How do you measure Dmax?

[John Lockhart]

This is the most appropriate forum I could find. How are you measuring the dmax of your prints? Are there ways to do this without special equipment, e.g., a scanner and photoshop? I would like to start having some more concrete assessment of the properties of my prints like the dmax and ES. As my printsget incrementally better it gets harder to judge how much the different variable in the process affect the final prints.

 

[gmikol]

John--

Realistically, you need some sort of specialized equipment, like a densitometer, or a spectrophotometer (like the X-Rite i1).

Spectrophotometers tend to be *really* expensive, but a B&W densitometer can be had on the auction site relatively inexpensively (I got a *very* good one about 5 years ago for $75). Try to find one that can do transmissive and reflective readings.

If estimating your density to 0.05 logD increments is good enough for you, get a reflective 21-step wedge from Stouffer and punch holes in each step, and then you can do a visual comparison and estimate your density. But this system breaks down the less neutral the blacks of your print are, depending on process. e.g. it would not work at all, really, for cyanotype.

If you don't already have one, definitely invest in a transmissive step wedge. Quickest and easiest way to measure exposure scale...print it in your process, count the number of steps that you can distinguish, multiply by 0.1, and there's your exposure scale in log E units.

Good luck--

Greg

 

[sanking]

John,

I don't have any idea how to measure print Dmax without a densitometer. Good thing is that with a bit of looking you can find one on ebay for not a lot of money. Some will measure both transmission and reflective reading, X-Rite 810 for example. And if you want to measure negatives for UV processes you need a UV reading densitometer (X-Rite 361T is the most common) if you use staining developers. And if you want a very portable reflection densitometer look for one of the X-Rite 400 series.

Sandy King

 

[Joe Lipka]

Reflection Densitometer is the way. I have an X-Rite 400 which is just dandy for reading print densities. It has a nice feature which measures percentage dot gain which directly translates into eye dropper readings in photoshop.

 

[pellicle]

Hi

I have used my scanner and purchased a set of charts from Stouffer. I put some of my information on my blog (here) and you can find another thread on this topic on this forum here where the OP also noted non linearity issues of the scanner.

Personally I find using a scanner (and its known issues) a reasonable tool. Phil Davis in Beyond the Zone system refers to adapting a spot meter as a densitometer, which clearly has similar issues of absolute accuracy (such as consistency of light source) to a scanner (which will have its own issues). With the use of a stouffer stepchart, photoshop and excel you can work out the specific issues with your scanner and then work with it.

What light frequencies are you using? I don't think you can use a Scanner for UV.

How accurate do you need? I on occasion use a plastic vernier caliper for measuring some things, while (such as setting the tappet clerances on my Ducati) use a G clamp type vernier tool (when I need 0.01mm tolerance).

 

[donbga]

This is the most appropriate forum I could find. How are you measuring the dmax of your prints? Are there ways to do this without special equipment, e.g., a scanner and photoshop? I would like to start having some more concrete assessment of the properties of my prints like the dmax and ES. As my printsget incrementally better it gets harder to judge how much the different variable in the process affect the final prints.

You can also utilize the densitometer feature of Vuescan Pro to measure the log values of print densities. Unfortunately the readings obtained from most scanners is not linear when encountering log values greater than 1.9 or so (at least that is what I encountered when I tested my scanner a few years ago).

One can fudge, I mean normalize the values of the readings if you have a calibrated reference when using a scanner for reflected density readings (for transmissive readings I don't think a scanner is a good instrument at all to use, fudge factors or not), but I would encourage you to look around for a tramission and reflection densitometer. The xRite 810 can usually be found for bargain prices these days. You may spend more on a calibration plaque and negative from xRite than you will for the densitometer. I've been using densitometers for almost 40 years now and I can recall when they sold for thousands. Today they are pennies on the dollar.

Another instrument to look out for is a spectrophotometer. Occasionally bargains can be found. A good friend purchased a nice XRite for almost nothing (relatively speaking) off the local Craig's List.

On the other hand I never use a densitometer any longer when building correction curves for digital negatives. A scanner will do the job properly if used correctly, but for this process no log density values are being generated.

As for actually measuring the print DMAX I rarely do that any longer as it really isn't important except in circumstances where one is testing a deviation from their normal work flow or materials have changed. IOW, if a black looks black enough it is.

Finally, a densitometer is very very handy if one is using BTZS software to generate film and or paper plots. I wouldn't want to tackle that with a scanner as the work of reading test strips is tedious enough. And accuracy of +/- 0.01 for film can be important. But use what you have, that is use a scanner and see how you get by with that.

Don