Hack your film: How to change your DX coding


by Bellamy /

2 min read

Hack your film: How to change your DX coding by Dan K
Dan K knocked up this little film hack piece for his Tumblr, and I thought it would be good on here too as I get a lot of people asking how to do this. A simple little hack that will allow you to change the DX coding on your film.

How to hack DX Encoding to make a 400ASA film can tell the camera that it is rated 1600ASA or 3200ASA: Just take a knife or a pair of scissors and scrape the black paint off the appropriate square in the top row. See the pictures above. Note that you have to remove one square of paint for 1600ASA, but two for 3200.

How it works: DX coding is a system to allow cameras so equipped to read the film speed and other information from a 135 (35mm) film canister. The left hand row as shown above is the common contact and the conductivity of the other squares give the data. The top of the two rows of DX coding tells the camera the film speed. By if you don’t like the code, just adjust it by altering the surface conductivity of the squares.

Why?: Not all cameras have a way to override the automatic DX setting, making it hard to push film or re-load the canister with faster film than the original factory load.

Bonus: If you take out the last square as well, technically you can re-code it up to 5000ASA, but not all cameras can read this last digit and would just read it as 3200ASA and in any case, you may not get good results pushing film as far as 2 2/3 stops.

Tip: If you recover the squares with sellotape, a sticker, or nail varnish (anything non-conductive) then you restore the coding. If you cover the common contacts, the camera will assume the can has no coding and will default to (usually) 100ASA.

BOSS LEVEL: Recover the squares with tape, mark the relevant setting and set the film speed you want in the street when you load the film!

About The Author
Dan K is a life-long enthusiast photographer. He celebrated his return to film by collecting just about every quality camera and lens that he could lay his hands upon. Along the way he has developed an encyclopaedic knowledge of film cameras and film processing. Follow him on twitter for a humorous look at photography techniques and technology from all eras. Follow him on Tumblr for his images, journey of photographic discovers and a generous helping of gear-porn.



Other articles on JCHhttps://www.japancamerahunter.com/tag/dan-k/

Text and images © Dan K. All rights reserved.

17 comments on “Hack your film: How to change your DX coding”

    Jeff Schiller April 11, 2014 at 10:52 am / Reply

    Thanks Dan. Can a false DX code of 800 ISO be set too?

      ZDP-189 April 11, 2014 at 7:10 pm /

      For 800ASA, I believe you scrape off only top row, column 2, I.e. the first black square

    Cliff April 11, 2014 at 11:42 am / Reply

    Thank you for sharing this. This will definitely come in handy for my Contax T2.

      ZDP-189 April 11, 2014 at 11:18 pm /

      I have a T2; it’s one of the better compacts for exposure control. I just get around the DX push problem with EV compensation. This tutorial was written for a friend with a Konica Big Mini F, which is less controllable; he complained that activating the only exposure control (backlight compensation +1.5) disabled the flash that he so loves. I had this old-school workaround and needed images to illustrate what I meant by “scraping off the lacquer”. I’ve done this once with a rock in desperation as the light disappeared, but he just loves the combination of pushed film and flash.

      If you do use flash, bear in mind the maximum (biggest f/) aperture of a compact camera is usually smaller than an interchangeable lens. Luckily the T2 has a f/16 maximum aperture and that allows it to achieve a 0.7m minimum flash distance. Presumably, the minimum flash distance for 3200ASA film (even pushed) would be 3.5m. Often the maximum aperture is only f/11 or even f/9 on a compact, so minimum flash distance may be very far indeed.

      ZDP-189 April 11, 2014 at 11:36 pm /

      Oops, I just checked my math: 3.9m minimum flash distance, based on GN11, F/16, 3200ASA.

      5m was for 5000ASA and I don’t think the T2 reads that high.

    Blaine April 11, 2014 at 10:14 pm / Reply

    What a great hack. I love pushing film and not every AF, SLR has manual ISO.

    Galih Jati April 12, 2014 at 9:01 am / Reply

    Ha ha ..nice trick for automatic camera film..I still use mechanical film camera, everything is on my control!

    clint April 13, 2014 at 4:44 am / Reply

    what if you wanted to rate down for overexposure?

    Carsten April 13, 2014 at 7:29 pm / Reply

    Excellent! What an amazing hack. Thanks a lot for sharing.

    TSL April 14, 2014 at 11:11 am / Reply

    I don’t scrape.

    I tape.

    I use an aluminum tape like this:


    If you want to uncover the aluminum tape comes right off. It is also conductive.

    Why not scrape? Well, it can leave flecks of paint somewhere, usually not good for the sensitive inner parts of a film camera. The Aluminum tape takes about 30 seconds to cut and tape on.

    Here is your DX code chart:


    Portra 400 shot at 800 is excellent.

    Shiroa May 14, 2014 at 3:33 pm / Reply

    Will this trick fools processing lab’s machine to automatically push our film? Thanks

    Christian November 30, 2015 at 10:32 pm / Reply

    During a sleepless night some months ago, I coded a very simple tool, that illustrates / helps with DX encoding:


    I am Jack's Brain December 1, 2015 at 12:38 am / Reply

    The aluminum tape is a great tip!

    Matt Harvey January 13, 2016 at 1:43 am / Reply

    Thanks…wish I’d known this 20 years ago when I was shooting with my Minolta 3xi. Frustrated me to no end that I had to use my old SRT-101 to push Tri-X or T-Max.

    Mike May 5, 2016 at 9:39 pm / Reply

    This is pretty awesome. My question: which parts would I cover or scratch off to lower the speed of my (color)film? Like from 400 to 200?

    Lynn November 13, 2018 at 3:05 am / Reply

    Wow. I wish I had known this ages ago – I have just removed the DX coding from some old film I need to use at a different shutter speed. Thank you so much.

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