Every so often someone asks whether there will be a version of BTZS Plotter for OS X. I can sympathize and understand where they are coming from but unfortunately the sad truth is that the development costs and time associated with such a project makes it just not financially feasible. The market for Plotter was never a large market even in its heyday but just as interest in film has tapered off over the years so has buying desktop oriented software.

The current version of Plotter was written 10+ years ago now. It was written specifically to bring Plotter to Windows since at that time, there was a version for the Mac. As such Plotter for Windows was written without any consideration of it being ported to other platforms. It is written using a software framework that down to its core, just isn’t suitable to porting. To “port” Plotter to other platforms at this point means starting from scratch and I mean really from scratch - going back to the BTZS book for a fresh start. There is virtually no code that can be shared – not even the code that reads and writes the file formats. It is simple just too Windows-centric.

As such I’d estimate that a complete re-write of Plotter to be somewhere between 1 and 2 man-years worth of effort. It is 10’s of thousands of lines of complex code, most of which hasn’t been touched for many, many years.

The good news is, Plotter for Windows runs just fine on OS X and you don’t even need to buy a copy of Windows or anything else to install it on OS X. Is it a native OS X application? Well no – but it runs and functions very well. The key to using this is an open source project called “Wine”, which is an emulation layer that allows Windows programs to be run on lots of platforms such as OS X and Linux.

Traditionally setting up Wine on OS X has been somewhat complicated for non-developers but that has changed now. Using a Wine package builder such as Wineskin, WineBottler, or Crossover makes this very easy. I just did it from scratch using Wineskin and including the time to download it took about 10 minutes from start to finish. In the end I had a Wine-Plotter application that I could just launch on OS X. It really is very easy. I just followed the excellent but short manual for Wineskin.

Here is a quick rundown of the process for installing Plotter on OS X from scratch:

  1. Download the Winery package to your Mac and launch it. If this is your first time of using Winery, you have to download a Wine Engine. I just used the latest available (WS9Wine1.7.0X)
  2. Select an Engine and Create a new Wrapper and give it a name – I called mine WinePlotter (a wrapper is a Mac App that you launch to run a Windows program)
    • Note: As part of the new package creation process you’ll see two notices about not having Mono and Gecko packages installed. You can just hit cancel for each as neither of these are needed by Plotter.
  3. Once the wrapper is created in your ~/Applications/Wineskin folder, open it like any other application. The first time it is run you’ll be presented with options. Click Install Software and point it at your WinPlotter.msi installer file. Once the installer finishes you’ll be ask to choose the .exe program to run when launched (it should be /Program Files/WinPlotter/Plotter.exe). Once Plotter is install, Quit the wrapper app as no other options should need to be set.
  4. To launch Plotter just open the finished wrapper app and Plotter will automatically launch.

From this point on you can use Plotter just like any other installed app. I know that not having Plotter as a native OS X application rubs some people the wrong way and I am sorry for that but given the constraints of time and development costs, this is the best option for those who want to use Plotter on their Mac at this point in time.

Postscript: A few of you have asked where to get Plotter from these days. Plotter as a product for sale has transitioned back to me from the View Camera Store. I’m working on making Plotter available as an online purchase. I’m now also looking into making a pre-packaged Wine version for Mac users. I’ll post more details when Plotter is available.

ExpoDev version 1.1 has been submitted for App Store approval and is waiting for release. Version 1.1 is a minor update that includes a few fixes and enhancements, most notably being that the Bellows Extension Factor calculator has been completely revamped. As you can see below, this new version now supports bellows extension factor compensation by using either the subject distance, the actual bellows extension, or a magnification factor.


When working with subject distances you can use either meters or feet and inches, as measured from the subject to the lens board. For Extension, the actual bellows extension is measured in millimeters. Magnification is a decimal magnification factor with 1.0 being a 1:1 reproduction factor.

ExpoDev will now directly tell you the calculated bellows factor and as such, ExpoDev no longer tries to determine whether a subject is a close-up or not. This leaves the photographer in charge of determining whether or not to apply a bellows factor as they see fit. ExpoDev does place some reasonable limits on factors though: if the calculated bellows factor results in less than 1/6th of a stop then no factor will be applied. 1/6th of a stop is well within the margin of error, all things considered. ExpoDev will also place a limit on the maximum factor of 65,536 (about 16 stops). In both of these cases, ExpoDev will let you know what is going on so that you, the photographer can make informed choices.

A few other minor improvements are included in this release. It is now possible to use lenses up to 2000mm and the minimum aperture has been increased to f/2048 (for pinhole photographers).

Today I am happy to announce that BTZS ExpoDev for iOS v1.0 has been approved and officially released. It won’t be searchable in iTunes for a few days or so, but in the meantime you can use these direct links:

Official app website with links to the app in iTunes, feature information, screenshots, the user manual, and info on how to get support:  http://TinyOctopus.net/ExpoDev

Direct link to BTZS ExpoDev in iTunes:

ExpoDev’s Depth of Field calculator was designed with the large format photographer in mind. There are many takes on DOF calculators but a lot of them are either too simplistic or make it needlessly complex for everyday use. ExpoDev’s DOF calculator strives to remain simple to use yet flexible enough for large format photographers who really want to maintain the clarity and visual integrity in their prints. Depth of Field is a complex topic though and I’m not going to go too deeply into it here. Instead, I’ll explain how ExpoDev’s DOF calculator works and how to use it to the greatest advantage. First though, I can’t escape a little background on DOF:

One key aspect of an effective DOF calculator is letting the photographer choose one very important parameter, the Circle on Confusion size (CoC). CoC values are typically expressed in millimeters. ExpoDev offers a selection of CoC values along with the suggested film format size they should be used with*.

There are a lot of opinions though on what CoC values should be used for particular film formats but it’s really a matter of personal choice and greatly depends on the enlargement factor to be used when making prints from your negatives. For instance with contact printing, a larger CoC can be used since there is no enlargement factor. With smaller film formats that will be enlarged, a smaller CoC should be used. The greater the enlargement factor, the smaller the CoC value needs to be.

Typically though, we don’t always think about enlargement factors while working in the field. To make things simpler (but not necessarily less flexible) ExpoDev makes one general assumption: that the larger the print size, the farther away the typical viewing distance will be. ExpoDev therefore assumes that the typical viewing distance will be roughly 1.5 times the diagonal measurement of the print size. This generally holds true for most viewers, whether it is a large print on a wall or a smaller print in their hands. This assumption allows ExpoDev to use one CoC value for each film size without making you think too much about enlargement factors. If however you want to increase the perceived sharpness of a print it is as simple as choosing a smaller CoC value in ExpoDev. This method retains the flexibility without making the user interface needlessly complex.

The important take-away here is that choosing the correct CoC value is what determines final perceived print sharpness and since ExpoDev gives you that control, you can make the DOF calculator work to suit your needs.

Now that we got that out of the way, we can get back to the features of ExpoDev’s Depth of Field calculator.

ExpoDev has three DOF calculators. The first one, Check mode, is the simplest and can be thought of more as a DOF checker. You simply tell ExpoDev what aperture you are using and the subject distance and it will calculate the Total DOF, the Near and Far planes, and the Hyperfocal distance for you.

The next DOF mode, Distance mode, allows you to tell ExpoDev the Near and Far focal planes and it will then tell you the Minimum Aperture to that can be used along with the Focal plane and total DOF. It also tells your one more important thing, the Optimal Aperture.

The Optimal aperture is the concept that print sharpness is really a balance between perceived sharpness and diffraction. There is both a minimal aperture to get the perceived print sharpness you want but there is also a point at which a smaller aperture starts to degrade the sharpness due to diffraction. The Optimal aperture is the aperture which balances these two effects. It is the midpoint where you get the greatest DOF with the least amount of diffraction. You can use either aperture when making your exposure to get the DOF you need, but for optimal print sharpness you sometimes might want to go with the optimal aperture vs. the minimum aperture.

The final DOF mode is called Focus Spread mode and is probably the most practical one to use as it requires no estimations or measurements of subject distances. Focus Spread mode is a way of easily focusing a view camera by measuring the distance that the focus rail has traveled between focusing on both the nearest and farthest points. If you measure and enter this distance (in mm), ExpoDev can then calculate both the minimum and optimal apertures that will make everything from the nearest point to the farthest point fall within the DOF. This makes it really easy to focus a view camera as it does not require you to stop down the lens at all until you are ready to make an exposure. You do all focusing while the lens is wide-open. The really great thing about this method is that it automatically takes into consideration any view camera movements that you are using. This makes figuring out which movements are improving the DOF as simple as measuring the changes in focus rail travel (i.e. if the distance is getting smaller, the movements are helping). You can find more information about this method here, http://www.largeformatphotography.info/how-to-focus.html in the “Procedure II” section.

Once ExpoDev has calculated an aperture to use for the desired DOF, it makes using that aperture easy by automatically settings the Exposure aperture to that value (if you are using Aperture exposure mode). There is also an app setting to tell ExpoDev which aperture to use when it sets one for you, either the minimum aperture or the optimal aperture.

Of course you can change the automatically selected aperture to use on the exposure tab at any time but if you do and that change negatively affects the calculated DOF (i.e. it decreases the DOF), ExpoDev will warn you when you are doing so.

That about covers the DOF calculator in ExpoDev for iOS. It is a significant improvement over the older Palm version of ExpoDev in many ways. It is quite powerful and flexible yet remains as easy to use as ever.

* Right now ExpoDev offers a few commonly used CoC values for different film formats. In the next version, ExpoDev will let you create your own set of CoC values to choose from much like it does for filters and lenses.

ExpoDev is very unique in that is uses highly accurate and test-produced reciprocity data for over 90 film and developer combinations. Phil Davis did the work of testing each and every film developer combination using selected exposure times up to 1,000 seconds or roughly 16 minutes. He also field-tested these results to ensure their accuracy. This is far above and much more specific than the data that film manufacturers publish for their films and developers, not to mention that ExpoDev's reciprocity data covers film and developer combinations across different manufacturers. Correction is not a one-size-fits-all curve; it is very unique to each film and developer combination.

What is meant by "selected exposure times" though. What this means is, when you tell ExpoDev that the shutter time you want to use is anywhere within the range of 1 to 1,000 seconds,  ExpoDev would then apply reciprocity failure correct and give you a corrected exposure time to use. This corrected exposure time may be a small adjustment for a selected exposure time of a few seconds or it may be several hours for a selected exposure time of 16 minutes (from 1 to 8 hours, depending on which film and developer combination you use).

There is a second part to reciprocity failure correction though and that is that the overall resulting negative density also changes with extended exposure times. Unlike exposure times negative density can change either direction, either increasing or decreasing depending on the film and developer combination used. ExpoDev's reciprocity data for these film and developer combinations includes how development time should be adjusted as well. This reciprocity data is used to apply an adjustment to the Average Gradient that is calculated as part of the exposure. It is this Average G value that is used to look up the development time that should be used to produce a negative that matches the target density desired (so that printing or scanning remains consistent and easy across all of your negatives).

Each Film Profile that you import into ExpoDev contains a two-part code expressed as a letter/number combination (e.g. D4, A6, etc…), The first part is for the exposure time adjustment code and the second part is the development adjustment code. For the exposure time adjustments there are 5 codes, A-E; for development adjustments, there are 7 codes, 1-7. When you export film test data from Plotter for Windows you select which code to use for that film/developer combination (Plotter has a table for all the film and developer combinations that were tested). Since you get to choose the code to use when you export your film test profile this also means that you can override the codes if your working processes need adjustments. You can even choose to export without any codes at all which will cause ExpoDev to skip reciprocity adjustment altogether.

In the next article I'll cover ExpoDev's adjustable Depth of Field calculator.

Until then I'm happy to say that ExpoDev version 1.0 has reached the final testing stages and if all goes well, it should be available in the Apple iTunes App Store very soon.

Flux and Mutability

The mutable notebook of David Jade