Sensitometer - Do I need one?

[fhovie]

I can say that certain items really changed the way I do photography. The spot meter. Glass negative carriers. Condenser heads. Pyro. Mixing my chemicals. All kinds of things that give me better control - better sharpness and more success in creating the images I visualize in a scene.

What I am not sure of is why I should continue to seek out a densitometer. With staining developers, I understand which unit I should get. I know that I can then shoot a grey card and see the density and compare it with a published ideal.

But!

I know what base fog is- I can print zone one. I have adjusted my negative development so I can print all ten zones or compress them or expand them 2 or more stops at will. If I have spanned my development process and anchored my film speed. What will a densitometer really do to make me better at my craft, considering all these things? Used, they almost cost what a lens would cost and I am considering replacing my 150mm Symmar for a newer APO lens. Please enlighten me! ThanksSSS - Frank

 

[sanking]

One does not need to know anything about sensitometry to make good photographs, but it can be a useful tool that will provide greater understanding of the relationship between film density range and process exposure scale, an understanding that is not only satifying but that can also save a lot of time and money in testing.

A very good work on the subject is Phil Davis' Beyond the Zone System. I particulary recommend his film testing method, which is based on giving five step wedges equal exposure, developing each for different times, reading the densities with a densitometer and plotting the curves. With this simple test, which can be done in an evening, you can figure out the time of development with a specific film/develper combination for a variety of SBR conditions. It would take days of field tests to provide you with as much information.

Now, there is a problem with densitometers and staining developers. Many densitometers have only one reading, a Visual reading based on a combination of Red, Green and Blue light. Unfortunately a Visual reading does not read the color of the stain and indicates a density range that is much less than the effective printing density range. Color densitomers have a blue reading channel and this is what you should use for graded silver gelatin papers since the density range as read will be very close to effective printing density range of these papers. For alternative processes that use UV light a densitometer capable of reading in UV mode is required since the blue channel is not capable of reading the UV stain.

So, for silver gelating printing, including AZO, a color densitoimeter with blue reading mode is needed for stained negatives. These are available commonly on ebay at a fraction of original cost since many labs that until recently wet processed have gone digital and are now discarding their densitometers and related types of equipment.

For printing stained negatives with any of the alternative processes (pt/pd, kallitype, carbon, albumen, salted paper, etc.) that use UV light sources you will need a densitometer capable of reading in UV mode since a blue channel reading will indicate a density range that is quite a bit below effective printing density range. This type of densitometer is much less common. Two that will work are the X-Rite 361T and the Gretag D-200 II (with accessory reading tube). UV reading densitometers tend to be quite a bit more expensive than regular color densitometers. On ebay you will typically find them in the printing/graphic arts area rather than in the photograhy area.

Sandy King

 

[Ole]

A film scanner is a good replacement, and quite often cheaper. Turn off all corrections and look at the histogram. Scan in colour mode, compare luminance, red, green and blue channel...

 

[Aggie]

..

 

[Loose Gravel]

No, you don't really need one, but sometimes it can make life a whole lot easier. If a friend has one, borrow it. It makes calibration faster, it makes making copy negs, or internegs, faster. It makes the science end of photography easier. If you have an interest here, then go for it. You don't have to spend much money to get a nice one. I use PMK, too, and I don't use a color densitometer. I use an Xrite 301 with a blue filter. This is the same as the blue channel on a color unit. This gets one pretty close and as close as you can get with any densitometer. To get closer you would need to run spectrals on all you materials and then you'd be way off in the deep end. When it comes down to it, it is only the final print that matters and not whether you have a densitometer.

I was just looking at ebay in closed auctions and noticed that there are many units that closed for under $100. I got mine for $30, as is, not working. Turned out to need a fuse and an aperture. Xrite will sell apertures, but cost more than I paid for unit, so I made one. I pull it out and use it about once a month.

 

[Jorge]

I agree with Sandy, a good densitometer can be had at E bay for $300. and is a great tool to have. As Sandy suggested I did my BTZS testing and printing is a snap. I read the low value, the high value and print according the SBR I have. When I started printing pt/pd I did all this by the zone system, so I got a good neg, but I had to test prints, with the densitometer and the BTZS my first print is always close in exposure and contrast. I had to eat some crow and admit the BTZS is far easier than the zone system, and the desitometer is a complemetary tool to read your negs.

If you are using only the zone system, then you dont need one. You can have your negs read at a photo lab and if you stick with the same developer/film combination then things should be laways the same.

 

[JHannon]

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (OleTj @ May 16 2003, 06:26 AM)</td></tr><tr><td id='QUOTE'>A film scanner is a good replacement, and quite often cheaper. Turn off all corrections and look at the histogram. Scan in colour mode, compare luminance, red, green and blue channel...</td></tr></table><span class='postcolor'>
This sounds like a good idea OleTj, I have been using my spotmeter with a reverse mounted 50mm lens as described in the BTZS book.

Using the film scanner, do I scan a film base+fog negative as a reference level?

Lots of great information here as usual....

Regards,
John

 

[Ole]

The way my (universal) scanner works, is that it measures a reference (no film) which is then set to 0. This gives a direct measurement of FB+F, as well as Dmax - although in bit depth, not density. But the actual units something is measured in in sot important, as long as it's repeatable. And for comparison purposes a film scanner is quite adequate.

Some scanner programs lets you read the density at any point on the preview, that's another neat way of doing it.