A densitometer that is. I've picked up a X-Rite 811 but not sure what to do with it. I've managed to find the manual online for the 810/811 with an addendum for the 811 but having read through both twice I'm none the wiser.
Bought a Stouffer 21 step wedge to use with my Analyser Pro and believe I can use it with the 811 too, but what do I do with it.
I've got all the books The Negative, Zone VI Workshop, Beyond Monochrome etc, but I'm just not getting it at the moment.
The best thing to do with it is figure out your top end density. You can take a neg that prints in the sky perfectly, and another that you have to burn in and figure out the difference in the density in those highlight areas. Then you can tune your development so that you don't exceed (in negative density) what the rest of your processes can do.
I'm sure you understand that the less you develop, the lighter those areas will be. With a densitometer you have an impartial judge for how high the density should be for any given level of development (N, N+ or N-).
Hope this helps,
Lenny
EigerStudios
Museum Quality Drum Scanning and Printing
A densitometer is a device that measures either the opacity of a film (transmission densitometry) or the reflectivity of a surface (reflection densitometry). The former is typically use to fine tune exposure, dynamic range (contrast) and development properties (developer, agitation, duration and temperature) of film while the later of the printing process. Often the two are studied together so that one can optimize all the steps when a photography is taken (more of that later).
In both cases what one does is to make different exposures either to the film or the paper and for each exposure measure the opacity or reflectivity, depending on the medium. When a wide enough exposure interval has been measured a plot can be made in which the abscissa corresponds to exposure level, typically a logarithmic axis, while the ordinate corresponds to the density or reflectivity. Each time a variable changes (film, developer, time, agitation, temperature etc), one of these plots should be made to understand its effect in the film or paper reaction to light.
Lets start with the film. Pick any uniform mate surface (target) and place it in a 45º degree to a diffuse light source but parallel to your film plan. It can be any shade of grey, or even color, but must be homogeneous - check with the spotmeter that the EVs do not change by more than 1/3. Using the spotmeter measure the exposure. The spotmeter will make that surface a medium grey exposure (zone V in the zone system)...some meters are calibrated for zone VI, but those are more commonly found inside 35mm cameras. Choose light intensity and aperture so that the shutter speed is between 1/8 and 1/30 (these are common sense values if the film you are characterizing has no significant reciprocity failure). It is not needed for the image to be focused, but the lens plane and the film plane should be parallel to the target. Make the exposure and in your notes write down the speed and aperture and the indication that it corresponds to the direct measurement of the spot meter. Now make exposures of -1 stop, -2 stops -3 stops, -4 stops and -5 stops. Do the same with +1 stop ....+5 stops. This is a lot of sheets and certainly not a very efficient, or cheap, way of doing this, but you get the idea. You can cut the sheets and load negative holders with strips or you can put a card inside the holder or you can use a medium format roll if there is one of the same film type (note that this is very economic and efficient, but can give wrong results since the substrate is different in roll and sheet). Once you have developed all those exposures with the exact same method and ambient variables, and have allowed them to dry, measure the transmission density for each exposure. If you plot the graph in Numbers (a spreadsheet), you should see a sigmoid curve (S shape plot). The middle zone is where you want to put the light range of a scene. The left horizontal line is the toe and the right horizontal is the shoulder. Changing agitation, duration and temperature you will see that plot change.
I typically fine tune my development to include 6 stops of exposure in the middle, linear, characteristic of the plot. This corresponds to zones 3 to 8. In my case zone 2 has very little detail and zone 9 too. But I know what I need to do if I the scene I am trying to photograph has more than 6 stops of usefull exposure. This, however, typically comes at the expense of a different grey gradation. This process also allowed me to figure out the Exposure Index (EI) of each film for a given developper. For instance, I am a big fan of Rodinal, which is a developper that brings down the speed. For instance Acros in my soup of Rodinal has an EI of 80. Delta 100 in the same soup has an EI of 50 and TriX and EI of 165. Something along these lines, but with different implications and physical meaning should be carried out for paper, but only if you care to enlarge. If all you do is scan than you only need transmission densitometry.
I am not trying to write a prime on densitometry. Much more capable people have done it in a much better and more detailed fashion. I was just trying to give a rough introduction so that you will find it important to read those sources. I most certainly recommend Ansel Adams books which go way beyond what I have explained here in a simplistic way. However, if you only need densitometry theory than those books are an overkill and I would probably recommend the articles by Phil Davys from BTZS on sensitometry which you can find here: http://www.btzs.org/Articles.htm. If you don't care for printing then skip part 2.
Happy reading and sensitometry experimentation.
raul
Ed,Originally Posted by Ed Bray
The X-Rite 810 is a great tool. My advice would be to pick up a copy of Phil Davis's Beyond the Zone System, 3rd or 4th edition, and immerse yourself in the understanding of developing negatives and prints, and sensitometry.
It will take a while to put all of this together, but if you do you will be able to answer all your questions and never have to depend on others for your understanding of film development. The book takes time to digest, but if you hang in there it will all make sense after some study. BTZS is a much more powerful tool than the Zone system. Some people who understand Zone dispute this, but when you query them you find they don't understand BTZS, which means their opinions are basically worthless in comparing Zone to BTZS.
Sandy
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The step wedges are essentially used for print sensitometry. By placing them in the light path to the paper you get a means of changing the exposure in a controlled way in the paper for later analysis of reflectivity (after drying).
Thanks all for your thoughts and help.
Sandy, I have a copy of Beyond the Zone system as I am an avid collector of Photographic books, I will just have to wade my way through all the boxes they are stored in and try to find it.
Sandy, I found my copy of Beyond the Zone System. All was going well and I even got all bar one bit of the exercises in Chapter 2 correct, Then I hit chapter 3 'How to read and interpret characteristic curves' and then my head exploded.
Going to take a break now and do some printing instead.
The first issue of the world journal of post factory photography can be found free online (a quick google search should turn it up). If my memory is correct this issue has a really nice concise beginners article on sensitometry. Granted it is skewed towards alt photo, but it is worth a read through. It has been quite awhile since I looked at it, but I don't remember falling asleep while reading it which says a lot for the way they handled the topic.
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