Chem Log adds precise C-41 development-time calculator

# What changed

Chem Log, a web app for tracking development chemicals, now includes a C-41 development-time calculator that factors in temperature, push/pull choices, kit size, and chemical usage. Instead of manual conversions and layered formulas, the tool returns a readable development time plus agitation technique. It also compensates automatically for chemical exhaustion and kit volume.

# Why this matters

C-41 is straightforward at standard conditions, but becomes fiddly when you: push or pull film, extend chemical life, change development temperature, or combine several of those adjustments. Typical rules of thumb—add 30% for one stop push, add a small percentage per roll for exhaustion—are usable but require careful tracking and math. Chem Log automates those calculations and integrates them with your usage history.

# How it works

• You record when you open or mix a chemical in Chem Log. You can tag that chemical when you mark a roll for development in Film Log. This links the developer to the roll's entry.
• When a chemical is marked as "C-41," the calculator computes an optimal time and agitation plan based on the recorded temperature and any push/pull preference you choose.
• The calculator accounts for exhaustion and the volume of the kit (how many rolls the kit has already processed and how large your kit is), adjusting times accordingly.

The author states the formulas are based on manufacturer instructions and on times verified during hands-on development. That verification informed simplifications to timing and agitation guidance so results are practical to follow.

# What was tested

The post notes testing with CineStill, Arista, and Flic Film C-41 kits. The author cautions that while C-41 is standardized, kits can differ, so the calculator's times are presented as a solid starting point rather than an absolute rule.

# Other changes in Analog.Cafe v3.34.43

• Chem Log: Added C-41 stand-development formula.
• Chem Log: New usage graph design and real-time chemical exhaustion calculation.
• Chem Log: Bug fix for chemicals not showing in Film Log, plus performance and sync improvements.
• film Q: Easier rotation and selection controls in modal previews.

# Practical takeaways for users

• If you already log mixing/opening times and tag developers in Film Log, the new calculator will produce times that factor in actual chemical age and use rather than approximate rules of thumb.
• Use the calculator results as the base plan. Because kits differ, verify on a test roll or follow any manufacturer-specific caveats first.

# Quick workflow to start using it

1. 1Record developer open/mix time in Chem Log when you set up a kit.

1. 1Set your target temperature and any push/pull preference in the calculator.
2. 2Follow the suggested time and agitation, and note results to refine future runs.

# Bottom line

The Chem Log C-41 calculator removes much of the manual arithmetic around push/pull adjustments, temperature changes, kit volume, and exhaustion by using recorded usage data plus manufacturer-based formulas verified by the author. The output is intended as a practical starting point and now includes stand-development options and real-time exhaustion tracking.