F-Stop timer for android

Discussion in 'Darkroom Equipment' started by jfdupuis, Apr 3, 2011.

  1. jfdupuis

    jfdupuis Member

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    Hi guys,

    Being in between jobs, I had some extra time and decided to write a f-stop timer application for my android. In the beginning, I thought it would be a quick job to implement that on these handy device, but in the end, I found myself coding more than 3000 lines of codes and making loads of new icons.

    I finally came up with a fully featured program (darkroom f-stop timer) that support dodging, burning and split printing. As I would like to continue to improve this one, please use this thread to suggest any improvement or desired features. I will then try to get my hands out of the trays and put them on the keyboard again to code some more.

    Cheers,

    Jeff
     
  2. brbeck

    brbeck Subscriber

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    Jeff,

    Do you have the Android interfaced with your enlarger? Or are you just using it to get times to enter in your linear timer?
     
  3. jfdupuis

    jfdupuis Member

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    Hi Beck,

    My enlarger didn't come with an android interface ... unfortunately. I use this program to get the correct amount of time for my current timer. Not having a digital input timer, I would use it with the focus switch. The program is a timer counting down for each exposure and bips at the end. So I can just switch it on and off manually. Accuracy is good enough on long exposures.
     
  4. Euter

    Euter Member

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    Great job, I just working on BT-controller for my enlarger. I have one request. It would be possible to add extension factors for grades? I have color head and have to calculate filtration extension factors on a calculator. Individual filtration extension setting for every grade and the application would be amazing :smile:
     
    Last edited by a moderator: Mar 28, 2012
  5. Mainecoonmaniac

    Mainecoonmaniac Subscriber

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    Some engineer needs to make a bluetooth enlarger timer that will interface with the Android or Iphone. Also use the camera as an enlarger meter/densitometer too!
     
  6. polyglot

    polyglot Member

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    You know you can get a plug to go in the bottom of a droid that gives you serial, etc? You can then plug an AVR or whatever into your droid and use that to do hardware interfacing, i.e. switching the enlarger directly from the phone. In fact, I'd be surprised if you couldn't use the CTS line or something on an FTDI chip to toggle your relay, no extra logic/micro required.

    How do you deal with the screen fogging your paper?

    PS your link seems broken ("We're sorry, the requested URL was not found on this server.")
    PPS devil's advocacy.
     
  7. Mainecoonmaniac

    Mainecoonmaniac Subscriber

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    Make the interface on the screen red and dim.
     
  8. PeterB

    PeterB Subscriber

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  9. jfdupuis

    jfdupuis Member

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    I just updated the application to include grade exposure compensation. The compensation need to be defined in the settings in stops. When the grade is changed, the difference between the old and new grade compensation value will be applied to the exposure. Let me know if this doesn't make sense.
     
  10. jfdupuis

    jfdupuis Member

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    I developed a bluetooth adapter that I describe here: http://www.droidinthedark.com/fstop-timer/enlarger-bt-adapter. I have release the code that the interface uses so that anyone can build it own using an arduino and a bluetooth module like the RN-42.

    The only problem with these is price. It turns out to be quite expensive to make only few of them. Just the cost of the PCB alone can go from 40$ a piece to 2$ depending on quantity. Hence, unless a group is formed to order them in batch, the prototype/DIY/open source approach will be the only way to go.
     
  11. jfdupuis

    jfdupuis Member

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    The only robust approach to interface the Android to some hardware are bluetooth and usb. Until recently, bluetooth was the only way to go to interface a device. However, Google has now introduce the USB host support for android device 3.1 and higher. Given that your phone has the hardware requirement, that is having a USB host capable chip, relying on the usb to make a connection to some hardware would be possible.

    As the bluetooth module is quite relatively expensive compare to the rest of the component, it would be possible to reduce the cost of the timer interface by using the usb interface.

    By using a user interface only using red and turning the brightness to a minimum does the job. The test I made with my phone didn't show any fogging.

    The only concern with using the android as timer in the darkroom is if the application gets overridden unexpectedly. For instance, by receiving a call. It's impossible with android to block other applications or to make your application monopolize the screen. As a work around, you can go to the art store and buy some transparent red sheets that you put over the screen. Or, you shut every network and enjoy your disconnected time in the darkroom :wink:
     
  12. Moopheus

    Moopheus Subscriber

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    How would the cost compare to buying a DA or RH timer? If it is not much cheaper, is there some other advantage?
     
  13. jfdupuis

    jfdupuis Member

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    I don't know the price of these timer, but 160$ is about what I evaluated.

    The really good thing about this timer is that it's linked to another application I've made, the Darkroom NoteKeeper http://www.droidinthedark.com/notekeeper. The exposure used to produce a print can quickly be saved in a database. For future reprint, the exposure sequence can be retrieved in a few clicks. The user interface of this timer is also very attractive and easy to use. Finally, I'm currently working on the development of a voice command interaction that will be available on the next major release.
     
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  15. polyglot

    polyglot Member

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    The advantages are that it is open source (if you want it to do something extra, just change the code yourself), a smartphone/tablet provides a much richer user interface and more processing power than the simple devices being sold as darkroom timers. They can become significantly smarter.

    For example, you could use the built-in camera to look at the enlarger output on the baseboard and from that, choose a printing grade and some dodge/burn suggestions (illustrated on the screen!) that will result in a fairly well-balanced print. The possibilities are hugely expanded.
     
  16. Moopheus

    Moopheus Subscriber

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    Yeah, that'll happen.

    Well, they sell meters that will do those things too. Admittedly, it's an add-on cost. But it's already there. And how smart do I really want this thing to be? I mean, the whole reason I do darkroom work is so that I do it. If I want the computer to do it, I might as well just do it in Photoshop.
     
  17. jfdupuis

    jfdupuis Member

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  18. blanconegro8rc

    blanconegro8rc Member

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    good day to all. I am at a loss as to how to determine the progression of f stopping using my enlarging timer. what is "the ballpark figure" in getting the increments. I am not good the numbers. I am requesting you guys if you can give me a starting point. lots of thanks!
     
  19. MattKing

    MattKing Subscriber

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    blanconegro8rc:

    Welcome to APUG.

    If you want a progression of times that has 1/2 stop increments, these numbers work well:

    2.8, 4, 5.6, 8, 11, 16, 22, 32, 45, 64, 90, 128 ...

    Ralph Lambrecht and Chris Woodhouse's excellent book, "Way Beyond Monochrome", has lots of useful information about these issues. Ralph posts here regularly, and his website (darkroommagic.com) has a bunch of useful aids in the Library section, including an f/stop timing table in pdf form here: http://www.darkroomagic.com/DarkroomMagic/Darkroom_files/f_stopTiming.pdf
     
  20. polyglot

    polyglot Member

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    The formula to convert stops to time is:
    T = 2 ^ stops

    put in any value of stops you like. Typically you test with exposures that are uniformly-spaced in stops, e.g. 2.5, 2.75, 3.0, 3.25, 3.5, 3.75, etc. Convert each of those using the above formula into seconds to get your sequence of printing times.

    If you want a nicely printed table, there are f/stop timing cheatsheets and spreadsheets you can download, or just enter the formula into Excel and print out a table of times against a table of stops. I recommend getting a copy of WBM2 as it has all the instruction you need for your printing; see also the FAQ in my signature for a very simplified intro to printing.

    Typically when you do a test strip, you will test initially with 0.5-stop intervals. Once you get something ballpark-right, you can do another strip at maybe 0.1-stop intervals.

    As a start, the default whole-stop aperture markings on a camera are half-stop values when used as enlarger times, i.e. 4, 5.6, 8, 11, 16, 22, etc. And the 1/3-stop sequence on an aperture is a 1/6-stop when used as times, i.e. 4, 4.5, 5, 5.6, 6.3, 7, 8, 9, 10, 11, 13, 14, 16, 18, 19, 22, etc. They are heavily rounded-off though for convenience but they are kind of close to the right progression.

    Edit: ha. I should type faster :wink:
     
  21. kodel

    kodel Member

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    I just bought Jeff' F-stop timer application. Great work, Jeff! I just have one minor change request:
    Can you provide a square area on the screen that lights up in red when the enlarger should be ON?
    The reason is I want to use a phototransistor taped to the screen to control a relay to switch my enlarger ON and OFF.
    I would suggest the top left area of the screen, since this is unused in the current UI.

    An alternative solution is to put out a continuous tone (e.g. 1000 Hz beep) during exposure. This would be a more robust way of switching on and off my relay.
     
  22. redtreephoto

    redtreephoto Member

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    Is this app now removed from Google Play? Pity.

    Sent from my HTC One using Tapatalk
     
  23. jfdupuis

    jfdupuis Member

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    I decided to release the application as open source, so I removed it from Google Play. You can find the source on bitbucket: https://bitbucket.org/jfdupuis/droidinthedark
     
  24. redtreephoto

    redtreephoto Member

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    That is extremely generous of you. I managed to download the zip but I am not a programmer. I am 100% confused with the folders and file types. I was hoping we could just install an apk? Is there an easy way to install? Thank you for responding so quickly.
     
  25. RobC

    RobC Member

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    You can just install it.

    goto bitbucket and select

    source / ftsoptimer / released / daroom timer 3.1 / darkroom FStopTimer 3.2.apk / view raw

    and save it. Move to android device download area, open that folder and install it.
     
  26. redtreephoto

    redtreephoto Member

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    Yes!! Thank you so much to both the developer and the guide ;-)