If you have a camera that can detect the film speed from the DX code on the film cartridge, you can fool it into thinking that the film is another speed. This is useful if you intend to push or pull the film in processing.
Tri-X is my 35mm black and white film of choice. I actually shoot Arista Premium 400 almost exclusively now because it’s the same film and it’s a lot less expensive. It’s an extremely versatile black and white negative film: I’ve seen people get acceptable results (for their purposes) at an exposure index from 100 to over 12,800. It works with tons of developers. It’s a good match with Diafine, my everyday developer. But I’m also enjoying developing it with Rodinal, or, as it’s now marketed, Adonal. Check the Massive Film Development Chart: Rodinal 1+50 = any ISO from 100 to 12,800.
I have a love-hate relationship with point-and-shoot cameras, but this Yashica T4 just fell back in my lap, so I thought I’d try shooting with it again.
So if I like to shoot Tri-X well above 400, and I’d like to use the Yashica T4 more often, what do I do? I hack the cartridge. It’s pretty easy, actually. I spent some time online looking for stickers to do the work for me (I bulk load a lot of my own film), but for factory-rolled film, the edge of a knife works best.
Here are the relevant DX codes for ISO on a film cartridge. If you wish to see them all (and what the other codes are for), read the Wikipedia article “DX Encoding.”
If you’re looking at a film cartridge, this is the top row if you have the film spool stem to your left. Black spaces are black paint, white spaces are silver/bare metal/conductive surface to make contact with the sensors in the film chamber of the camera.
The reason I’m keeping this simple for this post and for my own tests is that all of the speeds above 400 in the above chart are attainable by scraping black paint away. No need to add black paint (or electrical tape) anywhere.
Just score the area you’re going to scrape so you don’t scrape “outside the lines,” then using the edge of a knife, scrape away the paint until you’re left with bare metal.
Wipe off the dust (you don’t want that in your camera or on your film). Now write on the cartridge with the “new” EI is so you don’t forget, and you’re good to go.
Soon I’ll post with some results of hacked Arista Premium 400/Tri-X cartridges and the Yashica T4. I’ve taken photos two consecutive days with similar weather, and some of the same scenes.
If you’re hacking DX codes with success, let me know!
[EDIT 2015-02-10]
For some reason, when I originally wrote this post, I left out the ISO code for 1250, which is the speed I would shoot Arista Premium 400 and shoot Kodak Tri-X at for development in Diafine. I’ve updated the chart above. I wasn’t trying to keep it a secret, I promise! I was just too lazy to update the blog post until now.
David Shoots Film 
Good call on this. I have a GR1s with which you can’t manually adjust the ISO and I have to use this method to exceed 1600.
I just wish I had thought of it sooner!
Maybe this is a stupid question but I’m trying to understand this hacking stuff:
So you hack your Tri-x to ISO 3200?
This way your camera thinks its ISO 3200, (so all your film will be underexposed right?)
And you bring that back with the development proces?
I mean, i would like to go to 12,800 with Tri-x some time,
But what do I need the camera to think? (which iso?)
And if you don’t develop the film yourself, which instructions do you have to give to the shop that develops your film?
I hope you guys can help me out.
Kind regards!
Never a stupid question.
So you got the basics correct–you’re fooling the camera into underexposing the film, then “push” developing the film. We’ll get back to that.
DX encoding only goes up to ISO 5000. See here: http://en.wikipedia.org/wiki/DX_encoding
So you wouldn’t be able to shoot at 12,800 using a point-and-shoot camera that relies 100% on the DX code (or defaults to ISO 100 in the absence of the DX code). There are cameras that 1) use the DX code but 2) have manual ISO setting (advanced film SLRs) or 3) allow for exposure compensation of +1 to +2 stops, so in those cases you might be able to get the camera to your desired ISO or exposure index.
Do understand, this “hack” is really only relevant on compact automatic cameras that set aperture and shutter speed automatically. The Yashica T4/T5 is a cult favorite because it gives great results–same with the Ricoh GR series. On any SLR or rangefinder that includes a meter, you’re able to set the ISO manually.
Of course, you don’t actually need a meter in the first place, if you’re able to set aperture and shutter speed yourself. Just get an external meter or learn to meter by eye. Or be lazy, I mean adventurous, like me and set the lowest shutter speed that you think you can shoot without camera shake, and the widest aperture of your lens, then stand develop in Rodinal. https://davidshootsfilm.com/2010/09/27/i-think-im-in-love-stand-development-in-rodinal/
My hand-held Sekonics only go up to 8000, so in that case I would meter at ISO 6400, then close down one more stop (or move up to the next faster shutter speed) than the meter says to achieve 12,800.
So what to tell the developer (until you develop your own film which is really easy and awesome and fulfilling): each doubling of the ISO/EI number is one stop. So you’re asking them to take Tri-X 400 and develop it as if it were 12,800. So you would ask for a 5-stop push. Best to develop it yourself, join a community darkroom, or find a specialty processor who is willing to do that. The results are definitely in the eyes of the beholder at that point–you might love the results while someone else might hate them.
Anyway, let me know if that helps–I’m happy to clarify anything and continue the conversation.
So if I take a roll of 400 and change the code to 200 would it work like 800 iso film?
Sorry I am lost. Also I don’t get how it doesn’t overexpose the film.
Thanks
Hi,
No, the camera would “think” it’s 200 film and overexpose it. It’s a choice, obviously, and you would either under- or overexpose for effect. A lot of people don’t rely on “box speed” and choose a preferred speed after testing with various exposures and favored developers.
Maybe I’ll write more on this soon in a post. Thanks for stopping by!
Thanks! Super helpful chart and I love the tests you posted with the recipe. I’m going to try and trick my NikonL35AF into reading my Tri-X400 at 1600 and push it 2 stops.
By any chance have you tried pushing Cinestill BWXX (aka Kodak 5222) at all? The film is rated at 250 but I can’t find timetables anywhere and am scared to try and push.
Hi David,
Unless I’m mistaken, the Yashica T4 only has four contacts (out of six) for reading DX-codes. I believe it is missing two, just like most point-and-shoots. As such, it is incapable of reading DX values that represent anything but full stops from ASA 25-3200. In this post you mention modifying the DX code of a cartridge to rate TRI-X at 1250. That would be fine on a camera that has all six contacts (like most SLR’s) for reading a DX code in its entirety, but for most point-and-shoots it won’t work. A cartridge whose DX code represents a speed of 1000 or 1250 will be read as 800 by most point-and-shoot cameras because if they only have four contacts they’re only able to read values in full stops beginning at 25 and ending at 3200. They can’t read third-stop values in between each full stop. For example, Portra 160 will be read as and exposed at 100, and so will FP4 PLUS (ASA 125) and any other film rated between 100 and 200 with a matching DX code. Likewise, all films rated and DX-encoded between ISO 800 and 1600 will be read and exposed by most point-and-shoots as 800 speed film.
I know this is an old post, but I came across it and thought I’d mention this so that if anyone is using point-and-shoots and is confused because they’re getting unexpected results, maybe this will add some clarity on a potential reason why.
Take care!
Interesting! Thank you for posting this – it’s a great addition to the archive. Luckily 800 is only about a half-stop off from 1250 (or 1000, which is probably closer to my Diafine EI for Tri-X).
I’m trying to shoot HP5 Plus at 400 for this year, and to be honest I’ve not been “DX Hacking” for a few years.
Absolutely. Maybe the information will come in handy for someone someday who stumbles across it!
Yeah, when dealing with negative stocks (especially TRI-X in Diafine), the lack of third-stop precision between full stops is not really that big of a deal due to the latitude they have. Overexposing by even two-thirds of a stop is likely irrelevant. But if a person was bulk-loading cartridges of some perfectly stored, frozen slide film that was not rated at one of the full-stop values most point-and-shoots are able to read, but they didn’t realize the limitation of their camera and did some DX hacking thinking they could force it to expose the film at say 160 for instance, they could run into issues in a hurry as it would end up being overexposed at 100. For reversal film that obviously wouldn’t be good. They’d probably be better off slightly underexposing it at 200 by just loading it into a 200 DX-coded cartridge to begin with and not messing with modifying anything.
That said, for pushing or pulling stocks by a stop or two that are already rated at 50-3200 (in full-stop values) your trick works great. And when using point-and-shoots in low light conditions where it’s not possible or desirable to use flash, being able to hack the DX codes of HP5 or TRI-X to give you an EI of 1600 is incredibly useful.
Thanks!