Just acquired a Pentax Spot meter with Zone V Conversion

[Andrew O'Neill]

Expose for the shadows, develop for the highlights.

+1

[gnuyork]

Interesting that some find the stickers confusing. I have the zone modified Pentax digital spot and find it very intuitive. In fact I can't imagine it being any easier. What I find more difficult is finding where in a shadow I want it to fall on II/III. I just need more practice, I suppose. It doesn't help that I'm inconsistent with shooting film or digital.

[Kevin J. Kolosky]

In addition to the publications that have been recommended on this thread, I can highly recommend four others (if you can find them).
1. Kodak Professional Photoguide
2. Kodak Basic Photographic Sensitometry Workbook
3. Kodak Practical Sensitometry.
4. Your high school math book ( to do a basic review of base 10 logarithms).

You don't need all of this information to be successful, but if you want to understand what is really going on when you expose and develop a piece of film, and why you need a system of exposure and development, these publications will provide you with a very good basic understanding, which will in turn help you immensely to understand the zone system and the incident system and any other system you may choose to follow.

[Neal Chaves]

This may help. I've shared it before.


Years ago I learned an excellent method to find the correct developing time and EI for any film. The source was an article by William Mortensen. Mortensen wrote some excellent books and articles about basic sensitometry. The last time I did this test was when I abandoned Tri-X in HC100 and switched to HP5+ in Ilfotec HC due to cost about five years ago. I proceed as follows.

I set up my trays with my favorite developer HC110B (1:31), now Ilfotec HC (1:31). I pull out a sheet from the package in the dark. and then when the package is sealed again I turn on the room lights. This part of the test is done under the lights. I cut the sheet into five strips and mark them 1-5 by punching holes with a paper punch. Lets say the recommended time is 5:00. I want to see 3:00, 4:00, 5:00, 6:00 and 7:00, so I throw all the strips into the developer and agitate as usual until 3:00 when I move the No.1 strip over to the stop bath. Then I pull No.2 at 4:00, No.3 at 5:00, etc. I fix, wash and dry the strips as usual. What we are looking for is the best usable film DMax value. Obviously the film has been fully exposed! When strips dry lay down a page of news print on a table in good light. Find the strip through which the news print is barely visible. That's your developing time. Now to find the film speed.

Go outside in unchanging light conditions and expose five sheets and expose one at the manufacturers rating and then the other four at one half a stop and one stop less and one half a stop and one stop more. In the dark, develop them all together for your newly derived time. Contact print them together exposing and developing the paper for maximum usable paper DMax value through the film base plus fog negative rebate area. Pick out the best-looking contact print and you have your film speed.

Because my 7:00 negative looked the best on the first test, I did the test again with 7:00 as the central developing time and found that 8:00 was indeed too dense. This HP5+ time was the same as the as the developing time I had been using for Tri-X and film speed was also the same, EI400. I have also switched to Ilfotec HC developer due to cost and availability and find it to be a clone of HC110.

Many of the last generation of B&W gurus favored a development time of 5:00 for Tri-X and suggested an EI of 64-100. You can do the above test backwards, developing for 5:00 minutes and finding the film speed. I like 100. The difference between negatives exposed at 100 and developed for 5:00 and those exposed at 400 and developed for 7:00 is quite subtle. Both could be considered "normal" or N negatives. The 100 negative has slightly greater shadow and highlight detail that only a careful, knowledgeable viewer could detect. This slight improvement might not be worthwhile trading for two stops in the field. I do routinely rate HP5+ at 100 under powerful strobe light in the studio and it produces beautiful skin tones.

From here, if you are still with me, you can derive expansion and contraction schemes for both the 100 and 400 "normal negs". I do this by changing dilution rather than time. Make sure you have at least 1 oz. of the concentrated sauce for each 8X10 sheet or equivalent. For contractions I found that 3/4 oz. concentrate to 31 1/4 ozs. H20 yields an N-1 neg at a one stop loss in film speed and 1/2 oz. concentrate to 31 1/2 ozs. H20 yields an N-2 neg at a two stop loss in film speed. For expansions, 1 1/4 oz. of concentrate to 30 3/4 ozs. H20 yields an N+1 neg at a one stop gain in speed and 1 1/2 ozs. concentrate to 30 1/2 ozs. H20 produces an N+2 negative with a two stop gain in speed.

If you look at the chart of Tri-X film speed in Phil Davis' BTZS book you can easily pick out the film speed in HC110B 5:00 as EI 64.

Don't apply reciprosity exposure and development corrections for long exposures (1/2 sec. +) based on published data. Test for yourself and you may be surprised. I wasted a lot of time and effort producing long exposure negatives that were thick and flat. When I finally tested, I found no compensation was required for TXP or now HP5+ out to one minute.

[Jim Noel]

WHat a good explanation of Mortensen's method. I have used it for years with a variety of films and developers. I am a true Mortensen fan, and have been able to acquire each of his books.

[Drew Wiley]

Well, I use the same Pentax meters for both color and black and white work; and trying to accommodate the world to eight zones on a sticker is just too imprecise for me. But if ya gotta do it, you have a little middle gray triangle in the middle of the dial and two hands : one holds the meter; the other hand has five fingers, so you can simply count five EV values up or down from there, effectively ten zones, so even better. But ya gotta learn how to count fingers first, and I don't think Ansel taught that.

[neil poulsen]

I find the simple physical dial of the Pentax digital spotmeter much faster and more intuitive to use than any of those airplane cockpit screens loaded with a lot of redundant stuff. And having a tenth of an EV readout does not mean the meter is capable of a tenth of a EV accuracy. Even routine flare would affect that.

This is true for me as well. I have a Minolta Spotmeter F that has averaging, remembers readings, will give relative readings, etc. But similar to what a Pentax provides, all I really need is an EV (exposure value) and a way to tie an EV number to an exposure. The rest kind of gets in the way.

[Luis-F-S]

Drew, your posts really can be tiresome. You seem to demean others' approaches to photography, while aggrandizing your own. At one point you say, "I do critical film evaluation using lab instruments far more precise than any kind of field light meter," but then go out of your way to denigrate my spot meter as a "cockpit screen loaded with a lot of redundant stuff." Why can't you simply acknowledge other people's experiences and preferences without getting in a jab? There are an infinite variety of ways to produce great images, and we all choose our own path and tools to get there.

++1!!!!!!

For someone so brilliant how come we never see any work?

Me? I’ll stick to the Zone VI modified Pentax Digital meter.

[Vaughn]

This is true for me as well. I have a Minolta Spotmeter F that has averaging, remembers readings, will give relative readings, etc. But similar to what a Pentax provides, all I really need is an EV (exposure value) and a way to tie an EV number to an exposure. The rest kind of gets in the way.

Agree. If I want to make average images, I'll use a meter that averages! Just joking, of course.

[neil poulsen]

This may help. I've shared it before. . . .

Mortensen also advocated exposing for the highlights and developing for the shadows. Perhaps that's why he emphasized basing film speeds on maximum density?

I'm just the opposite, in that I expose for the shadows and develop for the highlights, which is consistent with Ansel Adam's zone system methodology. Consequently, I base film speeds on the minimum amount of light needed to bring an appreciable amount of density to the film. That is, what EI do I need to use so that a Zone I exposure creates a density on film (read with a densitometer) of 0.1 density units above film base plus fog.

But, is there not a logical inconsistency in the Mortensen approach? In basing the exposure on the shadows (a la Adams), whatever development one decides to use to increase or decrease contrast (based on the highlights) will have only a small amount of effect on the shadow densities that one wants to achieve. So, a subsequent change in development time doesn't undermine the initial exposure. (It does a little, but one can adjust for this.)

But using Mortensen's approach of exposing for the highlights, isn't it the case that, after deciding on an exposure, any subsequent change one might make to development time (based on the shadows) could substantially undermine that initial exposure? I suggest this, because changes in development time can have a huge effect on highlight densities on the negative.