Densitometer: spot-reading vs strip reading?

[cyrus]

I know that some people suggest either not using a denisiwhatsit at all, or suggest simply asking others to run tests for them --but on behalf of us thick-headed folks who insist on trying things out the hard way first, here's a question:

When looking for a densitometer, is it better if the model has "spot reading" ability (in other words, the arm that comes out where you can slide the film/negative under) or are the strip-reading models OK too (the models where you slip a piece of material into a slot)

[Jorge Gasteazoro]

I know that some people suggest either not using a denisiwhatsit at all, or suggest simply asking others to run tests for them --but on behalf of us thick-headed folks who insist on trying things out the hard way first, here's a question:

When looking for a densitometer, is it better if the model has "spot reading" ability (in other words, the arm that comes out where you can slide the film/negative under) or are the strip-reading models OK too (the models where you slip a piece of material into a slot)

The spot reading densitometers are better than the strip reading ones. They are more accurate, they do not limit you in size and generally they are cheaper, I can read my 8x10 and 12x20 negatives on the spot reading one, try that on a strip reading one.. . The strip reading ones, will limit you to 4x5, unless you want to use a sheet for every zone you will have to device a method to put more than one exposure in the sheet (A PITA, trust me I have tried it) and then you will not know if the reading was take from the center or best area for that exposure.....The strip reading ones were made for labs which required reading of a strip to mantain QC, they are not good for the hobbiest or person who wants to do testing at home.

[cyrus]

Thanks I had thought so - but I never used a strip densitometer before so I wanted to make sure!

[Jay DeFehr]

I have never used a strip-reading, or scanning densitometer, but I definitely like the idea. I do my film testing by exposing a test film in contact with a stepwedge in a sensitometer. A scanning densitometer would read the entire resulting stepwedge in a single pass, instead of my having to read and record each individual step separately, which provides two opportunities for error with every step read and recorded. Unless I'm misunderstanding the way a scanning densitometer works, which is certainly possible, it seems like a much better way to measure a stepwedge than the alternative of a spot-reading densitometer.

Jorge,

have you used a scanning densitometer? If so, am I correct in assuming it reads the entire stepwedge in a single pass? If that's true, what is the downside, other than the limitations of the size of film it can scan, which is no limitation at all, as far as I'm concerned, if it can scan up to 4x5. What am I missing?

Jay

[Jorge Gasteazoro]

I have used one and it does not read the entire strip in one pass, what is does is it stops when it senses a change in density advances a little bit and it reads that area, if you have strips well exposed like those done in a sensitometer then this is no problem as the edges are uniform and have the same density as the center but with sheets done by multiple exposures or by drilling the slide you might get edges which have higher density than the center, this will lead to errors in testing and processing.

Second objection is using it for judging printing exposure, having a densitometer that good only for readin test strips is a waste IMO. I have calibrated my printing so that I read the highlight with detail in the negative and the shadow with detail and from these two numbers I know what exposure and contrast solution to use. But I need to be able to read the negative, something that cannot be done with the scanning densitometer.

I dont know what densitometer you have, but mine has a pc connection where I can read the strip and it automagically is exported to the pc, I have never bothered to do this.

I have never used a strip-reading, or scanning densitometer, but I definitely like the idea. I do my film testing by exposing a test film in contact with a stepwedge in a sensitometer. A scanning densitometer would read the entire resulting stepwedge in a single pass, instead of my having to read and record each individual step separately, which provides two opportunities for error with every step read and recorded. Unless I'm misunderstanding the way a scanning densitometer works, which is certainly possible, it seems like a much better way to measure a stepwedge than the alternative of a spot-reading densitometer.

Jorge,

have you used a scanning densitometer? If so, am I correct in assuming it reads the entire stepwedge in a single pass? If that's true, what is the downside, other than the limitations of the size of film it can scan, which is no limitation at all, as far as I'm concerned, if it can scan up to 4x5. What am I missing?

Jay

[Eric Jones]

Jay,

What model of Sensitometer are you using? I've been looking at a few different ones for standard film testing. It seems they all allow you to use either blue or green light, which do you expose your test sheets with? Have you noticed any difference from your test results to your field results? Any additional info on how you work with one would be of much help.

Thanks,

Eric

[Jay DeFehr]

Hi Eric.

My sensitometer was originally a Tobias, but I completely rebuilt it, replacing the stepwedge, light source and timer to make it more useful for pictorial panchromatic film testing. The original 11-step scale and 2½ second exposure, with a pain-in-the-ass mechanical tungsten-light intensity adjustment made its usefulness too limited for regular use with a variety of films. I'm not aware of any sensitometer designed specifically for panchro pictorial films, and any X-ray film sensitometer will require similar modifications to the ones I made. My bench tests and field tests agree very closely.

In use, I simply set the exposure to match the film I'm testing, place the film under the pressure plate, and make the exposure. I then process the film, and read the densities with my color densitometer. Converting the sensitometer was demanding, and required the help of an electronics engineer friend, but it was well worth the effort, because it is now very simple to use with any film I want to test, and extremely accurate.

Jorge,

thanks for the insider info. I have a Noritsu DM-1 densitomer, which also has a PC port. I have no PC in my darkroom at the moment, but that's soon to change. I'm expanding my darkroom into an adjacent room, where I plan to set up a digital darkroom, or whatever the correct term is. I can understand why a scanning densitometer would be less than ideal for your uses, but one would be quite handy for me, I think, and they don't take up so much space that I would have to choose between the scanning densitometer, and the one I already have. Do you know of any UV scanning densitiometers? Maybe for Graphic arts/printing apps? Thanks again for the info.

Jay

[Jorge Gasteazoro]

Jorge,

thanks for the insider info. I have a Noritsu DM-1 densitomer, which also has a PC port. I have no PC in my darkroom at the moment, but that's soon to change. I'm expanding my darkroom into an adjacent room, where I plan to set up a digital darkroom, or whatever the correct term is. I can understand why a scanning densitometer would be less than ideal for your uses, but one would be quite handy for me, I think, and they don't take up so much space that I would have to choose between the scanning densitometer, and the one I already have. Do you know of any UV scanning densitiometers? Maybe for Graphic arts/printing apps? Thanks again for the info.

Jay

You do a lot of film testing so I guess for you it would be an advantage to have one of these, the one I used was for a color lab and it had the 3 color channels. I doubt you will find one for graphic arts/printing since they essentially need to read the plates as well which we all know are not 4x5. To keep it on topic, I would not recommend one of these for someone who does sporadic film testing or is planning on calibrating both neg and paper a la BTZS.

[Jay DeFehr]

Jorge,

I was under the impression that scanning densitometers read both film and paper, is that not true? The Graphic arts app does seem unlikely, but one never knows. Thanks.

Jay

[Ralph Barker]

Not that they are a replacement for a real densitometer, but several of the RH Designs enlarging meters have a densitometer mode that allows measuring relative densities of the projected image under an enlarger. For some purposes, this might be sufficient, considering that they are also great enlarging meters.