# ReactionFlash vs PhotoMetrix

The clearest difference is update cadence: PhotoMetrix at every 3 weeks against ReactionFlash's every 4 months. ReactionFlash's advantage is review sentiment (81% vs 67%). On price, ads, in-app purchases and monetization model there is nothing between them.

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

ReactionFlash ships an update every 4 months, PhotoMetrix every 3 weeks. The most recent releases landed on October 16, 2026 and October 11, 2026 respectively.

## The numbers

| Metric | ReactionFlash | PhotoMetrix |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.8 (41 ratings)](https://appshunter.io/ios/app/reactionflash/id432080813/reviews)** | — |
| Number of ratings | **41** | — |
| Positive reviews | **80.6% of reviews** | 66.7% of reviews |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 4 months | **Every 3 weeks** |
| Monetization | Free | Free |
| Size | 37 MB | 27 MB |
| Requires iOS | **14.0** | 15 |
| Devices | iPhone, iPod | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Elsevier Limited](https://appshunter.io/developer/1437273934) | [Gilson Augusto Helfer](https://appshunter.io/developer/1131751264) |

## What reviewers say

### ReactionFlash

[App page](https://appshunter.io/ios/app/reactionflash/id432080813)

This app serves as a comprehensive flashcard-style learning tool for named chemical reactions. It provides detailed information on reaction mechanisms and examples from scientific literature, with a quiz mode to test user knowledge.

**Highlights:** Learn named chemical reactions, Understand reaction mechanisms, View literature examples, Quiz mode for knowledge testing, Flashcard interface

**Features:** macOS Compatibility

**In-app purchases:** none


### PhotoMetrix

[App page](https://appshunter.io/ios/app/photometrix/id1220976347)

This application performs univariate and multivariate data analysis using image acquisition and RGB histograms. It supports various color systems and can export data and charts via email for validation with other software.

**Highlights:** Univariate analysis with Single Linear Correlation, Multivariate analysis with Principal Component Analysis (PCA), Image data acquisition via device camera, RGB histogram conversion, Support for RGB, HSV, HSL, and HSI color systems, Email export of data, analysis, and charts, Calculation of eigenvalues, eigenvectors, scores, and loadings

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is ReactionFlash free?

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

### Is PhotoMetrix free?

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

### Do ReactionFlash or PhotoMetrix have ads?

Neither ReactionFlash nor PhotoMetrix shows ads.

### Which is updated more often, ReactionFlash or PhotoMetrix?

ReactionFlash ships an update every 4 months, and PhotoMetrix every 3 weeks. Most recently, ReactionFlash was updated on October 16, 2026 and PhotoMetrix on October 11, 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.*