View Full Version : BTZS reflection readings

8-May-2014, 01:23

On reading the 4th version of the BTZS book by Phil Davis, I get the impression he really likes incident metering. There is a section called "Traditional Test Methods" which talks about the traditional zone system on pp126 then onto using the working charts as an example. He then leaves the discussion to go onto his pet subject of using incident metering in "An Alternative: Incident Metering". There are also references to graphs where he says, "Incident metering only!" in Fig 7.25 and others relating also only to incident metering in Figs 9.10a and 9.10b.

Surely the BTZS is not an incident metering only way of going about things?

Can someone who has purchased the software and uses this system confirm that they use reflective or incident metering as they see fit?

I'm also wanting someone to tell me what a minimum buy is for the software. Does one 'need' an iOS device from Apple nowadays? I know the Palm Pilot is cheap but if you are wanting a new (reliable) device must one buy into the Apple family? I think buying an iPad just to run the software is a bit steep! (I'm not an Apple worshipper they are too controlling for my taste ... you may have noticed this fact!)

So a minimum hardware specification to run all the BTZS software reliably if you could please.



8-May-2014, 04:48
I have the software on my iPad (and formerly on my Palm Pilot) - it does allow you to use either meter. So far as I know, an Apple device is the only thing you can get the software for now.

8-May-2014, 06:58
BTZS plotter for Windows has built in support for reflective metering in zones. You can buy the software at: http://tinyoctopus.net

I seriously doubt that you will have any problems in meeting the minimum hardware specifications. I currently run the program on Windows 7 and before that on XP. I have never had any stability issues. Apparently it works on all Windows versions back to 98.

I started using the system long before the IOS app was available, and instead of using a Palm Pilot I keep the necessary information I need in a small black book where I also record exposure information so I know how to develop my film. This practice may be slower than using the app, but for my needs it is perfectly satisfactory.

8-May-2014, 10:50
The data derived from BTZS testing methods as analyzed by WinPlotter supports both spot metering using N-Numbers as in the Zone System, and incident metering with SBR values. One you have entered the test data you can toggle back and forth between the two methods, and use the data from either method in your field work. Whether you measure subject luminance or illuminance some understanding of how to use the measurement is necessary for creative controls.

The Plotter program was originally written and used for Macintiosh computers. Phil Davis taught a couple of BTZS workshops at Clemson University in the 1980s and I still remember the group of students gathered around early MAC 512 KB computers entering the test data into Plotter. Sometime in the 1990s the program was ported over to the PC world and became known as WinPlotter. Sometime later Davis introduced the Expo/Dev program which ran on Palm Pilot. I used a Handspring with Palm operating system for some years for field work, but eventually the calculations became so evident the device was not used except for complicaeted calculations involving exposure compensation for filters, reciprocity and/or bellows adjustment. I own an iPhone but have no experience with the Expo/Dev type app for it so I would have to conclude it is not an essential part of BTZS for me. WinPlotter, on the other hand, is absolutely essential if you want to do the testing work yourself for maximum understanding of the photographic process.

Before Phil Davis and BTZS not many people considered the incident meter to be adequate for creative field work. Unfortunately that is still the case, but thanks to BTZS at least some people know better.


8-May-2014, 14:20

The main purpose of the post is to ascertain what hardware I need with the caveat that the hardware won't already be years old. I am doing paper and film testing myself so it looks as though I do need the WinPlotter but there must be an end point to it so I need to take the results into the field also.

I see on the TinyOctopus site that there is a BTZS Plotter program and a ExpoDev program. The BTZS Plotter needs Winblows to run and I guess that means it doesn't run on the same portable iOS device. I assume one needs both programs to do one's own testing and to take it into the field.

So the BTZS testing requires two pieces of hardware and two operating systems. I believe that one imports data into the field device using an email program?? So that means setting up and paying to have an email account on the portable device too. Let alone the cost of buying a 4G data account also.

The cost of BTZS testing is then:

A densitometer for reflection testing
A densitometer for transmission testing. This may be the same as the one above but if using UV mode and staining developers then it needs to be different.
An enlarger
A darkroom
Two pieces of software ExpoDev and BTZS Plotter
A computer with Windows
A mobile device with iOS
A data plan with the mobile device
An email account on the mobile device

In the field one needs to carry another piece of battery dependent equipment that has to be re-charged and physically protected...


It just occurred to me that this is another expensive route to go down... Perhaps seeing it up front like this might make some people baulk.

It might be appropriate for the maker of the software to think about all this too and make the ExpoDev software run on Windows as well as iOS at least? Obviously a single platform and OS would be most advantageous. Even better is to get the two programs onto a portable device that allows interfacing with the real world... something with say a USB port?

Andrew O'Neill
8-May-2014, 14:41
Just pick up a cheap densitometre on ebay and plot the curves by hand on graph paper. That's what I have done for years. Save all that money for film. Just my opinion.
I have an incident metre as a backup and it's definitely doable to get excellent negatives but I prefer to read the light coming off the scene so I use a reflective light metre. I do you BTZS methods but without all the gadgets.

8-May-2014, 15:18
You need a windows machine to run WinPlotter. If you want to take Expodev into the field, you need an Apple device - either iPhone or iPad. You can download the app directly to the iPhone or iPad without an email account - you only need to be able to reach the Apple app store, either by the phone or wifi for the iPad. You can use a public wifi.

8-May-2014, 18:43

You are very helpful thanks.

Excellent to get this information. It is such a shame that the software is in two pieces and not something more universal - across more platforms. The contenders to Apple iOS are not very viable at present from what I see but I think Apple should respect its competition. I wouldn't want to take on Google!

It is very good to see that I don't need a 4G data account. I've been leery of this for years. I signed up to a fixed price mobile account years ago and the phone company is regretting their offer!! I pay such a small amount for mobile comms it isn't funny. I'd hate to buy into the silly prices of today...

So the iPad is the only option that will do the WiFi ?? That's OK as I can do WiFi without a worry.

In the manner of Buzz Lightyear ... "To the iPad!"

9-May-2014, 01:55
A cheaper and less bulky route than running ExpoDev on an iPad is to get an iPod touch.

That said; I would start using BTZS without ExpoDev. If you like the system and find difficult the use of written tables in the field, you can always get ExpoDev and an iOS device later.

9-May-2014, 23:24
Thanks uhner. I think you are right. Locking into an iPad that doesn't have multiple users is a dead end. I'll carry bits of paper just fine but it would be nice to have a mobile device. I wonder if the app might not be written for the Android OS?

10-May-2014, 05:05
Another option would be to get Fred at the View Camera Store to do you film testing, then order a BTZS Power Dial from him. It's sort of a slide rule that helps you do exposure calculations. I've used one of these - make notes in a notebook of meter readings and use the Power Dial to determine exposure. You could also get the BTZS Lite CD from Fred, which is a much simpler explanation of BTZS than the book.