, in reflective mode, a small light inside the metering head turns on and not the big light source in the base. The aperture can be easily removed, so I figured there were more inserts. So far the densest film I had at hand was 3.34 so I guess it goes above 3. Thanks for the tip on the percentage reading!

You have a pair of density buttons (and another pair for percentage) in reflective and transmission mode.
In reflective mode - small light table removed - try to zero the percentage reading on unexposed paper using the black button.
Dmax is usually 4.5 or 5 ND i.e. rapid access or high contrast film depending on densitometer manufacturer or model. I've seen ancient densitometers unable to measure densities above 3.
Aperture cannot be replaced unless it is a threaded insert or other obvious way to remove easily. I assume the photodiode inside is calibrated for a specific amount of light i.e. original aperture.
For reflective mode you should look for a second light source near the sensor.

 

[ludwighagelstein]

You have a pair of density buttons (and another pair for percentage) in reflective and transmission mode.
In reflective mode - small light table removed - try to zero the percentage reading on unexposed paper using the black button.
Dmax is usually 4.5 or 5 ND i.e. rapid access or high contrast film depending on densitometer manufacturer or model. I've seen ancient densitometers unable to measure densities above 3.
Aperture cannot be replaced unless it is a threaded insert or other obvious way to remove easily. I assume the photodiode inside is calibrated for a specific amount of light i.e. original aperture.
For reflective mode you should look for a second light source near the sensor.

Tried it. In percentage mode the black button sets the value to 100. But for my purposes I don´t need that anyways. So essentially I know what I wanted to know now. Thanks a lot!