Track Your Film Chemical Use and Exhaustion
Add New Chemical
What is Chem Log, and how to use it: Get more out of your film development chemistry. Quick start guide. Track film + chemicals. Development time compensation charts. Chemical dilution calculator. Download your data. Support this blog & get premium features with GOLD memberships!
Get more out of your film development chemistry.
Have you ever wondered if your chemicals are still good to use with your precious film? What if they expired or lost their potency?
Your 1L/Quart C-41 chemistry can develop up to 28 rolls, but to get this much use out of it, you must recalculate the development times before each use (and use the mix up within two months). Chem Log can make those calculations for you.
You should also keep a note of the expiration times for each one of your chemicals. Chem Log will keep a record of your mix dates so that you won’t have to take unnecessary risks with expired chemicals.
Your black-and-white fixer can process up to 200 rolls, but once it exhausts, the quality of your negatives will worsen. Chem Log will keep a record of all the rolls that go through your chemistry.
As you get ready to develop, Chem Log will help you calculate dilutions precisely using a correct formula (not an approximation).
Chem Log is a powerful film photography app with a simple interface designed to make record-keeping effortless. It takes less than a minute to get started and just a few seconds to flip a toggle when developing.
Advanced users get to add and edit field notes, customize how the app behaves, and download usage data as a CSV document.
Quick start guide.
Enter your chemical’s name, select type, and click “Add.”
Once you’re ready to dispose of your chemical (after ~200 uses for black-and-white fixer, after the manufacturer’s expiration date passes, or when your chemical tests fail), hit “Edit” and click “Dispose.”
A record of all of your disposed chemicals will appear near the bottom. You can refer to it later, or you can immediately remove items by hitting “Delete.”
If you change your mind, you can move your chemicals from the “Disposed” section via the “Put Back” button.
Track film + chemicals.
Chem Log works best with Film Log — a popular app for keeping track of film across cameras. Film Log takes less than a minute to note your camera and film.
Once you fill your roll with photos, open Film Log and move your film/camera record to the “Done Shooting” row: hit the “Edit” button and then “Advance.” From there, you can move it to “In Development” once you’re ready to process. That’s when a pop-up will present you with your chemistry options — check all that applies and move your film/camera record to the “Scanned / Archived” when ready.
The Film Log app will keep a record of your film and cameras on Analog.Cafe servers.
If you change your mind, you can update which chemicals were used to develop your film roll by clicking the three dots next to your film roll in the Film Log app and then tapping “Edit Chemicals.” You can do this even after you mark your film as “Archived.”
Back in the Chem Log app, each of your chemical records will get a link named “Rolls” with a counter next to the mix date. You can click that link to see a list of all the film rolls you’ve processed with that chemical. You can click each of the rolls listed to open the Film Log app and highlight that exact roll for easy record retrieval.
Development time compensation charts.
C-41 colour film developers are meant to be reused. Unfortunately, each time a roll goes through the solution, it weakens. The amount by which it weakens depends on the volume and number of rolls processed.
To compensate for the weakened developer, manufacturers suggest using a formula: “add 2% to development times for each additional roll after the first few x rolls; x is based on the volume of chemical mixed.”
Chem Log uses your stats to automatically calculate extended development times for the standard 1L (quart) and 500ml (pint) kits. Use this data to ensure correct exposures with your negatives and safely extend the lifetime of your C-41 kits.
Chemical dilution calculator.
When developing black-and-white film, you may need to calculate the concentrate vs water (dilution) measurements. These measurements change depending on how much of the total solution you’d like to mix.
The formula to get the exact water and concentrate volumes isn’t particularly straightforward:
x = r × (v — x)
Where r is a dilution ratio (i.e., 1:25), v is the volume of the final solution, and x is the volume of the developer.
Chem Log makes these calculations easy. Click the purple “Dilution Calculator” button, enter your dilution ratio, and adjust the total solution volume. Your answers can be formatted in metric or imperial units.
Download your data.
You can download all your data from the Film Log app (including chemical usage data) into your spreadsheet software. Use this data to learn more about your processing techniques and store your data even if you stop using the app.
