# Lambert vs PDFocus

The clearest difference is update cadence: PDFocus at every 3 weeks against Lambert's every 5 months. Lambert's advantage is iOS requirement (16.6 vs 18.6). On price, ads, in-app purchases and device support there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

Lambert ships an update every 5 months, PDFocus every 3 weeks. The most recent releases landed on October 3, 2026 and October 2, 2026 respectively.

## The numbers

| Metric | Lambert | PDFocus |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[5.0 (4 ratings)](https://appshunter.io/ios/app/lambert/id341216494/reviews)** | — |
| Number of ratings | **4** | — |
| Positive reviews | 75.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 5 months | **Every 3 weeks** |
| Monetization | Free | — |
| Size | 3 MB | 3 MB |
| Requires iOS | **16.6** | 18.6 |
| Devices | iPhone, iPad | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Peter Appel](https://appshunter.io/developer/341216497) | [Dev First](https://appshunter.io/developer/1716876343) |

## What reviewers say

### Lambert

[App page](https://appshunter.io/ios/app/lambert/id341216494)

This application transforms your iPhone into a specialized geological compass. It accurately measures the dip direction and angle of geological strata, displaying real-time orientation data. Measurements can be enhanced with text and plotted on a map for easy transfer to your computer.

**Highlights:** Geological compass functionality, Measure dip direction and angle, Real-time stereographic projection, Wulff and Schmidt Net projection diagrams, Add text to measurements, Plot measurement localities on a map, Transfer data to computer

**Features:** macOS Compatibility

**In-app purchases:** none


### PDFocus

[App page](https://appshunter.io/ios/app/pdfocus/id6758308559)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Lambert free?

Lambert is free to download, with no in-app purchases.

### Is PDFocus free?

PDFocus is free to download, with no in-app purchases.

### Do Lambert or PDFocus have ads?

Neither Lambert nor PDFocus shows ads.

### Which is updated more often, Lambert or PDFocus?

Lambert ships an update every 5 months, and PDFocus every 3 weeks. Most recently, Lambert was updated on October 3, 2026 and PDFocus on October 2, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*