LIT OS 0.9 beta4 for the LIT DUO 1 Light Meter Released – Higher Spectrum Resolution, CRI and SSI, New ΔEV Mode

Firmware Update

by Nino LeitnerJuly 22^nd, 2026

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Swedish company LIT Systems has released LIT OS 0.9 beta4, the latest public test firmware for its LIT DUO 1 all-in-one light and color meter. The update brings 2.5x higher spectrum measuring resolution, new CRI and SSI readings, a new ΔEV exposure difference submode, faster measurements across the board, and a reworked Bluetooth protocol ahead of the final LIT OS 0.9 release, which is planned for mid-August 2026 at the latest.

The LIT DUO 1 has been on our radar for a while now. We first covered the pocket-sized meter when it was introduced with its seven measuring modes, followed the Kickstarter launch alongside the simplified LIT C1, and more recently, founder Marko Pirc joined Johnnie on our Focus Check podcast to talk about building a hardware product from scratch in Europe (embedded below in case you missed it, a genuinely amazing episode). With LIT OS 0.9 beta4, the company says it is delivering the largest set of new features and improvements yet, and owners can install it right away to help polish the firmware before the official release.

Spectrum mode gets CRI, SSI, and a sharper graph

The most substantial changes land in Spectrum mode. Measuring resolution of the spectrum and its on-screen graph increases by a factor of 2.5, and the mode now displays CRI and SSI values, although LIT Systems notes that both metrics will be further tweaked before the final release. SSI (Spectral Similarity Index) in particular has become an increasingly common reference for cinematographers evaluating LED fixtures, so having it on a pocket meter is a welcome addition.

Spectrum mode also gains Mired units for CCT and the ability to fully configure the displayed data across up to three sub-screens. According to the company, CCT accuracy has improved when measuring colder LED spectrums, and measuring duration is now 15 to 60% shorter depending on the ambient light level. A new “TUNE KELVIN” option in the Advanced Settings allows global tuning of CCT results, which is useful if you want to align the meter’s readings with a reference device you already trust. The same accuracy, speed, and tuning improvements apply to the dedicated Color Temperature mode, which additionally drops its “CCT” and “Tint” labels for a cleaner layout.

New ΔEV submode and faster exposure metering

On the exposure side, Cine mode receives a new ΔEV (Exposure Difference) submode with five memory spaces, a handy tool for checking lighting ratios and contrast between different areas of a scene. The ND filter setting moves onto the main screen, additional units can now be measured and displayed there as well, and the mode gains sounds. LIT Systems claims measuring duration is roughly 20% shorter, with improved display behavior during continuous measuring in darker ambient conditions.

Photo/Video mode follows suit with the same speed gains and adds the ability to measure shutter or ISO directly. In the general settings, a new global “Mute sounds” toggle appears, and the company has fixed the “TUNE AMBI EXPOSURE” and “FACTORY RESTORE” functions.

Color Engine 2.0, Bluetooth overhaul, and new apps on the way

Under the hood, beta4 introduces “COLOR ENGINE 2.0”, which LIT Systems describes as a completely new approach to calculating colorimetric units, again subject to further tweaking before the final release. The BLE protocol has been completely reworked and now includes encryption, laying the groundwork for the upcoming redesigned LIT Control apps for iOS, Android, and macOS, which are planned for release around the same time as the final firmware, as well as third-party integrations such as native support in the upcoming Blackout 3.0 control app. The company also states that all known reasons for LIT DUO 1 freezing have been fixed.

A few items remain on the work-in-progress list for the final LIT OS 0.9 release, including energy saving features such as auto-dimming the backlight, contrast ratio calculation in the ΔEV mode, improved battery level indicator accuracy, and better flash detection in high ambient levels. A roadmap for LIT OS 1.0 will follow once LIT OS 0.9 and the new apps are officially out.

For now, the beta can only be installed via USB-C from a Mac or PC. The process is straightforward: download the firmware file, boot the LIT DUO 1 into its firmware update mode, and copy the file onto the device, which mounts as an external drive. LIT Systems notes that the method works reliably on Apple Silicon Macs and standard Windows PCs, while Intel-based Macs and some Windows configurations can occasionally fail to recognize the device. Installing the beta cannot damage the meter and does not void the warranty, according to the company. Full instructions and the download are available on the LIT Systems website, and feedback can be sent directly to the developers.

Are you using the LIT DUO 1 on set, and which of the new LIT OS 0.9 features will help your workflow most? Don’t hesitate to let us know in the comments below!