E-59 Practical Densitometry

[conrad_hoffman]

This old Kodak publication seems quite rare. It's something we were given back in 1972 in the RIT photo program. Enjoy.

http://www.conradhoffman.com/papers_lib/Practical Densitometry E_59.pdf

 

[rodeo_joe1]

Thanks Conrad. An interesting old publication. 

However, in practise the only thing a densitometer is needed for is to check printable highlight densities and the Dmax of a bit of fully fogged film. Just simple process control to make sure your development etc is staying within acceptable limits. 

The density of detail-retaining highlights in a B&W negative shouldn't be much above 1.8D (although edging 2.0D is still OK). While the fully-fogged Dmax should be somewhere in the range of 2.8D to 3.2D. It depends on the film and developer and your own printing/scanning preference of course, but in general a Dmax under 2.8D would be considered under-developed and anything in the region of 3.5D or above as over-developed.

I really don't see the point in creating your own H&D curves with a stepwedge or whatever. It's already been done for you by the maker of the material. All you have to do is ensure that your processing is giving you a close approximation to what the maker's datasheets say you should be getting. 

My densitometer gets pulled down from the shelf and taken out of its box about twice a year. And then it usually only confirms what I can judge by eye.

I will add that a common beginner mistake is to aim for a good 'thick' negative and err on the side of overdevelopment. This does you no favours when it comes to printing or scanning and vainly trying to get some detail out of blocked up highlights. 

Edited April 4, 2023 by rodeo_joe1

[conrad_hoffman]

IMO, it's the understanding that's valuable, not so much needing to actually do it. Fer instance, the difference in max density and curves for various paper surfaces on page 5 is something everybody should know, be they wet process or digital users. The difference between gamma and contrast index and why they both exist is also useful. I figured there aren't many copies of the thing around, so at least now it's preserved for posterity. I pull my densitometer out every 5 years or so. Still works, but I hope it never needs a bulb. Apparently they're not made anymore and a replacement is $500! Somewhere I also have an old black Kodak  Model 1 (or 1A) that still works. No reflection with that.

[rodeo_joe1]

20 hours ago, conrad_hoffman said:

Still works, but I hope it never needs a bulb. Apparently they're not made anymore and a replacement is $500!

Swap it for a white LED! 

My densitometer came free when it was upgraded at my place of work and was going to be thrown away! It doesn't have its own light source, but was meant to be used with a light-box. I built a little tri-colour LED light-box to use with it; effectively turning it into a colour densitometer - a feature I've never actually found a practical use for BTW. 

FWIW those colour-changing LED strips contain dozens of little tri-colour LED modules. One of which could easily replace a small densitometer bulb. 

[David Lindquist]

Thank you for this Conrad. I'm a bit surprised I didn't get this publication back in the day. As you suggest maybe it wasn't that widely distributed, perhaps mainly to RIT students as required reading. Very good presentation of important principles. Back in the 70's I had one of those Kodak black plastic (Bakelite?) densitometers. It got replaced with a MacBeth (transmission only/black & white only/ analogue rather than digital readout) later back in the 70's. Its performance got wonky a few years ago so I replaced it with an Xrite with digital readout, easier for me to use at this point in my life.

Different people work different ways. I'd never claim one needs a densitometer to do good work but personally I like being able to use one. I remember many years ago hearing Oliver Gagliani advise that after getting your basic view camera kit together you should consider getting a densitometer before getting a second lens.

David

Edited April 5, 2023 by David Lindquist
mis-spelling

[rodeo_joe1]

Film made it far too easy to get anal over every step of the process. 

Telling people that a densitometer was an essential part of their kit is like saying to photographers today that they need a micrometer to make sure their SD card is the right thickness! 

[conrad_hoffman]

Well Joe, if you can't think of 337 ways to get anal over the digital process, you're just not trying very hard! 🙂 Actually, I do have an XQD card that's a bit too thick for the slot, but no matter how hard I clamp it with my micrometer, it doesn't seem to fit any better.

I had a MacBeth analog densitometer for a while and it was nothing but trouble. I think you needed two different heads for T and R. Now I've got an old X-Rite 811, which is great, but the $500 upper bulb replacement cost has me a bit worried. Heck, even the $90 for the lower bulb is too much. The instructions say that for commercial use you should replace the bulbs once a year.

[hjoseph7]

I have a hard copy of this manual at home. It came with my X-Rite/Kodak 810 Color Transmission/Reflexion Densitometer that is sitting in my darkroom collecting dust which I purchased over 15 years ago. Right now I can get about $600 on eBay for it, but I have not been able to bring myself to sell it, yet. This manual makes good (hard) reading on a rainy day. I had to go over some chapters several times before it really sunk in.  Unfortunatelly  you have to calibrate this Densitometer often with calibration cards. Mine only came with the B&W calibration card. The color calibration card from X-rite will cost you a whopping  $280 !

[conrad_hoffman]

AFAIK, the 810 is very similar to the 811, which calibrates with a black and white film of density patches, and a ceramic on steel reflection target, also monochrome. I'd be surprised if you could actually get that much, as they're old and no longer serviced or supported. Should check completed listings, but I'd vote for keeping it if you think you'll ever use it again. I haven't done film in decades but hope to after I retire.